Effect of additional nickel on crystallization degree evolution of expanded graphite during ball-milling and annealing

Expanded graphite (EG) and a mixture of EG and nickel (EG-Ni system) were ball-milled and subsequently annealed, respectively The products were characterized by X-ray diffraction (XRD). Raman spectra and transmission electron microscopy (TEM) After 10011 milling, the average crystallite thickness (L-c) of EG and EG-Ni system deceases from 145 to 80 and 9.6 nm, respectively, while the interlayer spacing (d(0 0 2)) increases from 0.3341 to 0 3371 and 0.3348 nm, respectively It can be concluded that ball-milling decreases the crystallization degree of EG, while the additional nickel restrains this process. For the samples ball-milled for 80 h, the disorder parameter I-D/(I-D + I-G) ratio of EG and EG-Ni system is in the range of 20.7-55 8% and 31 7-45.8%, respectively, implying that the presence of nickel is beneficial to more homogeneous ball-milling of EG When the samples after ball-milling for 80 h were annealed for 4 h, the average crystallite thickness of EG and EG-Ni system increases from 8 5 to 90 nm and from 11 8 to 15.5 nm, respectively. It is deduced that annealing improves the crystallization degree of ball-milled EG, and the additional nickel is helpful for this process (C) 2010 Elsevier B V All rights reserved