HIGH-TEMPERATURE OXIDATION BEHAVIOR OF CARBON MATERIALS IN AIR

The features of high-temperature oxidation in air of different home-produced carbon materials (pyrolytic carbon, carbon fibres and coatings and carbon-based composite materials) have been analyzed. It has been determined that the oxidation rates of carbon materials in air at temperatures of up to 800-degrees-C can differ rather greatly which is conditioned by peculiarities of their production technology, differences in porosity and density, degree of carbon graphitization in the samples, etc. In all cases the oxidation mechanism is determined by the nature of carbon-carbon linkages. The low-temperature region (up to 800-degrees-C) is kinetic in which the surface reaction rate of oxygen with carbon is limited. For the high-temperature region of the process, the slight dependence of the rate on temperature is typical. In the case of presence of silicon-bearing protective coatings on the carbon materials, the oxidation process depends on the mass transfer of oxygen and carbon oxides through a barrier layer of SiC and SiO2.