Microstructural control for strengthening of silicon carbide ceramics

Fine-grained (<1 pm) silicon carbide ceramics with high strength were obtai ned by using ultrafine (similar to 90 nm) beta-SiC starting powders and a s eeding technique for microstructural control, The microstructures of the as -hot-pressed and annealed ceramics without alpha-SiC seeds consisted of fin e, uniform, and equiaxed grains. In contrast, the annealed material with se eds had a uniform, anisotropic microstructure consisting of elongated grain s, owing to the overgrowth of P-phase on cu-seeds. The strength, the Weibul l modulus, and the fracture toughness of fine-grained SIC ceramics increase d with increasing grain size up to similar to 1 pm, Such results suggested that a small amount of grain growth in the fine grained region (<1 mu m) wa s beneficial for mechanical properties. The flexural strength and the fract ure toughness of the annealed seeded materials were 835 MPa and 4.3 MPa.m(1 /2), respectively.