ceramics 2013

CERAMIC & THEIR PROPERTIES

BMFB 332318-22/03/2013

What are ceramics? Classification of ceramics Thermal Properties of ceramics Optical Properties Mechanical Properties Electrical Properties

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http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf

A ceramic is an inorganic, nonmetallic solid prepared by the action of

heat and subsequent cooling. Ceramic materials may have a crystalline

or partly crystalline structure, or may be amorphous (e.g., aglass) .

— comes from the Greece word “keramicos”, which means burnt stuff

— broadly classed as inorganic, non-metallic materials

— usually a compound, or a combination of compounds, betweenmetallic and nonmetallic elements (mainly O, N, C, B)

— always composed of more than one element (Al2O3, SiO2, SiC, etc.)

— bonds are either totally ionic, or combination of ionic and covalent.

Periodic table with ceramics compounds indicated by a combination of one or more metallic elements (in light color) with one or more nonmetallic elements (in dark color).

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http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf

To be most frequently silicates, oxides, nitrides and carbides

Typically insulative to the passage of electricity and heat

More resistant to high temperatures and harsh environments than metals and polymers

Hard but very brittle6

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Silicate glass

TAXONOMY OF CERAMICS

Glasses Clay products

Refractories AbrasivesCements Advanced ceramics

Glass ceramics

Fireclay

Silica Basic

Special

Structural clay

products

Whitewares

Oxides

carbides

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CERAMICS

TRADITIONAL CERAMIC

Based primarily on natural raw materials; clay and silicaTendency to equate with low technologyHas been used for over 25, 000 years

TECHNICAL/ ADVANCED CERAMIC

‘special’, ‘technical’, ‘engineering’Exhibit superior/ specialized properties (mechanical properties, corrosion resistance, or electrical, optical, and/or magnetic properties)Require more sophisticated processingare mainly pure compounds or nearly pure compounds of primarily oxides, carbides, or nitridesHave generally been developed within last 100 years

Chemically prepared powders-Precipitation-Spray dry-Freeze dry-Vapor phase-Sol-gel

-Slip casting-Injection molding-Sol-gel-Hot pressing-HIPing-Rapid prototyping

-Electric furnace-Hot press-Reaction sinter-Vapor deposition-Plasma spraying-Microwave furnace

-Erosion-Laser machining-Plasma spraying-Ion implantationCoating

-Light microscopy-X-ray diffraction-Electron microscopy-Scanned probe microscopy-Neutron diffraction-Surface analytical methods

-Raw minerals-Clay-Silica

-Potters wheel-Slip casting

Flame kiln

-Erosion-Glazing

-Visible examination-Light microscope

Raw materials preparation

Forming

High-temperature processing

Finishing process

Characterization

Extreme hardness– High wear resistance– Extreme hardness can reduce wear caused by friction

Corrosion resistance Heat resistance

– Low electrical conductivity– Low thermal conductivity– Low thermal expansion– Poor thermal shock resistance

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Low ductility– Very brittle– High elastic modulus

Low toughness– Low fracture toughness– Indicates the ability of a crack or flaw to produce a catastrophic failure

Low density– Porosity affects properties

High strength at elevated temperatures

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Traditional Ceramics The older and more generally known

types (porcelain, brick, earthenware,

etc.)

Based primarily on natural raw

materials of clay and silicates

Applications:

building materials (brick, clay pipe,

glass)

household goods (pottery, cooking

ware)

manufacturing (abbrasives, electrical

devices, fibers) Traditional Ceramics

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Advanced Ceramics have been developed over the past

half century

Include artificial raw materials,

exhibit specialized properties,

require more sophisticated

processing

Applied as thermal barrier coatings

to protect metal structures, wearing

surfaces,

Engine applications (silicon nitride

(Si3N4), silicon carbide (SiC),

Zirconia (ZrO2), Alumina (Al2O3)) bioceramic implants

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Oxides: Alumina, zirconia Non-oxides: Carbides, borides, nitrides, silicides Composites: Particulate reinforced, combinations of

oxides and non-oxides

CERAMICS

Oxides

Nonoxides

Composite

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Oxide Ceramics:

Oxidation resistant

chemically inert

electrically insulating

generally low thermal conductivity

slightly complex manufacturing

low cost for alumina

more complex manufacturing

higher cost for zirconia.

zirconia

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Non-Oxide Ceramics:

Low oxidation resistance

extreme hardness

chemically inert

high thermal conductivity

electrically conducting

difficult energy dependent

manufacturing and high cost.

