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Description
This study explores the effect of heat treatment and helium (He) bubbles on the structure of SiC and the migration behaviour of silver (Ag) in SiC. Ag ions were implanted into two polycrystalline SiC substrates (Ag-SiC), and one of the Ag-SiC samples was also co-implanted with He ions (Ag + He-SiC); both implantations were carried out at 350 °C. The samples were then annealed sequentially from 1000 °C up to 1300 °C in steps of 100 °C for 5 hours. The implanted and subsequently annealed samples were characterized using Raman spectroscopy, transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), and atomic force microscopy (AFM). Both the single and dual implanted samples accumulated defects, while the SiC structure remained relatively crystalline. Helium implantation led to the formation of bubbles along the projected range. These bubbles appeared as surface blisters, and their exfoliation created holes, resulting in cavities in the highly defective region underneath the surface. Annealing the Ag-SiC and Ag+He-SiC samples restored most of the SiC crystal structure; however, successive annealing caused an increase in hole density. Consequently, larger cavities that facilitated He out-diffusion resulted in loss of Ag. These cavities also trapped Ag precipitates, leading to Ag retention within the SiC. These findings provide valuable insights into the mechanisms of Ag migration in SiC, which are important for enhancing the safety of nuclear fuels.
