Study on Thermophysical Properties of Partially Oxidized Polymer Derived SiC Composites

Abstract

SiC ceramics were synthesized by polymer derived method and microwave sintering processes. The as-produced SiC composites were developed by oxidizing the amorphous Si-C raw materials derived from a polymer precursor polycarbosilane. The products analyzed by X-ray diffraction (XRD), Fourier transmittance infrared spectroscopy (FTIR), and electronic microscopye consist of excess free carbon, β-SiC and SiO2 produced by the partial oxidation of amorphous Si-C on the surface of the starting particles. The thermophysical properties of the partially oxidized SiC composites were investigated by measuring the thermal diffusivity, the specific heat and thermal conductivity. The amount of SiO2 increased as the sintering temperature is increased, resulting in a reduction of thermal diffusivity and an increase of density due to improved liquid phase sintering of SiC particles. The thermal conductivity of samples decreased, instead of increased, as the sintering temperature was increased from 1100 °C to 1200 °C. The sample dwelled at 1200 °C, in this study, has highest density and a relatively low thermal conductivity, slightly over 0.7 W/(m·K) at room temperature.