OXIDATION BEHAVIOR OF 2D AND 3D CARBON-CARBON THERMOSTRUCTURAL MATERIALS PROTECTED BY CVD POLYLAYER COATINGS

The oxidation behavior of protected 2D or 3D carbon/carbon composites is studied. The best results are obtained with a C/C material covered by a coating composed of three layers deposited by chemical vapor deposition: a first layer of SiC, a second one of boron carbide or elemental boron and a third of silicon carbide. The oxidation resistance of such a material is improved in a large range of temperature from 450-degrees-C to 1500-degrees-C and times of 50 h or more, when the layer thickness is optimized. Even after the application of a flextural strain, the protection is maintained at T = 1300-degrees-C or 1500-degrees-C. The materials are also more airtight at room temperature before and after the oxidation tests. The mechanisms of the protection are explained with the help of the oxidation test results and morphological and chemical characterization of the oxidized samples.