Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology...

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Ceramics Ceramics - - Engineering Materials Engineering Materials Suranaree University of Technology October 2007 Introduction to ceramics Structures of ceramics Processing of ceramics General properties and applications of ceramics Engineering ceramics, glass and composites Outline T. Udomphol

Transcript of Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology...

Page 1: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

CeramicsCeramics-- Engineering MaterialsEngineering Materials

Suranaree University of Technology October 2007

• Introduction to ceramics

• Structures of ceramics

• Processing of ceramics

• General properties and applications of ceramics

• Engineering ceramics, glass and composites

Outline

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Page 2: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

ObjectivesObjectives

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• Students are required to understand basic structures,

properties and applications of ceramics as one of the most

important engineering materials.

• Identification and selection of appropriate ceramic

materials for the desirable applications should be made.

• Composite materials are introduced for properties and

applications that cannot be achieved from conventional

materials.

Page 3: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

ReferencesReferences

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• Smith, W.F, Hashemi, J., Foundations of material science and

engineering, 4th edition, McGraw-Hill International, ISBN 007-

125690-3.

• Callister Jr., W.D., Fundamentals of materials science and

engineering, 2001, John Wiley&Sons, Inc., ISBN 0-471-39551-X.

• Hull, D., Clyne, T.W., An introduction to composite materials,

2nd edition, 1996, Cambridge University Press, UK, ISBN 0-512-

38855-4.

Page 4: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Introduction to ceramics Introduction to ceramics

and classificationsand classifications

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Chapter 1

What is ceramic?

• Inorganic or non-metallic materials

• Primarily Ionic and covalent bonded

Interesting properties

• Hard and brittle

(depending on type of bonding)

• High melting point (Refractory)

• Wear resistance

• High hot hardness

Grinding wheel

Cemented carbides

Page 5: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Classification of ceramicsClassification of ceramics

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Chapter 1

Ceramics can be divided into various types

Conventional ceramics

Advanced ceramics

• Tableware /sanitary ware/ pottery

• Bricks / tiles

• Glass

• Refractory

• Electrical porcelain

• Bioceramics

• Cutting tools

• Semi-conductor, superconductor

• Ferro-magnetic materials

Bioceramics

Refractory

www.dynacer.com

Ceramic

cutting tools

Page 6: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Simple ionic arrangement

CN = coordinating number

Radius ratio = rcation/ranion

Page 7: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Cesium chloride (CsCl) crystal structure

• Simple ionic bonding (equal numbers of Cs+

and Cl-ions).

• CN = 8, radius ratio = 0.94

• Ex: CsCl, CsBr, TlCl, TlBr, AgMg, LiMg, AlNi

• Similar to BCC in metallic bonding (atomic packing factor = 0.68)

Page 8: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Example: Predict the coordinating number for the ionic solids CsCl and NaCl.

Use the following ionic radii for the prediction:

Cs+ = 0.170 nm Na+ = 0.102 nm Cl- = 0.181 nm

The radius ratio for CsCl is 94.0181.0

170.0

)(

)(==

+

nm

nm

ClR

Csr

Since this ratio is greater than 0.732, CsCl should

show cubic coordinator (CN = 8)

The radius ratio for NaCl is 56.0181.0

102.0

)(

)(==

+

nm

nm

ClR

Nar

Since this ratio is greater than 0.414, but less than

0.732, NaCl should show octahedral coordinator

(CN = 6)

Page 9: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Example: Calculate the ionic packing for CsCl. Ionic radii are Cs+ = 0.170 nm

and Cl- = 0.181 nm.

Let r = Cs+ and R = Cl-

nma

nmnma

Rra

405.0

)181.0170.0(23

223

=

+=

+=

CsCl ionic packing factor

68.0

)405.0(

)181.0()170.0(

)1()1(

3

3

343

34

3

3

343

34

=

+=

+=

−+

nmrnmr

a

ionClrionCsr

ππ

ππ

Page 10: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Sodium chloride (NaCl) crystal structure

• Highly ionic bonding (equal numbers of Na+

and Cl-ions).

• CN = 6,

• Radius ratio = 0.56

• Ex: MgO, CaO

, NiO, FeO

Page 11: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Interstitial sites in FCC and HCP crystal lattice

• Intersitial atoms (small) fit into empty voids/spaces in the lattice.

