Mechanical properties of silicon oxycarbide ceramic foams

The mechanical properties of ceramic foams obtained through a novel process that uses the direct foaming and pyrolysis of preceramic polymer/polyureth ane solutions were investigated. The elastic modulus, flexural strength, an d compressive strengths were obtained for foams in the as-pyrolyzed conditi on; values up to 7.1 GPa, 13 MPa, and 11 MPa, respectively, were obtained. The strength of the foam was virtually unchanged at temperatures up to 1200 degreesC in air; however, long-term exposure at 1200 degreesC led to a mod erate degradation in strength, which was attributed to the evolution of int rastrut porosity during the oxidation of residual free carbon, as well as d evitrification of the foams struts.