ferrites
TRANSCRIPT
EXPLORING MAGNETIC PROPERTIES OF FERRITES
Trivial to Advanced Applications
GARIMA Kotnala
Nanoscience amp Magnetism At the nanometer dimensions a large fraction of the atoms are at or
near the surface resulting in a large surface to volume ratio(SVR)
Increase in the SVR leads to increasing dominance of the behaviour of atoms on the surface of the particle over that of those in the interior of the particle This affects the properties of the particles in isolation and its interaction with other particles This is where quantum size effects starts playing its role
Magnetism essentially results from two electronic motion associated with the atom the orbital motion of the electron and the spin motion of the electron
On application of Magnetic field a net alignment of these magnetic dipoles occurs and the medium becomes magnetically polarized
MAGNETIC MATERIAL
In a magnetic material magnetic phenomena originate due to magnetic moment of unpaired electronic spins of atoms or ions
Theoretical and Experimental Metal Ion Magnetic Moments
Metal Ion Theoreticalmoment
Experimental moment
Mn2+ 5 46
Fe2+ 4 41
Co2+ 3 37
Ni 2 23
Cu2+ 1 13
Mg 0 11
Types Of Magnetic MaterialsPara
Ferro
Anti
Ferri (FERRITES)
Enforced Ferro
Those not having any permanent magnetic
moment ndash diamagnetic
materials and those having permanent magnetic moment
para ferro antiferro and
ferrimagnetic(Ferrites) materials
Magnetic Spins amp Dipoles The Magnetic spins in solid-state materials have
enabled significant advances in current informational and biological technologies including information storage magnetic sensors bio separation and drug delivery
The origin of the Magnetic potential is known as Magnetic dipoles
On application of Magnetic field a net alignment of these magnetic dipoles occurs and the medium becomes magnetically polarized
Magnetic Interactions Different types of magnetic interactions which allow the magnetic
moments in solids to communicate with each other to produce a long range order are
1 Magnetic dipolar interaction Each magnetic moment of the substance is subjected to a magnetic dipolar interaction with the other moments The magnetic dipolar interactions are found to be too weak to account for the ordering of most magnetic materials with higher ordering temperatures
2 Exchange interactions is the main phenomenon governing the long range magnetic order in ferro antiferro and ferromagnetic materials It is of quantum mechanical origin and electrostatic in nature It is very strong but acts between neighbouring spin moments only and falls off very rapidly with distance
3 Direct exchange interactions Interaction between neighbouring magnetic dipoles proceeds directly without the help of an intennediatory Often direct exchange is not found to be an important mechanism in controlling the magnetic properties because there is insufficient direct overlap between the neighbouring 16 magnetic orbitals Hence direct interactions are not found to be effective in rare earth metals and transition metals
Magnetic Interactions(Contd)4 Indirect Exchange or Super Exchange interactions In ionic solids Indirect exchange or superexchange interactions between non neighbouring magnetic ions is mediated by a nonmagnetic ion which is placed in between the magnetic ions Superexchange interactions involves the oxygen orbitals as well as metal atom (in ferrites)
Ferrites(M2+Fe23+O4
2-) ) The term ferrite is commonly used to describe a class of
magnetic oxide compounds that contain iron oxide as a principal component
Magnetite (Fe3 O4 ) also called loadstone is a genuine ferrite and was the first magnetic material known to the ancient people
Ferrimagnetic Materials are also called Ferrites
Ferrites are the modified structures of iron with no carbon and are composed of two or more sets of different transition metals( d-block elements group 3 to 12)
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Nanoscience amp Magnetism At the nanometer dimensions a large fraction of the atoms are at or
near the surface resulting in a large surface to volume ratio(SVR)
Increase in the SVR leads to increasing dominance of the behaviour of atoms on the surface of the particle over that of those in the interior of the particle This affects the properties of the particles in isolation and its interaction with other particles This is where quantum size effects starts playing its role
Magnetism essentially results from two electronic motion associated with the atom the orbital motion of the electron and the spin motion of the electron
On application of Magnetic field a net alignment of these magnetic dipoles occurs and the medium becomes magnetically polarized
MAGNETIC MATERIAL
In a magnetic material magnetic phenomena originate due to magnetic moment of unpaired electronic spins of atoms or ions
