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CERAMICS Duygu ALTINÖZ 20519517 Emine ÖZTAŞ 20519943 Melodi HASÇUHADAR 20772572 Merve ÇAY 20772639 11.11.2009 Hacettepe University KMU Outline What are ceramics? Classification of ceramics Thermal Properties of ceramics

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ceramics
CERAMICS
  • Duygu ALTINÖZ 20519517
  • Emine ÖZTAŞ 20519943
  • Melodi HASÇUHADAR 20772572
  • Merve ÇAY 20772639

11.11.2009

Hacettepe University

KMU

outline
Outline

What are ceramics?

Classification of ceramics

Thermal Properties of ceramics

Optical Properties

Mechanical Properties

Electrical Properties

Ceramic Processing

7.3.2014

spectrum of ceramics uses
Spectrum of Ceramics Uses

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

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what are ceramics
What are ceramics?

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).

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

what are ceramics5
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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ceramic crystal structures
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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ceramic crystal structures7
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
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

imperfections in ceramics
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 Frenkeldefects(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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properties of ceramics
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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properties of ceramics11
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
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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general comparison of materials13
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 ceramics15
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

classifications of ceramics
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

classification of ceramics17
Classification of ceramics

Oxides: Alumina, zirconia

Non-oxides: Carbides, borides, nitrides, silicides

Composites: Particulate reinforced, combinations of oxides and non-oxides

CERAMICS

Oxides

Nonoxides

Composite

classification of ceramics18
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 forzirconia.

zirconia

classification of ceramics19
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

classification of ceramics20
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

classifications of ceramics22
Classifications of ceramics

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

CERAMICS

amorphous

crystalline

Amorphous silicon and thin film PV cells

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

classifications of ceramics23
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

– Strong

– Hard

–Brittle

– Good corrosion resistance

  • a ceramic (crystalline) and a glass (non-crystalline)
thermal properties
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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thermal properties25
Thermal properties

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

thermal properties26
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)

  • http://global.kyocera.com/fcworld/charact/heat/images/thermalcond_zu.gif
thermal properties27
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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optical properties of ceramics
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

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

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optical properties of ceramics29
OPTICAL PROPERTIES OF CERAMICS

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

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slide30

OPTICAL PROPERTIES OF CERAMICS

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

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slide31

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

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

7.3.2014

slide32

MECHANICAL PROPERTIES OF CERAMICS

STRESS-STRAIN BEHAVIUR of selected materials

Al2O3

thermoplastic

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

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slide33

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

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

7.3.2014

slide34

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

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

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slide35

MECHANICAL PROPERTIES OF CERAMICS

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

7.3.2014

slide36

MECHANICAL PROPERTIES OF CERAMICS

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.htm

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

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

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slide37

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:

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

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

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slide38

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 forcesexperienced 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.htm

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slide39

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.

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

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slide40

MECHANICAL PROPERTIES OF CERAMICS

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.htm

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slide41

MECHANICAL PROPERTIES OF CERAMICS

Change in elastic modulus with the amount of porosity in SiOC ceramic foams obtained from a preceramic polymer

Porosity

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

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

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slide42

MECHANICAL PROPERTIES OF CERAMICS

  • Strength
  • 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

Strength distribution within batches

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

7.3.2014

slide43

MECHANICAL PROPERTIES OFCERAMICS

  • 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_toughness

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slide44

MECHANICAL PROPERTIES OF CERAMICS

Some typical values of fracture toughness for various materials

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

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electrical properties of ceramic
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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electrical properties of ceramic46
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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superconducting properties
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.

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preparation of raw materials
Preparation of Raw Materials

Crushing & Grinding(to get ready ceramic powder for shaping)

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powder processing
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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slip casting
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

slide52
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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difference between casting and molding
Differencebetweencastingandmolding
  • Slip Casting
  • Injection molding

Mixed raw materials are combined with solvating media and a dispersant

Then fed into an absorbent die.

The materials are dehydrated and solidified

raw materials are mixed with resin.

Then fed injected into the molding die

The mold is then cooled to harden the binder.

drying process
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.

7.3.2014

references
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/Ceramic_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

ceramics57
Ceramics

Thank You 

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