Radiation induced defects in graphite

The Raman intensity ratio I_D/I_G for: (a) graphite-rich pencil rods irradiated using x-ray doses up to 20 Gy; (b) a restricted view of the I_D/I_G response for the same group of media, limited to x-ray doses of no more than 6 Gy; (c1 and c2) an extended group of graphite-rich media irradiated using ⁶⁰Co gamma-rays; (d) a restricted view of the I_D/I_G response for a restricted group of the media shown in (c), with ⁶⁰Co gamma-ray doses limited to no more than 20 Gy; (e) 2B graphite-rich pencil rods irradiated using 6 MeV electrons, and: (f) irradiation of a subset of the media by thermal (0.025 eV) neutrons. The fluctuation of I_D/I_G with dose for carbon-rich human hair of nominal diameter 60 μm is indicated by the dashed line in (c) and (d). The values in parentheses indicate the percentage carbon content and the surface area-to-volume ratio of samples. The data are a re-organisation of that included in the studies of Abdul Sani et al. (2020, Bradley et al. (2019, 2021), Mat Nawi et al. (2021a,b), and Lam et al. (2021) such as to illustrate three prime dependencies, viz. surface to volume ratio, carbon content, and linear energy transfer, LET. (g) and (h) are combination graphs as indicated in the key to each.