Processing of ceramic foams from polymeric precursor-alumina suspensions

A polysilane was used as the precursor for silicon carbide (SiC) and differ ent amounts of it was dissolved in dichloromethane. Subsequently, between 1 0 to 80 %wt of alumina (Al2O3) powder was added into the solutions to make SiC-Al2O3 suspensions. Cubes of polyurethane (PU) foams with open cells in the size range 500-1200 mum were soaked in these suspensions and pyrolysed in flowing nitrogen to produce SiC-Al2O3, composite foams. Some foams were heated further in nitrogen to 1300 C. The foams produced consist of an open cell structure and hole-free solid struts which were also cracks free in t he polysilane-Al2O3 80:20wt% formulation. The retention of shape during pro cessing was excellent. Shrinkage observed after pyrolysis and further heati ng the foams was measured and can be controlled by varying the Al2O3 conten t. The foams produced have porosities in the range 87 to 95%. The maximum c ompressive strength of the pyrolysed foams prepared using the polysilane-Al 2O3 80:20 wt% formulation was 2.3MPa.