Abstract: SiC fiber reinforced SiC matrix composites (SiC/SiC composites) are considered as one of the promising structural materials for liquid type breeding blanket in the fusion energy system. The transmutation gas production rate in fusion reactor is significantly higher compared with fission reactors. An innovative method combining in-situ irradiation and TEM observation and MD simulation was utilized to evaluate the synergetic effects of helium and irradiation on SiC/SiC composites. A comprehensive experiment matrix including Kr irradiation, He pre-implantation with sequential Kr irradiation as well as simultaneous dual beam at 1073 K to 16 dpa and 2400 appm He (150 appm/dpa) was performed using 800 keV Kr and 50 keV He ions. With the support of MD results, the impact of relative concentration ratio of vacancies and helium atoms on the bubble evolution was systematically investigated and the corresponding mechanism was further unraveled, which provides the basis of limiting the bubble density in SiC/SiC composites. Additionally, the direct evidence for the competition of irradiation-assisted bubble growth and re-dissolution was in-situ observed in SiC matrix for the first time.

Key words: SiC, In-situ, Irradiation, TEM, Bubble, Molecular dynamics simulation