In situ ESR study of the HNO 3-Intercalate diffusion process in graphite intercalation compounds

Abstract

In situ conduction electron spin resonance (CESR), contactless conductivity and X-ray diffraction studies of HNO 3 molecule intercalation into highly oriented pyrolytic graphite (HOPG) plates are presented. The CESR lineshape, linewidth, intensity and position analysis allow us to establish: 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; c) an estimate of the constant of the two-dimensional diffusion of intercalate through the sample after its insertion into HOPG. Each of the intercalation mechanisms is 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.