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Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Ceramics (세라믹)
Associate Professor Su-Jin Kim
School of Mechanical Engineering
Gyeongsang National University
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
OCW
Ionic crystal structures
https://youtu.be/A3cPHn_OgVQ?list=PL8EAOgbez9XIWGbmcihctMO4bXSB4V8hm
Ceramic Crystal Structures
https://youtu.be/JILO8IppZis
Ceramics high temperature, hardness, chemical stable > brittle
https://youtu.be/9DopxIV4Css
Space Shuttle Heat Protection
https://youtu.be/oZg3x7yy80o
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
OCW
Cement and Concrete
https://youtu.be/woaUs5XnjUo
Glass (MIT kids 5min)
brittle, crack, rapid cooling, compressive stress on surface
https://youtu.be/1VrdUYbHvyo
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
KOCW
세라믹 결정구조
http://www.kocw.net/home/cview.do?lid=0f4393f1fb61cdd3
세라믹, 유리, 탄소, 강도시험
http://www.kocw.net/home/cview.do?lid=2f87428d88f9a817
세라믹스의 분류 및 활용 http://www.kocw.net/home/cview.do?lid=a0d249cb4b34f91b
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Ceramic
Pottery Aerospace
IC Medical Cutting
• Ceramics are compounds of metallic and non-metallic(O, N, C) elements.
• Bonding between atoms is ionic or covalent .
Glass
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
• Ionic bonding, Covalent bonding.
Ceramic Bonding
SiC: Covalent
CaF2: Ionic
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Ionic Bonding & Structure
• Ionic bonding
• Ionic radius - stable structures
- -
- - +
unstable
- -
- - +
stable
- -
- - +
stable
+ - e-
ZnS
NaCl
CsCl
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
General properties of ceramics
• High melting temperature
• High hardness (wear resistance)
• Chemical stability
• Electrical & thermal insulator
• Brittle (linear elastic)
• Compression strength >> Tension (sensitive to crack)
• Low thermal expansion
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Stress-Strain (응력-변형율)
• Room T behavior is usually elastic, with brittle
failure
250
50
Str
ess (
Mpa)
0.0008 Strain
Glass
Aluminum oxide
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Porosity (기공) Strneggth (강도)
• Porosity decreases modulus of elasticity and
fracture strengths.
Volume fraction porosity
Modulu
s o
f ela
sticity (
GP
a)
Fle
xura
l str
ength
(M
pa)
0 0.1 0.2 0.3 0.4 0.5 0.6
200
100
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
• 3-point bend test to measure flexural strength &
elastic modulus.
Flexural strength(굴곡강도)
F L/2 L/2
d = midpoint
deflection
cross section
R
b
d
rect. circ.
location of max tension
• Flexural strength: • Typical values:
Si nitride
Si carbide
Al oxide
glass (soda-lime)
250-1000
100-820
275-700
69
304
345
393
69
Material s fs (MPa) E(GPa)
22
3
bd
LFffs s (rect. cross section)
(circ. cross section) 3R
LFffs
s
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Ex) Ceramic for Heat Engines
• Advantages: – Run at higher temperature
– Excellent wear & corrosion resistance
– Low frictional losses
– Ability to operate without a cooling system
– Low density
• Disadvantages:
– Brittle
– Too easy to have voids-
weaken the engine
– Difficult to machine
• Possible parts – engine block, piston coatings, jet engines
Ex: Si3N4, SiC, & ZrO2
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Classification of Ceramics
Various types of ceramics are:
• Silicon Si: Silica SiO2
• Oxids O: Alumina Al2O3, Zirconia ZrO2
• Carbides C: Tungstem carbides WC, Silicon carbide SiC
• Nitrides N: Cubic boron nitride cBN, Titanium nitride TiN, Sialon
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Silicate Ceramics(규산염 세라믹)
• Most common elements on earth are Si & O
• SiO2 (silica) : The strong Si-O bonds lead to a high melting temperature (1710° C) for this material
• Quarz(석영), Glass(유리), Clay(점토) …
SiO 4 tetrahedron 4-
Si 4+
O 2 -
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Crystalline: Quartz send(규사), Rock crystal(수정)
Non-crystalline (amorphous): Glass (유리)
Silica, SiO2
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Alumina Silicate(규산알미늄) Al2O3 SiO2 H2O
• Refractories(내화벽돌) used in high temperature furnaces.
• Clay(점토) adjacent layers are bound by van der Waal’s forces.
