MECHANISM AND THE INTRINSIC RATES OF REDUCTION OF METALLIC OXIDES

The reduction of metallic oxides to metals represents an important class of heterogeneous reactions in which the role of nucleation and growth phenomena, although significant, has not been investigated fully. The micromechanism of reduction involves the formation of metallic nuclei and their subsequent growth at the expense of the parent phase. The present paper systematizes the evidence so far available and reports some experimental work on the nucleation and growth mechanisms in the reduction of wustite. The rate of nucleation, the mode of growth of a metallic nucleus and their relationship to a macroscopic rate parameter such as the mass rate of reduction have been fully explored. The method of determining the intrinsic rate of reduction from high temperature stage optical microscopic measurements has been placed on a firm quantitative basis. The influence of pore diffusion of gaseous species on the shape of the growing nucleus has been examined in some detail. © 1979 American society for metals and the metallurgical society of aime.