ceramicsmaterialspropthermalandmechanical-121004140222-phpapp01
TRANSCRIPT
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Traditional and engineering ceramicsTraditional and engineering ceramics
Suranaree University of Technology October 2007
T.
Udom
phol
Chapter 1
Traditional ceramics Clay Silica Feldspar+ +
2322
2322
6..
6..
SiOOAlONa
SiOOAlOK2SiOOHSiOOAl 2232 2.2.
Structural clay products : bricks,
sewer pipe, roofing tile
EX: Triaxial bodies: Whiteware,porcelain, chinaware, sanitary ware.
Reactions of a triaxial body
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Traditional and engineering ceramicsTraditional and engineering ceramics
Suranaree University of Technology October 2007
T.
Udom
phol
Chapter 1
Traditional ceramics
Triaxial whiteware chemical composition
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Traditional and engineering ceramicsTraditional and engineering ceramics
Suranaree University of Technology October 2007
T.
Udom
phol
Chapter 1
Traditional ceramics
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T.
Udom
phol
Chapter 1
Electron micrograph of an electrical
insulator porcelain (etched 10 s, 0oC,40% HF, silica replica)
quartz Mullite needles
High silica glass
Traditional and engineering ceramicsTraditional and engineering ceramics
Traditional ceramics
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T.
Udom
phol
Chapter 1
Traditional and engineering ceramicsTraditional and engineering ceramics
Slip casting processMaster and plaster moulds
Fresh cast
Dry
Slip casting
Colour paintFire
Suranaree University of Technology October 2007
http://www.lindawilsonceramics.co.za/3.html
Pottery
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T.
Udom
phol
Chapter 1
Traditional and engineering ceramicsTraditional and engineering ceramics
Slip casting processSlip casting process Sanitaryware
Slip casting in plaster moulds and demoulding
www.3emmegi.com
Suranaree University of Technology October 2007
Slip preparation
in ball millOHOHCaSOOHCaSO C
o
223
221
4
150
24 .2. +
Hemihydrate plaster produced from gymsum
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T.
Udomphol
Chapter 1
Traditional and engineering ceramicsTraditional and engineering ceramics
Engineering ceramics Contain more of pure compounds of oxides,
carbides, nitrides.
Ex:Al2O3, Si3N4, SiC, ZrO2 , refractory
oxides
Mechanical properties of engineering ceramics
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T.
Udomphol
Chapter 1
Traditional and engineering ceramicsTraditional and engineering ceramics
Engineering ceramics Alumina
Refractory tubing
High purity crucibles for high temp
High quality electrical applications
(low dielectric loss and high resistivity) Spark plug insulator
Microstructure of sintered, powdered aluminium
oxide doped with magnesium oxide
Alumina tubes
www.sentrotech.com
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T.
Udomphol
Chapter 1
Traditional and engineering ceramicsTraditional and engineering ceramics
Engineering ceramics Silicon nitride (Si3N4)
Dissociate at T > 1800oC.
Cannot be directly sintered reaction bonding.
Silicon nitride for engineering applications
Silicon powder
N2 flow
nitriding
Microporous Si3N4
High strength
nonporous Si3N
4
Hot pressing with
1-5%MgO
www.defazio-rotary.com
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T.
Udomphol
Chapter 1
Traditional and engineering ceramicsTraditional and engineering ceramics
Engineering ceramics Silicon carbide (SiC)
Hard refractory carbide.
Form skin of SiO2at high temp.
Resistance to oxidation at high temp.
Can be sintered 2100oC with 0.5-1%B.
Fibrous reinforcementin ceramic-
matrix composite material.
SiC fibre reinforced Titanium matrix
www.stork.com
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Suranaree University of Technology October 2007
T.
Udomphol
Chapter 1
Traditional and engineering ceramicsTraditional and engineering ceramics
Engineering ceramics Zirconia (ZrO2)
Polymorphic: tetragonal
monoclinic.
