Porosity and Strength of Silicon Carbide Foams Prepared Using Preceramic Polymers

Two types of polymeric precursors for silicon carbide (SiC) were dissolved in dichloromethane. Subsequently, between 10-80 wt% of silicon nitride (Si^sub 3^N^sub 4^) and titanium carbide (TiC) powder were added separately into the solutions to make SiC-Si^sub 3^N^sub 4^ and SiC-TiC suspensions. Cubes of polyurethane (PU) foams were soaked in precursor solution and suspensions and pyrolyzed in flowing nitrogen to produce SiC, SiC-Si^sub 3^N^sub 4^ and SiC-TiC composite foams. Some foams were heated further in nitrogen to 1600°C. Shrinkage observed after pyrolysis and further heating the foams was measured and can be reduced by varying the concentration of polymeric precursor, Si^sub 3^N^sub 4^ and TiC content. The foams produced have porosities in the range 85-96%. The average compressive strength of the foams is in the range of 1.1-1.6 MPa.[PUBLICATION ABSTRACT]