In SituInvestigations on the Oxidation of Metals

Abstract

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 investigatedin situby 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 CoKedge. By de-convolution of the spectra, the fractions of Co, CoO and Co3O4were determined as a function of time. During oxidation of the intermetallic compound CoGa only Ga is selectively oxidized andβ-Ga2O3is formed. Usingin situoptical 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 byin situX-ray diffraction (XRD). The results show that both monoclinic and tetragonal ZrO2exist in the oxide scale. The latter one is probably stabilized by compressive stress near the Zr/ZrO2interface.