Theoretical and Experimental Metal Ion Magnetic Moments
Metal Ion Theoreticalmoment
Experimental moment
Mn2+ 5 46
Fe2+ 4 41
Co2+ 3 37
Ni 2 23
Cu2+ 1 13
Mg 0 11
Types Of Magnetic MaterialsPara
Ferro
Anti
Ferri (FERRITES)
Enforced Ferro
Those not having any permanent magnetic
moment ndash diamagnetic
materials and those having permanent magnetic moment
para ferro antiferro and
ferrimagnetic(Ferrites) materials
Magnetic Spins amp Dipoles The Magnetic spins in solid-state materials have
enabled significant advances in current informational and biological technologies including information storage magnetic sensors bio separation and drug delivery
The origin of the Magnetic potential is known as Magnetic dipoles
On application of Magnetic field a net alignment of these magnetic dipoles occurs and the medium becomes magnetically polarized
Magnetic Interactions Different types of magnetic interactions which allow the magnetic
moments in solids to communicate with each other to produce a long range order are
1 Magnetic dipolar interaction Each magnetic moment of the substance is subjected to a magnetic dipolar interaction with the other moments The magnetic dipolar interactions are found to be too weak to account for the ordering of most magnetic materials with higher ordering temperatures
2 Exchange interactions is the main phenomenon governing the long range magnetic order in ferro antiferro and ferromagnetic materials It is of quantum mechanical origin and electrostatic in nature It is very strong but acts between neighbouring spin moments only and falls off very rapidly with distance
3 Direct exchange interactions Interaction between neighbouring magnetic dipoles proceeds directly without the help of an intennediatory Often direct exchange is not found to be an important mechanism in controlling the magnetic properties because there is insufficient direct overlap between the neighbouring 16 magnetic orbitals Hence direct interactions are not found to be effective in rare earth metals and transition metals
Magnetic Interactions(Contd)4 Indirect Exchange or Super Exchange interactions In ionic solids Indirect exchange or superexchange interactions between non neighbouring magnetic ions is mediated by a nonmagnetic ion which is placed in between the magnetic ions Superexchange interactions involves the oxygen orbitals as well as metal atom (in ferrites)
Ferrites(M2+Fe23+O4
2-) ) The term ferrite is commonly used to describe a class of
magnetic oxide compounds that contain iron oxide as a principal component
Magnetite (Fe3 O4 ) also called loadstone is a genuine ferrite and was the first magnetic material known to the ancient people
Ferrimagnetic Materials are also called Ferrites
Ferrites are the modified structures of iron with no carbon and are composed of two or more sets of different transition metals( d-block elements group 3 to 12)
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
MAGNETIC MATERIAL
In a magnetic material magnetic phenomena originate due to magnetic moment of unpaired electronic spins of atoms or ions
Theoretical and Experimental Metal Ion Magnetic Moments
Metal Ion Theoreticalmoment
Experimental moment
Mn2+ 5 46
Fe2+ 4 41
Co2+ 3 37
Ni 2 23
Cu2+ 1 13
Mg 0 11
Types Of Magnetic MaterialsPara
Ferro
Anti
Ferri (FERRITES)
Enforced Ferro
Those not having any permanent magnetic
moment ndash diamagnetic
materials and those having permanent magnetic moment
para ferro antiferro and
ferrimagnetic(Ferrites) materials
Magnetic Spins amp Dipoles The Magnetic spins in solid-state materials have
enabled significant advances in current informational and biological technologies including information storage magnetic sensors bio separation and drug delivery
The origin of the Magnetic potential is known as Magnetic dipoles
On application of Magnetic field a net alignment of these magnetic dipoles occurs and the medium becomes magnetically polarized
Magnetic Interactions Different types of magnetic interactions which allow the magnetic
moments in solids to communicate with each other to produce a long range order are
1 Magnetic dipolar interaction Each magnetic moment of the substance is subjected to a magnetic dipolar interaction with the other moments The magnetic dipolar interactions are found to be too weak to account for the ordering of most magnetic materials with higher ordering temperatures
2 Exchange interactions is the main phenomenon governing the long range magnetic order in ferro antiferro and ferromagnetic materials It is of quantum mechanical origin and electrostatic in nature It is very strong but acts between neighbouring spin moments only and falls off very rapidly with distance
