Analysis by means of electron paramagnetic resonance indicates that removal of the α1 fraction from modified coal pitch doubles the concentration of paramagnetic centers present in comparison with the initial pitch. Mesocarbon microspheres are formed in the modified pitch at 420°C, sharply increasing (by almost two orders of magnitude) the number of paramagnetic centers. Subsequent heating of the mesophase pitch to 600°C lowers the concentration of paramagnetic centers, on account of the thermostimulated formation of aromatic molecules and crosslinking of mesogen molecules as the mesocarbon microspheres coalesce to produce bulk mesophase. On the basis of the data obtained, the production technology for mesophase pitch and carbon fiber may be optimized.
Zakharov et al. (2025) studied this question.