• Two types of interstitial types : octahedral and tetrahedral

FCC-Octahedral

FCC-Tetrahedral

4 octahedral interstitial

sites/ FCC unit cell

8 tetrahedral interstitial

sites/ FCC unit cell

At type sites

Note: HCP structure is also close-packed-similar to FCC

4

1,4

1,4

1

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Chapter 1

Interstitial sites in FCC crystal lattice

Page 13: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Zinc Blend (ZnS) crystal structure

• Equivalent of 4 Zn2+

and 4 S2-

atoms

• CN= 4, (80% covalent character)

• Either Zn or S occupies lattice points

of FCC unit cell while the other occupies

haft the tetrahedral sites.

• Ex: CdS, InAs, InSb, ZnSe.

Page 14: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Calcium Fluoride (CaF2) crystal structure

• Consists of 4 Ca2+

and 8 F-atoms

• CN= 4, (80% covalent character)

• Either Ca occupies lattice points of

FCC unit cell while F occupies eight of

the tetrahedral sites.

• Ex: UO2, BaF2, AuAl2.

Note: unoccupied octahedral interstitial UO2 is used as nuclear fuel.

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Chapter 1

Anti fluorite crystal structure

• Consists of anions (O2-

) occupying

4 FCC unit sites and cations (Li+

)

occupying 8 tetrahedral sites.

• Ex: Li2O, Na2O, K2O, Mg2Si.

OLi

Page 16: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Corundum (Al2O3) crystal structure

• O locating at the lattice sites

of hexagonal close-packed

unit cell.

• Al occupying 2/3 of

octahedral sites to balance

electrical neutrality � give

some distortion

Note: There are only 2 Al 3+ for 3 O 2-

Page 17: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Spinel (MgAl2O4) crystal structure

• Typical for oxides (AB2O4).

• Oxygen ions form an FCC lattice

• A= metal ion (2+) and B= metal ion

(3+) occupying tetrahedral and

octahedral sites, depending of particular

type of spinel.

• Normally used for non-metallic

magnetic materials, electronic

applications.

O red, Al blue, Mg yellow;

tetrahedral and octahedral coordination

som.web.cmu.edu/structures/S060-MgAl2O4_web.jpg

Page 18: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Perovskite (CaTiO3) crystal structure

• Ca2+ (corners) and O2- (face centre) form and FCC lattice

• Ti4+ locating at octahedral sites at the centre of the unit cell.

• Typical for piezoelectric materials.

• Ex: SrTiO3, CaZrO3, SrZrO3, LaAlO3

Page 19: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Carbon and its allotropes

• Graphite

�Carbon atoms form layers of strongly

covalent bonded hexagonal array and

weak secondary bonded across layers.

�Anisotropic property- good thermal and

electrical conductivity on the basal plane.

�Density 2.26 g/cm3.

Page 20: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Carbon and its allotropes

• Diamond

� Cubic structure (covalent bond)

�Isotropic

� Density 3.51 g/cm3

�High thermal conductivity but

very low electrical conductivity

(insulator)

Page 21: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Carbon and its allotropes

• Buckminster Fullerene (Bucky ball)

�Made up of 12 pentagons and 20 hexagons (look like football)

� Contain 60 carbons covalently bonded, therefore C60.

�Possible applications in electronics industries, fuel cells, lubricants and

superconductors.

Page 22: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Carbon and its allotropes

• Carbon nanotube

•Hexagonal patterns on the tube

and pentagonal on the end cap.

• 20x stronger than steels (45 GPa).

• Can form ropes, fibres and thin

films

• Applications: chemical sensors,

fibre materials for composites,

electron producing cathode.

Page 23: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Silicate structures

• Mainly consist of silicon and oxygen.

• Ex, glass, clay, feldspar, micas.

• Cheap, abundant on earth’s crust.

• Important for engineering construction materials.

Basic structure

• Strong bonding of Silicate (SiO44-) tetrahedron

• 50% covalent 50% ionic

Page 24: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Silicate structures Island, chain and ring structures of silicates

• Strong bonding of silicate (SiO44-)

tetrahedron

• 50% covalent 50% ionic

• Each oxygen has one electron

available � can bond with other

positive ions.

• Ex: (Mg, Fe)2SiO4.

• Forming chains (MgSiO3)

• Forming rings (SiO32-)

(Be3Al2(SiO3)2)

Page 25: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

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Chapter 1

Silicate structures Sheet structure of silicates

• Three corners are bonded together with other three.

