Structural Transformation in Pyrolytic Graphite Accompanying Deformation

Electron microscopy and x-ray diffraction techniques have been used to follow the structural changes which accompany deformation in one lot of pyrolytic graphite when stress is applied parallel to the substrate direction. Basal slip and an increase in preferred orientation account for deformations up to 20%. Fracture across the basal planes with subsequent basal slip and an increase in porosity and a very slight increase in preferred orientation account for deformations above 20%. Rows of etch pits which may be dislocations parallel to the substrate direction were observed in a specimen heated without load to 3000°C.