A study of iron oxidation processes by Mössbauer spectroscopy

Abstract

The growth behaviour of Fe3O4 and α-Fe2O3 formed on iron at temps. ≅ 450-550°C has been studied by Mössbauer spectroscopy. Two main types of experiment were performed. First, using completely oxidized foils, i.e. all metal reacted, the further oxidation of Fe3O4 to α-Fe2O3 in oxygen was investigated. Second, the reduction by iron of α-Fe2O3 to Fe3O4 was followed by annealing partially oxidized foils in vacuum. Activation energies observed are 49 Kcal/mole for the growth of α-Fe2O3 upon Fe3O4 and 31 Kcal/mole for iron transport through Fe3O4. These relatively low energies suggest that both processes are controlled by short-circuit diffusion. © 1972 Pergamon Press.