Effect of implanted helium on thermal diffusivities of SiC/SiC composites

Taguchi, Tomitsugu; Igawa, Naoki   ; Jitsukawa, Shiro; Shimura, Kenichiro

SiC/SiC composites are one of the candidate materials for first wall in a fusion reactor because of their high strength at high temperature and low residual radioactivity after irradiation. In the fusion reactor, these materials are required to have high thermal diffusivity for heat exchange and reducing the thermal shock. Under fusion conditions, helium (He) and hydrogen (H) are produced in SiC. In this study, the effect of He ions implantation on the thermal diffusivities of SiC and SiC/SiC composite were investigated. In the results, the thermal diffusivities of SiC and SiC/SiC composites decreased after He ions implantation. However, the thermal diffusivities of SiC and SiC/SiC composites hardly reduced in the operation temperature of fusion reactor. The thermal diffusivities of He implanted specimens were partly recovered by annealing. The defect concentration induced by He implantation, X, in SiC/SiC composites was estimated. The X rapidly decreased around 500 C. The reason is that the He release from SiC starts at 500 C.