Evolution of reaction bonded SiC composite by mild oxidation: microstructure and mechanical properties

Reaction bonded silicon carbide (RBSC) ceramics were prepared by a combination of slip casting and liquid silicon infiltration, with random chopped carbon fiber as reinforcement. In this study, the influence of mild oxidation on the microstructure and mechanical properties of random chopped fiber reinforced RBSC composite has been evaluated. The results show that the mild oxidation treatment led to the formation of silica layer, the gasification of liquid silicon and the oxidation of chopped fiber. The siliconized fiber underwent an obvious volume expansion during oxidation compared with that of the RBSC matrix. Crystallization of silica occurred at 1100℃ on the material surface, and the content of cristobalite phase decreased with the increase of fiber content. Due to the microstructure evolution, a maximum fracture toughness of 5.8 MPa·m^0.5 was gained at the fiber volume fraction of 30%.