Publications

The distribution and chemical composition of inorganic components of a corrosion-inhibiting primer based on polyurethane is determined using a range of characterisation techniques. The primer consists of a Li2CO3 inhibitor phase, along with other inorganic phases including TiO2, BaSO4 and Mg-(hydr)oxide. The characterisation techniques included particle induced X-ray and γ-ray emission spectroscopies (PIXE and PIGE, respectively) on a nuclear microprobe, as well as SEM/EDS hyperspectral mapping. Of the techniques used, only PIGE was able to directly map the Li distribution, although the distribution of Li2CO3 particles could be inferred from SEM through using backscatter contrast and EDS. Characterisation was also performed on a primer coating that had undergone leaching in a neutral salt spray test for 500 h. Overall, it was found that Li2CO3 leaching resulted in a uniform depletion zone near the surface, but also much deeper local depletion, which is thought to be due to the dissolution of clusters of Li2CO3 particles that were connected to the external surface/electrolyte interface.

The first 24 hours it is immersed in a 0.5 M NaCl solution, a copper surface undergoes a series of transformations. A corrosion product layer is formed that acts as a barrier layer between the aggressive solution and the substrate, offering some protection to the material. This barrier layer itself is subsequently attacked and localized corrosion is observed. The evolution can be divided into three stages. In the first hour, a homogeneous corrosion layer is formed over the entire surface. In the next hours, the thickness of this layer keeps on increasing. After two hours local corrosion starts to appear, piercing the formerly grown oxide layer in certain places. This attack is localized mostly at the grain boundaries. After 20 hours of immersion almost all these local attack sites gradually get covered anew by the constantly growing corrosion product layer. Electrochemical Impedance Spectroscopy (EIS) studies conducted on these surfaces generate a response that is a combination of the response of both reactions, making it impossible to discriminate between global and local reaction properties [1,2]. Knowing the reaction products present on different parts of the surface would however represent a great deal of information if one needs to identify the reactions taking place on this surface. Extensive studies have already been carried out on these surfaces, but still some lack of clarity remains, illustrated by some yet unidentified features in electrochemical impedance spectra (EIS) recorded on these surfaces[1,2,3]. From the various works it becomes clear that multiple species have been identified to form on the surface. Among them Cu2O [4-8] CuCl [5,6,8,9-13] or CuO [14-19]. Auger spectroscopy was already used in various works dedicated to the study of copper corrosion. A number of papers has been published on the identification of copper oxides, formed on various substrates [20-23]. Also a limited amount of literature exists on the identification of copper chlorides [24]. Lineshape analysis was used in a number of works as a tool to discriminate between different copper compounds, concentrating however on thermally formed oxides and chloride compounds grown in modified vacuum conditions. The study presented in this work uses Field Emission AES (FE-AES) to identify different copper compounds on the same surface. All of these were formed during the corrosion process of copper in aqueous chloride containing solutions. Lateral distributions of the composition were visualized by Auger imaging. Identification of the compounds was done by comparing the recorded high resolution FEAES spectra on corroded surfaces with spectra obtained from reference materials. With the acquired reference spectra Target Factor Analysis (TFA) was carried out to analyze the chemical composition of the corrosion products. Both the in-depth product distribution in the uniform corrosion layer and the distribution of the products in and around a local corrosion site were studied.

This study investigates the buried interfacial bonding properties of carboxylic polymers on Zn by means of ATR-FTIR in a Kretschmann geometry and X-ray photoelectron spectroscopy (XPS). Poly(methyl vinyl ether-alt-maleic acid monobutyl ester) and cured propoxylated bisphenol A fumarate unsaturated polyester were applied on a set of differently treated Zn samples. In the Kretschmann geometry, a thin Zn layer and subsequently the polymer were applied on an internal reflection element (IRE). The buried metal–polymer interface was studied in situ by passing infrared beams through the metal layer and reaching the metal–polymer interface in the attenuated total reflection (ATR) setting. Moreover, the metal–polymer interfacial bonding density was evaluated by application of the polymer on a Zn foil and XPS analysis of the Zn layer and the top polymer coating. Furthermore, the interfacial bondings were mimicked by adsorption of succinic acid molecules as the representative model compounds. The differently treated Zn layers were found to be capable of adsorption of the carboxylic groups, resulting in the formation of carboxylates. A comparison of the interfacial bondings of the polymers with those formed by the molecular adsorption showed a resembling interfacial mechanism. Additionally, it was found that the deprotonation kinetics depend on the polymer weight, while the polymer–metal interfacial bonding density mainly depends on the Zn surface hydroxyl fraction as well as initial molecular weight.

No abstract is provided for this article.

In the production of hydrogen gas, the removal of hydrogen chloride (HCl) is of particular relevance for the chemical industry. Here we report the HCl removal performance of ZIF-8 metal organic framework demonstrated via fixed-bed (dynamic) measurements under process conditions. The measurements revealed an HCl removal capacity of 1.02 g/g, outperforming by far all traditional materials and other metal-organic framework previously tested. The ZIF-8, before and after the HCl contact, was characterized via SEM-EDX, XRD, TGA, ATR-FTIR, XPS and Raman spectroscopy. The results showed a dramatic change in textural, structural and chemical properties of ZIF-8 after HCl contact, where the MOF material undergoes a reaction and re-crystalizes into a salt complex.

