Exfoliation of nitric acid intercalated carbon fibers: effects of heat-treatment temperature of pristine carbon fibers and electrolyte concentration on the exfoliation behavior

Abstract

Effect of heat treatment temperature of mesophase pitch-based carbon fibers on the exfoliation behavior of derived intercalation compounds with nitric acid was studied. Carbon fibers heat-treated above 2500 °C gave intercalation compounds with mass increase of more than 80 mass% and resulted in a marked exfoliation by a rapid heating to 1000 °C, where no memory of original single fiber was observed. On those below 2000 °C, on the other hand, their residue compounds showed mass increase less than 80 mass% and the appearance after exfoliation at 1000 °C was similar to the original single fiber. On 1150 °C-treated carbon fibers, mass increase was only 13 mass% and no evidence of intercalation was detected even after electrolysis and, as a consequence, the formation of only small fissures along their fiber axis was observed, with no apparent exfoliation. The dependence on electrolyte concentration was also examined on 3000 °C-treated carbon fibers.