Abstract
Silicon carbides (SiC) are considered as one of the promising candidates for structural and core materials used in fusion reactor and high temperature gas-cooled reactor (HTGR) due to its high thermal stability, and good resistance to irradiation and chemical attack. Single crystal 3C-SiC with less intrinsic defects was used to precisely characterize the radiation-induced defects in 3C-SiC. In addition, there are limited discussions related to radiation effect of SA-Tyrannohex fiber-bonded composite at high temperatures. Therefore, in this study, single crystal 3C-SiC thin film and SA-Tyrannohex SiC fiber-bonded composite were irradiated at 1000℃ to 1350℃ with 7MeV Si3+ ion to simulate the neutron irradiation in reactors. The microstructure of the irradiated SiC was examined by using high resolution transmission electron microscope (HRTEM) and spherical aberration corrected scanning TEM (Cs-corrected STEM). In irradiated single crystal 3C-SiC, high resolution images showed that the planar defects were extrinsic stacking faulted loop with changing atomic sequences and intrinsic stacking faulted loop, i.e. vacancy loop. The atomic configurations were confirmed by STEM annular bright field image. However, no void has been found in single crystal 3C-SiC due to formation of vacancy loops, vacancies releasing from surface, or too small to be visible (<1 nm). In addition, dislocation loops, voids, and edge dislocations in SA-Tyrannohex SiC fiber-bonded composite after irradiation were investigated. This SiC composite are able to suppress void growth and lower the void density after high-temperature irradiation due to its small grain size (~300 nm). Besides, larger voids (with diameter 10-40 nm) formed in alumina with preferred orientation after irradiation perhaps resulting in degradation of strength of the SA-Tyrannohex SiC fiber-bonded composite.