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No abstract is provided for this article.

The occurrence of preferential grain etching (PGE) during alkaline etching of aluminum extrusion alloys from the 6XXX series is often linked to the presence of certain impurity elements such as zinc, causing an undesired etching appearance. In the presented work, an additional culprit in this context is identified, which has not been investigated yet. A clear relation between PGE and the presence of a subsurface shear layer is identified for extruded Al 6060 alloys containing 0.02 and 0.06 wt% Zn. This shear layer can be distinguished from the bulk of the metal by its difference in crystallographic texture as visualized by electron backscatter diffraction (EBSD). For the Zn enriched alloy, the <111>//ND grains are etched away faster than grains with other orientations, resulting in the grainy appearance typical for PGE. Independent of the Zn content in the alloy, once the shear layer is removed and <111>//ND grains are practically absent on the new surface, the depths variations caused by preferential etching disappear. Instead, the surface of the alloy is attacked uniformly by the caustic etch bath.

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The anodising process parameters (voltage, temperature, and electrolyte) control the morphology and the chemical composition of the resulting anodic oxide film by altering the balance between oxide growth and oxide dissolution reactions. The porosity of the oxide film is reduced by the addition of tartaric acid to a sulfuric acid electrolyte, while anodising at elevated temperatures enhances oxide dissolution, leading to wider pores and rougher surfaces. No significant changes in the oxide chemical composition as a function of anodising parameters was found; in particular, no tartrate incorporation took place. The resistance of uncoated anodic oxide films against aggressive media and galvanic stress as a function of anodising parameters has been studied by electrochemical methods. Anodising in a mixed tartaric and sulfuric acid electrolyte improves the resistance of the anodic oxide against galvanic stress and aggressive media in comparison to sulfuric acid anodising processes. However, the corrosion protection performance of the anodic oxide films in combination with a corrosion-inhibitor loaded organic coating is not governed by the blank oxide properties but by the adhesion-enhancing morphological features formed during anodising at elevated temperatures at the oxide/coating interface.

Dealloying is involved in materials science responsible for fabrication of nanoscale structures beneficially but for corrosion degradations detrimentally. Detailed understanding related to the latter is critical for designing corrosion-resistance alloys and dedicated inhibition systems. Thus, direct nanoscopic observations of nano-structural and compositional evolutions during the process are essential. Here using liquid phase-transmission electron microscopy (LP-TEM), for the first time, we show dynamic evolution of intricate site-specific local corrosion linked to intermetallic particles (IMPs) in aerospace aluminium alloys. To thoroughly probe degradation events, oxidation direction is controlled by purposefully masking thin specimens, allowing for observing top-view surface initiation to cross-sectional depth propagation of local degradations. Real-time capturing validated and supported by post-mortem examinations shows a dealloying-driven process that initiates at IMPs and penetrates into the depth of the alloy, establishing macroscopic corrosion pits. Besides, controversial mechanisms of noble-metal redistribution are finally elucidated.

No abstract is provided for this article.

Supported nanoparticle synthesis and assembly have application in a wide range of modern day applications. Key to the manipulation of the particle assembly is an understanding of the interaction between the particles and solvent. Here, we employ a comprehensive in situ approach, together with ex situ SEM imaging, to study supported palladium nanoparticles, electrodeposited from a 2:1 urea:choline Cl– DES. Using cyclic voltammetry, we confirm the expected adsorption of electroactive species onto the deposited particles. On the basis of our experimental results, we conclude that the electrodeposited nanoparticles assemble into 2-D superstructures, rich in adsorbed species. The abundance of these adsorbed species, within the superstructure, induces an anionic layer above them, which can be observed by ultrasmall-angle X-ray scattering (USAXS) as well as electrochemical impedance spectroscopy (EIS). The surface charge of the particles is, therefore, not neutralized locally, as is the case with traditional colloidal systems. We also show that these otherwise stable nanoparticles readily aggregate when the DES is removed. Thus, the stability of these particles is contingent upon the presence of the DES.

