Microstructural and elemental evolution of polycrystalline α-SiC irradiated with ultra-high-fluence helium ions before and after annealing

Abstract

Helium atoms are the main reaction products that affect the properties of SiC, which is an important structural material used in the nuclear industry. Understanding the behaviour of helium in SiC is important for predicting the lifetimes of SiC in nuclear power systems. Unfortunately, the behaviour of SiC toward ultra-high concentrations (near 50 at.%) of helium have not been investigated extensively. In this study, polycrystalline α-SiC was irradiated with 300 keV He2+ ions at a fluence of 7.3 × 1017 He2+/cm2 at room temperature, followed by annealing at 900 ℃ and 1200 ℃, with microstructural and elemental evolution investigated using transmission electron microscopy, energy-dispersive X-ray and Raman spectroscopies. The evolution of helium bubbles, as well as C and Si clusters were investigated by molecular dynamics simulations. Significant volume swelling occurred during helium irradiation, and the material recrystallised after annealing at 900 ℃. Stacking faults and dislocation loops were observed in the recrystallised and crystalline layers, respectively. This work is expected to provide insight into the damage mechanism of SiC exposed to ultra-high-fluence He ions and will provide references for the application of SiC in future advanced nuclear energy systems.