Applications of Ceramics 1. Structure and Properties tThe compressive strength is typically ten times the Structure: A crystalline material but more complex or n amorphous material tRansparency to light of some ceramics optical pplications(windows, photographic cameras, telescopes Mechanical Properties: .Slip does not occurs in ceramics: thus, brittle .Good thermal insulation use in ovens. the exterior tiles of the Shuttle orbiter etc. contains imperfection such as vacancies, interstitials, Good electrical isolation ceramics are used to isplaced atom and microcrack mIcrocracks make support conductors in electrical and electronic tension pplications. .Strengthening methods: uniform, smaller grains, Good chemical inertness applications in reactive minimizing porosity, inducing residual stress, reinforcement. heat treatment environments Plastic deformation in ceramics 2 Traditional ceramics CRystalline ceramics: Slip dislocation motion is fficult since ions of like charge have to be brought e Fired clay cement and natural abrasives based on silicates silica and mineral oxides. to close proximity large barrier for dislocation motion. Ceramics with covalent bonding slip is also Being able to fire the powder and water t easy: covalent bond strong ceramics brittle . Noncrystalline ceramie there is no regular Raw materials: kaolinite, silica (quartz is one form), bauxite (a pure form is corundum deform by viscous flow, i.e. by breaking and reforming silicon carbide other (like in a liquid) pOttery and Tableware viscosity is measure of glassy materials resistance to deformation 3 New Ceramics New Ceramics ISynthetic-Oxides, carbides, nitrides, borides and oxynitride (SiAlON) m Carbides OXides SiC, wC, TiC, TaC, Cr Cg- Alumina (Aluminum oxide)(AlO, w SiC- traditional ceramics used as abrasives powders from gOod hot hardness. Low thermal conductivity wolframite and scheelite corrosion resistance 9 TiC- Carburizing rutile or ilmenite aAbrasive electrical insulator bioceramics. cutting e TaC- Carburizing tantalum powders or tantalum +Zirconia(Zirconium oxide) t Chromium carbides-Carburizing chromium oxides Silica (SiO,)11 The compressive strength is typically ten times the tensile strength. Transparency to light of some ceramics Þ optical applications (windows, photographic cameras, telescopes, etc) Good thermal insulation Þ use in ovens, the exterior tiles of the Shuttle orbiter, etc. Good electrical isolation Þ ceramics are used to support conductors in electrical and electronic applications. Good chemical inertness Þ applications in reactive environments. Applications of Ceramics 1. Structure and Properties Structure: A crystalline material but more complex or an amorphous material Mechanical Properties: Slip does not occurs in ceramics: thus, brittle. contains imperfection such as vacancies, interstitials, displaced atom and microcracks. Microcracks make ceramics weaker in tension. Strengthening methods: uniform, smaller grains, minimizing porosity, inducing residual stress, reinforcement, heat treatment Crystalline ceramics: Slip dislocation motion is difficult since ions of like charge have to be brought into close proximity ® large barrier for dislocation motion. Ceramics with covalent bonding slip is also not easy: covalent bond strong Þ ceramics brittle Non-crystalline ceramic: there is no regular crystalline structure ® no dislocations. Materials deform by viscous flow, i.e. by breaking and reforming atomic bonds, allowing ions/atoms to slide past each other (like in a liquid). Viscosity is measure of glassy material’s resistance to deformation. Plastic Deformation in Ceramics 2 Traditional Ceramics Fired clay, cement and natural abrasives based on silicates, silica and mineral oxides. Being able to fire the powder and water mixture. Raw materials: kaolinite, silica (quartz is one form), bauxite (a pure form is corundum), silicon carbide Types Pottery and Tableware Brick and tile Refractories Abrasives 3 New Ceramics Synthetic - Oxides, carbides, nitrides, borides and oxynitride (SiAlON) Oxides Alumina (Aluminum oxide) (Al2O3 ) Produced synthetically from bauxite Good hot hardness, Low thermal conductivity corrosion resistance Abrasive, electrical insulator, bioceramics , cutting tool, spark plug etc. Zirconia (Zirconium oxide) Silica (SiO2 ) New Ceramics Carbides SiC, WC, TiC, TaC, Cr3C2 . SiC –traditional ceramics, used as abrasives. WC –Carburizing tungsten powders from wolframite and scheelite TiC –Carburizing rutile or ilmenite TaC - Carburizing tantalum powders or tantalum pentoxide Chromium carbides - Carburizing chromium oxides