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The dissociation of methane is not only an important reaction step in catalytic processes, but also of fundamental interest. Dynamical effects during the dissociative chemisorption of methane on metal surfaces cause significant differences in computed reaction rates, compared to what is predicted by typical transition state theory (TST) models. It is clear that for a good understanding of the catalytic activation of methane dynamical simulations are required. In this paper, a general blueprint is provided for performing dynamical simulations of the dissociative chemisorption of methane on metal surfaces, by employing either the quasi-classical trajectory or ring polymer molecular dynamics approach. If the computational setup is constructed with great care-since results can be affected considerably by the setup - chemically accurate predictions are achievable. Although this paper concerns methane dissociation, the provided blueprint is, so far, applicable to the dissociative chemisorption of most molecules. [ABSTRACT FROM AUTHOR]

The laser surface texturing (LST) technique has recently been used to enhance adhesion bond strength in various coating applications and to create structures with controlled hydrophobic or superhydrophobic surfaces. The texturing processing parameters can be adjusted to tune the surface's polarity, thereby controlling the ratio between the polar and dispersed components of the surface free energy and determining its hydrophobic character. The aim of this work is to systematically select appropriate laser and scan head parameters for high-quality surface topography of metal-based materials. A correlation between texturing parameters and wetting properties was made in view of several technological applications, i.e., for the proper growth of conformal layers onto laser-textured metal surfaces. Surface analyses, carried out by scanning electron microscopy and profilometry, reveal the presence of periodic microchannels decorated with laser-induced periodic surface structures (LIPSS) in the direction parallel to the microchannels. The water contact angle varies widely from about 20° to 100°, depending on the treated material (titanium, nickel, etc.). Nowadays, reducing the wettability transition time from hydrophilicity to hydrophobicity, while also changing environmental conditions, remains a challenge. Therefore, the characteristics of environmental dust and its influence on the properties of the picosecond laser-textured surface (e.g., chemical bonding of samples) have been studied while monitoring ambient conditions. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to review the current one-step electrodeposition of superhydrophobic coatings on metal surfaces. Design/methodology/approach: One-step electrodeposition is a versatile and simple technology to prepare superhydrophobic coatings on metal surfaces. Findings: Preparing superhydrophobic coatings by one-step electrodeposition is an efficient method to protect metal surfaces. Originality/value: Even though there are several technologies, one-step electrodeposition still plays a significant role in producing superhydrophobic coatings. [ABSTRACT FROM AUTHOR]

Vision-based defect recognition in the metal industry is an important and challenging task. Many mainstream methods based on supervised learning need a large amount of annotated defect data. However, the data acquisition in industrial scenarios is quite difficult and time-consuming. To alleviate the problem, in this paper, we propose a few-shot defect recognition (FSDR) method for metal surfaces by attention-embedding and self-supervised learning. The proposed method includes two stages,pre-training and meta learning. In the pre-training stage, an attention embedding network (AEN) is designed for better learning the defect local correlation of multi-receptive field and reducing the background interference, and to train a robust AEN without any annotations, a multi-resolution cropping self-supervised method (MCS) is developed for better generalizing the few-shot recognition task. Then, in the meta learning stage, to generate the embedding features, the defect images are encoded by the pre-trained AEN, and we also design a query-guided weight (QGW) to address the bias of embedding feature vector. The classification information is gained by computing the distance of the embedding feature vector of each category. We evaluate the proposed FSDR on the NEU dataset and the experiments show competitive results in 1-shot and 5-shot defect recognition tasks compared with the mainstream methods. [ABSTRACT FROM AUTHOR]

