Ceramics Introduction

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Introduction to Ceramics

Dr. Ashutosh S. Gandhi

Metallurgical & Materials EngineeringIndian Institute of Technology Madras

[email protected]


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Taxonomy of Ceramics

Glasses Clayproducts Refractories Abrasives Cements Advancedceramics

-optical-compositereinforce

-containers/household

-whiteware-bricks -bricks forhigh T

(furnaces)-sandpaper-cutting-polishing

-composites-structural -engine-rotors

-valves-bearings

Adapted from Fig. 12.1 and discussion in

Section 12.2-6,

Callisters Materials Science and

Engineering, Adapted Version..

-electronics-sensors

Mainly based on Callisters Materials Sceince & Engineering

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Structural Ceramics

Oxides, carbides and nitrides

Alumina (Al2O3), zirconia (ZrO2), silicon carbide (SiC),

tungsten carbide (WC), silicon nitride (Si3N4), titanium

nitride (TiN)

Oxynitrides: SiAlON

Borides and silicides

Zirconium diboride (ZrB2), titanium diboride (TiB2),

molybdenum disilicide (MoSi2)

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Need a material to use in high temperature furnaces.

Consider the Silica (SiO2) - Alumina (Al2O3) system.

Phase diagram shows:mullite, alumina, and cristobaliteas candidate refractories.

From Fig. 12.8,

Callisters Materials

Science and Engineering,

Adapted Version.(Fig. 12.8 is adapted from

F.J. Klug and R.H.

Doremus, "Alumina Silica

Phase Diagram in the

Mullite Region", J.

American Ceramic

Society70(10), p. 758,

1987.)

Application: Refractories

Composition (wt% alumina)

T(C)

1400

1600

1800

2000

2200

20 40 60 80 1000

alumina+

mullite

mullite+ L

mulliteLiquid

(L)

mullite+ cristobalite

crystobalite+ L

alumina + L

3Al2O3-2SiO2

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tensileforce

AoAddie

die

Die blanks:-- Need wear resistant properties!

Die surface:-- 4 mm polycrystalline diamond

particles that are sintered onto a

cemented tungsten carbide

substrate.

-- polycrystalline diamond helps control

fracture and gives uniform hardness

in all directions.

Courtesy Martin Deakins, GE

Superabrasives, Worthington,

OH. Used with permission.

From Fig. 23.2 (d),

Callisters Materials


Adapted Version.

Courtesy Martin Deakins, GE

Superabrasives, Worthington,


Application: Die Blanks4


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Tools:-- for grinding glass, tungsten,

carbide, ceramics

-- for cutting Si wafers

-- for oil drilling

bladesoil drill bits Solutions:

coated single

crystal diamonds

polycrystalline

diamonds in a resin

matrix.

Photos courtesy Martin Deakins,

GE Superabrasives, Worthington,


Application: Cutting Tools

-- manufactured single crystal

or polycrystalline diamonds

in a metal or resin matrix.

-- optional coatings (e.g., Ti to helpdiamonds bond to a Co matrix

via alloying)-- polycrystalline diamonds

resharpen by microfracturing

along crystalline planes.

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Applications: Advanced

Ceramics Ceramic Armor

Al2O3, B4C, SiC & TiB2

Extremely hard materials shatter the incoming projectile

energy absorbent material underneath

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Ceramics

Heat Engines

Advantages: Run at higher temperature

Excellent wear &corrosion resistance

Low frictional losses

Ability to operate without

a cooling system

Low density

Disadvantages:

Brittle

Too easy to have voids-

weaken the engine

Difficult to machine

Possible partsengine block, piston coatings, jet engines

Ex: Si3N4, SiC, & ZrO2

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Alumina Ceramics

Textile Industry Components

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Industrial Ceramic Components

Cutting Tool Inserts (Si3N4)

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Silicon Nitride Components

Bearing Rollers

Turbocharger Rotors

AFM Tip

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Stabilised Zirconia Articles12


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Metals

Alloys

Graphite

Ceramics

Semicond

PolymersComposites

/fibers

E(GPa)

Based on data in Table B2,Callisters Materials Science and Engineering,

Adapted Version.

Composite data based on

reinforced epoxy with 60 vol%

of aligned

carbon (CFRE),aramid (AFRE), or

glass (GFRE)

fibers.

