THE STRUCTURE OF GRAPHITIC MATERIALS -4.

The report discusses electron microscopic observations on synthetic graphite materials in both the ungraphitised and graphitised forms heated at 2,500C after various heat treatments and high temperature creep deformations. Moire fringe effects were reconciled with a turbostratic structure in which grains of graphite are subdivided into stacks of crystallites which are narrow in their c-direction and have small angular rotations in their respective basal planes. Electron diffraction patterns from this structure showed ring effects when the layer structure was normal to the electron beam, and elliptical effects when the beam was not normal to the layers. As the heat treatment temperature is raised the diffraction rings or ellipses become progressively spotty as the crystallites grow and minimise their misorientation in the basal planes, until finally, after heat treatment at 2,850C, single crystal spot patterns are observed indicating that either the misorientations almost disappeared or the crystallite size increased greatly. Author