Electron microscope study of interlamellar compounds of graphite with bromine, iodine monochloride and ferric chloride

Evidence is given of the existence of isolated dislocations in graphite-bromide and graphite-iodine monochloride, which are bounding the intercalated reactant layers. These boundary dislocations show stacking fault contrast to one side. The basal component of the Burgers vector lies along one of the three projections of the {112̄0} planes on the basal plane, compatible with the Burgers vectors of normal partial dislocations. It is therefore thought that the carbon hexagon networks on either side of a reactant layer are shifted in identical positions. Evidence is further given of a mechanism by which moving boundary dislocations leave numerous loops of occluded reactant behind on their way through the crystal. The islands of occluded reactant may account for at least part of the residual reactant retained in the crystal upon decomposition. Investigated and discussed are interactions of a boundary dislocation and a normal dislocation ribbon as well as the widening of dislocation ribbons presumably by preferential diffusion of reactant along the ribbon. The situation in the graphite-ferric chloride compound proved to be more complicated and the results not consistent. Evidence is given of isolated dislocations, which show no stacking fault contrast at one side. They separate however regions, resembling normal graphite, where normal dislocation ribbons are still present from regions where the contrast of the partials has become more diffuse, the partial dislocations assuming equidistant positions. It is therefore thought that these dislocations bound the intercalated ferric chloride layers. The widening of the contrast of the partials and their behaviour upon intercalation of FeCl₃ is interpreted as a result of the expansion of the interlayer spacing.