Youngs Moduli: Comparison

109Pa

0.2

8

0.6

1

Magnesium,

Aluminum

Platinum

Silver, Gold

Tantalum

Zinc, Ti

Steel, Ni

Molybdenum

Graphite

Si crystal

Glass-soda

Concrete

Si nitrideAl oxide

PC

Wood( grain)

AFRE( fibers) *

CFRE*

GFRE*

Glass fibers only

Carbon fibers only

Aramid fibers only

Epoxy only

0.4

0.8

2

4

6

10

2 0

4 0

6 08 0

10 0

200

600800

10 001200

400

Tin

Cu alloys

Tungsten

Si carbide

Diamond

PTFE

HDPE

LDPE

PP

Polyester

PSPET

CFRE( fibers)*

GFRE( fibers)*

GFRE(|| fibers)*

AFRE(|| fibers)*

CFRE(|| fibers)*

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Room Tvalues

Based on data in Table B4,Callisters Materials Science and

Engineering, Adapted Version.

a = annealedhr = hot rolled

ag = aged

cd = cold drawn

cw = cold worked

qt = quenched & tempered

Yield Strength : ComparisonGraphite/Ceramics/Semicond

Metals/Alloys

Composites/fibers

Polymers

Yieldstrength,sy(MPa)

PVC

H

ardtomeasure

,

sinceintension,fra

ctureusuallyoccursbeforeyield.

Nylon 6,6

LDPE

70

20

40

6050

100

10

30

2 00

3 00

4 00

5 006 007 00

10 00

2 0 00

Tin (pure)

Al(6061)a

Al(6061)ag

Cu(71500)hrTa (pure)Ti (pure)aSteel (1020)hr

Steel (1020)cd

Steel (4140)a

Steel (4140)qt

Ti (5Al-2.5Sn)aW(pure)

Mo (pure)Cu(71500)cw

Hardtomeasure,

inceramicmatrixandepoxymatrixcompo

sites,since

intension,frac

tureusuallyoccursbefo

reyield.

HDPEPP

humid

dry

PC

PET

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Tensile Strength : Comparison

Si crystal

Graphite/Ceramics/Semicond

Metals/Alloys

Composites/fibers

Polymers

Tensile

st

rength,

TS

(MPa)

PVC

Nylon 6,6

10

100

200300

1000

Al(6061)a

Al(6061)ag

Cu(71500)hr

Ta (pure)Ti (pure)a

Steel (1020)

Steel (4140)a

Steel (4140)qt

Ti (5Al-2.5Sn)aW(pure)

Cu(71500)cw

LDPE

PP

PC PET

20

3040

2000

3000

5000

Graphite

Al oxide

Concrete

Diamond

Glass-soda

Si nitride

HDPE

wood( fiber)

wood(|| fiber)

1

GFRE(|| fiber)

GFRE( fiber)

CFRE(|| fiber)

CFRE( fiber)

AFRE(|| fiber)

AFRE( fiber)

E-glass fibCfibersAramid fib

Room Temp. values

Based on data in Table B4,Callisters Materials Science and

Engineering, Adapted Version.

a = annealed

hr = hot rolled

ag = aged

cd = cold drawn

cw = cold worked

qt = quenched & tempered

AFRE, GFRE, & CFRE =

aramid, glass, & carbon

fiber-reinforced epoxy

composites, with 60 vol%

fibers.

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Honeycombs for Catalysts17


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Example: Oxygen sensor ZrO2 Principle: Make diffusion of ionsfast for rapid response.

Application: Sensors

A Ca2+impurity

removes a Zr4+and aO2- ion.

Ca2+

Approach:Add Ca impurity to ZrO2:

-- increases O2-vacancies-- increases O2-diffusion rate

referencegas at fixedoxygen contentO2-

diffusion

gas with anunknown, higher

oxygen content

-+voltage difference produced!

sensor Operation:

-- voltage differenceproduced when

O2-ions diffusefrom the external

surface of the sensor

to the reference gas.

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CeramicsElectronic Packaging

Chosen to securely hold microelectronics & provideheat transfer

Must match the thermal expansion coefficient of the

microelectronic chip & the electronic packagingmaterial. Additional requirements include: good heat transfer coefficient

poor electrical conductivity

Materials currently used include: Boron nitride (BN)

Silicon Carbide (SiC)

Aluminum nitride (AlN)

thermal conductivity 10x that for Alumina

good expansion match with Si

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High-kMaterials for Gate Dielectrics 20


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High-kMaterials for Gate Dielectrics21


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Dielectric Applications

-Al2O3: Spark-plug insilators

SiO2: Gate dielectrics

(Ba, Sr)TiO3: Dynamic random access memory

(DRAM)

Lead magnesium niobate (PMN): Chip

capacitors

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Advances in Superconductivity

This research area was stagnant for many

years.

Everyone assumed Tc,maxwas about 23 K

Many theories said you couldnt go higher 1987- new results published for Tc> 30 K

ceramics of form Ba1-xKxBiO3-y

Started enormous race.

