Publications

The knowledge of the composition and structure of hydrated films on aluminium is important for the bonding between aluminium and polymers. Native surface layers on aluminium consist of an anhydrous inner layer of amorphous A1203 and a hydrated outer layer, where the outer layer determines the adhesion properties. On the one hand the pseudoboehmite oxyhydroxide surface can be seen as a model for the chemistry found at the surface of the air-formed film after ambient exposure of the aluminium metal. On the other hand pseudoboehmite layers are promising for improving the adhesion between polymers and aluminium. Spectroscopic Ellipsometry in the visible (VISSE) and IR (IRSE) are powerful tools for the morphological (thickness and refractive index) and chemical characterisation of oxides formed on aluminium. Both optical techniques are used to study anodizing and hydration under boiling water conditions of aluminium. The growth in thickness and the chemical composition of the oxide formed is shown. The porosity of the layer together with the chemical composition is obtained and the changes as a function of boiling time are presented. In addition the above type of hydration is applied on the anodically formed barrier oxide film. IRSE shows that the hydration of this type of film by immersion in boiling water results in the conversion of aluminium oxide to pseudoboehmite. Finally the further oxidation of a native oxide film on aluminium is measured; the results are compared with the growth of the hydrated layers.

The combination of the functionalities of Fiber Bragg Gratings (FBGs) and Photonic Crystal Fibers (PCFs) has unveiled new potential for FBG based sensors. The fabrication of FBGs in PCFs has been reported in literature. However, using dedicated PCFs to improve the sensitivity of FBG-based sensors has received only limited attention. In this report we therefore show how to eliminate some of the drawbacks of FBGs in conventional step-index fibers for sensor applications by exploiting the design flexibility of PCFs. The added value of PCFs stems from the ability to design an optical fiber in which an FBG acts as a sensor with a selective sensitivity, e.g. a sensor that is sensitive to strain but not to temperature. For this purpose we use a PCF with a birefringence on the order of 10^-3, which is one order of magnitude larger than for conventional birefringent fibers. The two FBG reflection peaks are therefore significantly separated from each other, e.g. 2 nm, which makes these FBGs suited for sensing purposes since both peaks can be unambiguously and accurately identified. As a conclusion we summarize the advantages and disadvantages of our approach to design and fabricate selective FBG-based sensors.

This study investigates the Volta potentials of the differently treated zinc surfaces and the interface dipole moments after adsorption of carboxylic acid and anhydride molecules on zinc surfaces by means of scanning Kelvin probe (SKP). The interfacial bonding properties of carbonaceous contamination as well as adsorbed succinic acid, myristic acid, and succinic anhydride molecules with zinc substrates have been investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The variation of the Volta potential due to the treatments applied on zinc was evaluated by means of SKP. Moreover, the dipole moments of adsorbed carboxylic acid and anhydride molecules were measured and correlated to surface hydroxyl fractions and oxide electronic properties. The results clearly showed that the zinc Volta potential varies with the oxide composition, resistance, and the configuration of the molecules adsorbed.

Lithium based inhibitors in aerospace coatings are seen as excellent replacements for their chromium counterparts which are both carcinogenic and heavier. However, Li is generally difficult to detect and following changes in its distribution due to corrosion is impossible with many standard techniques. Combining MeV Particle Induced Gamma and X-ray emission provides a powerful tool and in this paper we summarise some recent experiments on such coatings using the CSIRO Nuclear Microprobe. PIGE mapping of the LiCO3 particles and their patterning illustrates how the method will be extremely useful in monitoring surface corrosion.

Aiming the assessment of novel, environmentally friendly corrosion inhibitors that can substitute chromate‐based ones, this work describes and validates a method for the rapid screening of water‐soluble inhibitors. The technique involves a fixed potential being applied between identical electrodes while immersed in an inhibitive solution and with the absence 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 the inhibitor, is then characterized. The incorporation of nine pairs of different metallic wires into a single assembly enables the effect of inhibitors on different metals to be assessed rapidly. The methodology presented allows approximately 30 electrochemical experiments to be performed per hour. In order to prove the usefulness of the proposed rapid screening technique (multielectrode), results obtained with the multielectrode are validated by comparison to the results obtained with a single electrode using only AA2024‐T3. The accuracy, reproducibility and parameter dependence has been assessed with the variation of inhibitor type and solution pH. Low absolute errors are found when studying inhibitors with good performance, giving confidence that no good inhibitors would be missed by this rapid screening method. The effect of cross‐contamination has been assessed and found to be negligible for almost all the pH range. Copyright © 2009 John Wiley & Sons, Ltd.

No abstract is provided for this article.

Organosilane pre-treatments have been studied intensively during the last years in order to replace hexavalent chromium conversion treatments. The aim of this study is to follow in-situ the formation of this organosilane layer in solution. Two in-situ techniques, spectroscopic ellipsometry and electrochemical quartz crystal microbalance, were used to investigate the mechanism and the kinetics of this protective film formation. In-situ measurements highlight that the organosilane film observed after the drying process is not formed into the solution, but during the emersion and drying step. Hence, it has been possible to characterise the presence of a very thin organosilane layer in the order of a few monolayers using the in-situ techniques. This layer is responsible for the adhesion and growth of the overall organosilane layer observed ex-situ after drying.