Two-dimensional (2D) allotropes of tellurium (Te), recently coined as tellurene, are currently an emerging topic of materials research due to the theoretically predicted exotic properties of Te in its ultrathin form and at the single atomic layer limit. However, a prerequisite for the production of such new and single elemental 2D materials is the development of simple and robust fabrication methods. In the present work, we report three different 2D superstructures of Te on Au(111) surfaces by following an alternative experimental deposition approach. We have investigated the superstructures using low-temperature scanning tunneling microscopy and spectroscopy, Auger electron spectroscopy (AES), and field emission AES. Three superstructures (13 × 13, 8 × 4, and √11 × √11) of 2D Te are observed in our experiments, and the formation of these superstructures is accompanied by the lifting of the characteristic 23 × √3 surface reconstruction of the Au(111) surface. Scanning tunneling spectroscopy reveals a strong dependence of the local electronic properties on the structural arrangement of the Te atoms on the Au(111) support, and we observe superstructure-dependent electronic resonances around the Fermi level and below the Au(111) conduction band. In addition to the appearance of the new electronic resonances, the emergence of band gaps with a p-type charge character has been evidenced for two out of three Te superstructures (13 × 13 and √11 × √11) on the Au(111) support.

This study investigates the influence of surface conditioning on the deposition of Zr-based conversion films on AA6014. For that purpose, different treatments were used to control the formation of well-defined oxides layers with different hydroxyl fractions and similar thicknesses prior to the conversion layer formation process. The elemental distribution and surface chemistry of the treated samples before and after the formation of the Zr-based conversion layer were evaluated by Auger Electron Spectroscopy (AES) depth profiling and X-ray Photoelectron Spectroscopy (XPS). Moreover, the Open Circuit Potential (OCP) evolution as a function of time was recorded during the formation of the Zr-based conversion layers in order to evaluate the electrochemical surface activity and formation mechanism in-situ. The results have shown that a higher initial hydroxyl fraction encourages the formation of a thicker Zr-based layer.

No abstract is provided for this article.

The deposition of n-octylphosphonic acid on aluminum oxide was studied. The substrate was pretreated in order to achieve a root-mean-square roughness of <1 nm, a hydroxyl fraction of 30%, and a thickness of approximately 170 nm. It was proven using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) that, rather than a monolayer, an organic multilayer was formed. The growth mechanism was identified as a Stranski−Krastanov one. It was also shown that the use of AFM, probing the surface topography, is essential for a reliable quantification and interpretation of data obtained with XPS.

No abstract is provided for this article.

No abstract is provided for this article.

Organic coatings are extensively used in various industries (e.g., automotive, aerospace) to protect the aluminum surface against corrosion. A crucial parameter determining the lifetime of coated metals is the durability of the metal/polymer bonding, in which a clear understanding of molecular-level interfacial chemistry lacks due to the challenges in probing the buried metal/polymer interfaces. In this study, the scanning Kelvin probe (SKP) technique was used to monitor the interfacial bonding-induced potential changes on the aluminum oxide surfaces (electropolished, acid-pretreated, alkaline-pretreated, and pseudoboehmite) after the application of an epoxy coating or, alternatively, model compounds (N,N′-dimethylsuccinamide and N-methyldiethanolamine) representing interfacial functional groups of epoxy/aluminum interface. The observed potential changes are then discussed in terms of hydroxyl fraction, adsorption amount, and bonding mechanisms, as characterized by X-ray photoelectron spectroscopy (XPS). Furthermore, the potential of the pseudoboehmite oxide, exhibiting the highest chemical interaction after the application of an epoxy coating or model compound, was investigated as a function of the pretreatment duration. It is shown that the N-methyldiethanolamine molecules are the major potential-decreasing component of the epoxy coating. Although the magnitude of potential drop is mainly controlled by the hydroxyl fraction of the oxides in the case of model compound deposition, such a correlation is not observed after the application of epoxy coating, supposedly due to the segregation of the model compounds creating an excess amount of molecules at the interface region with respect to the bulk polymer.