Microstructure and defect evolution of nuclear graphite under temperature-dependent ion irradiation

Abstract

Nuclear graphite plays a vital role in GEN-IV reactors and is expected to function in the harsh environments such as high temperature and high-dose irradiation. The ion irradiation behaviour of ET-10 nuclear graphite in comparison with highly orientated pyrolytic graphite (HOPG) was reported in this work, to explore the combined effects of ion irradiation and temperature. Ion irradiation experiments were carried out using 190 keV H+ and 1.8 MeV Ar+ at different doses. SRIM simulation, scanning electron microscopy (SEM) and Raman spectroscopy were employed to characterize the microstructural changes and defect evolution of graphite specimens under different irradiation conditions. The vein structure in HOPG graphite and the vertical scale-like structure in ET-10 graphite caused by ion irradiation were observed. The effects of temperature on ion irradiation could be divided into two stages of recovering and saturation according to mutual analysis of SEM and Raman. It was also found that the recovery degree of the half-width at half maximum (HWHM) for the G band was greater than that of ID/IG, probably because the deformed or ruptured graphite layers were difficult to recover at rising temperatures and/or could even be enhanced. HWHM(G), ID/IG, and La was comprehensively discussed, giving an overall perspective of defect evolution and crystallite size changes under temperature-dependant ion irradiation.