Ceramics

CERAMICS

 Duygu ALTINÖZ 20519517

 Emine ÖZTAŞ 20519943

 Melodi HASÇUHADAR 20772572

 Merve ÇAY 20772639





11.11.2009

Hacettepe University

KMU









02.12.2011

OUTLINE



 What are ceramics?

 Classification of ceramics



 Thermal Properties of ceramics



 Optical Properties



 Mechanical Properties



 Electrical Properties



 Ceramic Processing







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02.12.2011

SPECTRUM OF CERAMICS USES









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

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02.12.2011

WHAT ARE CERAMICS?









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





 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). 4

02.12.2011

WHAT ARE CERAMICS?

 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 brittle



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02.12.2011

CERAMIC CRYSTAL STRUCTURES

 ceramics that are predominantly ionic in nature

have crystal structures comprised of charged ions,

where positively-charged (metal) ions are called

cations, and negatively-charged (non-metal) ions

are called anions – the crystal structure for a given

ceramic depends upon two characteristics:









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02.12.2011

CERAMIC CRYSTAL STRUCTURES

1. the magnitude of electrical charge on eachcomponent

ion, recognizing that the overallstructure must be

electrically neutral







2. the relative size of the cation(s) and anion(s),which

determines the type of interstitial site(s) for the

cation(s) in an anion lattice







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EXAMPLE OF CRYSTAL STRUCTURE









Rock salt structure(AX)(NaCl ) Fluorite structure(AX2)(CaF2)









Perovskite structure(ABX3)(BaTiO3) Spinel structure(AB2X4)(MgAl2O4)

http://www.eng.uwo.ca/es021/ES021b_2007/Lecture%20Notes/Chap%2012-13%20SN%20-%20Ceramics.pdf 8



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IMPERFECTIONS IN CERAMICS

 Include point defects and impurities

 Non-stoichiometry refers to a change in composition

 the effect of non-stoichiometry is a redistribution of

the atomic charges to minimize the energy

 Charge neutral defects include the Frenkel defects(a

vacancy- interstitial pair of cations) and Schottky

defects (a pair of nearby cation and anion vacancies)

 Defects will appear if the charge of the impurities is

not balanced



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02.12.2011

PROPERTIES OF CERAMICS

 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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02.12.2011

PROPERTIES OF CERAMICS

 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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GENERAL COMPARISON OF MATERIALS

Property Ceramic Metal Polymer



Hardness Very High Low Very Low



Elastic modulus Very High High Low



Thermal expansion High Low Very Low



Wear resistance High Low Low



Corrosion resistance High Low Low









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02.12.2011

GENERAL COMPARISON OF MATERIALS

Property Ceramic Metal Polymer



Ductility Low High High



Density Low High Very Low



Electrical conductivity Depends High Low

on material



Thermal conductivity Depends High Low

on material



Magnetic Depends High Very Low

on material





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CLASSIFICATION OF CERAMICS









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CLASSIFICATION OF CERAMICS

 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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02.12.2011

CLASSIFICATIONS OF CERAMICS



 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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02.12.2011

CLASSIFICATION OF CERAMICS



Oxides



CERAMICS

Nonoxides





Composite









 Oxides: Alumina, zirconia

 Non-oxides: Carbides, borides, nitrides, silicides

 Composites: Particulate reinforced, combinations of oxides and

non-oxides



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02.12.2011

CLASSIFICATION OF CERAMICS



 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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02.12.2011

CLASSIFICATION OF CERAMICS



 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)

http://images.google.com.tr/imgres?imgurl=http://www.made-in-

china.com/image/2f0j00avNtpdFnLThyM/Silicon-Carbide-Ceramic-Foam-

Filter-CFS-.jpg&imgrefurl

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CLASSIFICATION OF CERAMICS

 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

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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CLASSIFICATION OF CERAMICS









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CLASSIFICATIONS OF CERAMICS



amorphous

CERAMICS

crystalline





 Amorphous

 the atoms exhibit only short-range

order



 no distinct melting temperature

(Tm) for these materials as there is

with the crystalline materials

Amorphous silicon and thin film PV cells

 Na20, Ca0, K2O, etc

http://images.google.com.tr/imgres?imgurl=http://simeonintl.com/sitebuilder/images/A-Si_Solar-

510x221.jpg&imgrefurl=http://simeonintl.com/Solar.html&usg=__ktCHUAO742PE0hh3U1fGw8go

PrM=&h=221&w=510&sz=17&hl=tr&start=68&sig2=9OC7pTtJz2SuK_AKdrqTAA&um=1&tbnid=x 22

