Thermal tests on B4C-overlaid carbon fibre reinforced composites under disruption heat load conditions

Abstract

Abstract High heat flux experiments (550–1600 MW m−2, 2–10 ms) in the JAERI electron beam irradiation system (JEBIS) were carried out on B4C-overlaid carbon fibre reinforced composites (CFCs), on which the B4C was overlaid with a thickness of 50–800 μm by using three coating methods, chemical vapour reaction (CVR), low pressure plasma spraying and chemical vapour deposition. Investigations were made with respect to changes of weight, surface morphology, surface atomic composition and crystal orientation of B4C. Severe exfoliation and large weight losses of the B4C layers were observed in the samples except for the sample produced by the CVR method. Weight losses of the samples increased with the heat flux under the identical absorbed energy. A preferential evaporation of boron was observed only in the melted area of the B4C under lower heat flux conditions (550 MW m−2, 5 ms), the evaporated thickness was a few micrometres. However, under higher heat flux conditions (1600 MW m−2, 2 ms), the atomic ratio of the boron to carbon did not change. The present results suggest that the B4C-overlaid CFCs produced by the CVR method can be applied to the divertor materials of JT-60U.