ON THE OXIDATION RESISTANCE OF CARBON-CARBON COMPOSITES OBTAINED BY CHEMICAL VAPOR INFILTRATION OF DIFFERENT CARBON CLOTHS

Materials of widely differing properties were used as substrates for the preparation of carbon-carbon composites by chemical vapor deposition of carbon from a propylene-nitrogen mixture at atmospheric pressure and 750-degrees-850-degrees-C. The pyrolytic carbon yields were found to be independent of the surface area of the carbon-fabric substrate. The oxidation behavior of the composites and their individual components was studied over the entire burn-off range (0%-100%). The structure of the starting and partially reacted composites was investigated by X-ray diffraction and scanning electron microscopy. No synergistic effects were observed when the reactivities of the individual components were significantly different. It is thus concluded that a straightforward analysis of the complete burn-off profile of a composite, together with the knowledge of the structure and reactivity of the individual components, is necessary and can be sufficient for a fundamental understanding of its oxidation resistance.