Fabrication and mechanical properties of silicon carbide silicon nitride composites with oxynitride glass

Abstract

A microstructure that consisted of uniformly distributed, elongated beta-Si3N4 grains, equiaxed beta-SiC grains, and an amorphous grain-boundary phase was developed by using beta-SiC and alpha-Si3N4 powders. By hot pressing, elongated beta-Si3N4 grains were grown via alpha --> beta phase transformation and equiaxed beta-SiC grains were formed because of inhibited grain growth. The strength and fracture toughness of SiC have been improved by adding Si3N4 particles, because of the reduced defect size and the enhanced bridging and crack deflection by the elongated beta-Si3N4 grains. Typical flexural-strength and fracture-toughness values of SiC-35-wt%-Si3N4 composites were 1020 MPa and 5.1 MPa.m(1/2) respectively.