chapt11_ceramics - Properties:-- T m for glass is moderate,...

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Unformatted text preview: 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.-- porosity in ceramics tends to lower strength and thermal conductivity Glasses Clay products Refractories Abrasives Cements Advanced ceramics-optical -composite reinforce -containers/ household-whiteware -bricks-bricks for high T (furnaces)-sandpaper -cutting -polishing-composites -structural engine -rotors -valves -bearings-sensors Taxonomy of Ceramics Need a material to use in high temperature furnaces. Consider the Silica (SiO 2 ) - Alumina (Al 2 O 3 ) system. Phase diagram shows: mullite , alumina, and crystobalite as candidate refractories. (adapted from F.J. Klug and R.H. Doremus, "Alumina Silica Phase Diagram in the Mullite Region", J. American Ceramic Society 70 (10), p. 758, 1987.) Application: Refractories Composition (wt% alumina) T(C) 1400 1600 1800 2000 2200 20 40 60 80 100 alumina + mullite mullite + L mullite Liquid ( L ) mullite + crystobalite crystobalite + L alumina + L 3Al O -2SiO tensile force A o A d die die Die blanks:-- Need wear resistant properties! Die surface:-- 4 m polycrystalline diamond particles that are sintered onto a cemented tungsten carbide substrate.-- polycrystalline diamond helps control fracture and gives uniform hardness in all directions. Courtesy Martin Deakins, GE Superabrasives, Worthington, OH. Used with permission. Adapted from Fig. 11.8 (d), Callister 7e . Courtesy Martin Deakins, GE Superabrasives, Worthington, OH. Used with permission. Application: Die Blanks Tools:-- for grinding glass, tungsten, carbide, ceramics-- for cutting Si wafers-- for oil drilling blades oil drill bits Solutions: coated single crystal diamonds polycrystalline diamonds in a resin matrix....
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This note was uploaded on 07/07/2010 for the course CHEM 3302 taught by Professor ... during the Spring '10 term at University of Minnesota Morris.

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chapt11_ceramics - Properties:-- T m for glass is moderate,...

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