This study focuses on depositing Ni/W-Al2O3 nanocomposites onto a low-carbon substrate using the pulse electrodeposition technique. The effects of pulse current density on microstructural characteristics, microhardness, phase structure, and wear/corrosion properties of Ni/W-Al2O3 nanocomposites were investigated. Among the investigated nanocomposites, Ni/W-Al2O3 deposited at 0.6 A/dm2 current density showed the finest structure with average Ni-W grain and Al2O3 nanoparticle sizes of 66.7 nm and 39.1 nm, respectively. The Ni/W-Al2O3 nanocomposite deposited under the same conditions exhibited a maximum microhardness of ~ 825.7 HV, while also demonstrating the lowest corrosion current density of ~ 0.72 A/cm2. After 60 min of wear testing, wear loss of Ni/W-Al2O3 nanocomposite deposited at 0.6 A/dm2 was recorded as 42.8 mg, indicating its excellent wear resistance. In contrast, Ni/W-Al2O3 nanocomposite deposited at 0.8 A/dm2 displayed the highest wear loss value of 101.5 mg. [ABSTRACT FROM AUTHOR]

The paper deals with the task of automated segmentation of images of defects metal surfaces. The aim of the study is to improve segmentation algorithms using deep learning methods. The expediency of using the U-Net neural network, which is effective in the tasks of semantic image segmentation, is substantiated. With the help of a special architecture, the network can create segmentation masks with high efficiency. The training dataset for the neural network contained images of four classes of defects, including chips, cracks, and stains. As a result of analyzing the distribution of defect classes in the training dataset, it was concluded that the classes were unbalanced, which negatively affects the training results. To evaluate the quality of network training, a set of metrics such as Accuracy, F1 Score, and IOUScore is considered. The feasibility of using these metrics is analyzed, taking into account the features of the training data set. It is proved that under conditions of significant imbalance of classes, the Accuracy metric does not reflect the real quality of the model. The influence of different variants of the ResNet architecture backbone on the training results is analyzed. It is determined that the best results are shown by the ResNet18 model, which managed to obtain a Dice coefficient of 69 % and an IOUScore of 53 % on the test data set. It is proved that an increase in the number of model parameters does not always lead to an improvement in the reliability of the results. The article provides examples of test images and defect masks and countures predicted by the neural network. [ABSTRACT FROM AUTHOR]

The development of approaches for the non-thermal sterilization of instruments is an urgent task to ensure the safety of meat industry products, where the use of hot water leads to the formation of condensates and a deterioration in the hygienic condition of the premises. In this study, an installation for sterilizing knives was created, which works by activating aqueous salt solutions with a glow discharge. The power consumption of the installation reactor is only 125–150 Wh. The temperature rise of the sterilizing agent used is about 1.1 ± 0.2 °C/min/L. The effectiveness of the installation for plasma-activation of aqueous solutions of chloride and sodium sulfate by glow discharge (PAW) in relation to the inactivation of microorganisms, including Staphylococcus aureus, Salmonella typhimurium, Pseudomonas gessardii and L. monocytogenes, on steel surfaces was evaluated. Samples of stainless steel (parts of knives) were used in two versions (new and artificially aged). Mono- and polyspecies bacterial biofilms were grown on the surface of the samples. The treatment was carried out by immersing samples of steel plates in plasma-activated aqueous solutions. It was found that the treatment of plates in a knife sterilizer for 1 min had an effective effect on the inhibition of all types of studied bacteria. [ABSTRACT FROM AUTHOR]

We studied the surface-enhanced Raman spectra of amino acids D-alanine and DL-serine and their mixture on silver nanoisland films (SNF) immersed in phosphate-buffered saline (PBS) solution at millimolar amino acid concentrations. It is shown that the spectra from the amino acid solutions differ from the reference spectra for microcrystallites due to the electrostatic orientation of amino acid zwitterions by the metal nanoisland film. Moreover, non-additive peaks are observed in the spectrum of the mixture of amino acids adsorbed on SNF, which means that intermolecular interactions between adsorbed amino acids are very significant. The results indicate the need for a thorough analysis of the Raman spectra from amino acid solutions, particularly, in PBS, in the presence of a nanostructured silver surface, and may also be of interest for studying molecular properties and intermolecular interactions. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the structural evolution of a two-dimensional (2D) supramolecular assembly system, which is steered by the thermally activated deprotonation of the primary organic building blocks on a Ag(111) surface. Scanning tunneling microscopy revealed that a variety of structures, featuring distinct structural, chiral, and intermolecular bonding characters, emerged with the gradual thermal treatments. According to our structural analysis, in combination with density function theory calculations, the structural evolution can be attributed to the successive deprotonation of the organic building blocks due to the inductive effect. Our finding offers a facile strategy towards controlling the supramolecular assembly pathways and provides a comprehensive understanding of the 2D crystal engineering on surfaces. [ABSTRACT FROM AUTHOR]

