Reduction of deuterium permeation through SiC/SiC composites by plasma-spray deposited eutectic Al-Si

This paper deals with the formation of a deuterium permeation barrier on SiC/SiC composites, proposed as low activation structural materials for the first wall of a fusion reactor. An Al-11.22 mass% Si eutectic layer has been applied to SiC/SiC substrate by a plasma spraying process and subsequently heat treated to maximize the interfacial bond strength. Permeation measurements were performed in the temperature range 300-750 K using deuterium at pressures in the range 0.5-150 kPa. A linear dependence of permeation rate on pressure was measured. The efficiency of the coating as a deuterium permeation barrier is discussed in terms of the heat treatment temperature. The best result was achieved by heat treating the sample (SiC/SiC + Al-11.22 mass% Si) at 933 K for 2 hours.