Silicon carbide cermic foam filter (CFS)

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http://images.google.com.tr/imgres?imgurl=http://www.made-in-china.com/image/2f0j00avNtpdFnLThyM/Silicon-Carbide-Ceramic-Foam-Filter-CFS-.jpg&imgrefurl

Ceramic-Based

Composites:

Toughness

low and high oxidation

resistance (type related)

variable thermal and electrical

conductivity

complex manufacturing

processes

high cost.Ceramic Matrix Composite (CMC) rotor

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http://images.google.com.tr/imgres?imgurl=http://www.oppracing.com/images/cmsuploads/Large_Images/braketech%2520cmc%2520rotor%2520oppracing%2520cbr1000rr.jpg&imgrefurl

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Amorphous

the atoms exhibit only short-

range order

no distinct melting

temperature (Tm) for these

materials as there is with the

crystalline materials

Na20, Ca0, K2O, etc

Amorphous silicon and thin film PV cells

CERAMICS

amorphous

crystalline

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http://images.google.com.tr/imgres?imgurl=http://simeonintl.com/sitebuilder/images/A-Si_Solar-510x221.jpg&imgrefurl=http://simeonintl.com/Solar.html&usg=__ktCHUAO742PE0hh3U1fGw8goPrM=&h=221&w=510&sz=17&hl=tr&start=68&sig2=9OC7pTtJz2SuK_AKdrqTAA&um=1&tbnid=xQRh5yfCftf89M:&tbnh=57&tbnw=131&prev=/images%3Fq%3Damorphous%2Bceramic%26ndsp%3D18%26hl%3Dtr%26rlz%3D1G1GGLQ_TRTR320%26sa%3DN%26start%3D54%26um%3D1&ei=9Kv1SrTfAoej_gbrz6WtAw

Crystalline

atoms (or ions) are arranged in

a regularly repeating pattern in

three dimensions (i.e., they

have long-range order)

Crystalline ceramics are the

“Engineering” ceramics

– High melting points

– Strong

– Hard

– Brittle

– Good corrosion resistance

a ceramic (crystalline) and a glass (non-crystalline)

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Most important thermal properties of ceramic materials:

Heat capacity : amount of heat required to raise material

temperature by one unit (ceramics > metals)

Thermal expansion coefficient: the ratio that a material

expands in accordance with changes in temperature

Thermal conductivity : the property of a material that

indicates its ability to conduct heat

Thermal shock resistance: the name given to cracking

as a result of rapid temperature change

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Thermal expansion

The coefficients of thermal

expansion depend on the bond

strength between the atoms that

make up the materials.

Strong bonding (diamond,

silicon carbide, silicon nitrite) →

low thermal expansion

coefficient

Weak bonding ( stainless steel)

→ higher thermal expansion

coefficient in comparison with

fine ceramics

Comparison of thermal expansion coefficient between metals and fine ceramics

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Thermal conductivity

generally less than that of metals such as steel or copper

ceramic materials, in contrast, are used for thermal insulation due to

their low thermal conductivity (except silicon carbide, aluminium

nitride)

•http://global.kyocera.com/fcworld/charact/heat/images/thermalcond_zu.gif11.04.23

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Thermal shock resistance

A large number of ceramic materials are sensitive to thermal shock

Some ceramic materials → very high resistance to thermal shock is

despite of low ductility (e.g. fused silica, Aluminium titanate )

Result of rapid cooling → tensile stress (thermal stress)→cracks and

consequent failure

The thermal stresses responsible for the response to temperature

stress depend on:

-geometrical boundary conditions

-thermal boundary conditions

-physical parameters (modulus of elasticity, strength…)25

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REFRACTION

Light that is transmitted from one medium into another, undergoes refraction.

Refractive index, (n) of a material is the ratio of the speed of light in a vacuum (c = 3 x 108 m/s) to the speed of light in that material.

n = c/v

http://matse1.mse.uiuc.edu/ceramics/prin.html26

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http://matse1.mse.uiuc.edu/ceramics/prin.html27

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OPTICAL PROPERTIES OF CERAMICS

Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 28

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OPTICAL PROPERTIES OF CERAMICS

ABSORPTION

•Color in ceramicsMost dielectric ceramics and glasses are colorless.