Over the past decade, interest has increased in controlling the wettability of metal surfaces with various liquids. In particular, the use of hydrophobic functional surfaces improves the efficiency and reliability of thermal power plants and systems operating in various areas of life. One of the most promising ways to achieve a hydrophobic state of structural materials is surface modification using laser equipment: laser ablation. As a result of exposure to laser radiation, melting, evaporation and recrystallization of the surface layer of the metal occur. By varying the parameters of exposure to laser radiation, it is possible to form a relief with specified geometric characteristics on a metal surface. The creation of hydrophobic metal surfaces using laser equipment includes the following steps: choosing the type of laser source, determining the radiation parameters and the trajectory of the laser beam over the surface, preparing the initial surface, forming the relief, and reducing the surface energy after laser ablation. This paper presents an overview of the results of research on the creation of hydrophobic metal surfaces based on the formation of a structured relief. In most studies, a relief was formed on the surface of metal samples in the form of equidistant lines, a grid, or had no pronounced structure (irregular structure). It has been established that the hydrophobic state of a metal surface with the highest contact angles (more than 150°) is achieved by laser texturing of the relief in the form of equidistant lines or a grid with a step not exceeding 100 μm. The maximum contact angle (approximately 179°) was obtained by forming a relief in the form of a grid with mutually perpendicular lines equidistant at 15 and 20 µm. [ABSTRACT FROM AUTHOR]

Electrocatalytic denitrification is a promising technology for removing NOx species (NO3−, NO2− and NO). For NOx electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NOxRR. At low potential we classify metals by the binding of *NO versus *H. Analogous to classifying CO2 reduction by *CO vs. *H, Cu is able to bind *NO while not binding *H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity‐volcano. For metals that does not bind NO the reaction stops at NO, similar to CO2‐to‐CO. At potential above 0.3 V vs. RHE, we speculate a low barrier for N coupling with NO causing N2O formation. The work provides a clear strategy for selectivity and aims to inspire future research on NOxRR. [ABSTRACT FROM AUTHOR]

Electrocatalytic denitrification is a promising technology for removing NOx species (NO3−, NO2− and NO). For NOx electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NOxRR. At low potential we classify metals by the binding of *NO versus *H. Analogous to classifying CO2 reduction by *CO vs. *H, Cu is able to bind *NO while not binding *H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity‐volcano. For metals that does not bind NO the reaction stops at NO, similar to CO2‐to‐CO. At potential above 0.3 V vs. RHE, we speculate a low barrier for N coupling with NO causing N2O formation. The work provides a clear strategy for selectivity and aims to inspire future research on NOxRR. [ABSTRACT FROM AUTHOR]

Purpose: We investigated the recovery and extraction efficiency of DNA from three metal surfaces (brass, copper, steel) relevant to forensic casework, and plastic (control) using two different swabbing systems; Rayon and Isohelix™ swabs, with sterile water and isopropyl alcohol respectively, as the wetting solutions. Methods: Twenty nanograms of human genomic DNA were applied directly to Isohelix™ and Rayon swabs; and to the metal and plastic substrates. All substrates were left to dry for 24 h, followed by single wet swabbing and extraction with the DNA IQ™ System. DNA extracts were quantified using real time quantitative PCR assays with SYBR green chemistry. Results: DNA was extracted from directly seeded Isohelix™ swabs with a high efficiency of 98%, indicating effective DNA-release from the swab into the extraction buffer. In contrast, only 58% of input DNA was recovered from seeded Rayon swabs, indicating higher DNA retention by these swabs. Isohelix™ swabs recovered 32 – 53% of DNA from metal surfaces, whilst the Rayon swabs recovered 11—29%. DNA recovery was lowest from copper and highest from brass. Interestingly, Rayon swabs appeared to collect more DNA from the plastic surface than Isohelix™ swabs, however, due to the lower release of DNA from Rayon swabs they returned less DNA overall following extraction than Isohelix™ swabs. Conclusion: These results demonstrate that DNA samples deposited on metal surfaces can be more efficiently recovered using Isohelix™ swabs wetted with isopropyl alcohol than Rayon swabs wetted with sterile water, although recovery is affected by the substrate type. [ABSTRACT FROM AUTHOR]

