Methods for making ceramic matrix composites using precursor polymers to refractory metal carbides and metal borides

The present invention provides a method for making a ceramic matrix composite comprising forming an infiltrated fiber reinforcement by infiltrating a plurality of plies of a fibrous material with a precursor polymer which decomposes to a substantially pure product selected from the group consisting of a refractory metal carbide and a refractory metal boride, and exposing the infiltrated fiber reinforcement to conditions effective to cure the precursor polymer and to decompose the precursor polymer to said substantially pure product.