Imperfections in natural graphite

Abstract

Lattice or surface imperfections in graphite may play an important role as active sites in its oxidation. Thin films of a natural graphite, Madagascar flake, examined by electron microscopy revealed the presence of flat graphite sheets whose basal planes were predominantly normal to the electron beam. Dislocations lying in the basal planes were frequently observed, the estimated mean density being 10 9/cm 2. Graphite has a high incidence of stacking faults. Basal plane dislocations frequently split into partials which bound ribbons of stacking fault, 650–1000 Å wide. If these ribbons of stacking fault occur at the same level in the film they often interact to form stable networks. From measurements of the radius of curvature of dislocation nodes, the stacking fault energy has been estimated to be approximately 0.25 erg/cm 2. Because of the fortuitous relative rotation of graphite sheets, Moiré patterns have been observed with dislocations imaged as extra inserted fringes.