Abstract
Magnetic susceptibility, electron spin resonance and analytical data are presented for chars and carbons prepared at 300–3000°C from polyvinyl and polyvinylidene chloride, representative of graphitizing and “non-graphitizing” materials respectively. The diamagnetic susceptibilities of the carbons formed from the respective polymers apparently reflect the differences in crystallite growth and organization accompanying their treatment at high temperature; but the development of unpaired electron spins in the polyvinylidene chloride chars exhibited certain anomalies, characterized by two maximal values of the electron spin concentration in chars formed in the region of 450 and 950°C respectively. The presence of traces of nitrogen in certain high-temperature carbons prepared from polyacrylonitrile, has no distinctive effect on their magnetic properties. The magnetic behavior of the carbons formed above about 800°C, and exhibiting a transition from positive to negative temperature dependence of susceptibility when prepared in the region of 1500°C, can be explained, at least qualitatively, on the basis of the two-dimensional electron gas model of carbon.
Published Version
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