ELECTRON-SPIN-RESONANCE BEHAVIOR OF PITCH-BASED CARBONS IN THE HEAT-TREATMENT TEMPERATURE-RANGE OF 1100-2000-DEGREES-C

An electron spin resonance (ESR) study in combination with X-ray diffr action has been made on carbons prepared from a coal-tar pitch through heal treatments in the range of 1100-2000 degrees C. ESR spectra were observed for specimens heat-treated at 1100 degrees C or less and 150 0 degrees C or higher, but hardly detected for those treated ca 1250 d egrees C unless a high amplification technique was employed. The heat treatment time dependence measurement supports that carbon layer segme nts formed by the carbonization reaction are combined each other in a large scale at near 1250 degrees C so as to remove the structural defe cts carrying unpaired electrons. (C) 1998 Elsevier Science Ltd. All li ghts reserved.