An EPR study of carbonization of some iron-containing materials

Carbonization of a 1:1 mixture of Turgai slime and Chilik clay and of a sim pler system, Fe3O4, was studied by the EPR method. For all materials, the i ntensity of magnetic resonance signals reached a maximum at certain carboni zation temperatures and then sharply decreased as the carbonization tempera ture increased further. Intensity growth was caused by the formation of clu sters of Fe3+ ions and finely dispersed reduced iron particles. A decrease in the intensity of magnetic resonance signals was caused by the onset of a ctive carbonization of these materials.