Modified ceramic structures

A shaped self-supporting ceramic matrix composite body comprising a ceramic matrix incorporating at least one preform, said preform comprising a shaped body of filler material which is capable of supporting its own weight and maintaining dimensional fidelity and interconnected porosity without any means of support located external to any surface of said preform, said ceramic matrix being disposed within at least a portion of said interconnected porosity so as to embed the filler material and said ceramic matrix consisting essentially of about 60-99 percent by weight of an essentially single phase polycrystalline oxidation reaction product consisting essentially of a material selected from the group consisting of alumina, aluminum nitride and silicon nitride, and the remainder of said ceramic matrix consisting essentially of at least one metallic constituent and interconnected porosity, wherein a second ceramic component selected from the group consisting of chromia and silica is disposed in at least a portion of said porosity, said self-supporting ceramic matrix composite body corresponding substantially in shape to the configuration of said at least one preform.