electronic ceramics and cermets

8/8/2019 Electronic Ceramics and Cermets

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Electronic Ceramics

By: Marvel Mathias

Reg No. 100926019



INTRODUCTION

Electronic ceramics describes a class of inorganic, non

metallic materials utilized in the electronic industry.

The polycrystalline inorganic solids comprised of randomly

oriented grains are intimately bonded together.

Electronic ceramics are often combined with metals and

polymers to meet requirements of high technology

applications, computers, telecommunications, sensors and

actuators.



PROPERTIES

Insulating property

Electrical conductivity

Dielectric strength

Superconducting properties

Piezoelectric properties

Magnetic properties



MANUFACTURING METHOD

The following steps are followed:

Powder preparation

Powder processing

Green forming

Densification



Powder Preparation

Mixing/ Calcination

Co-precipitation

Hydro-thermal processing

Metal organic decomposition

Powder Processing

As little as possible processing is to be done to achieve the

targeted standard performance.

Powder processing is done to remove undesirable

contaminants and other defects arising during powder

preparation.



Green forming

Uni-axial pressing- Disk capacitors, transducers.

It is a powder compaction method in which uni-axial pressure

applied to the powder placed in a die between two rigid punches.



Cold isostatic pressing- Simple and complex shapes :spark plugs

Cold isostatic pressing (CIP)

is conducted at room temperature.

A flexible (commonly polyurethane) mold immersed in a

pressurized liquid medium (commonly water) is used in the cold

isostatic pressing method.



Colloidal casting- Complex shapes: porcelain insulators

A polymerizable solvent was employed to disperse ceramic particles

to form a colloidal ceramic suspension with good fluidity.

After casting, the solvent was polymerized into a polymer, resulting

in solidification of the colloidal suspension.



Extrusion- Thin sheets, rods, tubes : thermocouple insulator,

catalytic convertor etc.

Extrusion ram forces the ceramic paste through a die, resulting in a

long product (rods, bars, long plates, pipes) of regular cross-section,

which may be cut into pieces of required length.



Injection moulding- Small complex shapes: ZrO2-O2 sensors

It is the method of compaction of ceramic powder fed and injected

into a mold cavity by means of a screw rotating in cylinder.



MATERIAL METHODS

PT, PZT, PLZT Solgel, Sputtering

Diamond Chemical Vapor Deposition(CVD)

SiO2, BaTiO3 Sol-gel, Sputtering, CVD

New developments in thin film electronic ceramics



Densification

It is usually carried out to eliminate porosity.

Methods used are:

Pressure less sintering

Hot pressing

Hot isostatic pressing



ADVANTAGES

Chemically inert

Able to withstand high temperature

Less prone to corrosion

Provide safety and stability

Prevent component failure and electric shutdowns

Allow flow of electricity



LIMITATIONS

Fragile and brittle

Weakness in tension

Relatively poor shock resistance

Difficult to obtain complex shapes with close tolerances which

drive up the cost.



APPLICATIONS

Cellphones, computers, television and other consumer

electronic products.

Ceramic spark plugs

Ceramics help improve antennae performance. So widely

used in GPS applications.

Used in transistors which process ones and zeros of digital

world.



Resistor and

sensors

Piezoelectrictransducers

Hard and

soft ferritesMultilayercapacitors

Substratesand

insulators

Optical

fibres, disks

and displays

Electronic ceramics market



Function Material Products

Insulators Porcelain, glass, steatite High voltage insulation

Packaging Al2O3, BeO IC substrates,Packaging(MMCs)

Dielectric strength BaTiO3, SrTiO3, Ti02 Capacitors

Piezoelectric SiO2 Oscillators, filters,

motors, actuators, etc

Magnetic Inductors, transformers,

memory devices

Semi conductors (Ba,La)TiO3, V2O3,

Fe2-xTixO3,

ZnOBi2O3, MgCr2O4-TiO2, CdS, SiC

Solar cells, Electric

heaters, pH sensor, PTC,

NTC-resistors, humiditysensor

Conductors RuO2, NaAl11O17,

Zr1-2xY2xO2-x,

Yba2Cu3O7-;

Resistors, solid

electrolytes, oxygen

sensors,

superconductors

Mn1-x ZnxFe2O4,

Ni1-xZnxFe2O4



Electronic ceramic insulator

Ceramics used in lamps, temp.

controller



CERMETS



INTRODUCTION

The name CERMET is derived from CERamic-METallic.

CERMET is defined as a heterogeneous combination of

metal(s) or alloy(s) with one or more ceramic phases in which

the latter constitutes approximately 15 to 85% by volume and

in which there is relatively little solubility between metallic

and ceramic phases at the preparation temperature.

Cermets have been around since 1929 but gained importance

in the mid 70s due to attempts at improving performance.



COMPOSITION AND PROPERTIES

1) Refractory Oxide-Base Cermets- are cermets of metal-

bonded refractory oxides.

Have good thermal stability and load bearing strength at high

temperatures.

Oxide-base cermets of greatest commercial interest are chromium

bonded, alumina base materials.

Good erosion and wear resistance.

Excellent resistance to molten metals and oxidation.

Refractory oxide contributes to hardness, refractoriness and resistance to

oxidation.



2) Carbide-Base Cermets

Easier to bond, but have poor load bearing characteristics.

Carbide base cermets include:

Titanium carbides bonded with metals such as

nickel, cobalt, chromium and molybdenum.

Tungsten carbide bonded with cobalt.

Chromium carbides bonded with nickel and copper



3) Aluminide-Base Cermets- include:

Molybdenum-bonded aluminides have good high

temperature stability and resistance to oxidation but poor

stength and thermal shock resistance.

Nickel bonded aluminides have good thermal shock

resistance, high temperature oxidation resistance and good

ductility at room temperature but poor strength.



4) Boride-Base Cermets- are brittle and do not posses

high load bearing ability.

Boride-base cermets include:

Chromium-bonded molybdenum boride

Iron-bonded Iron boride

Iron-bonded manganese boride

Chromium boride bonded with nickel, iron or cobalt



5) Nitride-base cermets- consist of titanium carbide and

titanium nitride bonded with chromium or a nickel-cobalt

alloy.

6) Silicide-Base Cermets- possess better strength at high

temperatures than any other types except for oxide base

cermets.



MANUFACTURING METHOD

Cermets are fabricated by normal ceramic forming operations and

subsequent sintering.

These operations include:

Both cold and hot pressing,

Extruding and

Casting.

Thermite process is used for bonding the ceramic and metal phases.

The distribution of the phase determines the properties.

Cermet protective coatings may be applied by flame spraying.



ADVANTAGES

Good thermal shock resistance

High strength and hardness

Wear resistance

Corrosion resistance

Good electrical conductivity

Good thermal conductivity



DISADVANTAGES

Poor impact resistance

Poor conformability

Expensive

Are difficult to machine.



APPLICATIONS

Brake and clutch linings due to greater weights and speed of

equipment.

Used as non lubricating bearings in the temperature range from

700-1500°F

.

Used in machining on cutting tools.

For reducing friction in machine parts.

Used in resistors, capacitors and vacuum tubes.

Military applications include light weight protective coating on

clothings and friction reducing surface layer on nuclear submarines.



In bio medical industry Cutting tools

End mill with cermetinserts



A cermet tool in a turning application



THANK YOU

electronic ceramics and cermets

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