3 Direct exchange interactions Interaction between neighbouring magnetic dipoles proceeds directly without the help of an intennediatory Often direct exchange is not found to be an important mechanism in controlling the magnetic properties because there is insufficient direct overlap between the neighbouring 16 magnetic orbitals Hence direct interactions are not found to be effective in rare earth metals and transition metals
Magnetic Interactions(Contd)4 Indirect Exchange or Super Exchange interactions In ionic solids Indirect exchange or superexchange interactions between non neighbouring magnetic ions is mediated by a nonmagnetic ion which is placed in between the magnetic ions Superexchange interactions involves the oxygen orbitals as well as metal atom (in ferrites)
Ferrites(M2+Fe23+O4
2-) ) The term ferrite is commonly used to describe a class of
magnetic oxide compounds that contain iron oxide as a principal component
Magnetite (Fe3 O4 ) also called loadstone is a genuine ferrite and was the first magnetic material known to the ancient people
Ferrimagnetic Materials are also called Ferrites
Ferrites are the modified structures of iron with no carbon and are composed of two or more sets of different transition metals( d-block elements group 3 to 12)
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Types Of Magnetic MaterialsPara
Ferro
Anti
Ferri (FERRITES)
Enforced Ferro
Those not having any permanent magnetic
moment ndash diamagnetic
materials and those having permanent magnetic moment
para ferro antiferro and
ferrimagnetic(Ferrites) materials
Magnetic Spins amp Dipoles The Magnetic spins in solid-state materials have
enabled significant advances in current informational and biological technologies including information storage magnetic sensors bio separation and drug delivery
The origin of the Magnetic potential is known as Magnetic dipoles
On application of Magnetic field a net alignment of these magnetic dipoles occurs and the medium becomes magnetically polarized
Magnetic Interactions Different types of magnetic interactions which allow the magnetic
moments in solids to communicate with each other to produce a long range order are
1 Magnetic dipolar interaction Each magnetic moment of the substance is subjected to a magnetic dipolar interaction with the other moments The magnetic dipolar interactions are found to be too weak to account for the ordering of most magnetic materials with higher ordering temperatures
2 Exchange interactions is the main phenomenon governing the long range magnetic order in ferro antiferro and ferromagnetic materials It is of quantum mechanical origin and electrostatic in nature It is very strong but acts between neighbouring spin moments only and falls off very rapidly with distance
3 Direct exchange interactions Interaction between neighbouring magnetic dipoles proceeds directly without the help of an intennediatory Often direct exchange is not found to be an important mechanism in controlling the magnetic properties because there is insufficient direct overlap between the neighbouring 16 magnetic orbitals Hence direct interactions are not found to be effective in rare earth metals and transition metals
Magnetic Interactions(Contd)4 Indirect Exchange or Super Exchange interactions In ionic solids Indirect exchange or superexchange interactions between non neighbouring magnetic ions is mediated by a nonmagnetic ion which is placed in between the magnetic ions Superexchange interactions involves the oxygen orbitals as well as metal atom (in ferrites)
Ferrites(M2+Fe23+O4
2-) ) The term ferrite is commonly used to describe a class of
magnetic oxide compounds that contain iron oxide as a principal component
Magnetite (Fe3 O4 ) also called loadstone is a genuine ferrite and was the first magnetic material known to the ancient people
Ferrimagnetic Materials are also called Ferrites
Ferrites are the modified structures of iron with no carbon and are composed of two or more sets of different transition metals( d-block elements group 3 to 12)
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Magnetic Spins amp Dipoles The Magnetic spins in solid-state materials have
enabled significant advances in current informational and biological technologies including information storage magnetic sensors bio separation and drug delivery
The origin of the Magnetic potential is known as Magnetic dipoles
On application of Magnetic field a net alignment of these magnetic dipoles occurs and the medium becomes magnetically polarized
Magnetic Interactions Different types of magnetic interactions which allow the magnetic
moments in solids to communicate with each other to produce a long range order are
1 Magnetic dipolar interaction Each magnetic moment of the substance is subjected to a magnetic dipolar interaction with the other moments The magnetic dipolar interactions are found to be too weak to account for the ordering of most magnetic materials with higher ordering temperatures