Chemical throwing power, being the distance over which an inhibitor is able to protect a defect effectively, is an important parameter for active protective coatings. This study investigates the chemical throwing power of lithium-based leachable corrosion inhibitors exhibiting different leaching kinetics, from coatings at different inhibitor loading concentrations. The results demonstrate that Li-salt loaded coatings provide corrosion protection of defect areas up to a width of 6 mm. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to detect the lateral spread of Li in the defect areas and provide the chemical speciation of corrosion protective layers in the defect areas.

In the transition to environmental friendly pretreatment of aerospace aluminum alloys, chromic acid anodizing (CAA) is being replaced by sulfuric acid (SAA), phosphoric acid (PAA), or phosphoric-sulfuric acid (PSA) anodizing. While generally the main concern is controlling the film morphology, such as the pore diameter, oxide-, and barrier layer thickness, little is known on how the anodic oxide chemistry affects the interactions at the interface upon adhesive bonding. To study the link between surface chemistry and interfacial bonding, featureless oxides were prepared by stopping the anodizing during the formation of the barrier layer. A model was developed to quantify the relative amounts of OH–, PO43–, and SO42– by curve-fitting the XPS data. Calculations showed that almost 40% of the surface species in PAA oxide are phosphates (PO43–), whereas about 15% are sulfates (SO42) in SAA. When both anions were present in the electrolyte, phosphate incorporation was inhibited. Studies of the interaction between this set of Cr(VI)-free oxides and diethylenetriamine (DETA)—an amine curing-agent for epoxy resin—showed that all oxides interact with the nitrogen of DETA. However, larger ratios of Lewis-like acid–base bonding between the amine electron pair and the acidic hydroxyl on phosphate surface sites were observed.

No abstract is provided for this article.

The modern development of nanotechnology requires the discovery of simple approaches that ensure the controlled formation of functional nanostructures with a predetermined morphology. One of the simplest approaches is the self-assembly of nanostructures. The widespread implementation of self-assembly is limited by the complexity of controlled processes in a large volume where, due to the temperature, ion concentration, and other thermodynamics factors, local changes in diffusion-limited processes may occur, leading to unexpected nanostructure growth. The easiest ways to control the diffusion-limited processes are spatial limitation and localized growth of nanostructures in a porous matrix. In this paper, we propose to apply the method of controlled self-assembly of gold nanostructures in a limited pore volume of a silicon oxide matrix with submicron pore sizes. A detailed study of achieved gold nanostructures' morphology, microstructure, and surface composition at different formation stages is carried out to understand the peculiarities of realized nanostructures. Based on the obtained results, a mechanism for the growth of gold nanostructures in a limited volume, which can be used for the controlled formation of nanostructures with a predetermined geometry and composition, has been proposed. The results observed in the present study can be useful for the design of plasmonic-active surfaces for surface-enhanced Raman spectroscopy-based detection of ultra-low concentration of different chemical or biological analytes, where the size of the localized gold nanostructures is comparable with the spot area of the focused laser beam.

Argon gas cluster ion beams (Ar-GCIBs) provide new opportunities for molecular depth profiling and imaging of organic materials and biological samples, thanks to recent technological developments that have led to the construction of new SIMS spectrometers where the traditional issues related to their low lateral resolution along with poor mass resolution and mass accuracy are overcome. The present fundamental contribution on SIMS molecular depth profiling investigates the variations of the secondary ion signals observed at the organic–inorganic hybrid interface when using Ar-GCIB as the analytical beam. With this in mind, depth profiling experiments were performed with a ToF-SIMS spectrometer using different analysis beams: 30-keV Bi5 + versus 10-keV Arn + with a cluster size (n) of 800, 1500, 3000 and 5000 atoms, respectively. A 10-keV Ar3000 + beam was used for sputtering in all the experiments. Irganox 1010 and model polymers such as polystyrene (PS) and poly (methyl methacrylate) (PMMA) oligomers were chosen. Silicon wafer and a polymer-based substrates were employed to test materials with different stiffness, which is directly related to their Young’s moduli, an important parameter in this study. Ar-GCIB depth profiles systematically show ion signal enhancement of the characteristic fragments of PS and Irganox 1010 when approaching the interface with the silicon substrate, that can reach up to 60% for [M1010-H]− in Irganox films deposited onto silicon wafers. This enhancement increases with increasing n in both ion polarities. These results point out some ionization effects on the observed signal enhancement at the interface. The experimental observations will be explained on the basis of the physics of the impact of large argon clusters on different target materials and the energy confinement of the ion projectile in the organic overlayers. Finally, the thickness of organic films on rigid substrates in the nanoscale appears to be a crucial parameter to dramatically improve the sensitivity to molecular fragments when using large Ar cluster ions as analysis beams.

Metal-organic framework HKUST-1 was synthesized on a porous copper mesh using an electrochemical synthesis technique. By partially oxidizing the mesh in a controllable manner, thin crystal layers could be synthesized without structurally damaging the supporting mesh. Good control over the crystal size could be obtained by varying the water content of the synthesis mixture. This technique allows the formation of crystal layers overgrowing the porous copper support at mild temperatures and short synthesis times.