PREPARATION OF CARBON MATERIAL WITH SIC-CONCENTRATION GRADIENT BY SILICON IMPREGNATION AND ITS OXIDATION BEHAVIOR

A carbon material with SiC-concentration gradient was prepared by a silicon impregnation process. In order to prepare the carbon material with a SiC-concentration gradient without any adhesion of metallic silicon, the weight of silicon powder per physical surface area of the carbon substrate was in the range of 3.9-4.1 g cm(-2) and then heating the carbon substrate in silicon powder at 1450 degrees C for 3 h, but the amount of silicon powder beyond this range resulted in the adhesion of metallic silicon. The concentration of SiC along the thickness in the sample obtained decreased rapidly up to 0.5 mm gradually in a range of 0.5-1.0 mm. A remarkable improvement in the oxidation resistance was observed on the sample with a SiC-concentration gradient at 1400 degrees C, which was due to the formation of a protective film of SiO2 glass on the surface. In the results of the thermal shock test in the sample, no destructions and no cracking of the samples were observed.