2 Exchange interactions is the main phenomenon governing the long range magnetic order in ferro antiferro and ferromagnetic materials It is of quantum mechanical origin and electrostatic in nature It is very strong but acts between neighbouring spin moments only and falls off very rapidly with distance
3 Direct exchange interactions Interaction between neighbouring magnetic dipoles proceeds directly without the help of an intennediatory Often direct exchange is not found to be an important mechanism in controlling the magnetic properties because there is insufficient direct overlap between the neighbouring 16 magnetic orbitals Hence direct interactions are not found to be effective in rare earth metals and transition metals
Magnetic Interactions(Contd)4 Indirect Exchange or Super Exchange interactions In ionic solids Indirect exchange or superexchange interactions between non neighbouring magnetic ions is mediated by a nonmagnetic ion which is placed in between the magnetic ions Superexchange interactions involves the oxygen orbitals as well as metal atom (in ferrites)
Ferrites(M2+Fe23+O4
2-) ) The term ferrite is commonly used to describe a class of
magnetic oxide compounds that contain iron oxide as a principal component
Magnetite (Fe3 O4 ) also called loadstone is a genuine ferrite and was the first magnetic material known to the ancient people
Ferrimagnetic Materials are also called Ferrites
Ferrites are the modified structures of iron with no carbon and are composed of two or more sets of different transition metals( d-block elements group 3 to 12)
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Magnetic Interactions Different types of magnetic interactions which allow the magnetic
moments in solids to communicate with each other to produce a long range order are
1 Magnetic dipolar interaction Each magnetic moment of the substance is subjected to a magnetic dipolar interaction with the other moments The magnetic dipolar interactions are found to be too weak to account for the ordering of most magnetic materials with higher ordering temperatures
2 Exchange interactions is the main phenomenon governing the long range magnetic order in ferro antiferro and ferromagnetic materials It is of quantum mechanical origin and electrostatic in nature It is very strong but acts between neighbouring spin moments only and falls off very rapidly with distance
3 Direct exchange interactions Interaction between neighbouring magnetic dipoles proceeds directly without the help of an intennediatory Often direct exchange is not found to be an important mechanism in controlling the magnetic properties because there is insufficient direct overlap between the neighbouring 16 magnetic orbitals Hence direct interactions are not found to be effective in rare earth metals and transition metals
Magnetic Interactions(Contd)4 Indirect Exchange or Super Exchange interactions In ionic solids Indirect exchange or superexchange interactions between non neighbouring magnetic ions is mediated by a nonmagnetic ion which is placed in between the magnetic ions Superexchange interactions involves the oxygen orbitals as well as metal atom (in ferrites)
Ferrites(M2+Fe23+O4
2-) ) The term ferrite is commonly used to describe a class of
magnetic oxide compounds that contain iron oxide as a principal component
Magnetite (Fe3 O4 ) also called loadstone is a genuine ferrite and was the first magnetic material known to the ancient people
Ferrimagnetic Materials are also called Ferrites
Ferrites are the modified structures of iron with no carbon and are composed of two or more sets of different transition metals( d-block elements group 3 to 12)
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Magnetic Interactions(Contd)4 Indirect Exchange or Super Exchange interactions In ionic solids Indirect exchange or superexchange interactions between non neighbouring magnetic ions is mediated by a nonmagnetic ion which is placed in between the magnetic ions Superexchange interactions involves the oxygen orbitals as well as metal atom (in ferrites)
Ferrites(M2+Fe23+O4
2-) ) The term ferrite is commonly used to describe a class of
magnetic oxide compounds that contain iron oxide as a principal component
Magnetite (Fe3 O4 ) also called loadstone is a genuine ferrite and was the first magnetic material known to the ancient people
Ferrimagnetic Materials are also called Ferrites
Ferrites are the modified structures of iron with no carbon and are composed of two or more sets of different transition metals( d-block elements group 3 to 12)
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Ferrites(M2+Fe23+O4
2-) ) The term ferrite is commonly used to describe a class of