Al2O3%
T(°C)
1400
1600
1800
2000
20 40 60 80 100 0
alumina
+mullite mullite 3Al2O3-2SiO2
+ L
Liquid (L)
mullite + crystobalite
crystobalite+L
alumina+L
SiO2
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Oxides (산화물), O
• Excellent wear resistance (Vickers hardness 10 GPa)
• High rigidity (Young’s ratio 300GPa)
• High electric resistance (>1015Ωcm)
• White color tone
• Ex) Alumina(Al2O3) Zirconia(ZrO2)
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Alumina, Al2O3
• Powder Sintering
• Bauxite(Al2O3 H2O) Aluminum ingot
https://youtu.be/H7TuwEUAhAI
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Zirconia, ZrO2
• High melting point (2700C), Low thermal conductivity (4.0 W/mK )
• Refractories for iron casting
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Nitrides (질화물) N
• Cutting materials and hard coatings: TiN, SiN
• Hexagonal boron nitride, h-BN : a layered structure is a useful high-temperature (~900°C) lubricant
• Gallium nitride (GaN) : blue light LED
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Cubic boron nitride, CBN
• CBN is widely used as an abrasive.
• Insolubility in iron alloys at high temperatures. Tool for cutting or grinding steel alloy.
• High thermal conductivity and electrical resistivity.
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Carbides (탄화물) C
• Metal + Carbon C, Black color tone
• Tungsten carbides WC (초경) : Cutting tools
• Titanium carbide TiC : Cutting tools, CVD coating
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Silicon Carbide, SiC
• Popular abrasive
• Carbon-fiber-reinforced silicon carbide (C/SiC)is used for brake discs
• Semiconductor: MOSFET
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Diamond • SCD (Single Cristal Diamond) is covalent bonded single
crystal of Carbon C
• It is hardest in the world but decompose in air at 973 K.
• PCD (Poly Crystal Diamond) is used to cut aluminum alloys, ceramics, and stone. But it is soluble in iron alloy to give carbides.
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Graphite(흑연)
• Graphite is a layered structure of carbon C.
• Weak van der Waal’s forces between layers
• Planes slide easily over one another – low friction good solid lubricant
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Carbon nanotubes
• Sheet of graphite rolled into a tube, Ends capped with fullerene hemispheres
• It has high strength and electrical current-carrying capability.
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Limestone(석회암) CaCO3
• Application: Cement, Glass, Tile, Ceramic
• Gypsum(석고 CaSO4 H2O) board for insulation & soundproofing
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Ceramic Products
1. Structural: bricks, floor and roof tiles
2. Refractories: iron making crucible
3. Whitewares: tableware, pottery, bathroom
4. Special: implants, disk brake, bearing
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Fine particle(Quartz, Clay, Feldspar) + wet state plasticity form dry state Sintering(소결) by fire Porcelain
Porcelain (도자기)
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Powder Sintering (분말 소결)
15 m
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
• Glass is non-crystalline (amorphous) NaO2CaO6SiO2
• Some elements replaced by MgO, Al2O3 and K2O
• They are resistant to chemical attacks and ranked by
their resistance to acid, alkali or water corrosion.
Glass (유리)
Si 4+
Na +
O 2 -
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Glass vs. Glass-ceramic
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Glass Properties
• Easy processing (medium melting temperature)
• Transparent
• High hardness
• Corrosion resistance
• Fragile(brittle)
• Bulk formed glass has low strength(<40 MPa) due to microcracks on the surface, but the strength of glass fiber is about 2 GPa stronger than steel.
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
• Glasses: - do not crystallize
- change in slope in spec. vol. curve at
glass transition temperature, Tg
- transparent
- no crystals to scatter light
• Crystalline materials: - crystallize at melting temp, Tm - have abrupt change in spec.
vol. at Tm
Specific volume vs Temperature
T
Specific volume
Supercooled Liquid
solid
T m
Liquid (disordered)
Crystalline (i.e., ordered)
T g
Glass
(amorphous solid)
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
• Viscosity decreases with T
• Impurities lower Tdeform
Glass Viscosity(점도) vs. T and Impurities V
isco
sity [P
a ×
s
]
1
10 2
10 6
10 10
10 14
200 600 1000 1400 1800 T(°C)
T deform : soft enough
to deform or “work”
annealing range
Tmelt
strain point
• fused silica: > 99.5 wt% SiO2
• soda-lime glass: 70% SiO2
balance Na2O (soda) & CaO (lime)
• Vycor: 96% SiO2, 4% B2O3
• borosilicate (Pyrex):
13% B2O3, 3.5% Na2O, 2.5% Al2O3
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Brittle Fracture (취성 파괴)
• Micro cracks amplify tensile stress Low fractural
strength & tensile strength.
Fracture surface of glass rod
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
• Annealing: --removes internal stress caused by uneven cooling.
• Tempering: --puts surface of glass part into compression
--suppresses growth of cracks from surface scratches.
--sequence:
Heat Treating Glass
further cooled
tension
compression
compression
before cooling
hot
surface cooling
hot
cooler
cooler
--Result: surface crack growth is suppressed.
Ceramic
Material Science
© 2013 Su-Jin Kim, GNU
Beaker Green house glass Display cover
Products