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Manfred Martin, N. Lakshmi, U. Koops, H.-I. Yoo
In Situ Investigations on the Oxidation of Metals
Keywords: Oxidation, In-Situ X-ray Absorption, In-Situ X-ray Diffraction, Parabolic Growth
High temperature oxidation processes of metals are important solid state reactions from a fundamental point of view and also concerning technical applications. The kinetics of these solid state reactions was investigated in situ by X-ray absorption spectroscopy (XAS), optical microscopy and X-ray diffraction (XRD) at elevated temperatures and defined oxygen partial pressures. Oxidation of thin cobalt foils in air was studied by means of quick X-ray absorption spectroscopy (QEXAFS) at the Co K edge. By de-convolution of the spectra, the fractions of Co, CoO and Co3O4 were determined as a function of time. During oxidation of the intermetallic compound CoGa only Ga is selectively oxidized and β-Ga2O3 is formed. Using in situ optical microscopy and evaluating the interference colors it is shown that different crystallographic orientations of the intermetallic compound CoGa result in oxide scales of different thicknesses. Finally we present first experimental results on the oxidation of zirconium which were obtained by in situ X-ray diffraction (XRD). The results show that both monoclinic and tetragonal ZrO2 exist in the oxide scale. The latter one is probably stabilized by compressive stress near the Zr/ZrO2 interface.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 221, 11/2007
Pages: 1499 - 1508