Mixed with CaO, MgO and Y2O3 Partially stabilized zirconia (PSZ).
1170oC
Volume expansion
Heat treatment Cubic structure
www.azom.com
Zirconia
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Mechanical properties of ceramicsMechanical properties of ceramics
Suranaree University of Technology October 2007
T.
Udomphol
Chapter 1
Brittle
High strength (varying from 0.7 7000 MPa)
Better compressive strength than tensile (5-10 times)
refractory; porous ceramics; glasses 1000
MaterialsLevel of strength
(MPa)
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Mechanical properties of ceramicsMechanical properties of ceramics
Suranaree University of Technology October 2007
T.
Udomphol
Chapter 1
Deformation mechanisms
Lack of plasticity due to ionic and covalent bonding (directional). Stressing of covalent crystal separation of electron-pair
bonds without subsequent reformation brittle
Deforming of ionic single crystal (MgO or NaCl) shows
considering amount of plastic deformation under compressive
force. However ionic polycrystals are brittle due to crack formation
at grain boundaries.
NaCl structure showing slip on
the (110) plane [110] direction
or AA and on the (100) plane[010] direction BB
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Mechanical properties of ceramicsMechanical properties of ceramics
Suranaree University of Technology October 2007
T.
Udomphol
Chapter 1
Factors affecting strength of ceramics
Depending on amount of defectsgiving stress concentration
Surface cracks
Porosity
Inclusions
Excessive grain sizes
No plastic deformation during crack
propagation from defects very brittle.
Note:
Fabrication
Should control
chemical composition
microstructure
surface condition
temperature
environment
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Mechanical properties of ceramicsMechanical properties of ceramics
Suranaree University of Technology October 2007
T.
Udomphol
Chapter 1
Toughness of ceramics
Low toughness due to covalent-ionic bonding. Using hot pressing, reaction bonding to improve toughness.
Fibre-reinforced ceramic matrix composites.
Fracture toughness of ceramics
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Mechanical properties of ceramicsMechanical properties of ceramics
Suranaree University of Technology October 2007
T.
Udomphol
Chapter 1
Toughness of ceramics Example
A reaction-bonded silicon nitride has a strength of 300 MPa and a
fracture toughness of 3.6 MPa.m1/2, What is the largest-size internal
crack that this material can support without fracturing? Given Y = 1
( )( )
mma
MPa
mMPaKa
aYK
f
IC
fIC
8.451058.4
300
.6.3
5
2
2
2
2
==
==
=
Therefore the largest internal crack 2a = 91.6 m
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Mechanical properties of ceramicsMechanical properties of ceramics
T.
Udo
mphol
Chapter 1
Transformation toughening of Partially Stabilized Zirconia (PSZ)
Zirconia+ (CaO, MgO or Y2O3) PSZ (metal stable)
Sintering at 1800oC+rapid cooling to RT+
reheating at 1400oC to give fine precipitates
Suranaree University of Technology October 2007
Tetragonal monoclinic
under stressing
Volume expansion
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Mechanical properties of ceramicsMechanical properties of ceramics
Suranaree University of Technology October 2007
T.
Udo
mphol
Chapter 1
Fatigue failure of ceramics
Fatigue failure in ceramics is rare due to lack ofplastic deformation during cyclic loading.
Fatigue cracking of polycrystalline alumina under cyclic loading
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Mechanical properties of ceramicsMechanical properties of ceramics
Suranaree University of Technology October 2007
T.
Udo
mphol
Chapter 1
Abrasive property of ceramics
Hard and brittle Used as cutting, grinding and polishing tools.
www.moldmakingtechnology.com
Ceramic grinding wheels
Ceramic cutting tools
Aluminium oxide Silicon carbide
Titanium nitride
Tungsten carbide
Boron nitride
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Thermal properties of ceramicsThermal properties of ceramics
Suranaree University of Technology October 2007
T.
Udo
mphol
Chapter 1
Low thermal conductivity
due to ionic-covalent
bonding insulator.
