Silicon oxycarbide foams from a silicone preceramic polymer and polyurethane

Ceramic open-cell foams were obtained from a preceramic polymer (a silicone resin) and blown polyurethanes, by pyrolysis at 1200 degrees C in nitrogen. Silicon carbide submicron powders were also added to the silicone resin to give SiOC + SiC composite foams. The morphology of the foams was dependent on the architecture of the blown polyurethanes. The crushing strength as well as the elastic modulus increased with increasing relative density, reaching values as high as 14 and 450 MPa, respectively. Some of the foams displayed an excellent thermal stability (resistance to oxidation in air and decomposition in inert atmosphere) up to elevated temperatures.