The effects of 5 MeV carbon ion irradiation on micro-fine grain graphite

5 MeV carbon ion irradiation effects on micro-fine grain graphite samples are investigated. The X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscope (FESEM), and high-resolution transmission electron microscope (HRTEM) are used to study changes due to irradiation. At a dose of 0.5 dpa, the isolated defects (monovacancies) were generated with a low density within graphitic regions, which contribute considerably to the sharp reduction of graphitic amount in irradiated material but insignificantly to the activation of Raman disordered band. HRTEM images show the accumulation of these defects in clusters between (002) basal planes leading to the increase of lattice parameter and d-spacing in c-direction. Samples irradiated with a dose of 1 dpa initiate an annealing process in the material resulting in defects annihilation. The enhancement of the graphitization degree is obviously correlated with the reduction of disordered material. After irradiation of high dose (3–5 dpa), the high concentration of defects leads to the formation of stable planar V₆ rings. These rings are found to survive even at the higher temperature, but the graphitization degree remains nearly unchanged.