Processing and thermal properties of an Mo5Si3C–SiC ceramic

Abstract

Composite ceramics containing w25 vol% of the Mo–Si–C ternary compound and SiC (referred to as MS) were reaction hot pressed up to 96% relative density. The electrical resistivity of the composite processed at 2150 C decreased fromw4.60 U cm at room temperature to 4.15 U cm at 700 C. Thermal conductivity of the MS ceramics processed at 2150 C was above 100 W/m K at room temperature, decreasing to between 62 and 68 W/m K at 500 C. Using the Eucken model for thermal conductivity, the interconnected SiC phase in the MS materials was calculated to have a room temperature thermal conductivity between 160 and 170 W/m K. As compared to a baseline SiC composition, the continuous SiC in the MS materials had an average increase in thermal conductivity of w50% over the temperature range of room temperature to 500 C. This increase in thermal conductivity was attributed to the accommodation of impurities that would typically be present in SiC grains and grain boundaries (e.g., N and O) into the ternary phase.