Thermal analysis of the oxidation of natural graphite - effect of particle size

The oxidation of natural graphite particles with a prismatic (flake-like) structure was investigated by thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). The objective of this study is to examine the relationship between the relative fraction of edge sites and the oxidation behaviour of graphite. The approximate prismatic structure of the natural graphite provided a model geometry from which the relative fraction of edge and basal plane sites was determined. The three thermal parameters, ignition temperature (T-i), temperature maximum (T-m) in the DTA curves, and the temperature at which 15 % carbon weight loss is attained (T-15), were determined for a series of natural graphite samples (average particle size, 2-40 mu m) using simultaneous TGA/DTA. The results reported in this study support the observation that the fraction of edge sites has a strong influence on the thermal parameters (T-i, T-m and T-15) for the oxidation of graphite. (C) 2000 Elsevier Science B.V. All rights reserved.