Electron spin resonance behavior of pitch-based carbons in the heat treatment temperature range of 1100–2000 °c Original Research Article

An electron spin resonance (ESR) study in combination with X-ray diffraction has been made on carbons prepared from a coal-tar pitch through heat treatments in the range of 1100–2000 °C. ESR spectra were observed for specimens heat-treated at 1100 °C or less and 1500 °C or higher, but hardly detected for those treated ca 1250 °C unless a high amplification technique was employed. The heat treatment time dependence measurement supports that carbon layer segments formed by the carbonization reaction are combined each other in a large scale at near 1250 °C so as to remove the structural defects carrying unpaired electrons.