Electron microscope studies of dislocation structures in graphite

Abstract

Abstract Dislocations in a variety of single-crystal flakes of graphite (hexagonal crystal structure) have been studied by transmission electron microscopy. All the dislocations observed are parallel to the layer plane with Burgers vectors in this plane. Dislocations occurred as pairs, approximately 1000 Å apart, with Burgers vectors of the type ⅓a<101̄0> giving together a unit lattice translation of a along one of the three coplanar hexagonal axes. The area between these two partials contains a stacking fault corresponding to the rhombohedral structure discussed by Lipson & Stokes. The stacking fault energy is shown to be ~ 1/10 erg/cm2 and to be substantially independent of temperature up to 900 °C. Two interactions have been observed; one is a direct one to form a network with extended and contracted nodes and the other an indirect one between dislocations on different slip planes and due to the long-range stress fields of the dislocations. An assymmetry observed in the latter interaction can be explained by the different line tensions of edge and screw dislocations. All dislocations are glissile and no interaction leading to sessile dislocations has been found.