Processing of preceramic polymer to low density silicon carbide foam

A method is described here for preparing lightweight and low cost polymer-derived silicon carbide foam by impregnation of preceramic polymer in polyurethane foam. A series of silicon carbide foams with various density (0.035–0.35 g/cm3), porosity (87–98%) and thermal conductivity (0.05–0.12 W/m·K) were prepared using allylhydropolycarbosilane as a base material. Surface analysis shows that the resultant foams have an open and interconnected porous structure. Phase analysis shows that it has cubic crystal structure. There was no evidence of cracks or damage even after treating the silicon carbide foamwith concentrated hydro!uoric acid for 12 days. Fromthe oxidation resistance experiment, it can be concluded that the silicon carbide foamis stable up to 1500 °C in air and 2000 °C in argon.