magnetic oxide compounds that contain iron oxide as a principal component
Magnetite (Fe3 O4 ) also called loadstone is a genuine ferrite and was the first magnetic material known to the ancient people
Ferrimagnetic Materials are also called Ferrites
Ferrites are the modified structures of iron with no carbon and are composed of two or more sets of different transition metals( d-block elements group 3 to 12)
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Role Of Ferrites In NanoscienceNanoscience concerns with synthesizing modifying and characterizing materials having at least one spatial dimension in the size range of 1-100 nm
Attention towards the ferrites nanomaterials is due to their great scientific and technological importance because of the following reasons
Ferrites are iron containing complex oxides with technically interesting magnetic and electrical properties
Development of new ferrites enhancement of existing ferrites characteristics and improvement of the ferrites manufacturing process began in 1950rsquos
e spintronic devices giant magnetoresistance based (GMR) sensors magnetic random access memories and other novel gadgets based on nanomagnetism
There are mainly two types of ferrites called soft and hard ferrites Soft ferrites are the magnetic materials that do not retain their magnetism after
being magnetized These types of materials include cobalt nickel zinc manganese and magnesium ferrites with spinel structure They are extensively used in the cores of transformers where they must respond to a rapidly oscillating field
Hard ferrites are permanent magnets because they can retain their magnetism after being magnetized For hard ferrites the loop is broad having coercivity greater than 10 kAm-1
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Why Ferrites over Other MaterialsUSES AND APPLICATIONS Recently ferrite materials have received extensive
applications in magnetic devices humidity sensors gas sensors catalysts photocatalytic hydrogen production pigments and anticorrosive agents
Applications as Sensors Recently some composite oxides such as spinel
ferrite (M2+M2 3+O4 ) have attracted research interest due to their versatile practical applications Spinel magnetic oxides (ferrites) are very sensitive to humiditygases A great advantage of ferrites is their porosity which is necessary for a humidity sensor
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
CRYSTAL STRUCTURE OF FERRITES
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Structure Of Ferrites The general chemical formula of a ferrite
molecule is M2+Fe23+O4
2- where M2+ represents a divalent metal ion such as Zn2+ Fe2+ Mg2+ Mn2+ Cd2+ etc
Ferrites crystallize in the form of a cubic structure Each corner of a ferrite unit cell consists of a ferrite molecule
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Cry
The small filled circles represent metal ions the large open or shaded circles represent oxygen ions (a) tetrahedral or A sites (b) octahedral or B sites and (c) one-fourth of the unit cell of a cubic ferrite A tetrahedron and an octahedron are marked
CRYSTAL STRUCTURE OF FERRITES
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
14
i) Regular spinel structureIn this type each divalent metal ion occupies 1 tetrahedral site and each trivalent metal ion occupies 1 octahedral site Totally in an unit cell there will be 8 tetrahedral (8 A) sites and 16 octahedral (16B) sites
Hence the sites A and B combined to form a regular spinel ferrite structures as shown in FigThe schematic representation of zinc ferrite molecule as shown in Fig
Fig Regular spinel structure
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
bull In a ferrite unit cell there are 8 molecules Therefore in a ferrite unit cell there are 8 divalent metal ions 16 ferric ions and 32 Oxygen ions
bull If only the oxygen ions in ferrite crystal are considered it is found that they constitute a close packed face centered cubic structure
bull In these arrangement it is found that for every four O2 ions there are 2 octahedral sites (surrounded by 6 O2
ions) and one tetrahedral site (surrounded by4 O2 ions) The metal ions are distributed over these tetrahedral sites
(A sites) and octahedral sites (B sites) T h u s i n f e r r i t e s t h e n u m b e r o f o c t a h e d r a l s i t e s i s t w i c e t h e n u m b e r o f t e t r a h e d r a l s i t e s
Normally there are two types of structures in ferrites Regular spinel and Inverse spinel
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
16
Inverse spinel structure In this type half of the B sites (8sites) are occupied by divalent metal ions and the remaining half of the B sites (8 sites) and all the A sites are occupied by the trivalent metal ions as shown in Fig