This study illustrates pervasive challenges in studying wetting dynamics, including dynamic contact angles, on irregularly roughened surfaces. We demonstrate that asymmetric water droplet shapes occur more than 50% of the time during static and dynamic contact angle measurements on sandblasted Zn-plated stainless steel with a polymeric overcoat. The pinning that causes the asymmetric drop shape distortion on horizontal surfaces also influences the sliding behavior on inclined surfaces. These effects lead to a poor correlation between the measured dynamic contact angles and the observed sliding angles (critical tilt angles). Our work emphasizes that large variations in the values of these dynamic wetting parameters are inherent to the heterogeneity of the surface roughness, and thus they limit the usefulness of standard dynamic wetting criteria. These findings have implications for academic and industrial research focused on making coated materials that have consistent wettability properties throughout their usage life cycle. [ABSTRACT FROM AUTHOR]

The characteristics of different shapes of nonmetallic inclusions (NMIs) are determined using different methods. In this respect, various shapes of NMIs, including spherical, octahedral, elongated, bar‐like, plate‐like, polyhedral, and irregular inclusions, are observed in different steels and ferroalloys. The inclusions are investigated using three methods: 1) 2D investigations on a polished cross section (2D method); 2) 3D investigations on a film filter after electrolytic extraction and filtration (EE method); and 3) 3D investigations on a metal surface after electrolytic extraction (MS method). In addition, scanning electron microscopy (SEM) with an energy‐dispersive spectrometer (EDS) is used for the determination of the chemical composition of inclusions. The advantages and limitations of different methods for investigations of different shaped inclusions are discussed. The results show that the 2D method is less precise to detect the morphology, size, and number of inclusions; however, the EE and MS methods are used to determine a more accurate morphology. Furthermore, the MS method is found to be more advantageous in detecting large‐sized inclusions. This study also shows that the results on both the film filter and metal surface should be grouped together to obtain more comprehensive information of the inclusion characteristics. [ABSTRACT FROM AUTHOR]

The modification of metal electrode surfaces with functional organic molecules is an important part of organic electronics. The interaction of the buckminsterfullerene fragment molecule pentaindenocorannulene with a Cu(100) surface is studied by scanning tunneling microscopy, dispersion‐enabled density functional theory, and force field calculations. Experimental and theoretical methods suggest that two adjacent indeno groups become oriented parallel to the surface upon adsorption under mild distortion of the molecular frame. The binding mechanism between molecule and surface is dominated by strong electrostatic interaction owing to Pauli repulsion. Two‐dimensional aggregation at room temperature leads to a single lattice structure in which all molecules are oriented unidirectionally. Their relative arrangement in the lattice suggests noncovalent intermolecular interaction through C−H⋅⋅⋅π bonding. [ABSTRACT FROM AUTHOR]

A method is developed for applying metallic, intermetallic, or ceramic coatings to a metal surface by means of ultrasound (high-frequency acoustic vibrations). The method may also be used to reinforce metallic surfaces by means of particles of another metal or ceramic. Under the action of ultrasound, chemical reactions and solid-phase diffusion are accelerated. That is accompanied by strong adhesion of the metal matrix to the particles; solid-phase transformations; and the formation of intermetallides, oxides, carbides, nitrides, and other compounds, depending on the surrounding gas and the powder composition. As a result, a composite coating or layer with nanostructure or microstructure is formed on the surface. [ABSTRACT FROM AUTHOR]

