Ceramic Material Science © 2013 Su-Jin Kim, GNU Ceramics ( 세라믹 ) Associate Professor Su-Jin KimSu-Jin Kim School of Mechanical Engineering Gyeongsang National University

Ceramic Material Science © 2013 Su-Jin Kim, GNU Ceramic Pottery Aerospace Memory Medical Cutting

Ceramic Material Science © 2013 Su-Jin Kim, GNU Ceramic Properties: - T m for glass is moderate, but large for other ceramics. - Small toughness, ductility; large moduli & creep resist. Applications: - High T, wear resistant, novel uses from charge neutrality. Fabrication - some glasses can be easily formed - other ceramics can not be formed or cast.

Ceramic Material Science © 2013 Su-Jin Kim, GNU Ceramics Ceramics are compounds of metallic and non- metallic(O, N, C) elements. Bonding between atoms is ionic or covalent.

Ceramic Material Science © 2013 Su-Jin Kim, GNU Classification of Ceramics Various types of ceramics are: Silicon Si: Silica SiO 2 Oxids O: Alumina Al 2 O 3, Zirconia ZrO 2 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 SiO 2 (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, SiO 2

Ceramic Material Science © 2013 Su-Jin Kim, GNU Alumina Silicate ( 규산알미늄 ) Al 2 O 3 SiO 2 H 2 O Refractories( 내화벽돌 ) used in high temperature furnaces. Clay( 점토 ) adjacent layers are bound by van der Waal’s forces. Al 2 O 3 % T(°C) alumina +mullite mullite 3Al 2 O 3 -2SiO 2 + L Liquid (L)(L) mullite +crystobalite crystobalite+L alumina+L

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 (>10 15 Ωcm) White color tone Ex) Alumina(Al 2 O 3 ) Zirconia(ZrO 2 )

Ceramic Material Science © 2013 Su-Jin Kim, GNU Alumina, Al 2 O 3 Powder  Sintering Bauxite(Al 2 O 3 H 2 O)  Aluminum ingot

Ceramic Material Science © 2013 Su-Jin Kim, GNU Zirconia, ZrO 2 High melting point (2700  C), 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 ) CaCO 3 Application: Cement, Glass, Tile, Ceramic Gypsum( 석고 CaSO 4 H 2 O) 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 General properties of ceramics Ceramics are brittle, have high compressive strength and hardness at elevated temperatures, high elastic modulus, low toughness, low density, low thermal expansion, and low thermal and electrical conductivity. 1. Mechanical properties Sensitivity to cracks, impurities and porosity Strength in tension is lower than compressive strength. 2. Physical properties Low specific gravity and have high melting temperatures.

Ceramic Material Science © 2013 Su-Jin Kim, GNU Mechanical properties Consider to be linearly elastic and 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. Low thermal conductivity and high electric resistance. Thermal expansion coefficient is lower than metals and plastics. Optical properties can be modified by varying their composition and treatment.

Ceramic Material Science © 2013 Su-Jin Kim, GNU Stress-Strain ( 응력 - 변형율 ) Room T behavior is usually elastic, with brittle failure Stress (Mpa) Strain Glass Aluminum oxide

Ceramic Material Science © 2013 Su-Jin Kim, GNU Porosity ( 기공 ) Porosity decreases modulus of elasticity and fracture strengths. Volume fraction porosity Modulus of elasticity (GPa) Flexural strength (Mpa)

Ceramic Material Science © 2013 Su-Jin Kim, GNU 3-point bend test to measure flexural strength & elastic modulus. Flexural strength( 굴곡강도 ) F L/2  = 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) Material  fs (MPa) E(GPa) (rect. cross section) (circ. cross section)

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: Si 3 N 4, SiC, & ZrO 2

Ceramic Material Science © 2013 Su-Jin Kim, GNU Glass is non-crystalline (amorphous) NaO 2 CaO6SiO 2 Some elements replaced by MgO, Al 2 O 3 and K 2 O 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 Glasses suspended Parison Compressed air

Ceramic Material Science © 2013 Su-Jin Kim, GNU Glass vs. Glass-ceramic

Ceramic Material Science © 2013 Su-Jin Kim, GNU Specific volume (1  ) vs Temperature (T): Glasses: - do not crystallize - change in slope in spec. vol. curve at glass transition temperature, T g - transparent - no crystals to scatter light Crystalline materials: - crystallize at melting temp, T m - have abrupt change in spec. vol. at T m Glass Properties 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 T deform Glass Viscosity( 점도 ) vs. T and Impurities fused silica 96% silica soda-lime glass Viscosity [Pa   s] T(°C) T deform : soft enough to deform or “work” annealing range Pyrex T melt strain point fused silica: > 99.5 wt% SiO 2 soda-lime glass: 70% SiO 2 balance Na 2 O (soda) & CaO (lime) Vycor: 96% SiO 2, 4% B 2 O 3 borosilicate (Pyrex): 13% B 2 O 3, 3.5% Na 2 O, 2.5% Al 2 O 3

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 before cooling hot surface cooling hot cooler --Result: surface crack growth is suppressed.

Ceramic Material Science © 2013 Su-Jin Kim, GNU Reference