SILICON-CARBIDE PLATELET SILICON-CARBIDE COMPOSITES

alpha-silicon carbide platelet/beta-silicon carbide composites have be en produced in which the individual platelets were coated with an alum inum oxide layer. Hot-pressed composites showed a fracture toughness a s high as 7.2 MPa.m(1/2). The experiments indicated that the significa nt increase in fracture toughness is mainly the result of crack deflec tion and accompanying platelet pullout. The coating on the platelets a lso served to prevent the platelets from acting as nucleation sites fo r the alpha- to beta-phase transformation, so that the advantageous mi crostructure remains preserved during high-temperature processing.