Structure and chemical reactivity of ball-milled graphite

Nanostructured carbon powders are prepared from graphite powder in a planetary mill using WC, stainless steel, and agate milling tools. The evolution of microstructure and chemical reactivity is studied by X-ray diffraction and combustion methods,, respectively. The specific surface area of milled samples is determined by BET measurement and the impurity content is estimated by spark source mass spectroscopy There is no monotonous relationship between reactivity and specific surface area of particles and agglomerations of particles. In contrast to impurity contents, distortion of atomic short- and medium-range order is shown to be essential for the observed enhancement of chemical reactivity. A statistical model for the milling process is formulated and used to discuss the experimental data. As a result, an expression for the dependence of combustion temperature on milling time is proposed.