Processing of Reaction-Bonded Silicon Carbide Without Residual Silicon Phase

Reaction-bonded silicon carbide free of the residual silicon phase that has previously limited upper use temperatures and mechanical properties has been synthesized by the infiltration of carbonaceous preforms using alloyed silicon melts. In this approach, rejection of the alloying components from the primary reacted silicon carbide phase into the remaining liquid forms a secondary refractory silicide, in a potentially broad and controllable range of volume fractions. Dense SiC-MoSi/sub 2/ materials free of residual silicon and residual carbon have been synthesized. In addition to a fully-infiltrated monolith, surface coatings on a carbon body have been synthesized by control of processing parameters. In each, the absence of free silicon and incorporation of the secondary phase is expected to improve mechanical properties. 14 references.