Processing of Al2O3SiC composites in aqueous media

Abstract Two processing routes for the composite system Al 2 O 3 SiC (SiC content ranging from 2.5 to 25 vol%) in water have been developed, using SiC powder with a chemically modified surface. For each system, slurry properties were optimised by measuring adsorption isotherms and rheological behaviour. Slurries with high solid loadings (47 vol%) and homogeneous SiC distribution could be realised. Green bodies of high densities (up to 62% of theory) for various SiC contents were prepared by slip casting into a porous mould and drying in air. Pressureless sintering was conducted under different atmospheres (N 2 or Ar) and temperatures (1690 to 1950 °C). Sintering conditions to obtain high densities strongly depend on the SiC content and on the processing route of the composite. Best results for one processing route were obtained for 10 and 15 vol% SiC samples, each reaching densities of 97.5% of theory when sintered for 1 h in N 2 at 1880 °C. A sample prepared by the other developed system, containing 5 vol% of SiC could be densified up to 98.2% of theory when sintered for 1 h in N 2 at 1800 °C.