Low Thermal Expansion Coatings for Carbon/Carbon Composites

Two classes of materials are considered for low expansion protective coatings for carbon/carbon composites. They include composites containing particles which undergo allotropic phase transformations accompanied by negative volume changes with increasing temperature and anisotropic oxides which demonstrate low expansion due to microcracking. Conditions for failure of coatings by either cracking or spallation due to thermal mismatch are evaluated.