Transcript Slide 1

CERAMICS
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Duygu ALTINÖZ
Emine ÖZTAŞ
Melodi HASÇUHADAR
Merve ÇAY
20519517
20519943
20772572
20772639
11.11.2009
Hacettepe University
KMU
07.07.2015
OUTLINE
What are ceramics?
 Classification of ceramics
 Thermal Properties of ceramics
 Optical Properties
 Mechanical Properties
 Electrical Properties
 Ceramic Processing
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SPECTRUM OF CERAMICS USES
http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf
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WHAT ARE CERAMICS?
http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf
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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).
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WHAT ARE CERAMICS?
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To be most frequently silicates, oxides, nitrides and
carbides
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Typically insulative to the passage of electricity and
heat
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More resistant to high temperatures and harsh
environments than metals and polymers
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Hard but very brittle
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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 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
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IMPERFECTIONS IN CERAMICS
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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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PROPERTIES OF CERAMICS
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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 CERAMICS
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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
Hardness
Very High
Low
Very Low
Elastic modulus
Very High
High
Low
High
Low
Very Low
Thermal expansion
Polymer
Wear resistance
High
Low
Low
Corrosion resistance
High
Low
Low
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GENERAL COMPARISON OF MATERIALS
Property
Ceramic
Metal
Polymer
Ductility
Low
High
High
Density
Low
High
Very Low
Electrical conductivity Depends
on material
High
Low
Thermal conductivity Depends
on material
High
Low
Magnetic
High
Very Low
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Depends
on material
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CLASSIFICATION OF CERAMICS
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CLASSIFICATION OF CERAMICS
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Traditional Ceramics
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the older and more generally known
types (porcelain, brick, earthenware,
etc.)
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Based primarily on natural raw materials
of clay and silicates
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Applications;
building materials (brick, clay pipe, glass)
household goods (pottery, cooking ware)
manufacturing ( abbrasives, electrical
devices, fibers)
Traditional Ceramics
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CLASSIFICATIONS OF CERAMICS
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Advanced Ceramics
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have been developed over the past half
century
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Include artificial raw materials, exhibit
specialized properties, require more
sophisticated processing
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Applied as thermal barrier coatings to
protect metal structures, wearing
surfaces,
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Engine applications (silicon nitride
(Si3N4), silicon carbide (SiC), Zirconia
(ZrO2), Alumina (Al2O3))
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bioceramic implants
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CLASSIFICATION OF CERAMICS
Oxides
CERAMICS
Nonoxides
Composite
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Oxides: Alumina, zirconia
Non-oxides: Carbides, borides, nitrides, silicides
Composites: Particulate reinforced, combinations of oxides and
non-oxides
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CLASSIFICATION OF CERAMICS
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Oxide Ceramics:
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Oxidation resistant
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chemically inert
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electrically insulating
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generally low thermal conductivity
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slightly complex manufacturing
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low cost for alumina
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more complex manufacturing
higher cost for zirconia.
zirconia
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CLASSIFICATION OF CERAMICS
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Non-Oxide Ceramics:
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Low oxidation resistance
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extreme hardness
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chemically inert
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high thermal conductivity
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electrically conducting
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difficult energy dependent
manufacturing and high cost.
Silicon carbide cermic foam filter (CFS)
http://images.google.com.tr/imgres?imgurl=http://www.made-inchina.com/image/2f0j00avNtpdFnLThyM/Silicon-Carbide-Ceramic-FoamFilter-CFS-.jpg&imgrefurl
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CLASSIFICATION OF CERAMICS
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Ceramic-Based Composites:
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Toughness
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low and high oxidation resistance
(type related)
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variable thermal and electrical
conductivity
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complex manufacturing processes
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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
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Amorphous
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the atoms exhibit only short-range
order
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no distinct melting temperature
(Tm) for these materials as there is
with the crystalline materials
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Na20, Ca0, K2O, etc
Amorphous silicon and thin film PV cells
http://images.google.com.tr/imgres?imgurl=http://simeonintl.com/sitebuilder/images/A-Si_Solar510x221.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
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QRh5yfCftf89M:&tbnh=57&tbnw=131&prev=/images%3Fq%3Damorphous%2Bceramic%26ndsp
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1&ei=9Kv1SrTfAoej_gbrz6WtAw
CLASSIFICATIONS OF CERAMICS
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Crystalline
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atoms (or ions) are arranged in a
regularly repeating pattern in
three dimensions (i.e., they have
long-range order)
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Crystalline ceramics are the
“Engineering” ceramics
– High melting points
a ceramic (crystalline) and a glass (non-crystalline)
– Strong
– Hard
– Brittle
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– Good corrosion resistance
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THERMAL PROPERTIES
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most important thermal properties of ceramic materials:
Heat capacity : amount of heat required to raise material temperature by
one unit (ceramics > metals)
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Thermal expansion coefficient: the ratio that a material expands in
accordance with changes in temperature
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Thermal conductivity : the property of a material that indicates its ability to
conduct heat
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Thermal shock resistance: the name given to cracking as a result of rapid
temperature change
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THERMAL PROPERTIES
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Thermal expansion
Comparison of thermal expansion coefficient between metals and fine ceramics
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The coefficients of thermal
expansion depend on the bond
strength between the atoms that
make up the materials.
