Synthesis of silicon carbide from polysilanes: effect of hydrosilane and vinyl groups

Several chlorosilane monomers were used to synthesise 18 different co- and ter-polysilanes. The soluble solid fraction of these polymers,which are pot ential precursors for ceramics, has been characterised by gel permeation ch romatography ann Fourier transform-infrared spectroscopy. The ter-polymer p recursors, some of which can be synthesised with high yields (70 wt-%), sof ten below 100 degrees C and can be melt processed. The precursors have been pyrolysed in nitrogen to 900 degrees C to determine the ceramic yield whic h was dependent on the composition of each polysilane. Further hearing to o ver 1100 degrees C produced crystalline silicon carbide. Possible reaction mechanisms involved in the pyrolysis process are presented. Some of the ter polymer precursors synthesised with high yields also gave silicon carbide y ields close to the maximum theoretical values obtainable. BCT/314.