Thermal properties of polycarbosilane derived porous silicon carbide composites

Sub-micron sized silicon carbide powders mixed with a liquid polycarbosilane as binder can be cold pressed, cured and pyrolzyed to form silicon carbide composites without the use of sintering aids or solvents. We have surveyed a variety of powder types, sizes and size distributions and several modes of mixing, pyrolyzing and re-infiltrating to develop composites with useful thermal and mechanical properties. This paper describes the preparation of these formulations and reports their thermal properties (coefficient of thermal expansion, thermal diffusivity and thermal conductivity) to 1000°C as well as mechanical properties at ambient and elevated temperatures. The thermal results are compared with those of amorphous SiC prepared from pure polycarbosilane.