HIGH HEAT LOAD EXPERIMENTS FOR SIC AND B4C COATED GRAPHITE

Bulk boronized graphites and SiC converted CFC were irradiated by an electron beam with a heat flux ranging from 2 to 6 MW/m(2) for a time period up to 120 s in ACT of NIFS. The surface temperature was observed to be as high as 2600 degrees C. The evaporation amounts of metal and carbon contents were measured by a weight loss method. The depth composition profile and surface morphology before and after irradiation were also examined. The boron content largely evaporated at a temperature higher than about 1700 degrees C. The evaporation rate of boron was observed to rapidly increase both with boron concentration and surface temperature. After the boron evaporation, the evaporation of the carbon occurred at a temperature higher than 2000 degrees C. For the SiC converted CFC, the silicon largely evaporated at a temperature above 1500-1600 degrees C. The present results show that both the bulk boronized graphite and the SiC converted CFC should be used in an environment with a relatively low temperature, less than 1500-1700 degrees C.