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Strong bonding (diamond,
silicon carbide, silicon nitrite) →
low thermal expansion
coefficient
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Weak bonding ( stainless steel)
→ higher thermal expansion
coefficient in comparison with
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fine ceramics
THERMAL PROPERTIES
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Thermal conductivity
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generally less than that of metals such as steel or copper
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ceramic materials, in contrast, are used for thermal insulation due to their
low thermal conductivity (except silicon carbide, aluminium nitride)
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•http://global.kyocera.com/fcworld/charact/heat/images/thermalcond_zu.gif
THERMAL PROPERTIES
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Thermal shock resistance
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A large number of ceramic materials are sensitive to thermal shock
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Some ceramic materials → very high resistance to thermal shock is despite of low
ductility (e.g. fused silica, Aluminium titanate )
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Result of rapid cooling → tensile stress (thermal stress)→cracks and consequent
failure
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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
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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http://matse1.mse.uiuc.edu/ceramics/prin.html
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OPTICAL PROPERTIES OF CERAMICS
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http://matse1.mse.uiuc.edu/ceramics/prin.html
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OPTICAL PROPERTIES OF CERAMICS
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Callister, W., D., (2007), Materials Science And Engineering, 7 th Edition,
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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
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Carter, C., B., Norton, M., G., Ceramic Materials Science And Engineering,
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MECHANICAL PROPERTIES OF CERAMICS
STRESS-STRAIN BEHAVIUR of selected materials
Al2O3
thermoplast
ic
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http://www.keramvaerband.de/brevier_engl/5/5_2.htm
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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
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Callister, W., D., (2007), Materials Science And Engineering, 7th Edition,
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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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Callister, W., D., (2007), Materials Science And Engineering, 7th Edition,
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MECHANICAL PROPERTIES OF CERAMICS
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Callister, W., D., (2007), Materials Science And Engineering, 7th Edition,
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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.
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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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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
Carbides
20 - 30
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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http://www.dynacer.com/hardness.htm
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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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http://www.keramverband.de/brevier_engl/5/3/4/5_3_4.htm
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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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http://www.keramverband.de/brevier_engl/5/3/4/5_3.htm
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MECHANICAL PROPERTIES OF CERAMICS
A comparison of typical mechanical characteristics of some ceramics with grey
cast-iron and construction steel
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http://www.keramverband.de/brevier_engl/5/5_2.htm
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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
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http://www.keramverband.de/brevier_engl/5/3/5_3_2.htm
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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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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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http://www.subtech.com/dokuwiki/doku.php?id=fracture_toughness
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MECHANICAL PROPERTIES OF CERAMICS
KIc (MPa-m1 / 2)
Material
Metals
Aluminum alloy (7075) 24
Steel alloy (4340)
Titanium alloy
Aluminum
Ceramics
Aluminum oxide
Silicon carbide
Soda-lime-glass
Concrete
Polymers
Polystyrene
Composites
50
44-66
14-28
3-5
3-5
0.7-0.8
0.2-1.4
Some typical values of
fracture toughness for
various materials
0.7-1.1
Mullite fiber reinforced1.8-3.3
mullite composite
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http://en.wikipedia.org/wiki/Fracture_toughness
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ELECTRICAL PROPERTIES OF CERAMIC
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Electrical conductivity of ceramics varies with
 The
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charge transport mechanisms are frequency
dependent.
 The
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Frequency of field applied effect
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 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
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Despite of very low electrical conductivity of most of the ceramic materials,
there are ceramics, possessing superconductivity properties (near-to-zero
electric resistivity).
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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).
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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
•
Crushing &
Grinding (to get
ready ceramic powder
for shaping)
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POWDER PROCESSING
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Ceramic powder is converted into a useful
shape at this step.
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Processing techniques
 Tape
casting
 Slip casting
 Injection molding
http://janereynoldsceramics.co.uk/images/ceramic1.jpg
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SLIP CASTING
•
•
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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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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
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Slip Casting
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Mixed raw materials are
combined with solvating
media and a dispersant
Then fed into an absorbent
die.
The materials are dehydrated
and solidified
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Injection molding
raw materials are mixed
with resin.
Then fed injected into the
molding die
The mold is then cooled to
harden the binder.
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DRYING PROCESS
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Water must be removed from clay piece before
firing
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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
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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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CERAMICS
Thank You 
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