Publications

Cation transport from defect site to delamination front and oxygen reduction at the polymer/metal interface are the two processes that are proposed to control the kinetics of cathodic delamination. However, it was suggested that instead the ingress of cations at the delamination front controls the kinetics, shown first for weak coatings. Here, the validation also for resistant industrial coatings is reported. It is also shown that cations mainly serve for pulling down the potential at the front while the electron flow supporting ongoing oxygen reduction at the delaminated interface is compensated by hydroxyl ion migration towards the defect.

This paper complements our recently published work on the development of a high-throughput scanning technique for corrosion inhibitors named multielectrode. The multielectrode set-up, fully described in the previous work, combines nine pairs of different metals in a single multi-metal electrode configuration. In the working procedure a fixed potential is applied between identical metallic electrodes while immersed in an inhibitor solution, without the use of a reference electrode. The current flowing between the electrodes is measured and the combined electrochemical response of the anodic and cathodic reactions, with and without inhibitor, is then characterized. The methodology allows approximately 30 electrochemical experiments to be performed per hour, the rapid identification of inhibitors able to protect different metals, and the rapid detection of the optimal inhibitor concentration. The present work evaluates the influence of solution pH on the anticorrosion performance of three different inhibitors (CeCl3, Ce(dbp)3 and K2Cr2O7) on 2024-T3 aluminium alloy (AA2024-T3) by means of conventional potentiodynamic polarization analysis and the multielectrode technique reported previously. The usefulness of the high-throughput multielectrode technique to detect the influence of the solution pH on the anticorrosive performance of different inhibitors has been studied and its correlation with traditional potentiodynamic polarization testing evaluated. The possible reasons for non-correlation between techniques are studied, and those considered important, highlighted. The combined dependence of corrosion inhibition on factors including pH, inhibitor type, and metal cross-contamination was also investigated showing that the multielectrode is a robust technique to detect efficiency changes due to pH variations.

For the characterisation of Al surfaces after thermo mechanical processing of rolled strips TEM is imperative. Especially cross-sectional TEM specimens highlight the multi-layered structures of the surface area. The specimen preparation of cross-sections is a critical step in TEM analysis. A common technique is ultramicrotomy, where a diamond knife is used to cut electron transparent slices. The major disadvantage of the method - especially in the case of aluminium - is the strong mechanical deformation resulting from cutting. Another technique is the conventional ion beam milling. In order to provide views of subsurface regions, the sample surfaces are initially glued together, then cut perpendicular to the sheet surface, mechanically thinned, cut to form disks, dimpled, and ion beam thinned. Here, a new method for preparing cross-sectional TEM specimens of aluminium surfaces is introduced: Focused Ion Beam thinning (FIB), which became a standard method for preparation in the semiconductor industry. This technique has the potential of introducing nearly no chemical and structural modifications in the specimen. TEM lamellae of equal thickness can be produced in less than two hours and the success rate is nearly 100%. As an example for this new preparation method the paper reports about a (S)TEM investigation of a FIB prepared specimen of the surface of an AlMg0.5 hot rolled strip.

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Advances in fiber optics and CCD technology in the last decades have allowed for a large reduction in outer diameter (from centimeters to submillimeter) of endoscopes. Attempts to reduce the outer diameter even further, however, have been hindered by the trade-off, inherent to conventional endoscopes, between outer diameter, resolution and field of view. Several groups have shown the feasibility of further miniaturization towards so called micro-endoscopes, albeit at the cost of a very reduced field of view. In previous work we presented the design of an ultra-high NA (0.928) Coherent FiberBundle (CFB) that, in combination with proximal wave front shaping, could be used to circumvent this trade-off thus paving the way for even smaller endoscopes. In this paper we analyze how the modal properties of such an ultra-high NA CFB determine the required input field to achieve any desired output field. We use the periodicity of the hexagonal lattice which characterizes a CFB, to define a unit cell of which we analyze the eigen-modes. During the modal analysis, we also take into account realistic variations in lattice constant, core size and core shape due to the limitations of the fabrication technology. Realistic values for these types of fabrication-induced irregularities were obtained via SEM images of a CFB fabricated according to the aforementioned design. The presence of these irregularities results, for a desired output, in the required input to be different from the required input for a defect-free CFB. We find that of the different types of fabrication-induced irregularities present in the CFB, variations in core ellipticity have the biggest impact on the required input for a given desired output.

