D AY 22: O VERVIEW OF A DVANTAGES OF C ERAMICS temperature resistance high hardness low density corrosion resistance

S PECIAL D ESIGN C ONSIDERATIONS FOR C ERAMICS brittleness difficulty of manufacture.

MaterialMelting Temperature, C NaCl801 Iron, Fe1535 Aluminum Ni based superalloy W3300 Al2O32045 SiC2500* Si3N41900* ZrO22700 Melting Temperature

MaterialLinear Thermal Exp. Coef. (cm/cm  C x 106) NaCl40 Nylon 6,6144 Polycarbonate122 Fe alloys12 Al alloys21-24 Ni based superalloy12-17 W4.5 Al 2 O SiC Si3N ZrO29-10 Thermal Expansion

Modulus of Elasticity MaterialElastic Modulus (psi x 106) NaCl6.4 Nylon 6, Polycarbonate1.9-3 Fe alloys30 Al alloys10 Ni based superalloy 30.4 W58 Al2O SiC30-70 Si3N444 ZrO220

Electrical Conductivity MaterialResistivity (ohm-m) Nylon 6, Polycarbonate10 14 Fe alloys10 -7 Al alloys10 -8 Ni based superalloy W10 -8 Al2O SiC10 9 Si3N ZrO210

Thermal Conductivity MaterialThermal Conductivity W/m-K Nylon 6,60.24 Polycarbonate0.20 Fe alloys52 Al alloys Ni based superalloy W155 Al2O SiC70-80 Si3N ZrO22-3 Graphite Diamond

Ductility MaterialFracture Toughness MPa  m Nylon 6, Polycarbonate2.2 Ni based superalloy Al alloys20-60 Fe metal ZrO27-12 SiC5-6 Si3N44-6 Al2O34-6

Strength Richerson, 1992

C OMMON S TRUCTURAL C ERAMICS silicon carbide (SiC) silicon nitride (Si3N4) zirconia (ZrO2) alumina (Al2O3)

PropertyCeralloy ECeralloy NCeralloy 147-1ECeralloy ProcessSinter Hot PressReaction Bonded Density (g/cc) Density (% Theoretical)>99.3>99.5> Flexural Strength RT Weibull Modulus Elastic Modulus (GPa) Poisson's Ratio Hardness HV(0.3) Kg/mm Fracture Toughness (MPa m1/2) Abrasive Wear Resistance Parameter *** Thermal Exp Coeff /C; Thermal Cond 25 C Thermal Shock Parameter (C)** Elecrical Resistivity (ohm- cm) 10^14 Applications Cutting Tools, Wear Components Automotive Components, Bearings, Wear Components Semiconductor Components, Wear Components Electrical Insulators, Sputtering Targets, Semiconductor Components Key Features Impact Strength, Net Shape Fabrication Strength, Hertzian Contact Strength, Structural Reliability, Net Shape Fabrication High Purity, Excellent Mechanical Properties High Purity, Net Shape Fabrication

M ANUFACTURING C ERAMICS The following methods are used to shape the ceramics. Please not that (wetted) powder is key.

S INTERING This is a process in which the small chunks of powder loose their identity, as the whole (porous) part is bonded. Temperature and often pressure are needed. Shrinkage has to be understood.

D IE P RESSING (U NIAXIAL P RESSING ) Most common and rapid for small ceramic components where speed of manufacture means more than strength and uniformity. Pressure, and densification is variable through the mold. The object will have varying properties, and maybe differential shrinkage on sintering. Hot pressing is a combination of sintering and die-pressing happening at once.

I SOTACTIC P RESSING Pressure transmitted to the powder from a compressed fluid. More uniformity, less porosity An elastomer (rubber mold) serves as the interface. Slower rate of production. Best for cylindrical shapes, eg. Spark plug. Hot isotact pressing (HIP) combines sintering and isotactic pressing.

E XTRUSION We add a plasticizing agent, which is later cooked away during sintering.

S LIP C ASTING Make a slurry by adding liquid to the powder. Pour into a porous mold. Fluid is absorbed by the mold leaving a drier layer of powder along the walls. Pour off remaining slurry, slip. Opening the mold reveals the thin-walled object. Ready to be sintered.

