Abstract: A thermal treatment process for improving thermo-mechanical properties of ceramic matrix composite materials such as silicon carbide (SiC) matrix composites is described. The treatment process removes excess silicon and/or other process-related defects from the SiC-based matrix as well as the fiber interfacial coating. This invention can be practiced with minimal strength loss for as-fabricated composites formed from high-strength continuous-length ceramic and carbon-based fibers that are functionally stable to 1600° C. and above. The invention provides a method for significantly improving composite thermal conductivity and creep resistance, and for reducing composite porosity.

Abstract: A strong and tough SiC/RBSN composite material comprises silicon fibers and a reaction bonded silicon nitride matrix. This composite material may be used at elevated temperatures up to at least 1400.degree. C.

Abstract: Alternate layers of mats of specially coated SiC fibers and silicon monotapes are hot pressed in two stages: In the first a die is heated to about 600.degree. C. in a vacuum furnace and maintained at this temperature for about one-half hour to remove fugitive binder.In the second stage the die temperature is raised to about 1000.degree. C. and the layers are pressed at between 35 MPa and 138 MPa. The resulting preform is placed in a rector tube where a nitriding gas is flowed past the preform at 1100.degree. C. to 1400.degree. C. to nitride the same.