QRh5yfCftf89M:&tbnh=57&tbnw=131&prev=/images%3Fq%3Damorphous%2Bceramic%26ndsp

%3D18%26hl%3Dtr%26rlz%3D1G1GGLQ_TRTR320%26sa%3DN%26start%3D54%26um%3D

02.12.2011 1&ei=9Kv1SrTfAoej_gbrz6WtAw

CLASSIFICATIONS OF CERAMICS

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



– Strong



– Hard



– Brittle



– Good corrosion resistance 23

02.12.2011

THERMAL PROPERTIES

 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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02.12.2011

THERMAL PROPERTIES

 Thermal expansion

Comparison of thermal expansion coefficient between metals and fine ceramics

 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

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02.12.2011

fine ceramics

THERMAL PROPERTIES

 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)









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02.12.2011 •http://global.kyocera.com/fcworld/charact/heat/images/thermalcond_zu.gif

THERMAL PROPERTIES

 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…)



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02.12.2011

OPTICAL PROPERTIES OF CERAMICS



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





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02.12.2011 http://matse1.mse.uiuc.edu/ceramics/prin.html

OPTICAL PROPERTIES OF CERAMICS









29

02.12.2011 http://matse1.mse.uiuc.edu/ceramics/prin.html

OPTICAL PROPERTIES OF CERAMICS









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02.12.2011 Callister, W., D., (2007), Materials Science And Engineering, 7 th Edition,

OPTICAL PROPERTIES OF CERAMICS



ABSORPTION



•Color in ceramics

Most dielectric ceramics and

glasses are colorless.



By adding transition metals

(TM)

Ti, V, Cr, Mn, Fe, Co, Ni









31

02.12.2011 Carter, C., B., Norton, M., G., Ceramic Materials Science And Engineering,

MECHANICAL PROPERTIES OF CERAMICS

STRESS-STRAIN BEHAVIUR of selected materials









Al2O3









thermoplast

ic









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02.12.2011 http://www.keramvaerband.de/brevier_engl/5/5_2.htm

MECHANICAL PROPERTIES OF CERAMICS



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









33

02.12.2011 Callister, W., D., (2007), Materials Science And Engineering, 7th Edition,

MECHANICAL PROPERTIES OF CERAMICS

Stress is computed from,

• specimen thickness

•the bending moment

•the moment of inertia of the cross section





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

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02.12.2011 Callister, W., D., (2007), Materials Science And Engineering, 7th Edition,

MECHANICAL PROPERTIES OF CERAMICS









35

02.12.2011 Callister, W., D., (2007), Materials Science And Engineering, 7th Edition,

MECHANICAL PROPERTIES OF CERAMICS

Hardness





Hardness implies a high

resistance to deformation and is

Technical ceramic

associated with a large modulus of

components are therefore

elasticity. characterised by their stiffness

and dimensional stability.

In metals, ceramics and most

polymers, the deformation Hardness is affected from

considered is plastic deformation of porosity in the surface, the grain

the surface. For elastomers and size of the microstructure and the

some polymers, hardness is defined effects of grain boundary phases.

at the resistance to elastic

deformation of the surface.





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

http://www.keramvaerband.de/brevier_eng/5/3/%_3_5.htm

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02.12.2011 http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Mechanical/Hardness.htm

MECHANICAL PROPERTIES OF CERAMICS

Test procedures for determining the hardness according to Vickers, Knoop

and Rockwell.



Some typical hardness values for ceramic materials are provided below:

Material Class Vickers Hardness (HV) GPa



Glasses 5 – 10



Zirconias, Aluminium Nitrides 10 - 14



Aluminas, Silicon Nitrides 15 - 20



Silicon Carbides, Boron 20 - 30

Carbides

Cubic Boron Nitride CBN 40 - 50



Diamond 60 – 70 >







The high hardness of technical ceramics results in favourable wear resistance.

Ceramics are thus good for tribological applications.

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02.12.2011 http://www.dynacer.com/hardness.htm

MECHANICAL PROPERTIES OF CERAMICS

Elastic 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.









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02.12.2011 http://www.keramverband.de/brevier_engl/5/3/4/5_3_4.htm

MECHANICAL PROPERTIES OF CERAMICS

Density





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.









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02.12.2011 http://www.keramverband.de/brevier_engl/5/3/4/5_3.htm

MECHANICAL PROPERTIES OF CERAMICS

A comparison of typical mechanical characteristics of some ceramics with grey

cast-iron and construction steel









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02.12.2011 http://www.keramverband.de/brevier_engl/5/5_2.htm

MECHANICAL PROPERTIES OF CERAMICS

Change in elastic modulus with the amount of

Porosity porosity in SiOC ceramic foams obtained from a

preceramic polymer



Technical ceramic materials have

no open porosity.



