Advanced engineering materials at high temperatures

Materials that are available at the present time for use as engineering components are highly limited in their performance at temperatures above about 1000°C in corrosive environments. There is probably no satisfactory material for service in air above 1400°C and there is only a restricted selection of materials in view including silicon nitride based materials, silicon carbide based materials, and carbon–carbon–silicon carbide composites. This article summarizes the findings of several recent workshops concerned with high–temperature engineering ceramics, and covers nitrogen ceramics, ceramic–ceramic composites, ceramic coatings, Zr02–based ceramics, non–oxide ceramics, ceramic toughening mechanisms, and the microstructure and processing of engineering ceramics. Progress towards improved ceramic properties is not automatic, and many severe problems remain. Developments are needed in: oxidation resistant coatings for carbon–carbon composites, and for super alloys; particulate dispersants of controlled morphology suitable for Si3N4–based and SiC–based materials; high–stability fibres with non–reactive interfaces in refractory matrices; sintering mechanisms of monolithic and of composite ceramics; other high–temperature materials such as borides, silicides, carbides; detection of small flaws in ceramics; data on the mechanical properties of ceramics at temperatures above 1400°C; other methods of preparation of ceramic microstructures; ceramic toughening mechanisms and their interactions.