ceramics 2013
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ceramic propertiesTRANSCRIPT
CERAMIC & THEIR PROPERTIES
BMFB 332318-22/03/2013
What are ceramics? Classification of ceramics Thermal Properties of ceramics Optical Properties Mechanical Properties Electrical Properties
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http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf
A ceramic is an inorganic, nonmetallic solid prepared by the action of
heat and subsequent cooling. Ceramic materials may have a crystalline
or partly crystalline structure, or may be amorphous (e.g., aglass) .
— comes from the Greece word “keramicos”, which means burnt stuff
— broadly classed as inorganic, non-metallic materials
— usually a compound, or a combination of compounds, betweenmetallic and nonmetallic elements (mainly O, N, C, B)
— always composed of more than one element (Al2O3, SiO2, SiC, etc.)
— bonds are either totally ionic, or combination of ionic and covalent.
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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http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf
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 brittle6
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Silicate glass
TAXONOMY OF CERAMICS
Glasses Clay products
Refractories AbrasivesCements Advanced ceramics
Glass ceramics
Fireclay
Silica Basic
Special
Structural clay
products
Whitewares
Oxides
carbides
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CERAMICS
TRADITIONAL CERAMIC
Based primarily on natural raw materials; clay and silicaTendency to equate with low technologyHas been used for over 25, 000 years
TECHNICAL/ ADVANCED CERAMIC
‘special’, ‘technical’, ‘engineering’Exhibit superior/ specialized properties (mechanical properties, corrosion resistance, or electrical, optical, and/or magnetic properties)Require more sophisticated processingare mainly pure compounds or nearly pure compounds of primarily oxides, carbides, or nitridesHave generally been developed within last 100 years
Chemically prepared powders-Precipitation-Spray dry-Freeze dry-Vapor phase-Sol-gel
-Slip casting-Injection molding-Sol-gel-Hot pressing-HIPing-Rapid prototyping
-Electric furnace-Hot press-Reaction sinter-Vapor deposition-Plasma spraying-Microwave furnace
-Erosion-Laser machining-Plasma spraying-Ion implantationCoating
-Light microscopy-X-ray diffraction-Electron microscopy-Scanned probe microscopy-Neutron diffraction-Surface analytical methods
-Raw minerals-Clay-Silica
-Potters wheel-Slip casting
Flame kiln
-Erosion-Glazing
-Visible examination-Light microscope
Raw materials preparation
Forming
High-temperature processing
Finishing process
Characterization
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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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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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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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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Oxides: Alumina, zirconia Non-oxides: Carbides, borides, nitrides, silicides Composites: Particulate reinforced, combinations of
oxides and non-oxides
CERAMICS
Oxides
Nonoxides
Composite
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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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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)
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http://images.google.com.tr/imgres?imgurl=http://www.made-in-china.com/image/2f0j00avNtpdFnLThyM/Silicon-Carbide-Ceramic-Foam-Filter-CFS-.jpg&imgrefurl
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
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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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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
Amorphous silicon and thin film PV cells
CERAMICS
amorphous
crystalline
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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
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)
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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)
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 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
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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.gif11.04.23
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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…)25
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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.html26
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http://matse1.mse.uiuc.edu/ceramics/prin.html27
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OPTICAL PROPERTIES OF CERAMICS
Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 28
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OPTICAL PROPERTIES OF CERAMICS
ABSORPTION
•Color in ceramicsMost 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, 29
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MECHANICAL PROPERTIES OF CERAMICS
STRESS-STRAIN BEHAVIUR of selected materials
Al2O3
thermoplastic
http://www.keramvaerband.de/brevier_engl/5/5_2.htm30
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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
Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 31
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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
Stress is computed from,• specimen thickness•the bending moment•the moment of inertia of the cross section
MECHANICAL PROPERTIES OF CERAMICS
Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 32
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MECHANICAL PROPERTIES OF CERAMICS
Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 33
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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.
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.htmhttp://www.keramvaerband.de/brevier_eng/5/3/%_3_5.htm
http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Mechanical/Hardness.htm34
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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 >
Test procedures for determining the hardness according to Vickers, Knoop and Rockwell.
