SILICON-CARBIDE PLATELET-REINFORCED SILICON-NITRIDE COMPOSITES

Different grades of high aspect ratio SiC platelets were used to reinf orce Si3N4. Dispersion of additives (4 wt % Y2O3 and 3 wt % Al2O3)was achieved by ball milling in ethanol using alumina balls, while dispers ion of platelets was done by ball milling using plastic balls. Consoli dation of the composites was carried out by uniaxial hot pressing. A s light decrease in flexural strength was measured, while significant in creases in elastic properties, fracture toughness and Weibull modulus were noted. Microstructure and crack-propagation studies as well as re inforcement mechanisms are presented.