ESR Study of Glass-Like Carbons

Abstract ESR studies were carried out on a variety of glass-like carbons made from different precursors heat-treated in the range 300–2500 °C. It was found that the behaviors of unpaired electrons were nearly identical. The temperature dependence of ESR spectrum showed that the behavior of localized unpaired electrons in the glass-like carbons changed to that of delocalized ones at HTT about 2500 °C. The ESR spectrum of the glass-like carbons heat-treated at 800 °C consisted of a single line under a pressure of above 10−4 Torr but split into two components when air was admitted. This strong interaction with unpaired electrons and air (oxygen molecules) is caused by the active structure related to micropores in the glass-like carbons. We suppose that the polyene type radicals are the most suitable as the active structure to interpret the behavior of unpaired electrons in glass-like carbons heat-treated at 800 °C. As another major point in this study, it was found that there is a correlation between unpaired electron concentration and the g value.