Effect of extended ball milling on graphite

Graphite has been milled for up to 1000 It in a laboratory scale tumbling ball mill under vacuum. Raman spectroscopy of the powders indicated the increasing dominance of D-type graphitic sp(2) bonding over G-type bonding with increasing milling time. Diamond-like sp(3) bonding and possibly fullerene-like bonding also became evident after milling. TEM of the 100 It sample showed the presence of ribbons which were composed of sheets showing defects, delamination, translation, warping and curvature. Interplanar spacings of 0.40-0.50 nm were measured with the spacing increasing towards the edge of the ribbons where delamination was evident. Thermogravimetric analysis in argon of the powder after exposure to air showed an increasing mass loss with milling time indicating the presence of chermsorbed gas. Using TG-FTIR the gas was found to be a mixture of CO2 and an unidentified gas (probably oxygen). BET surface area measurements showed a maximum in the surface area; however, this was shown to be massively in error for the longer milling times due to the presence of the chemisorbed gas. (C) 2002 Elsevier Science B.V. All rights reserved.