Dislocation patterns in graphite

A detailed analysis is given of the dislocation patterns observed by means of electron microscopy in graphite single crystal flakes.
It is found that the dislocations are ribbons consisting of two partials of the Shockley type separated by a strip of stacking fault. All patterns can be interpreted in a consistent way on the basis of this model and on the assumption that only small energy stacking faults occur, i.e. faults consisting of a lamella of rhombohedrally stacked material. The stacking fault energy is obtained from the width of the dislocation ribbons and from the shape of extended nodes of partials with known Burgers vector. The dependence of the width of the ribbon on the agle between the direction of the ribbon and the Burgers vector is
checked and it is shown that this can be used to determine an effective Poisson's ratio.
The possible interactions between ribbons are discussed from a theoretical point of view and compared with observed configurations.