AL2O3-SIC COMPOSITES FROM ALUMINOSILICATE PRECURSORS

Al2O3 and SiC composite materials have been produced from mixtures of aluminosilicates (both natural minerals and synthetic) and carbon as precursor materials. These composites are produced by heating a mixture of kaolinite (or synthetic aluminosilicates) and carbon in stoichiometric proportion above 1550-degrees-C, so that only Al2O3 and SiC remain as the major phases. A similar process has also been used for synthesizing other composite powders having MiXtUreS of Al2O3, SiC, TiC, and ZrO2 in different proportions (all compounds together or selective mixtures of some of them), as desired. The microstructure of hot-pressed dense compacts, produced from these powders, revealed that the SiC phase is distributed very homogeneously, even occasionally within Al2O3 grains on a nanosize scale. The homogeneous distribution of SiC particles within the system produced high fracture toughness of the hot-pressed material (K(IC) approximately 7.0 MPa.m1/2 ) and having Vicker's hardness values greater than 2000 kgf/mm2.