The effect of gamma ray irradiation on the structure of graphite and multi-walled carbon nanotubes

Graphite and multi-walled carbon nanotubes (MWCNTs) irradiated by gamma-rays were studied by X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The results show that gamma-irradiation improves the degree of structural order in graphite and an irradiation dose of 200 kGy is the most effective. However, gamma-irradiation decreases the degree of graphitization of the nanotubes because of the generation of defects in the carbon atom lattice and produces an amorphous structure through knock-on displacements and sputtering of carbon atoms. When the irradiation dose exceeds 200 kGy the defect dynamics change and the nanotubes are annealed. Curvature-induced strain, reduced dimensionality and a large surface area of the CNT are responsible for the difference between graphite and MWCNTs after gamma-irradiation.