In previous studies, transmission electron microscopy (TEM) was used to probe the oxidation of either an intermetallic alloy, Fe 3Al, or an ODS (oxide dispersion strengthening) FeCrAl alloy strengthened by very small Y 2O 3 particles, PM2000. Moreover, it seems that, in many cases, several transition phases can be simultaneously present. Indeed, the most common technique, the XRD, provides patterns for various Al 2O 3 which are relatively close to each other. Moreover, one difficulty associated with the understanding of the influence of transition Al 2O 3 on the further oxidation resistance concerns the fact that, as mentioned in, the techniques which allow us to detect and characterize transition Al 2O 3 formed as thin layers (1 to 3 μm) are scarce and provide ambiguous answers. Nowadays, it is not clear whether the growth of transition Al 2O 3 as a first step improves the protective properties of the further formed α-Al 2O 3 film. Before reaching the most stable Al 2O 3, alumino-former materials developed transition Al 2O 3 among which the most common are γ, δ, and/or θ phases. In this prospect, α-Al 2O 3 is a very good candidate. Several studies have shown that the oxide layers as SiO 2, Cr 2O 3, and α-Al 2O 3 provide a satisfactory protective role, a protection based on the formation of a layer of α-Al 2O 3.
This resistance can be achieved when the chosen materials develop through oxidation, an oxide film which acts as a diffusion barrier while keeping a good adherence. Most of the metallic materials functioning at high temperature need to have oxidation resistance. This allowed us to clearly differentiate the transition Al 2O 3 from the α-Al 2O 3 and, amongst the transition Al 2O 3, to differentiate the characteristic of the IR spectrum of γ- δ phases from that of the θ phase. For this objective, a study of the PM2000 oxidation at various temperatures was conducted by means of XRD, IR spectroscopy, XPS analysis, EDX analysis, and SEM observations. The aim of this work is to evaluate the use of IR spectroscopy and XPS analysis to probe the structural varieties of Al 2O 3. FTIR and XPS signatures were obtained for various oxidation temperatures and compared with those known from the literature about calcination of Al 2O 3 precursors. This work is an original example to compare the results obtained after calcination of Al 2O 3 hydroxides and oxidation of alumino-formers alloys.
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