Exfoliation of Graphite and its applications

Abstract

Exfoliated graphite (EG) has been manufactured as a pristine material for flexible graphite sheets (FGS) in huge amount in the world. It is produced through rapid heat-treatment of residue compounds of natural graphite flakes with sulfuric acid up to a high temperature around 1000°C. After its heat-treatment, it consists of fragile worm-like particles, which are formed by exfoliating perpendicularly to the basal plane of graphite. FGS have been manufactured through compression without any binder of the EG. This FGS is widely used as electronic components heat radiation material, gasket and packing materials of all fields from the high temperature to low temperature. Recently, FGS is also used for the gasket and packing material as a replacement of the asbestos. One of another applications in the EG, it shows a large amount of sorption capacity of heavy oils very quickly, 1 g of lump of the EG sorbed more than 80 g heavy oil. It is much larger than the package of adsorbents ever used. Estimation of pore structure for EG was carried out through mercury porosimetry. Its large sorption capacity relates to the pore structure of EG. Inside pores in the worm like particles were determined from the analysis of fractured surface of the EG particles which are prepared by cleaving, with the aid of image processing by assuming ellipsoidal form. As a consequence, the large sorption capacity strongly relates to large space in the worm like particles. It is considered that a demand of graphite particles to prepare the EG will be increased in future because of replacement of asbestos and increasing in demand for electronic components.