We report on a new approach to obtain highly homogeneous silica-monolithic columns, applying a sol−gel fabrication process inside a rectangular pillar-array column (1 mm in width, 29 μm in height and 33.75 mm in length) having a cross-sectional area comparable to that of a 200 μm diameter circular capillary. Starting from a silicon-based pillar array and working under high phase-separation-tendency conditions (low poly(ethylene glycol) (PEG)-concentration), highly regular silica-based chromatographic systems with an external porosity in the order of 66−68% were obtained. The pillars, 2.4 μm in diameter, were typically clad with a 0.5 μm shell layer of silica, thus creating a 3.4 μm total outer pillar diameter and leaving a minimal through-pore size of 2.2 μm. After mesopore creation by hydrothermal treatment and column derivatization with octyldimethylchlorosilane, the monolithic column was used for chip-based liquid-chromatographic separations of coumarin dyes. Minimal plate heights ranging between 3.9 μm (nonretaining conditions) and 6 μm (for a retention factor of 6.5) were obtained, corresponding to domain-size-reduced plate heights ranging between 0.7 and 1.2. The column permeability was in the order of 1.3 × 1013 m2, lower than theoretically expected, but this is probably due to obstructions induced by the sol−gel process in the supply channels.

Peralkaline rhyolites are a rare magma type, typically associated with continental rift settings, and characterised by excess alkalis relative to alumina a

The Zinc level in many 6000 Al alloys (Al-Mg-Si-type) was set to a maximum of 0.03 wt% as common industrial practice. Concentrations above 0.03 wt% can modify the alkaline etching mechanism causing the surface to go from a desired smooth look associated with a grain boundary attack (GBA), into an undesired speckled appearance due to preferential grain etching (PGE), visible after anodizing. This significantly limits the ambition of reducing the carbon footprint of Aluminum by increasing the amount of recycled material in the production process. Because Cu has been reported to counteract this negative effect of Zn, the present study is dedicated to contribute to the understanding of this interaction and is focused on Zn and Cu in peak aged AlMgSi alloys. The chemical composition of the various precipitates formed in two Al6063 alloys was studied by means of TEM and EDX, whereby Zn was found in the Q phase (AlMgSiCu) grain boundary precipitates. Two alloys, with different content of Cu and Zn were studied. The Zn/Cu ratio in the bulk was similar for both alloys, but the level of Zn in the Cu containing Q particles in the grain boundaries was different. The increased Zn concentration in Q phase precipitates is believed to decrease the potential of the precipitates with respect to the surrounding matrix. Thus, the Cu/Zn ratio in these alloys is extremely important as it defines the potential differences that in turn cause either GBA or PGE.

No abstract is provided for this article.

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Allyl methacrylate (AMA) was deposited on aluminium using atmospheric dielectric barrier discharge plasma. AMA posseses two CC bonds which have very different reactivities and the efficiency of the plasma on polymerising the two different kinds of double bonds was evaluated. The Fourier transform infrared spectra and the nuclear magnetic resonance spectra of the plasma coatings were compared with those of conventionally synthesised poly(AMA). The influence of the monomer feed on the ester, the vinyl and the allyl functionalities of the coatings were investigated. Plasma coatings showed lower concentration of non‐reacted allyl groups than conventional poly(AMA) suggesting a more cross‐linked network. Pull‐off adhesion tests were performed after the deposition of the a topcoat to evaluate the potential use of the AMA based coatings as adhesion promoter. magnified image

In this paper the local healing efficiency of shape-memory polymers as a new alternative for the protection against corrosion of damaged coated metals is studied by scanning electrochemical microscopy (SECM). These measurements allowed us to evaluate the local corrosion activity at a damaged self-healing polymer coating on an aluminum alloy before and after the thermally healing process of the shape-memory polymer film. SECM operating in redox-competition mode is applied to monitor in situ the reduction of oxygen as a cathodic process in the corrosion onset at a coating defect as a function of exposure time in 0.05 M NaCl solution. It is proven that the physical repair of the film in the defect leads to a recovery of the local barrier properties of the coated system and subsequent protection of the aluminum alloy.