Porosity can be generated through

the appropriate selection of raw

materials, the manufacturing

process, and in some cases through

the use of additives.



This allows closed and open pores

to be created with sizes from a few

nm up to a few µm.

http://www.ucl.ac.uk/cmr/webpages/spotlight/articles/colombo.htm









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02.12.2011 http://www.keramverband.de/brevier_engl/5/3/5_3_2.htm

MECHANICAL PROPERTIES OF CERAMICS

Strength

Strength distribution within batches

The figure for the strength of

ceramic materials, [MPa] is

statistically distributed depending

on



•the material composition

•the grain size of the initial

material and the additives

•the production conditions

•the manufacturing process









http://www.keramverband.de/brevier_engl/5/3/3/5_3_3.htm

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02.12.2011

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







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02.12.2011 http://www.subtech.com/dokuwiki/doku.php?id=fracture_toughness

MECHANICAL PROPERTIES OF CERAMICS

Material KIc (MPa-m1 / 2)

Metals

Aluminum alloy (7075) 24

Steel alloy (4340) 50

Titanium alloy 44-66 Some typical values of

Aluminum 14-28 fracture toughness for

Ceramics various materials

Aluminum oxide 3-5

Silicon carbide 3-5

Soda-lime-glass 0.7-0.8

Concrete 0.2-1.4

Polymers

Polystyrene 0.7-1.1

Composites

Mullite fiber reinforced-

1.8-3.3

mullite composite



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02.12.2011 http://en.wikipedia.org/wiki/Fracture_toughness

ELECTRICAL PROPERTIES OF CERAMIC

 Electrical conductivity of ceramics varies with

 The 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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02.12.2011

ELECTRICAL PROPERTIES OF CERAMIC



 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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02.12.2011

SUPERCONDUCTING PROPERTIES

 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. 47

02.12.2011

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PREPARATION OF RAW MATERIALS





• Crushing &

Grinding (to get

ready ceramic powder

for shaping)









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POWDER PROCESSING

 Ceramic powder is converted into a useful

shape at this step.



 Processing techniques

 Tape casting

 Slip casting



 Injection molding









http://janereynoldsceramics.co.uk/images/ceramic1.jpg

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02.12.2011

SLIP CASTING









• A suspension of seramic powders in water , slip, is poured

into a porous plaster mold

• Water from the mix is absorbed into the plaster to form a

firm layer of clay at the mold surface

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02.12.2011

http://global.kyocera.com/fcworld/first/process06.html



•Raw materials are mixed with resin to provide the necessary fluidity

degree.

•Then injected into the molding die



•The mold is then cooled to harden the binder and produce a "green"

compact part (also known as an unsintered powder compact).

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02.12.2011

DIFFERENCE BETWEEN CASTING AND

MOLDING

 Slip Casting

 Mixed raw materials are

combined with solvating

media and a dispersant

 Then fed into an absorbent

die.

 The materials are dehydrated  Injection molding

and solidified  raw materials are mixed

with resin.

 Then fed injected into the

molding die

 The mold is then cooled to

harden the binder.

53



02.12.2011

DRYING PROCESS



 Water must be removed from clay piece before

firing



 Shrinkage is a problem during drying. Because

water contributes volume to the piece, and the

volume is reduced when it is removed.









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REFERENCES

 http://www.azom.com/details.asp?ArticleID=2123

 www.accuratus.com/materials.html

 http://global.kyocera.com/fcworld/charact/heat/thermaexpan.html

 http://www.keramverband.de/brevier_engl/5/4/5_4.htm

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

 http://www.virginia.edu/bohr/mse209/chapter13.htm

 http://ceramics.org/learn-about-ceramics/structure-and-properties-of-ceramics/

 http://www.keramverband.de/brevier_engl/5/5_1.htm

 http://me.queensu.ca/courses/MECH270/documents/Lecture20CeramicsA.pdf

 http://www.tarleton.edu/~tbarker/2033/Notes_Handouts/Powerpoint_notes/Cera

mic_Materials_Module_7.pdf

 http://users.encs.concordia.ca/~mmedraj/mech221/lecture%2018.pdf

 http://media-2.web.britannica.com/eb-media/85/1585-004-168972D1.gif

 http://global.kyocera.com/fcworld/first/process06.html



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02.12.2011

CERAMICS





Thank You 









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