Microstructural Changes and Kinetics of Reduction of Hematite to Magnetite in CO/CO2 Gas Atmospheres

The microstructures of porous magnetite formed on gaseous reduction of dense hematite have been examined using high-resolution scanning electron microscopy. It has been shown that cellular pores are formed on reduction in the temperature range 573 K to 973 K (300 degrees C to 700 degrees C). Dendritic shaped gas pores are formed on reduction at temperatures between 1073 K and 1273 K (800 degrees C and 1000 degrees C). The apparent chemical reaction rate constant for the reduction of hematite to magnetite in CO/CO2 gas mixtures has been derived from measurements of product thickness against reaction time; the rate constant is described by the relation phi(CO) = 0.232exp(76,000/RT) mu m s(-1) atm(-1). (C) The Minerals, Metals & Materials Society and ASM International 2019