Graphite microstructure and implications for thermal applications

Graphite has been of interest in thermal applications for many decades, due to its comparatively high thermal conductivity and other useful physical properties. Recently, studies on graphene have started to reveal the true potential of two-dimensional sp2 carbon as a thermal conductor. However, practical, high purity, graphitic materials do not achieve the high values of thermal conductivity predicted and measured for graphene. The reason for this is known to be a combination of various effects, including graphite crystallinity and microstructure. While Raman spectroscopy and X-ray diffraction offer a means to estimate crystallite sizes in the nanometre range, techniques for analysing large crystals are limited. Due to the planar nature and covalent bonding of graphite, attack by oxygen is only possible at the exposed edges and crystal defects. Thus a mild oxidative treatment provides insights into the microstructure and underlying crystallinity of different graphitic materials. An extremely wide variety of graphitic materials are currently produced on an industrial scale. Through an understanding of the production processes and insights provided by oxidative studies the bulk performance of these materials can be understood. In addition, possible production routes can be identified which may yield materials of superior crystallinity at low cost. This work is used a basis for analysing the performance of graphitic additives and matrices in thermal energy storage applications.