Microstructure of Reaction-Bonded Silicon Carbide including Molybdenum Disiliside

Abstract

Residual silicon in the reaction-bonded silicon carbide (RBSiC) can be replaced by refractory MoSi₂ by using Si-Mo alloy as infiltrants instead of pure Si. Transmission electron microscopy of these materials clarified the following results. The MoSi₂ existed in the SiC grain boundaries and many fine grains of SiC were found in the MoSi₂ phase. The carbon particles were thought to be dissolved into the Si melt including Mo and reprecipitated as SiC particles in the solution-reprecipitation mechanism. The Mo concentration in the Si-Mo melt increased with the reprecipitation of SiC particles, and the MoSi₂ was precipitated in the grain boundaries. The presence of the fine SiC particles in the MoSi₂ phase suggests that the carbon have a fairly strong interaction with silicon in the melt and diffuse not as isolated atoms, but as C-Si pairs.