Preparation And Properties Of High-temperature Anti-oxidation Coatings On Carbon Materials

Carbon materials exhibit low density, high strength, strong corrosion resistanceand excellent high temperature properties, such as low coefficient of thermalexpansion under high temperature and increasing strength with growing temperaturebetween1000℃and1300℃, which make carbon materials widely used in functionalmaterials and high temperature materials area. However, carbon materials start tooxidize around400℃, then their mechanical properties will be influenced and declinewith the increasing of the weight loss which limits those applications. Therefore, inorder to make full use of those excellent performance, it is necessary to make furtherstudy on carbon materials.In this study, the silicon carbide were deposited on carbon materials by chemicalvapor deposition (CVD) with methyltrichlorosilane (MTS) as the precursor inMTS-Ar-H2system. The substrate materials were provided by a carbon fiber Co.,LTD.,including carbon slab, carbon felt and carbon/graphite composite material. In order toanalyse the effects of water bath temperature for MTS, deposition temperature anddeposition time on CVD SiC, silicon carbide on different kind of carbon substrate wereobtained under different conditions and their oxidation-resistance were investigated.The results showed that mass gain rate of coating under the conditions that waterbath temperature of60℃, deposition temperature of1000℃and deposition time of3his the biggest. X-ray diffraction analysis showed that the coating material was SiC.Oxidation test showed that the initial oxidation temperature of the coated material as:carbon slab——500℃, carbon felt——650℃and carbon/graphite composite material——700℃；The initial oxidation temperature of the substrate materials as: carbon slab——400℃, carbon felt——450℃and carbon/graphite composite material——550℃.The analysis of mass gain rate and weight loss of coated materials under differentconditions showed that SiC coating on carbon felt demonstrated good anti-oxidationproperty under the same deposition conditions, carbon/graphite composite materialtook second. This result was associated with the density and structure of the substratematerials, SiC coating could protect porous carbon materials more effectively.