The schematic representation of a ferrous ferrite molecule is shown in Fig
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
17
The anti parallel alignment of a ferrous ferrite molecule in inverse spinel structure is explained by the calculation of its magnetic moment In a ferrous ferrite molecule there are one ferrous ion and 2 ferric ions
When the Fe atom is ionized to form the Fe2+ ions there are 4 unpaired 3d electrons left after the loss of two 4s electrons
When the Fe atom is ionized to form the Fe3+ ions there are 5 unpaired 3d electrons left after the loss of two 4s electrons and one 3d electron It is shown in the following electronic configuration
IonNo of
electrons3d electronic configuration
Ionic magnetic moment
Fe 2+ 24 4microB
Fe 3+ 23 5microB
Table 3d electronic configuration of Fe2+ and Fe3+
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Behaviour Of Ferrites(Ferrimagnetic)
Below the Magnetization Compensation point Ferrimagnetic material is MagneticAt the Compensation Point the magnetic Components cancel each other
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Properties Of Ferrites(M2+Fe2
3+O42-) )
bull The susceptibility () is very large and positive It is represented by = C (T) when T gt TN
When TltTN they behave as ferrimagnetic materialsbull Mechanically they have pure iron character They have low tensile
strength and are brittle and softIn these all valence electrons are tied up by ironic bonding and they are bad conductors with high resistivity of 1011 m
bull Ferrites are manufactured by powder metallurgical process by mixing compacting and then sintering at high temperatures followed by age hardening in magnetic fields
bull They are soft magnetic materials and so they have low eddy current losses and hysteresis losses
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
EXCHANGE INTERACTION
The cooperative interaction of magnetic moments results into ferro- ferri- and antiferromagnetism below a critical temperatureThe energy associated with this interaction as a function of magnetic moments of two neighboring atoms i and j as
Depending on whether the coefficient nij is positive or negative the magnetic moments mi and mj tend to align parallel or antiparallel with each other respectively and exchange energy density
and
The frac12 factor is due to summation over i amp j the interaction of each pair is counted twice
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
The average value of energy at temp T is
where
Hm is the molecular or exchange field
DOMAIN WALL
The region of the materials in which the cooperative effect extends are known as magnetic domain The boundaries between neighboring domains are called domain walls Each domain behave as a tiny magnet composed of smaller magnets (atomic spins) Adjacent domains have their respective spins oriented 180o or less frequently 90o to each other through domain wall Under AC magnetic field the domain wall move in response to the variations in the field strength resulting in alternating growth and contraction of the domains with the changes in direction of the exciting field The movement of the domain walls through a magnetic material gives rise to losses which are usually dissipated as heat
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Schematic Illustration of Domain Structure at Various Stages of the Magnetization Process
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Variations in Hysteresis Curves There is considerable variation in the hysteresis of different magnetic materials
In magnetic particle testing the level of residual magnetism is important Residual magnetic fields are affected by the permeability which can be related to the carbon content and alloying of the material A component with high carbon content will have low permeability and will retain more magnetic flux than a material with low carbon content
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
The hysteresis curves of two different materials are shown in the graph
Relative to the other material the materials with the wide hysteresis loop has bull Lower Permeability bull Higher Retentivity bull Higher Coercivity bull Higher Reluctance bull Higher Residual Magnetism
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
The material with the narrower loop has
bull Higher Permeability
bull Lower Retentivity
bull Lower Coercivity
bull Lower Reluctance
bull Lower Residual Magnetism
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Synthesis Of Ferrites Synthesis techniques play an important role in controlling the size and surface area of materials The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods that is sol-gel sonochemical solvothermal precipitation mi- croemulsion
Sol-Gel Method In this method the formation of a gel provides a high degree of homogeneity
