Synthesis and characterization of balloons and porous blocks of β-SiC using silicone and urethane foam

A process to form different shapes of β-SiC was developed using precursors composed of silicone compounds and urethane foam. Two types of low molecular weight silicone, a Pt catalyst for curing, and a catalyst regulator were impregnated into urethane foam chips with different porosities and bulk densities, and cured at 200 °C for 1 h in air. Formed precursors were converted into β-SiC by pyrolysis at 1600 °C for 1–5 h in argon. Depending on the type of urethane foam, β-SiC balloons and β-SiC blocks with high porosities and low bulk densities were obtained. In addition, fine particles of β-SiC smaller than 100 nm were also obtained by crushing the blocks. For a disk formed by 5 h pyrolysis at 1500 °C, N2 gas permeability, electric conductivity, and oxidation resistance at 900 °C in air were measured. The results indicated that the disk may be used as a gas permeable heater. The process is simple, and the materials for this process are not hazardous and commercially available at low cost.