The salinization and contamination of metal surfaces by chloride‐containing aerosols is of great importance with regard to corrosion phenomena of damaged coated metal surfaces and stainless steels in the maritime sector and in offshore applications. Detailed questions have to be answered to clarify whether and to what extent salinization of the surface has an influence on the adhesion and durability of coatings in repairing applications and on pitting occurrence on stainless steels under atmospheric conditions. The questions arise which degree of salinization is reached after which period of time and how a defined and reproducible salinization can be simulated in the laboratory for further systematic investigations. The article is dedicated to these questions. Results of a field trial on the Island of Heligoland are presented and a simple procedure for a defined loading of metal surfaces with chlorides at a laboratory scale using a design of experiments (DoE) approach is introduced. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effects of the surface modification of 316L stainless steel (SS) by low-temperature plasma nitriding on endothelial cells for stent applications. Results: X-ray diffraction (XRD) confirmed the incorporation of nitrogen into the treated steel. The surface treatment significantly increased SS roughness and hydrophilic characteristics. After 4 h the cells adhered to the nitride surfaces and formed clusters. During the 24 h incubation period, cell viability on the nitrided surface was higher compared to the polished surface. Nitriding reduced late apoptosis of rabbit aorta endothelial cell (RAEC) on the SS surface. Conclusion: Low temperature plasma nitriding improved the biocompatible of stainless steel for use in stents. [ABSTRACT FROM AUTHOR]

Inert metal surfaces present more chances of hosting organic intact radicals than other substrates, but large amounts of delocalized electronic states favor charge transfer and thus spin quenching. Lowering the molecule–substrate interaction is a usual strategy to stabilize radicals on surfaces. In some works, thin insulating layers were introduced to provide a controllable degree of electronic decoupling. Recently, retinoid molecules adsorbed on gold have been manipulated with a scanning tunneling microscope (STM) to exhibit a localized spin, but calculations failed to find a radical derivative of the molecule on the surface. Now the formation of a neutral radical spatially localized in a tilted and lifted cyclic end of the molecule is presented. An allene moiety provokes a perpendicular tilt of the cyclic end relative to the rest of the conjugated chain, thus localizing the spin of the dehydrogenated allene in its lifted subpart. DFT calculations and STM manipulations give support to the proposed mechanism. Spinning on the surface: An allene formed by a sigmatropic reaction on retinoic acid shows a long‐lived magnetism on a gold surface after dehydrogenation. An allene moiety provokes a perpendicular tilt of the cyclic end relative to the rest of the conjugated chain, thus localizing the spin of the dehydrogenated product in its lifted subpart. [ABSTRACT FROM AUTHOR]

In this work we present a model for the surface oxide film growth considering the influence of space charge. The space charge field Esp is assumed proportional to the charge of moving metal ions and electrons in the oxide layer. The surface charge field Eox decreases as the Cabrera and Motts’ oxide thickness X grows to its limit X1 (Eox = VM/X). Eox remains constant for further growth of the oxide film (Eox = VM/X1). The obtained equation for the growing rate of the oxide film covers two stages. The first stage is characterized by a negligible space charge and is described by the typical inverse logarithmic law. During transition from thin to thick film, the oxidation growth rate is described by a direct logarithmic law which is confirmed by many experiments. At the end of this stage, the drift of metal ions is replaced by their diffusion that leads to parabolic law. [ABSTRACT FROM AUTHOR]

Abstract: Multimetallic clusters have long been investigated as molecular surrogates for reactive sites on metal surfaces. In the case of the μ4‐nitrido cluster [Fe4(μ4‐N)(CO)12]−, this analogy is limited owing to the electron‐withdrawing effect of carbonyl ligands on the iron nitride core. Described here is the synthesis and reactivity of [Fe4(μ4‐N)(CO)8(CNArMes2)4]−, an electron‐rich analogue of [Fe4(μ4‐N)(CO)12]−, where the interstitial nitride displays significant nucleophilicity. This characteristic enables rational expansion with main‐group and transition‐metal centers to yield unsaturated sites. The resulting clusters display surface‐like reactivity through coordination‐sphere‐dependent atom rearrangement and metal–metal cooperativity. [ABSTRACT FROM AUTHOR]