and reduces the need for atomic diffusion during the solid- state calcinations[18] A solution of the appropriate precursors is formed first followed by conversion into a homogeneous oxide (gel) after hydrolysis and condensation Drying and sub- sequent calcination of the gel yields an oxide product
Precipitation Method In the precipitation method the precipitation of substances normally soluble
under the employed conditions An inclusion occurs when the impurity occupies a lattice site in the crystal structure of the carrier resulting in a crystallo- graphic defect which can occur when the ionic radius and charge of the impurity are similar to those of the carrier An occlusion occurs when an adsorbed impurity is physically trapped inside the crystal as it grows
Ball Milling A ball mill is a key piece of equipment for grinding It is widely used for
cement silicate products new type building materials fireproof materials chemical fertilizers black and non- ferrous metals glass ceramics etc Ball milling increases the surface area of a solid ma- terial and allows preparation of the desired grain size
Solid-State Reaction Method Solid-state synthesis methods are the most widely used This method involves
mixing of raw materials and can take place with both wet and dry processes
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
POWER LOSS IN IRON CORE OF TRANSFORMERMOTOR CORE LOSSES EPSTEIN FRAME
A PRECISION WEIGHT THAT FAILS THE MAGNETISIUM TEST SHOULD NOT BE FURTHER CALIBRATED(SI STANDARDS) REQUIREMENT MGNETIC FIELD STRENGTH AND SUSCEPTIBILITY
All auto vacuum valves and MPFI engine (multi point fuel injection) automobiles uses magnetic solenoid valve
Magnetic field indicator for residual magnetism measurement used in air craft industry
All electronic watches use ferrite magnet Modern car uses more than 50 magnets in its machinery Magnetically levitated trains(MEGLEV) with high speed amp comforts without
wheels Magneto-optical (MO) materials for magnetic memory applications World production for magnetic material is 62800000 tonnes a year India produces only 05 of world
CONDUCTING POLYMER INCORPORATED WITH MAGNETIC MATERIAL ACTS AS EXCELLENT ELECTROMAGNET INTERFERENCE SHEILD
IMPORTANCE OF MAGNETIC MEASUREMENT(LEAVING APART FROM ROUTINE MEASUREMENT)
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Example Of Versatile Ferrite-Magnesium
Magnesium Magnesium - Lightest among commonly used metals (1113088 17
gcm3) Melting point is 650 1113088C and it has HCP structure Is very reactive and readily combustible in air Can be used
as igniter or firestarter Pure Mg has adequate atmospheric resistance and moderate
strength Properties of Mg can be improved substantially by alloying 1113088
Most widely used alloying elements are Al Zn Mn and Zr
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Magnesium Alloys
Mg alloys Impact and dent resistant have good damping capacity - effective for high-speed applications
Due to its light weight superior machinability and ease of casting Mg and its alloys are used in many applicationsndash Auto parts sporting goods power tools aerospace equipment fixtures electronic gadgets and material handling equipment
Automotive applications include gearboxes valve covers alloy wheels clutch housings and brake pedal brackets
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
MAGNESIUM FERRITE AS HUMIDITY SENSOR
Recent trend in sensor is towards ferrites as ceramic sensors a high potential candidate due to its unique structure grain grain boundaries pores and semiconducting property This porous surface allows water vapors to pass easily through the pores and condensation of water vapors in capillary-like pores through grain neck This increases the sensivity of the humidity sensors and increases wide scope of using ferrite material
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
CONDUCTION MECHANISM
In humidity sensing initially chemical adsorption and dissociation of water molecules takes place Further adsorption leads to the formation of H3O+ ions Conduction occurs when H3O+ releases a proton to neighboring water molecule which accepts it while releasing another proton and so forth This is known as
Grotthuss chain reaction
GROTTHUSS MECHANISM (Protonic Conduction)
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Conduction on the Surface of the Material
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
In this direction we have focused on MgFe2O4 ferrite compound with rare earth doping Since magnesium ferrite has high porosity and electrical resistance of the order of mega ohms This is desirable for humidity sensing The series of samples were prepared by doping of cerium oxide in 2 wt 4 wt amp 6 wt in pure magnesium ferrite
