Structural irradiation damage and recovery in nanometric silicon carbide

Silicon carbide is one of the candidate materials for core components of some nuclear reactor projects (Gen-IV). In order to improve their thermo-mechanical properties, materials with nanometric grain size are considered. For such materials, nearly no data concerning their behaviour under irradiation are available. In this paper, we study the damage and subsequent recovery of a nanostructured 3C-SiC ceramic. Samples were irradiated at room temperature with 4 MeV Au ions and subsequently annealed. Their structural modifications are analysed with a grazing incidence X-ray diffraction method. Results show that these nanoceramic materials present the same damage kinetics during irradiation as conventional micrometric grained SiC, with total amorphisation at the highest fluence. However, while the recrystallisation of a conventional ceramic is expected to occur through an epitaxial recrystallisation from the non-damaged parts of the large grains, the nanometric material is healed only after annealing at 1000 °C through mechanisms that can be attributed to a heterogeneous nucleation and growth of β crystallites in the totally amorphised grains