Also used as refractoriesin metal, chemical and
glass industries.
Thermal conductivity ofceramic materials
Ch t 1
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Thermal properties of ceramicsThermal properties of ceramics
Suranaree University of Technology October 2007
T.
Udo
mphol
Chapter 1
Ceramic refractory materials
A mixture of ceramic compounds Low-high temperature strength
Low bulk density (2.1-3.3 g.cm-3)
Porosity insulating
Refractory bricks (60% Al2O3)
for hot blast furnace
img.alibaba.com
Basic refractory
Acidic refractory
Mainly based on SiO2andAl2O3
Mainly based on magnesia (MgO),
lime (CaO) and Cr2O3
Ch t 1
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Thermal properties of ceramicsThermal properties of ceramics
Suranaree University of Technology October 2007
T.
Udo
mphol
Chapter 1
Chapter 1
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Thermal properties of ceramicsThermal properties of ceramics
Suranaree University of Technology October 2007
T.
Udo
mphol
Chapter 1
Acidic refractory Basic refractory
Silica refractoryhas high
refractoriness, high mechanical
strength and rigidity at high
temperature. Fireclays (fine plastic clays +
flint + coarse clay or grog)
High alumina refractories
contains 50-99% alumina,
giving higher fusion temperature
(more expensive than fireclay).
Basic refractory consists of
mixtures of MgO, CaO and Cr2O3.
High bulk density
High melting point
Good resistance to chemical
attack (basic slag, oxides)
Ex92-95% MgO used for liningin basic-oxygen steelmaking
process
Chapter 1
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Thermal properties of ceramicsThermal properties of ceramics
T.
Udo
mphol
Chapter 1
Ceramic tile insulation for the space shuttle orbiter
Suranaree University of Technology October 2007
About 24,000 ceramic tiles (70%) of silica-fibre compoundareused for insulating external surface of space shuttle.
Chapter 1
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Thermal properties of ceramicsThermal properties of ceramics
T.
Udo
mphol
Chapter 1
Ceramic tile insulation for the space shuttle orbiter
Suranaree University of Technology October 2007
Microstructure of LI900 high-temperaturereusable surface insulation (HTRS)
High temperature reusable surface(HTRS) made from 90% silica fibres
and 10% empty space.
Density = 0.144 g.cm-3
Temp ~ 1260oC
media.nasaexplores.com
upload.wikimedia.org
Borosilicate coating
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udo
mphol
Chapter 1
Transparency
Hardness and strength
Corrosion/chemical resistance
Vacuumtight enclosure
Insulator
Properties of glassBlown glass
www.geocities.com
Tinted or heat-absorbed glass
www.arch.tu.ac.th
Definition of glass
An inorganic and noncrystallinematerial which maintains its
amorphous microstructure below its
glass transition temperature.
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udo
mphol
Chapter 1
Glass transition temperature (Tg)
Unlike solidified metal, a glassliquid does not crystallize but
follow anAD path.
Viscous Plastic Glassy
Temp (decrease)
The faster cooling rate,
the higher values of Tg.Solidification of crystalline and amorphous
materials showing a change in specific volume
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udo
mphol
p
Structure of glass Glass forming oxide - SiO2
Si-O tetrahedron Ideal crystalline silica
(crystobalite)Simple silica glass with
no-long range order
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udo
mphol
p
Structure of glass Glass modifying oxides - Na2O, K2O, CaO, MgO
Oxygen from Na2Obreaks up
silica network, leaving oxygen
atoms with an unshared electron.
Na+ or K+ ions fits into interstices
of network.
Network modified glass (soda-lime glass)
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
Structure of glass Intermediate oxides in glass -Al2O3 , Pb2O3
Oxides such asAl2O3 orPb2O3cannot form glass network but
join into an existing network.Aluminosilicate glass
provides higher temperature than
common glass.