Butyl rubber as a commercial elastomer has got many applications in various products such as tires, protective clothes, sealants, hose (steam and automotive), inner coating of tanks, etc. Considering these usages, butyl rubber might be subjected to acidic or alkaline environments. Acid and alkaline materials can diffuse through the rubber and cause degradation of its structure which leads to deterioration of rubber properties including adhesion strength. In this study, the effects of environments having different pH values on adhesion strength between rubber compounds--based on butyl rubber and bromobutyl rubber--and aluminum surface are investigated. Samples were immersed in solutions with different pH values of 0.7, 3, 7, 11 and 13.7. By conducting tensile and tack tests, changes in adhesion strength and tackiness property of samples are studied. Considering the broad range of examined pH values, results demonstrate that solutions with more acidic and alkaline pH values severely reduce adhesion strength and leads to about 60% reduction in adhesion. However, pH values closer to neutral pH have a less negative effect and cause up to 49% decrement in adhesion strength. Furthermore, Samples which were immersed in alkaline solutions lost their tackiness property, whereas the samples which were immersed in acidic solution retained their tackiness. However, in these cases, tack property was reduced to 1/7 of its value before being immersed in the acidic solution. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the impact of hydrodynamic forces on the multiplication ofE. coli, and biofilm formation and dispersion. The experiments were provided in a flow chamber simulating a cleaning-in-place system. Biofilm biomass was measured using a crystal violet dye method. The results show that hydrodynamic forces affect not only biofilm formation and dispersion but the multiplication ofE. coliin the first place. We found more biofilm biomass on the rough surface than on the smooth one. The results of the biofilm formation test show that laminar flow promotes the biofilm growth over 72 h, meanwhile turbulent flow after 48 h causes decrease in biomass. The results of the biofilm dispersion test, in contrast, show that laminar flow removed less biofilm from both materials that turbulent flow did. Therefore, taking into account these findings in cleaning-in-place technology can substantially reduceE. colimultiplication and biofilm formation. [ABSTRACT FROM PUBLISHER]

The effect that the ionizing radiation caused by radioactive contamination of soil exerts on the surface of carbon steel 20 samples, on their corrosion resistance, and on operation reliability according to lowcycle fatigue tests (taking into account that fatigue is one of the main causes of failures resulting from corrosion and mechanical damage of thin-wall metal structures, in particular, of pipelines) was studied. It was shown that even low activity levels (below maximum permissible levels) caused corrosion loss of the metal and a decrease in the operation reliability. Synergistic protective compounds suppressing the destructive radiation effects and ensuring reliable operation of metal structures due to chelation of the surface metal atoms were developed using computer simulation. [ABSTRACT FROM AUTHOR]

Chirality is a property of matter which manifests at any length scale and can equally appear as quantum phenomena and in three-dimensional macroscopic structures. However, while chirality can be easily achieved by removing the inversion symmetry operation in hexagonal or tetragonal metal structures, chirality in metals is an unusual and barely developed phenomenon. Nevertheless, chirality can greatly alter mechanical and functional features of materials, making them suitable for catalysis, optics, electromagnetism, thermoelectricity and superconductivity; properties strictly dependent on the anisotropy of the crystal and on the direction of the applied force. This review aims to extend the definition of chirality to describe nanoclusters, metal surfaces and crystals and to provide an interdisciplinary overview on how symmetry can affect their properties. This review was submitted as part of the 2016 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged. [ABSTRACT FROM AUTHOR]

The energetics at organic-metal interfaces are, to large extend, determined by the structure of the molecular adsorbate on the substrate surface. As shown by low-energy electron diffraction (LEED) the zigzag shape of picene leads to a peculiar monolayer structure on Ag(111), Ag(110), and Cu(111) with one molecule in the unit cell lying essentially flat and the other one adopting an edge-on orientation. The adsorbate-substrate coupling is weak as shown by ultraviolet photoelectron spectroscopy (UPS). This is in striking contrast to monolayers of straight pentacene, where all molecules lie flat and are strongly coupled, involving charge transfer complex formation on most of these surfaces. The peculiar packing structure of picene leads to weak interfacial coupling on clean metal surfaces. In contrast, pentacene is chemisorbed on Ag and Cu surfaces involving electron transfer from the substrate. [ABSTRACT FROM AUTHOR]

