Study of Fracture Behavior of Very Fine‐Grained Silicon Carbide Ceramics

Abstract

Dense, fine‐grained silicon carbide (SiC) ceramics were fabricated by a hot‐pressing technique using pyrolyzed polycarbosilane powders. Hot‐isostatic pressing treatments were also applied to some of these hot‐pressed samples. The grainsize range of the obtained sintered bodies was from 0.2 to 1.4 μm, which was much finer than that of ordinary sintered SiC ceramics. Relationships among sintering conditions, microstructures, and fracture toughness of the obtained ceramics were investigated. A clear grain‐size dependence of fracture toughness was observed in this very fine‐grain region (0.2 to 1.4 μm). Fracture toughness showed its maximum (5.1 MPa.m 1/2 ) at the average grain size of ∼0.7 μm. Also, the fracture toughness of the samples having similar grain sizes increased with increasing relative density.