• Unit formula (Si2O52-)

• Can form kaolinite.

• Ex: Talc.

5242

2

42

2

52 )()( OSiOHAlOHAlOSi →+ +−

Page 26: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Silicate structures Silicate networks

• Silica (SiO2 network)

• All four corners of SiO44- share

oxygen atoms.

• Three basic silica structures,

quartz, tridymite and crystobalite

High quartz tridymite crystoballite

867oC 1470oC

Silica liquidLow quartz

1710oC573oC

www.dreamtime.bz/quartz Quartz

Page 27: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Silicate structures Silicate networks

• Feldspar

Potassium feldspar

geology.about.com

• Industrially important

• Three dimensional silicate network

• Al3+ replaces some of Si4+ and the

charge is balanced by Na+, K+, Ca2+ ,

Ba2+ at the interstitial sites.

232

2322

2322

6..

6..

6..

SiOOAlCaO

SiOOAlONa

SiOOAlOK

Page 28: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Simple ceramic crystal structuresSimple ceramic crystal structures

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Chapter 1

Silicate mineral composition

Page 29: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Forming

• Pressing

• Isostatic pressing

• Extrusion

• Casting

Ceramic particles are normally mixed with binders or

lubricants in the dry, plastic or liquid to form into shapes.

Thermal treatments

• Drying

• Sintering

• Vitrification

Page 30: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Pressing • Ceramic particulates can be pressed in the dry, plastic

or wet condition in the die to form shaped products.

Dry pressing• Refractory

• Rapid, uniform and good tolerance

• Ex: alumina, titanate, ferrite

Filling

Pressing

Ejection

Page 31: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Isostatic pressing

• Powder is placed within a deformable container

and subjected to hydrostatic pressure.

• Simultaneous densification, low porosity.

• Near net shape process �100% material

utilization.

• High operating cost.

Hot isostatic pressing (HIP).

/www.sintec-keramik.com

Page 32: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Hot Isostatic Pressing (HIP)• Components are loaded

into furnace, which is placed

into pressure vessel.

• Temperature and pressure

are raised simultaneously

and held.

• Cooling is carried out as

the gas is released.

• Components are removed

from the furnace.

Page 33: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Cold Isostatic Pressing

• Powder is sealed in a flexible

mould (or ‘bag’), of for example

polyurethane and then subjected

to a uniform hydrostatic

pressure.

• Ex: refractories, bricks, spark

plug insulator, carbide tools,

crucible, bearings

CIP graphite blocks

Page 34: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Example of isostatic pressing of spark plug insulator

Mould

a) Pressed blank

b) Turned insulator

c) Fired insulator

d) Glazed and decorated

Page 35: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Slip casting

Main steps

1. Slip preparation

2. Slip casting

3. Draining

4. Trimming, removing

and finishing

• Forming thin-wall complex

shapes of uniform thickness.

• Can be done in vacuum.

Page 36: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Extrusion • Plastic state forming under high pressure

• Producing refractory bricks, sewer pipes, hallow tiles,

technical ceramics, electrical insulators.

Page 37: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Thermal treatments

• Drying

• Sintering

• Vitrification

Important state in making ceramics stronger

Drying • To remove water (and organic

binders) before firing

• Improving green strength

• Carried out at 100-300oC.

www.ceramic-drying.co.uk

Page 38: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Sintering Small particles are bonded together by solid state diffusion

Porous Denser, more coherentT < Tm

• Atomic diffusion takes place

at the area of contact to form

necking

• Particles get larger and

material is denser with

sintering time.

• Providing equilibrium grains.

• Lowered surface energy

Ex: Alumina, beryllia, ferrite and titanates

Page 39: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Example of MgO sintering at 1430oC in air at various times

Sintering temp Porosity

Page 40: Ceramics - Engineering Materials Outline -Engineering Materials Suranaree University of Technology October 2007 • Introduction to ceramics • Structures of ceramics • Processing

Processing of ceramicsProcessing of ceramics

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Chapter 1

Vitrification

Ex: Porcelain, structural clay products, electronic components

Suranaree University of Technology October 2007

• The glass phase liquifies and fill the pores in the material.

• Then solidifies to form a vitreous matrix that bonds the

unmelted materials upon cooling.