I NJECTION M OLDING This method holds the most promise for mass production of complex shapes as evidenced by its use in producing ceramic turbocharger rotors. A combination of 60-70% powder mixed with an organic binder to provide flow is injected into a mold. Prior to sintering, burnout of the binder must be done. Current restrictions include small wall thickness. Because of the cost of equipment, this is only cost-effective for large volumes, and for simple shapes, the dry pressing methods are more cost-effective.

R EACTION B ONDING A solid powder and a gas or liquid react during sintering to densify and bond. In Reaction Bonded Silicon Nitride, silicon powder is fired in the presence of high pressure nitrogen gas, and the reaction forms Si 3 N 4. Advantage: very low shrinkage. Disadvantage: high porosity and lower strengths.

M ORE R EACTION B ONDING Reaction bonded silicon carbide, RBSC, is made by infiltrating liquid silicon into a compact of carbon and silicon carbide. The Si reacts with the carbon to form SiC which then bonds with the original SiC particles. Pores are filled with liquid Si. Consequently, high temperature strength falls off at silicon's melting temperature. Dimensional changes with RBSC can be less than 1%. One interesting variation is to use carbon fibers rather than carbon particles.

E NGINE P RODUCTS Kyocera engine products include cam rollers, turbocharger rotors, glow plugs, cylinder liners, seals, pistons, piston pins, valve and valve guides, fuel injection parts and various custom made components made from a wide selection of advanced ceramic materials. Ceramic Piston Head and Rings Ceramic Cam Roller Ceramic Seal Assembly Ceramic Turbocharger Rotor

T EXTILE M ANUFACTURING Kyocera's wide range of ceramic materials, such as alumina, cermet, sapphire, zirconia and silicon nitride, coupled with excellent forming and finishing capabilities provides the basis for expanding the applications of ceramic textile components. Guides and Finish Tips

S EAL, P UMP AND V ALVE Kyocera seal, pump and valve products include alumina faucet discs, alumina and silicon carbide automotive water pump seals, alumina appliance seals, alumina blood seals, zirconia containment shells and various custom made components made from a wide range of advanced ceramic materials. Shafts and ValvesPump Parts

Hip implants Advantages of Ceramics Low friction Biocompatibility Compressive strength

Hip implants Disadvantage of Ceramics Low Ductility m/article/ media

A RMOR

A RMOR

THERMAL SHOCK RESISTANCE

A LUMINA Alumina is the most widely used advanced ceramic material. It offers very good performance in terms of wear resistance, corrosion resistance and strength at a reasonable price. Its high dielectric properties are beneficial in electronic products. Applications include armor, semiconductor processing equipment parts, faucet disc valves, seals, electronic substrates and industrial machine components.

S ILICON C ARBIDE Silicon carbide has the highest corrosion resistance of all the advanced ceramic materials. It also retains its strength at temperatures as high as 1400°C and offers excellent wear resistance and thermal shock resistance. Applications include armor, mechanical seals, nozzles, silicon wafer polishing plates and pump parts.

S ILICON N ITRIDE Silicon nitride exceeds other ceramic materials in thermal shock resistance. It also offers an excellent combination of low density, high strength, low thermal expansion and good corrosion resistance and fracture toughness. Applications include various aerospace and automotive engine components, papermaking machine wear surfaces, armor, burner nozzles and molten metal processing parts.

Z IRCONIA Zirconia has the highest strength and toughness at room temperature of all the advanced ceramic materials. The fine grain size allows for extremely smooth surfaces and sharp edges. Applications include scissors, knifes, slitters, pump shafts, metal-forming tools, fixtures, tweezers, wire drawing rings, bearing sleeves and valves.

S UMMARY OF M ATERIALS Hot-pressed silicon nitride (HPSN) has the strongest specific strength (strength/density) at 600 o C of any material. It has excellent thermal shock resistance. Sintered silicon nitride (SSN) has high strength and can be formed into complex shapes. Reaction-bonded silicon nitride (RSBN) can be formed into complex shapes with no firing shrinkage. Hot-pressed silicon carbide (HPSC) is the strongest of the silicon carbide family and maintains strength to very high temperatures (1500 o C). Sintered silicon carbide (SSC) has high temperature capability and can be formed into complex shapes Reaction-bonded silicon carbide (RSBC) can be formed into complex shapes and has high thermal conductivity. Partially stabilized zirconia (PSZ) is a good insulator and has high strength and toughness. It has thermal expansion close to iron, facilitating shrink fit attachments.