Formation of oxidation resistant graphite flakes by ultrathin silicone coating

Two types of silicone compounds and a trace amount of Pt catalyst were impregnated into exfoliated graphite (EG) by sorption and cured under different conditions. By this process, graphite sheets composing EG were coated with very thin (<< 1 gm) silicone layer. Thus, obtained precursors were converted to oxidation resistant graphite flakes by the beat-treatment at a temperature in a range of 1000- 1300 degrees C for 1 h in inert atmosphere. The coatings were intact and they were mixtures of Si-C-O glass-like composites and amorphous silica, which were confirmed by SEM, XRD and MAS-NMR. As formed graphite flakes showed instantaneous mass losses of 5-13% by oxidation at 1000 degrees C for 1 h in pure O-2, but after that the mass change was very small. By removing free carbons on the surface beforehand, the mass loss became less than 1% for all products. The mass loss of the sample molded into a disk-shape was about 1% after the first cycle (1 h) of repetitive oxidation at 1000 degrees C in air but from the second cycle an appreciable mass loss was not observed up to 20 h. The present method is promising for the production of oxidation resistant graphite flakes. (c) 2004 Elsevier B.V. All rights reserved.