Structural transformations induced in graphite by grinding: Analysis of 002 X-ray diffraction line profiles

The x-ray diffraction line profiles of the 002 reflections of graphite samples ground in a ball mill for periods up to 90 hours were studied using newly developed peak analysis methods that permitted separation of overlapping peaks having different peak positions, intensities, and line-breadths. For 3.354A ≤ d002 ≤ 3.375A a continuous range of single phases characterized by symmetrical peaks of increasing breadths was observed, but peaks whose centroids fell between 3.375A and 3.55A were asymmetrical and composed of a superposition of symmetrical peaks of increasing breadths characterized by 3.375A, 3.40A, 3.44A, and 3.55A spacings. There is some indication of a phase characterized by a 3.49A interlayer spacing. These results confirm previous reports of discrete 002 spacings in carbons and disordered graphite and suggest that elemental carbon(s) are composed of mixtures of these metastable graphite phases.