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
Glass composition
Silica glass
Soda-lime glass
Borosilicate glass
(Pyrex glass)
Lead glass
No radiation damage
Reduced Tm ~ 730oC
Low thermal expansion
Shielding from high
energy radiation
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
Viscous deformation of glasses
Glass remains its viscous(supercooled) liquid above Tg.
Temp > Tg Viscosity
RTQ
oe+=
= viscosity of the glass
o = pre-exponential constantQ = molar activation energy for
viscous flow
R = gas constantT = absolute temperature
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
Viscosity reference points
Working point
Softening point
Annealing point
Strain point
Viscosity = 104 poise (103 Pa.s) fabrication
Viscosity = 108 poise glass flows at an appreciate
rate under its own weight (and surface tension).
Viscosity = 1013 poise relieving internal stresses
Viscosity = 1014.5 poise glass is rigid with slow
rate of stress relaxation.
Note: glass are usually melt at temp relating to viscosity = 102poise
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
Example A 96 % silica glass has a viscosity of 1013 P at its annealing point of940oC and a viscosity of 108P at its softening point of 1470oC.
Calculate the activation energy in kJ/mol for the viscous flow of thisglass in this temperature range.
Tanneal= 940+273 = 1213 K, ap =1013 P
Tsoftening= 1470+273 = 1743 K, ap =108
P
RTQ
oe+=
5
8
13
1010
1011exp ==
=
spapsp
ap
TTR
Q
molkJQ
KK
Q
/382
1743
1
1213
1
314.8exp105
=
=
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
Fabrications of glass
Forming sheet and plate glass
Blowing, pressing and casting of glass
Float glass process molten glass ribbon moves on the top of
molten tin in a reducing atmosphere.
Remove glass sheet when the glass surface is hard enough
then pass to annealing furnace called lehrto remove residual
stresses.
For deep, hallow shapes like bottles, jars, light bulbs envelops.
Blowing air to force molten glass into moulds.
Pressinga plunger into a mold containing molten glass.
Castinginto open moulds.
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
Float glass process
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
a) Reheat , b) final blow stage of a glass blowing machine process
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
Pyrex glass Borosilicate glass
Low thermal expansion Inert to almost all materials with the exception of
hydrofluoric acid, hot phosphoric acid and hot alkalies.
2.0%Al2O3
13.0%B2O
3
0.5K2O
4.0%Na2O
81%SiO2
Approximate composition
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Udomphol
b) after centre has cooled.a) After surface has cooled from high
temperature near glass-softening temperature.
The surface cools first (by rapid air cooling) and contract while
the interior is warm, developing compressive on the surface andtensile in the middle.
Tempered glass
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Ud
omphol
Distribution of residual stresses across the
sections of glass thermally tempered and
chemically strengthend
Tempered glass
Tempering effect increases
the strength (4 x stronger than
annealed glass.
Has higher impact resistancethan annealed glass.
Ex: Auto side window, safety
glass for doors.
Chapter 1
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GlassGlass
Suranaree University of Technology October 2007
T.
Ud
omphol
Laminated glass
Plastic interlayer(PVB-poly vinyle butyral)is sandwiched with floated/annealed glass.
Safety glass: Breaking like a spider web.
Laminated glass
www.dupont.com
Spider web breaking pattern
http://en.wikipedia.org/
Chapter 1
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GlassGlass
T.
Ud
omphol
Laminated glass
www.goodandquickglass.comSuranaree University of Technology October 2007
Chapter 1
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GlassGlass
T.
Ud
omphol
Chemical strengthened glass
Suranaree University of Technology October 2007
Submerging sodium aluminosilicate glass in a bath containing a
potassium saltat T~ 450-500oC for 6-10 h.
Replacing Na ions with
larger K ions on the glasssurface.
Producing thin
compressive stresses at
the surface and tensile
stresses in the centre.
Distribution of residual stresses across the section of glass
thermally tempered and chemically strengthened.
Used in supersonic aircraft glazing,
ophthalmic lenses.