In situ conduction electron spin resonance, contactless conductivity and X-ray diffraction studies of HNO3 molecule intercalation into highly oriented pyrolytic graphite plates were presented. The conduction electron spin resonance line-shape, line-width, intensity and position analysis permitted the establishment of: a) individual reaction steps, b) two different intercalation mechanisms: a slow diffusion of the intercalate through faces parallel to the c-axis in the whole thickness of a sample and a relatively faster nucleation of a new phase in near surface galleries; and c) an estimate of the constant of the two-dimensional diffusion of intercalate through the sample after its insertion into highly oriented pyrolytic graphite. Each of the intercalation mechanisms was characterized by an 'induction period', in which the graphite takes up comparatively little intercalate, and by an index of the stage appearing on its own.

In Situ ESR Study of the HNO3-Intercalate Diffusion Process in Graphite Intercalation Compounds. Ziatdinov, A.M., Mishchenko, N.M.: Journal of Physics and Chemistry of Solids, 1997, 58[7], 1167-72