HETEROGENEOUS KINETICS IN THE FEO O2 SYSTEM

Studies of re-equilibration kinetics for the wustite phase (Fe1 - yOt) were performed by using high temperature thermogravimetry in the 1100-1275 K temperature range. The experiments involved both oxidation and reduction within the po, range corresponding to wustite non-stoichiometry varying between 0.063 < y < 0.10. The following data of the chemical diffusion coefficient were determined for oxidation and reduction runs, respectively: D ̃oxid = 5.58 × 102 exp (- 215±10.5[kJ mol-1] RT)cm2 s-1 D ̃red = 3.48 × 103 exp (- 222±9.0[kJ mol-1] RT)cm2 s-1. Experiments performed at different dilution of the CO/CO2 mixture indicated that the oxidation kinetics is bulk diffusion controlled over the whole temperature and po ranges under study. It has been found that D̃ decreases by a factor of 4 as y increases from 0.063 to 0.10. This effect is considered in terms of defect interactions. © 1990.