Abstract
Silicon carbide composites are considered as the plasma facing material in fusion reactors. Therefore, high dose neutron irradiation and helium accumulation due to emission of alpha-particles from (n,α) nuclear reaction in fusion reactor are significant issues in mechanical property. This thesis will focus on the effect of ion irradiation on void formation in different processed SiC/SiCf composites under high temperature environments. In this study, The novel SiC composite – SA-Tyrannohex SiC fiber-bonded composite was irradiated by 5.1 MeV-Si2+ and 300 keV-He+ at 1300℃ to 1500℃, respectively. The dose was up to 150 dpa and the helium accumulation concentration was 15000 appm. The microstructure evolution of irradiated SiC was examined by transmission electron microscopy. The average diameter of cavities induced by Si2+ irradiation increased both with the increasing temperature and irradiation damage, up to 2.5 nm at 150 dpa/1500℃. However, the number density of cavity was almost saturated at 50 dpa. No helium bubble was abserved in the 15000 appm irradiated sample at 1300℃ and 1500℃. Comparison to Hi-Nicalon Type-S compsite、Tyranno-SA composite and CVD polycrystalline SiC, SA-Tyrannohex fiber-bonded composite appears to has excellent resistance to cavity formation due to small grain size during Si2+ and He+ irradiation at high temperatures.