Y Ba2Cu3O7-x Tc= 90 K

Tl2Ba2Ca2Cu3Ox Tc= 122 K

tricky to make since oxidation state is quite important

Values now stabilized at ca. 120 K

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Magnetic Ceramics

-Fe2O3: Recording tapes Mn0.4Zn0.6Fe2O4: Transformer cores in touch

tone telephones

BaFe

12O

19: Permanent magnets in loudspeakers

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Transmittance:--Aluminum oxide may be transparent, translucent, or

opaque depending on the material structure.

Adapted from Fig. 1.2,Callisters Materials


Adapted Version.

(Specimen preparation,

P.A. Lessing; photo by S.

Tanner.)

single crystal

polycrystal:

low porosity

polycrystal:

high porosity

OPTICAL PROPERTIES26


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Optical Applications

Doped SiO2: Optical fibres

-Al2O3: Transparent envelopes in street lamps

Doped ZrSiO4: Ceramic colours (pigments)

Doped (Zn, Cd)S: Fluorescent screens Pb1-xLax(ZryTi1-y)1-x/4O3: Thin-film optical switches

Nd doped Y3Al5O12(YAG): Solid-state lasers

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Thermal Conductivity: Comparison

increasingk

PolymersPolypropylene 0.12Polyethylene 0.46-0.50Polystyrene 0.13Teflon 0.25

By vibration/rotation of chainmolecules

CeramicsMagnesia (MgO) 38Alumina (Al2O3) 39Soda-lime glass 1.7Silica (cryst. SiO2) 1.4

By vibration ofatoms

MetalsAluminum 247Steel 52Tungsten 178Gold 315

By vibration ofatoms andmotion ofelectrons

k (W/m-K) Energy TransferMaterial

Selected values from Table 19.1Callisters Materials Science and Engineering,

Ada ted Version.

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Application:

Space Shuttle Orbiter

Silica tiles(400-1260C):--large scale application --microstructure:

Fig. 19.2W, Callister 6e. (Fig. 19.2W adapted from L.J.Korb, C.A. Morant, R.M. Calland, and C.S. Thatcher, "The

Shuttle Orbiter Thermal Protection System", Ceramic

Bulletin, No. 11, Nov. 1981, p. 1189.)

Fig. 19.3W, Callister 5e. (Fig. 19.3W courtesy the

National Aeronautics and Space Administration.)

Fig. 19.4W, Callister 5e. (Fig. 219.4W courtesy

Lockheed Aerospace CeramicsSystems, Sunnyvale, CA.)

Thermal Protection System

reinf C-C(1650C)

Re-entry TDistribution

silica tiles(400-1260C)

nylon felt, silicon rubbercoating (400C)

~90% porosity!

SiO2fibersbonded to one

another during

heat treatment.

100mm

Chapter-opening photograph, Chapter 23, Callister 5e

(courtesy of the National Aeronautics and Space

Administration.)

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Heat Transfer

Thermal Barrier CoatingsCritical Enabling Technology for

Gas Turbine Engines(Aviation & Power Generation)

Superal loy

Bond Coat

Thermal Barr ier

TGO

State of the Art TBC Systems

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CT Scan

Artificial JointsCeramics in Biomedical

Applications

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Useful Properties of Ceramics

High melting points

High hardness & compressivestrength

Wear resistance

Chemical inertness

Catalysis

Biocompatibility

Good electrical insulation

High dielectric constant

Ferroelectricity

Piezoelectricity

Good electrical conduction

Superconductivity

Semiconductivity (SiC, ZnO)

Ionic conduction (fuel cells,sensors)

Good thermal insulation Refractories

Good thermal conductivity

SiC, AlN

Magnetism

Optical transmission Optical birefringence

Electro-optical properties

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Etymology of Ceramic

The word ceramic is derived from the

Greek word keramos, which means

potters clay or pottery.

Its origin (apparently) is in a Sanskrit term

meaning to burn.

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Definitions of Ceramics Barsoum, Ceramics can be defined as solid compounds that are formed

by the application of heat, and sometimes pressure, comprising of

at least one metal and a non-metallic elemental solid (e.g. TiC) or a non-metal (e.g. TiO2),

a combination of at least two non-metallic elemental solids (e.g. GaN, TiB2),

or a combination of at least one non-metallic elemental solids and a non-

metal (e.g. SiO2).

Diamond and graphite not included in this definition! Kingery: Ceramics can be defined as inorganic non-metallic solids.

Si, Ge included in ceramic materials! (Along with GaN, GaAs)

Glass is a supercooled liquid, with characteristics of a solid. Hence, the

definition of the solid state must be taken in its broadest sense.

Ice has properties similar to most ceramics, but its a molecular solid. Predominance of ionic or covalent bonding is essential for a material to

be classified as a ceramic. So, ceramics can be defined as inorganic,

non-metallic, non-molecular solids with predominantly ionic or covalent

bonding.

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Ceramics Introduction