Oxide at the Al-rich Fe0.85Al0.15(110) surface

Abstract

The formation of an ultra-thin aluminum oxide film at Fe0.85Al0.15(110) surface (A2 random alloy) has been studied by a variety of surface sensitive techniques (X-ray photoemission, low-energy electron diffraction, surface X-ray diffraction and scanning tunneling microscopy) supplemented by ab initio atomistic simulations. Since iron is not oxidized in the used conditions, the study focused on the coupling between aluminum oxidation and segregation processes. Compared to the bare surface, whose average composition (Fe0.6Al0.4) is closer to the B2-CsCl structure over a ∼ 3 nm depth, the oxidation hardly affects the subsurface segregation of aluminum. All the structural and chemical fingerprints point to an oxide film similar to that found on NiAl(110). It is a bilayer (∼ 7.5Å thick) with a composition close to Al10O13 and a large (18.8 × 10.7)Å 2 nearly rectangular unit cell; an almost perfect match between substrate periodicity and the (1 × 2) oxide supercell is found. Nevertheless, microscopy reveals the presence of anti-phase domain boundaries. Measured Al 2p and O 1s core level shifts match calculated ones; their origin and the relative contributions of initial/final state effects are discussed. The ubiquity of the present oxide on different supports asks for the origin of its stability.

An In Situ and Real-Time Plasmonic Approach of Seed/Adhesion Layers: Chromium Buffer Effect at the Zinc/Alumina Interface

“…The case is relevant to the development of advanced high-strength steels (AHSS) used by the automotive industry to lighten car weight to comply with energy saving rules. To improve mechanical properties, AHSS grades involve electropositive elements such as Al whose drawback is the oxygen-induced segregation at steel surfaces. − The resulting surface oxide then degrades the adhesion of the anticorrosive Zn coating during the galvanization process. , The issue has motivated a series of studies − on the model Zn/α-Al 2 O 3 (0001) interface. First-principle simulations ,, have shown the effectiveness of Cr > Fe > Ni in promoting strong metal–oxygen and metal–zinc bonds and shifting cleavage from interfacial to cohesive.…”

Competitive Formation of Ultra-thin Alumina Films at the Fe0.85Al0.15(110) Surface

“…Alumina films of a similar structure are observed on several supports of various symmetries and compositions [NiAl(110), , Fe 0.47 Al 0.53 (110), Cu-9 at %Al(111), Al/Ni(111), and the complex metallic alloy γ-Al 4 Cu 9 (110)] . We have previously found a similar structure at the (110) surface of Fe 0.85 Al 0.15 , a ferritic random A 2 body-centered alloy.…”

“…STM images were processed using WSxM software for flattening, line profile, and Fourier transform. Aluminum segregation profile, oxide composition, and chemistry have been analyzed by XPS (see refs and for details) under a Al-Kα monochromatic excitation (1486.6 eV; Phoibos 100 hemispherical analyzer with a delay-line detector from SPECS) at a pass energy of 20 eV for angles ranging from normal (Θ = 0°) to grazing emission (Θ = 70°). The binding energy scale of the analyzer has been calibrated on the Fermi edge of coinage clean metals.…”

“…(An example is given by the Fe 0.85 Al 0.15 alloy under study. It serves as a model ,,− for steel grades alloyed with light elements such as Al used by industry to lighten cars. The drawback is that the oxygen-induced segregation of those elements forms surface oxides which challenge galvanization of steel. − More favorable conditions in terms of adhesion (i.e.…”

Core level shifts as indicators of Cr chemistry on hydroxylated α-Al2O3(0001): a combined photoemission and first-principles study

“…The subject was inspired by advanced high strength steels which are alloyed with electropositive elements (including aluminium) and used to lighten car weight to comply with energy saving rules. A shortcoming is that the corresponding steel grades are difficult to galvanize 26,27 because, due to oxygen-induced segregation, steel sheets are covered with oxides (in particular alumina [28][29][30] ) at the end of cold rolling and recrystallization annealing. In such a context, the Zn/Cr/α-Al 2 O 3 (0001) model stack is of general relevance for the study of the mechanisms at work in the buffer effect.…”