The kinetics of reduction of thin (136μm) flat hematite specimens by He-H2 gas mixtures were investigated at 310 and 377°C in a thermogravimetric apparatus. The values of the rate constant k_s for the interfacial reaction were determined from the experimental weight loss data. These were combined with the previous results for reduction with pure hydrogen to obtain the following relation:
log/k_s=-1.484(±0.106)-3172(±72)•T^-1
(k_s: g•atm O•cm^-2•s^-1•atm^-1)
The activation energy was found to be 60745 (±1380), J•mol^-1 which is in reasonably good agreement with the published results. The reduction of hematite conformed to a first-order behavior with respect to hydrogen partial pressure. The scanning electron micrographs of reduced specimens showed “star-shaped” pore formations with the pore-sizes significantly larger than those observed in specimens reduced with pure hydrogen.