SYNTHESIS AND THERMALLY-INDUCED CERAMIZATION OF A NONOXIDIC POLY(METHYLSILSESQUICARBODIIMIDE) GEL

A novel polymeric organosilicon gel with the composition [MeSi(NCN)(1. 5)](n) synthesized by the reaction of MeSiCl3 with Me3Si-N=C=N-SiMe3 i s reported. The reaction is performed without any solvent and with cat alytic amounts of pyridine and provides highly cross-linked poly(methy lsilsesquicarbodiimide) in the form of a stable non-oxidic gel with un usual low open porosity (< 1 m(2) g(-1)). The Si-C-N gel transforms to an amorphous silicon carbonitride ceramic, SiC1.1N1.6, by the thermal ly induced ceramization at 1200 degrees C in inert atmosphere (argon), The gel-derived silicon carbonitride is thermally stable up to 1450 d egrees C, The synthesis, characterization and pyrolysis behavior of th e new polyorganosilicon gel is discussed. (C) 1997 John Wiley & Sons, Ltd.