By adding transition metals (TM)Ti, V, Cr, Mn, Fe, Co, Ni

Carter, C., B., Norton, M., G., Ceramic Materials Science And Engineering, 29

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MECHANICAL PROPERTIES OF CERAMICS

STRESS-STRAIN BEHAVIUR of selected materials

Al2O3

thermoplastic

http://www.keramvaerband.de/brevier_engl/5/5_2.htm30

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Flexural Strength

The stress at fracture using this flexure test is known as the flexural strength.

Flexure test :which a rod specimen having either a circular or rectangular cross section is bent until fracture using a three- or four-point loading technique


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For a rectangular cross section, the flexural strength σfs is equal to,

L is the distance between support points

When the cross section is circular,

R is the specimen radius

Stress is computed from,• specimen thickness•the bending moment•the moment of inertia of the cross section



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Hardness

Hardness implies a high resistance to deformation and is associated with a large modulus of

elasticity.

In metals, ceramics and most polymers, the deformation considered is plastic deformation of the surface. For elastomers and some polymers, hardness is defined at the resistance to elastic deformation of the surface.

Technical ceramic components are therefore characterised by their stiffness and dimensional stability.

Hardness is affected from porosity in the surface, the grain size of the microstructure and the effects of grain boundary phases.

http://www.dynacer.com/hardness.htmhttp://www.keramvaerband.de/brevier_eng/5/3/%_3_5.htm

http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Mechanical/Hardness.htm34

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Material Class Vickers Hardness (HV) GPa

Glasses 5 – 10

Zirconias, Aluminium Nitrides 10 - 14

Aluminas, Silicon Nitrides 15 - 20

Silicon Carbides, Boron Carbides

20 - 30

Cubic Boron Nitride CBN 40 - 50

Diamond 60 – 70 >

Test procedures for determining the hardness according to Vickers, Knoop and Rockwell.

Some typical hardness values for ceramic materials are provided below:


The high hardness of technical ceramics results in favourable wear resistance. Ceramics are thus good for tribological applications.

http://www.dynacer.com/hardness.htm35

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MECHANICAL PROPERTIES OF CERAMICSElastic modulus

The elastic modulus E [GPa] of almost all oxide and non-oxide ceramics is consistently higher than that of steel.

This results in an elastic deformation of only about 50 to 70 % of what is found in steel components.

The high stiffness implies, however, that forces experienced by bonded ceramic/metal constructions must primarily be taken up by the ceramic material.

http://www.keramverband.de/brevier_engl/5/3/4/5_3_4.htm36

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MECHANICAL PROPERTIES OF CERAMICSDensity

The density, ρ (g/cm³) of technical ceramics lies between 20 and 70% of the density of steel.

The relative density, d [%], has a significant effect on the properties of the ceramic.

http://www.keramverband.de/brevier_engl/5/3/4/5_3.htm37

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A comparison of typical mechanical characteristics of some ceramics with grey cast-iron and construction steel

http://www.keramverband.de/brevier_engl/5/5_2.htm38

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MECHANICAL PROPERTIES OF

CERAMICS

Toughness

Ability of material to resist fracture

affected from,

•temperature•strain rate•relationship between the strenght and ductility of the material and presence of stress concentration (notch) on the specimen surface

http://www.subtech.com/dokuwiki/doku.php?id=fracture_toughness39

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Some typical values of fracture toughness for various materials

http://en.wikipedia.org/wiki/Fracture_toughness40

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Electrical conductivity of ceramics varies withThe Frequency of field applied effect

charge transport mechanisms are frequency dependent. The temperature effect

The activation energy needed for charge migration is achieved through thermal energy and immobile charge career becomes mobile.

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Most of ceramic materials are dielectric. (materials, having very low electric conductivity, but supporting electrostatic field).

Dielectric ceramics are used for manufacturing capacitors, insulators and resistors.

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Despite of very low electrical conductivity of most of the ceramic

materials, there are ceramics, possessing superconductivity

properties (near-to-zero electric resistivity).

