Poly[(silylene)diacetylene]/fine metal oxide powder dispersions: use as precursors to silicon-based composite ceramics

A synthetic route to silicon-based composite ceramics that employs organosi licon polymer/metal oxide precursors is described. The precursor materials were obtained by dispersing metal oxides in the poly[(silylene)diacetylenes ] 1. Subsequent pyrolysis of the dispersions above 1400 degrees C under var ious experimental conditions afforded beta-SiC-based metal carbides and met al nitrides, metal silicides and Si3N4-based composites of defined composit ions, in high ceramic yields. Under atmospheres of argon or of nitrogen, th e precursor-to-ceramic conversion involved two critical transformations: i) the thermal cross-linking of 1 leading to an irreversible encapsulation of the oxide particle inside the polymeric matrix and ii) the carbothermal re duction of the oxide constituents by the carbon resulting from the degradat ion of polymer 1 to produce either the final carbide or the final nitride u nder the pyrolysis conditions. Moreover, it is shown that the encapsulation of the oxide particles inside a reactive matrix led to the formation of pa rticle-tailored micro-scale reactors in which the reduction process took pl ace with high efficiency.