Reduction of Oxide Mixtures of (Fe2O3 + CuO) and (Fe2O3 + Co3O4) by Low-Temperature Hydrogen Plasma

Abstract

The paper presents experimental results pertaining to the reduction of oxide mixtures namely (Fe2O3 + CuO) and (Fe2O3 + Co3O4), by low-temperature hydrogen plasma in a microwave hydrogen plasma set-up, at microwave power 750 W and hydrogen flow rate 2.5 x 10(-6) m(3) s(-1). The objective was to examine the effect of addition of CuO or Co3O4, on the reduction of Fe2O3. In the case of the Fe2O3 and CuO mixture, oxides were reduced to form Fe and Cu metals. Enhancement of reduction of iron oxide was marginal. However, in the case of the Fe2O3 and Co3O4 mixture, FeCo alloy was formed within compositions of Fe70Co30, to Fe30Co70. Since the temperature was below 841 K, no FeO formed during reduction and the sequence of Fe2O3 reduction was found to be Fe2O3 -> Fe3O4 -> Fe. Reduction of Co3O4 preceded that of Fe2O3. In the beginning, the reduction of oxides led to the formation of Fe-Co alloy that was rich in Co. Later Fe continued to enter into the alloy phase through diffusion and homogenization. The lattice strain of the alloy as a function of its composition was measured. In the oxide mixture in which excessive amount of Co3O4 was present, all the Co formed after reduction could not form the alloy and part of it appeared as FCC Co metal. The crystallite size of the alloy was in the range of 22-30 nm. The crystal size of the Fe-Co alloy reduced with an increase in Co concentration.