Enhanced resistance to He ions irradiation damage of nanocrystalline SiC coating

This study focuses on the He ions irradiation damage resistance of nanocrystalline SiC coatings in reactors, revealing the crucial role of grain boundaries. It was found that in the nanocrystalline SiC coating, high-density grain boundaries (GBs) and stacking faults (SFs) formed a GBs-SFs network. This network preferentially captured He atoms, inhibited the nucleation and growth of He bubbles and dislocations within the lattice. Meanwhile, the decrease in He atoms within the lattice accelerates the recombination of lattice defects. Although the abundant grain boundaries lead to extensive nucleation of dislocations, they restrict the growth of dislocations. Eventually, large He bubbles, continuous gas-filled disc (CGD) type platelets, and black-spot were formed at the grain boundaries. Compared with traditional coarse-crystalline CVD-SiC, this unique defect structure remarkably reduced the hindrance to dislocation movement and enhanced the coating’s resistance to irradiation hardening. This provides key reference for the research on optimizing the in-reactor service performance of SiC through grain-boundary regulation strategies.