Lanthanum (yttrium)-barium-copper oxide ceramic may be

superconducting at temperature as high as 138 K. This critical

temperature is much higher, than superconductivity critical

temperature of other superconductors (up to 30 K).

The critical temperature is also higher than boiling point of liquid

Nitrogen (77.4 K), which is very important for practical application

of superconducting ceramics, since liquid nitrogen is relatively low

cost material.

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Types of ceramics

Applications: Automotive

Spark plugs, water pump seals, catalytic converter.

Heat engine: Higher operating

temperatures ⇒ Better fuel efficiency

Lower frictional forces & ability to operate with no cooling system

Excellent wear & corrosion resistance

Lower densities ⇒ Decreased engine weight 48

Disadvantages: Brittle Too easy to have voids weaken the engine Difficult to machine

Applications: Aerospace

Coating of metal heat engine parts ⇒ improved wear &/or high temperature damage.

Their low densities ⇒ lighter turbine blades VS superalloys

Materials considered: Si3N4, SiC and ZrO2

Draw back: disposition to brittle & catastrophic failure.

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Helicopter gas turbine

Applications: Aerospace

• Engines ; Shielding a hot running airplane engine from damaging other components.

• Airframes; Used as a high-stress, high-temp and lightweight bearing and structural component.

• Missile nose-cones; Shielding the missile internals from heat.

• Space Shuttle tiles • Space-debris ballistic shields -- Ceramic

fiber woven shields offer better protection to hypervelocity (~7 km/s) particles than aluminum shields of equal weight.

• Rocket Nozzles; Withstands and focuses the exhaust of the rocket booster.

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Applications: Electronics

Chosen to securely hold microelectronics & provide heat transfer

electrically insulating. low dielectric characteristics. thermally conductive.

standard bearer. low thermal conductivity & poor electrical

conductivity.

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Packaging of integrated circuits --(substrate):

Aluminum oxide:

good thermal & electrical properties.

bonding with metals: poor. payoff for metal pattern to stick:

Mo paste + additive @ 1600C or special direct Cu bonding.

Aluminum nitride Materials currently used include:

• Boron nitride (BN)• Silicon Carbide (SiC)• Aluminum nitride (AlN)– thermal conductivity 10x that for Alumina– good expansion match with Si

Applications: BiomaterialAlumina in orthopedic implants Excellent corrosion

resistance Wear resistance High strength Biocompatibility

53a) Extensive arthritis damage, b) same

hipafter total hip replacement

Various component for total hip prostheses including the stem with an alumina femoral head, and alumina AC cup, and a metal base for the AC cup

Bone joint

Alumina in dental implants

Ceramic Biomaterials (Alumina, Hydroxyapatite, Zirconia etc)• Biocompatibility• Bond well to bone (implant-tissue attachment)• Corrosion resistance• High stiffness• Wear resistance

Artificial root which supports tooth replacement and crown (porcelain).

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High-strength Al2O3 joint prostheses of complex shape for femur joint component.

Summary of applications:i ) ElectronicsIC packaging and substrates : Al2O3 (insulation) , AlN, BeO, SiCCapacitor: BaTiO3, SrTiO3

Thermistor-Spinel (NiMn)3O4, NiMnCo)3O4, KTaNbO3

Varistor - ZnO2Piezoelecctric –PZT(lead zirconate titanate). PLZT (lead

lanthanum zirconate titanate), LiNbO3, LiTaO3Ferroelectric – BaTiO3, Pb(TiZr)O3, K(TaNb)O3, LiTaO3

Ferrite –SrFe12O19, Y3Fe5O12

Sensors –oxygen sensors (Y-doped ZrO2), humidity sensors (Ti-doped MgCr2O4)

Hydrocarbon gas sensor (doped SnO2)Superconductores – Ba2YCu3O7-x

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Example: ceramic soleplate for irons

System Development with Si3N4 Ceramics

A soleplate of a high-quality iron hasto meet specific requirements: easy glidehigh mechanical strength and hardness good thermal conductivity non-stick properties

Silicon nitride ceramics fulfill these requirements much better than currently used materials like aluminum or stainless steel.

Heating element is directly applied on the ceramic soleplate by screen printing and subsequently is co-fired with the soleplate to achieve a strong bonding.

ceramics 2013

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