Project
A High-Temperature Mössbauer Study of Atomic Transport and Corrosion in the System Fe-S-O

Prof. Dr. K. D. Becker
Institut für Physikalische und Theoretische Chemie
der TU Braunschweig

In the study of atomic disorder and transport phenomena in solids, the iron oxides FeO, Fe₃O₄, and Fe₂O₃ have played the role of model systems due to their widely varying degrees of disorder and nonstoichiometry. In comparison to the iron oxides, iron sulfides have received much less attention, despite the fact that Fe_1-yS can exhibit similarly large deviations from exact stoichiometry as wüstite at even lower temperatures.

A striking consequence of the high disorder in FeO and FeS is the extremely rapid diffusion of cations in these compounds. Such high diffusion coefficients of iron will give rise to diffusion-broadening of Mössbauer lines. It is one of the aims of the present project to study atomistic details of iron migration and point defect structure in iron(II) sulfide by in-situ Mössbauer experiments performed at varying sulfur partial pressures. A similar study will also be attempted in Fe₃S₄, which is isostructural to the spinel Fe₃O₄. Iron sulphides also play a role in biomineralisation and in extraterrestrial environments. In this context, Mössbauer spectra obtained at controlled sulfur activities may contribute to improved structural insights.

In addition to atomic transport and defect structure in pure iron sulfides, another series of experiments will be devoted to the reactivity and its kinetics in the system Fe-S-O, focusing on corrosion. Especially the corrosion of iron by sulfur and by sulfur- and oxygen-containing atmospheres like SO₂, at dry and humid conditions, will be at the centre of interest.