Abstract
Oxidation behavior of LaB6-coated C/C composites heat-treated at 500°C and 2000°C was investigated. LaB6 began to oxidize at about 500°C and converted completely to the oxides at about 1300°C. In the flowing air, LaB6 converted to the stable oxides that were not catalytically active to the oxidation of the C/C composites. In case of soot treatment, LaB6 showed effective resistance against oxidation and this effect extended above 1000°C. In case of 2000°C treatment, the diffusion of lanthanum and boron on the surface of the C/C composite was detected by energy dispersion X-ray analysis. By X-ray quantitative analysis, it was suggested that the diffusion of lanthanum and boron enhanced the ordering of graphitic structure of carbon and lowered the active sites in the C/C composites. A particular effect of oxidation resistance was illustrated by oxidation kinetic analysis.