SEM pictures of pure MgFe2O4 and 4 wt CeO2
added MgFe2O4
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Increase in humidity sensing of MgFe2O4 due to CeO2 addition
For the improvement of sensitivity at lower humidity and shortening of time response 2wt 4wt and 6wt CeO2 was added in MgFe2O4 Samples were prepared by solid state reaction method By adding CeO2 bulk porosity of the MgFe2O4 was increased from 25 to 26
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
By the addition of cerium oxide the sensivity at low RH increased and showed a better linearity than the pure magnesium ferrite sample
The 4 wt cerium oxide addition in pure magnesium ferrite serving as nuclei for particle growth and favoring the ripening of the particles So that particles grow in size and decrease in number As a result porosity decreases hence electrical resistance also decreases from 51MΩ to 44MΩ
It exhibits a better sensitivity at low humidity values due catalytic active cerium ions provides high surface charge to water vapors At higher RH values the conductivity is dominated by more water vapor condensation into the large canals and electrolytic conduction begins which dominates over protonic conduction
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
MgSO4 LiNO3 Fe(NO3)39H2O NaOH and NaCl (1-xx2810) mixed amp ground
for 50-60 min (exothermic action) Wet Paste
Prefired at 750oC in air 3h Powder
washed several times heat overnight at 120oC
Dried Powder pelletized amp sintered at 850oC 2h
Rectangular Pellets (Mg1-xLixFe2O4)
Synthesis Process
NaOH convert metal nitrates amp sulfates into hydroxides
NaCl restricted the growth of grains to keep the size as small as possible
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
SEM micrographs of (i) pure MgFe2O4 (ii) Mg08Li02Fe2O4(iii) Mg06Li04Fe2O4 and (iv) Mg04Li06Fe2O4
Humidity response curve
Substitution of lithium in magnesium ferrite enhances the smaller grain size distribution providing higher surface area
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
ADVANTAGES OF FERRITES
1 High resistivity2 Widefrequencyrange(10kHzto50MHz) 3 Low cost4 Large selection material5 Shape versatility6 Economical assembly7 Temperature and time stability8 High Qsmall package
Ferrites have a paramount advantage over other types of magnetic materials high electrical resistivity and resultant low eddy current losses over a wide frequency range
Ferrites are routinely designed into magnetic circuits for both low- level and power applications
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
39
Ferrites are used in digital computers and data processing circuits Ferrites are used to produce low frequency ultra sonic waves by magnetostriction principle Ferrites are widely used in non-reciprocal microwave devices Examples for non-reciprocal microwave devices are Gyrator Isolator and Circulator Ferrites are also used in power limiting and harmonic gyration devicesFerrites can also be used in the design of ferromagnetic amplifiers of microwave signals Ferrite core can be used as a bitable elementThe rectangular shape ferrite cores can be used as a magnetic shift registerHard ferrites are used to make permanent magnets The permanent magnets (hard ferrites) are used in instruments like galvanometers ammeter voltmeter flex meters speedometers wattmeter compasses and recorders
APPLICATION OF FERRITES
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-
Microwave Applications Ferrite
At microwave frequency from 109 Hz region the only bulk magnetic materials available are ferrites Microwave frequencies demand high-resistivity ferrites Mn-Zn ferrites are not used for that purpose Ni ferrite Mg-Mn ferrites and more recently the garnet Y3Fe5O12 have been used for microwave applications As in recording heads hot pressed and single-crystal ferrites have been produced To keep the resistivity high in microwave ferrites excess Fe is avoided to eliminate Fe2+
Magnetic Power Loss
Concepts and Realization of its Measurements
- Slide 1
- Nanoscience amp Magnetism
- Slide 3
- Types Of Magnetic Materials
- Magnetic Spins amp Dipoles
- Magnetic Interactions
- Magnetic Interactions(Contd)
- Ferrites(M2+Fe23+O42-) )
- Role Of Ferrites In Nanoscience
- Why Ferrites over Other Materials
- CRYSTAL STRUCTURE OF FERRITES
- Structure Of Ferrites
- Cry
- Slide 14
- Slide 15
- Slide 16
- Slide 17
- Behaviour Of Ferrites(Ferrimagnetic)
- Properties Of Ferrites (M2+Fe23+O42-) )
- Slide 20
- Slide 21
- Slide 22
- Slide 23
- Slide 24
- Slide 25
- Synthesis Of Ferrites
- IMPORTANCE OF MAGNETIC MEASUREMENT (LEAVING APART FROM ROUTINE
- Example Of Versatile Ferrite-Magnesium
- Magnesium Alloys
- Slide 30
- CONDUCTION MECHANISM
- Slide 32
- Slide 33
- Slide 34
- Slide 35
- Slide 36
- Slide 37
- ADVANTAGES OF FERRITES
- Slide 39
- Slide 40
-