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Highly (l00) oriented Fe0.94O, when physically contacted with graphite, is reduced in various CO partial pressures at isothermal temperatures between 1173 and 1473 K. The reducing behaviors were studied in situ using optical microscopy. The results indicated that the reduction of FeO + CO → Fe + CO2 took place anywhere on the surface of the Fe0.94O at temperatures above 1173 K. The reaction did not start nor spread from the point where the Fe0.94O–graphite were in physical contact. The moving rate of the Fe/Fe0.94O interface is classified into three regions (as a function of PCO and also temperature): the slow moving region at low temperatures; the stepwise moving region at medium temperatures and low PCO; and the constant and fast moving region at high PCO or high temperatures.

In the present work, mixtures of magnetite and carbon black powers were irradiated by a constant microwave power supply of 2.8 kW at 2.45 GHz. The temperature was measured as a function of the irradiation time from 220°C. The progress of the reduction was examined by XRD analyses of reaction products at various temperatures in the range 400–1200°C. Under the present experimental conditions magnetite selectively absorbs microwave energy below approximately 650°C; meanwhile carbon black absorbs it in the whole temperature range. The reduction of magnetite to wustite was observed to occur from at least a measured temperature of 400°C but did not occur homogenously inside the mixture. At 800°C, the reduction of wustite to iron started and occurred almost homogeneously inside the reacting mixture mass.A general conclusion of this work is that microwaves are absorbed and used in their path within the irradiated mass by the material of highest absorbing microwave power.