High temperature behaviour of ceramic foams from SI/SIC-filled preceramic polymers

Foams of a preceramic polymer were manufactured using a self-foaming process of a Si/SiC filled poly siloxane resin at 270°C. In a subsequent pyrolysis process at 1000°C, Si-O-C micro composite foams with a high structural isotropy, spherical cells and dense struts were obtained. The ceramic foams exhibit a high compression strength exceeding 4 MPa at a total porosity of 70-80%. The Young's modulus, shear modulus and compression strength were measured at temperatures up to 1200°C. The foams were oxidized up to 200 hours and the effect of the oxidation on the surface microstructure was examined by scanning electron microscopy. Formation of porosity in the struts resulted in a reduction of the compression strength, which, however, remained stable at prolonged oxidation treatment after 10 hours. The foams were subjected to thermal shock quenching with a temperature difference of 1100°C and 1400°C for up to 10 cycles. This treatment reduced the Young's modulus and compression strength less than 20%.