Surface morphology and microstructure evolution of IG-110 graphite after xenon ion irradiation and subsequent annealing

- Severe swelling of graphite crystallites was induced by Xe ion irradiation.
- Swelling did not cause cracking which was ascribed to irradiation-induced creep.
- Anisotropic swelling caused many more contracted pores than expanded pores.

IG-110 graphite samples were polished and irradiated with Xe ions at various fluences, then annealed at high temperatures up to 1100 °C. After irradiation, small hills were found on the polished surfaces, indicating an anisotropic swelling induced by irradiation. Around 30% swelling at a fluence of 2 × 1015 ions/cm2 was characterized using atomic force microscopy. Severe swelling of the graphite crystallites caused stresses between adjacent crystallites, but leaved no intergranular cracks on the polished surface, which was ascribed to irradiation-induced creep of graphite. The pore morphology was affected by the anisotropic swelling. We found many contracted pores but only one expanded pore, indicating a decreased porosity induced by irradiation. After annealing at 1100 °C, TEM characterization showed clearly increased lattice order and decreased width of the (002) diffraction arc, indicating the annihilation of dislocations and recovery of basal plane rotations. Annealing-induced recrystallization of damaged graphite led to recovery of the crystallites' swelling and many small cracks appearing on the samples' surfaces.