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Description
This study investigates the effects of helium (He) co-implantation and swift heavy ion (SHI) irradiation on the structural evolution and migration behaviour of silver (Ag) in polycrystalline silicon carbide (SiC), followed by thermal annealing. SiC samples were first implanted with 360 keV Ag ions at room temperature to a fluence of 2 × 10¹⁶ cm⁻², producing significant amorphization. A subset of these samples was subsequently co-implanted with 17 keV He ions at 500 °C to a fluence of 1 × 10¹⁷ cm⁻², inducing partial recrystallization and forming helium nanobubbles. All samples were then irradiated with 167 MeV Xe ions at room temperature to a fluence of 1 × 10¹⁴ cm⁻², followed by annealing at 1000 °C for 5 hours. SHI irradiation further modified the microstructure. Ag-only samples exhibited partial recrystallization, indicating effective defect recovery, whereas He co-implanted samples showed more limited recovery, demonstrating that helium suppresses defect annealing under irradiation. He implantation also generated surface whiskers, which decreased in height after irradiation, suggesting partial surface healing. No measurable Ag migration occurred during He co-implantation or SHI irradiation. After annealing, helium release, enhanced atomic mobility, and cavity shrinkage produced a denser population of smaller, more uniform cavities that act as effective Ag trapping sites. In He co-implanted samples, bubble growth and coalescence influenced recrystallization kinetics, serving both as defect sinks and barriers to full recovery. Ag in both sample types shifted toward the SiC bulk, likely driven by stress fields formed during annealing. While Ag loss was negligible in Ag-only samples, He co-implanted samples showed noticeable Ag loss, and surface modifications associated with helium release became more pronounced. These results underscore helium’s significant role in governing defect evolution, cavity development, silver behavior, and the thermal stability of SiC, with important implications for fission-product retention and the performance of TRISO fuel.
| Apply for student award at which level: | PhD |
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| Consent on use of personal information: Abstract Submission | Yes, I ACCEPT |