Some typical hardness values for ceramic materials are provided below:
MECHANICAL PROPERTIES OF CERAMICS
The high hardness of technical ceramics results in favourable wear resistance. Ceramics are thus good for tribological applications.
http://www.dynacer.com/hardness.htm35
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MECHANICAL PROPERTIES OF CERAMICSElastic 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.
http://www.keramverband.de/brevier_engl/5/3/4/5_3_4.htm36
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MECHANICAL PROPERTIES OF CERAMICSDensity
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.htm37
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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.htm38
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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
http://www.subtech.com/dokuwiki/doku.php?id=fracture_toughness39
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MECHANICAL PROPERTIES OF CERAMICS
Some typical values of fracture toughness for various materials
http://en.wikipedia.org/wiki/Fracture_toughness40
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Electrical conductivity of ceramics varies withThe 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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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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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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Types of ceramics
Applications: Automotive
Spark plugs, water pump seals, catalytic converter.
Heat engine: Higher operating
temperatures ⇒ Better fuel efficiency
Lower frictional forces & ability to operate with no cooling system
Excellent wear & corrosion resistance
Lower densities ⇒ Decreased engine weight 48
Disadvantages: Brittle Too easy to have voids weaken the engine Difficult to machine
Applications: Aerospace
Coating of metal heat engine parts ⇒ improved wear &/or high temperature damage.
Their low densities ⇒ lighter turbine blades VS superalloys
Materials considered: Si3N4, SiC and ZrO2
Draw back: disposition to brittle & catastrophic failure.
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Helicopter gas turbine
Applications: Aerospace
• Engines ; Shielding a hot running airplane engine from damaging other components.
• Airframes; Used as a high-stress, high-temp and lightweight bearing and structural component.
• Missile nose-cones; Shielding the missile internals from heat.
• Space Shuttle tiles • Space-debris ballistic shields -- Ceramic
fiber woven shields offer better protection to hypervelocity (~7 km/s) particles than aluminum shields of equal weight.
• Rocket Nozzles; Withstands and focuses the exhaust of the rocket booster.
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Applications: Electronics
Chosen to securely hold microelectronics & provide heat transfer
electrically insulating. low dielectric characteristics. thermally conductive.
standard bearer. low thermal conductivity & poor electrical
conductivity.
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Packaging of integrated circuits --(substrate):
Aluminum oxide:
good thermal & electrical properties.
bonding with metals: poor. payoff for metal pattern to stick:
Mo paste + additive @ 1600C or special direct Cu bonding.
Aluminum nitride Materials currently used include:
• Boron nitride (BN)• Silicon Carbide (SiC)• Aluminum nitride (AlN)– thermal conductivity 10x that for Alumina– good expansion match with Si
Applications: BiomaterialAlumina in orthopedic implants Excellent corrosion
resistance Wear resistance High strength Biocompatibility
53a) Extensive arthritis damage, b) same
hipafter total hip replacement
Various component for total hip prostheses including the stem with an alumina femoral head, and alumina AC cup, and a metal base for the AC cup
Bone joint
Alumina in dental implants
Ceramic Biomaterials (Alumina, Hydroxyapatite, Zirconia etc)• Biocompatibility• Bond well to bone (implant-tissue attachment)• Corrosion resistance• High stiffness• Wear resistance
Artificial root which supports tooth replacement and crown (porcelain).
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High-strength Al2O3 joint prostheses of complex shape for femur joint component.
Summary of applications:i ) ElectronicsIC packaging and substrates : Al2O3 (insulation) , AlN, BeO, SiCCapacitor: BaTiO3, SrTiO3
Thermistor-Spinel (NiMn)3O4, NiMnCo)3O4, KTaNbO3
Varistor - ZnO2Piezoelecctric –PZT(lead zirconate titanate). PLZT (lead
lanthanum zirconate titanate), LiNbO3, LiTaO3Ferroelectric – BaTiO3, Pb(TiZr)O3, K(TaNb)O3, LiTaO3
Ferrite –SrFe12O19, Y3Fe5O12
Sensors –oxygen sensors (Y-doped ZrO2), humidity sensors (Ti-doped MgCr2O4)
Hydrocarbon gas sensor (doped SnO2)Superconductores – Ba2YCu3O7-x
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Example: ceramic soleplate for irons
System Development with Si3N4 Ceramics
A soleplate of a high-quality iron hasto meet specific requirements: easy glidehigh mechanical strength and hardness good thermal conductivity non-stick properties
Silicon nitride ceramics fulfill these requirements much better than currently used materials like aluminum or stainless steel.
Heating element is directly applied on the ceramic soleplate by screen printing and subsequently is co-fired with the soleplate to achieve a strong bonding.