No abstract is provided for this article.

The Devanathan-Stachurski-cell is the most commonly used electrochemical technique for the investigation of the hydrogen trapping properties of a material. In this set-up, a flux of hydrogen atoms diffuses through a metal membrane under study. The atoms are subjected to the heterogeneities naturally present in the lattice of the metal, acting as traps. This matter influences the diffusion of hydrogen, which is strongly microstructure related. In this paper, we apply a numerical model to different iron-alloys to determine the hydrogen trapping parameters characterizing the materials. We highlight the complexity of the hydrogen trapping mechanism which needs to be further investigated.

Funding Acknowledgements Type of funding sources: None. Background The feasibility of additive manufacturings (AMs) as peri-procedural tools has already been established. In order to extend their use to intra-procedural tools for surgical, interventional, or electrophysiology procedures, AMs must be able to convey specific data from cardiac imaging and to come into contact with both biological tissue and energy sources. Methods A resin (MED625FLX) and a urethane thermoplastic elastomer (TPU) were chosen as materials for AMs, printed in a variety of thicknesses and configurations. Geometry test was conducted to compare the properties of materials before and after sterilization. In-vitro test was carried out in a wet lab to validate the safety related to propagation of energy underneath the material during application of power sources; three different sources (cryothermal, bipolar radiofrequency, unipolar radiofrequency) were tested. The release of debris derived from the AM on the biological tissue was verified both with electron microscopy and Raman spectroscopy. Results Geometries below 1 mm and above 2.5 mm did not pass the test after sterilization for both materials. A total of 100 energy applications were delivered during in-vitro testing. Temperature was kept constant. The type of material used for the AM, the energy-type delivered and the factorial combination of distance/material and distance/energy-type had a significant p-value for temperature changes on the tissue underneath the AM (Temperature*Material p=0,003; Temperature*Energy p<0,001; Temperature*Material*Position p=0,02; Temperature*Position*Energy p<0,001). Post-hoc test using Dunn's procedure showed significant p-values for distance (Temperature*Position p<.001) and energy-type erogated (Temperature*Energy*Cryo-biRF p<.001; Temperature*Energy*Cryo-uniRF p<.001; Temperature*Energy*biRF-uniRF p<.001), while there were no significant differences of temperature in relation to AM thickness and material. Raman spectroscopy on biological tissues revealed that no AM particles >1μm were released. Conclusions The use of AMs in intra-operative cardiac procedures may be feasible and safe, and it can be employed as a reliable integration of cardiological imaging into tangible localisation of certain specific structures or pathological substrates.

Visual Spectroscopic Ellipsometry (VISSE) was used to analyze thin organic coatings on steel. VISSE allows a fast and non-destructive determination of the coating's thickness and optical constants. Therefore, an optical model was devised to describe the steel/polyacrylic system. To test this model, the measured color of the system was compared to the one generated by the optical model. This comparison revealed that the color originates from interference. Besides thickness and optical constants of the layer, it is equally important to obtain information about how the polyacrylic film is formed on the substrate. Subsequently, the optical model was then used to study the formation of a thin organic layer from an aqueous polyacrylic dispersion at three different temperatures (23 °C, 33 °C and 60 °C). VISSE measurements showed a decrease in layer thickness and an increase in the refractive index of the layer as a function of the drying time for temperatures above the Minimal Film forming Temperature. In order to determine the amount of voids in the acrylic layer, the model was adapted to include a Bruggemann Effective Medium Approximation. It allowed the extraction of the amount of air at every instant during the drying of the layer. It is thus possible to study a polyacrylic layer on a steel substrate using VISSE.

The effect of zirconium-based conversion of thermally vaporized zinc, aluminium and magnesium on the chemisorption of dimethylsuccinate was studied using attenuated total reflection – Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. Two competing chemisorption mechanisms contribute to interfacial bond formation. Hydrogen interactions on one hand were shown to occur between metal hydroxides and non-hydrolysed ester-groups of the molecule. On the other hand, both native and zirconium-treated substrates were shown to form interfacial carboxylate bonds with dimethylsuccinate, evidencing their capability of hydrolysing ester groups towards more reactive acid groups. Both interactions were shown to correlate to the metal oxide acid-base properties.

In this paper the different steps involved in an integrated methodology to measure, analyze and model electrochemical systems in a correct and reliable way are shown for Al-rich metallic coated steel with an additional organic coating. This methodology is based on the use of an odd random phase multisine excitation signal and was proposed by our group previously. The use of this multisine excitation signal decreases the measurement time. Moreover, it allows to perform a rigourous data-analysis and to quantify the signal-to-noise ratio, the level of non-linear and non-stationary behaviour. It was shown that by using this technique the optimal measurement conditions can be chosen based on a trade-off between signal-to-noise ratio and non-linear behaviour. Moreover, in the modeling procedure the noise, non-linearities or non-stationarities can be taken into account. The methodology allows a statistical evaluation of the proposed model for the coated metal, indicating whether model errors are still present or not.