Water and its fragments are present on metal surfaces under all but the most extreme conditions, acting both as a reactive species and as a ligand in ways that have yet to be fully explored. This review focuses on experimental studies of the chemical species and hydrogen bonding structures that form in the first layer adsorbed on a metal surface. The development of non-invasive probes that avoid dissociating water, or disrupting fragile bonding structures, now allows experiments to distinguish between different structural models for water and its fragments at the surface, allowing us to test the accuracy of modern structural calculations and provide a better picture of how the metal surface influences the structures and chemical species present. We start by describing the behaviour of Pt(1 1 1), whose redox chemistry is important in electrochemical fuel cells and has been studied in detail, providing a good reference system against which to discuss the effect changing the surface symmetry and metal reactivity has on the interface structure. Evidence for the presence and the role of hydroxyl and hydrated ‘hydronium’ species is described and we discuss the outlook for future experiments and identify some questions that remain to be resolved. [ABSTRACT FROM PUBLISHER]

Graphene, a two-dimensional (2D) material with unique electronic properties, appears to be an ideal object for the application of surface-science methods. Among them, a family of scanning probe microscopy methods (STM, AFM, KPFM) and the corresponding spectroscopy add-ons provide information about the structure and electronic properties of graphene on the local scale (from [ABSTRACT FROM AUTHOR]

We review the recently developed three-dimensional (3D) atom-superposition approach for simulating scanning tunneling microscopy (STM) and spectroscopy (STS) based on ab initio electronic structure data. In the method, contributions from individual electron tunneling transitions between the tip apex atom and each of the sample surface atoms are summed up assuming the one-dimensional (1D) Wentzel-Kramers-Brillouin (WKB) approximation in all these transitions. This 3D WKB tunneling model is extremely suitable to simulate spin-polarized STM and STS on surfaces exhibiting a complex noncollinear magnetic structure, i.e., without a global spin quantization axis, at very low computational cost. The tip electronic structure from first principles can also be incorporated into the model, that is often assumed to be constant in energy in the vast majority of the related literature, which could lead to a misinterpretation of experimental findings. Using this approach, we highlight some of the electron tunneling features on a prototype frustrated hexagonal antiferromagnetic Cr monolayer on Ag(111) surface. We obtain useful theoretical insights into the simulated quantities that is expected to help the correct evaluation of experimental results. By extending the method to incorporate a simple orbital dependent electron tunneling transmission, we reinvestigate the bias voltage- and tip-dependent contrast inversion effect on the W(110) surface. STM images calculated using this orbital dependent model agree reasonably well with Tersoff-Hamann and Bardeen results. The computational efficiency of the model is remarkable as the k-point samplings of the surface and tip Brillouin zones do not affect the computational time, in contrast to the Bardeen method. In a certain case we obtain a relative computational time gain of 8500 compared to the Bardeen calculation, without the loss of quality. We discuss the advantages and limitations of the 3D WKB method, and show further ways to improve and extend it. [ABSTRACT FROM AUTHOR]

Carbon monoxide is a ubiquitous molecule in surface science, materials chemistry, catalysis and nanotechnology. Its interaction with a number of metal surfaces is at the heart of major processes, such as Fischer-Tropsch synthesis or fuel-cell optimization. Recent works, coupling structural and nanoscale in situ analytic tools have highlighted the ability of metal surfaces and nanoparticles to undergo restructuring after exposure to CO under fairly mild conditions, generating nanostructures. This Minireview proposes a brief overview of recent examples of such nanostructuring, which leads to a discussion about the driving force in reversible and non-reversible situations. [ABSTRACT FROM AUTHOR]

An inspection of mechanically damaged areas on manufactured metal parts is necessary to produce high-quality products. A scanning probe on a sample is necessary for a conventional surface inspection system, which is time-consuming. We propose a novel high-speed detection method for defects on metal surfaces with rolling indentations. To obtain a large field of view in a measurement, we used a laser sheet that was expanded with a laser line generator and also used an expanded collimated beam, rather than a small laser spot as used in conventional techniques. Furthermore, we used an obliquely incident laser beam to suppress the effect of the rolling indentations surrounding defects, and also applied spatial frequency filtering to extract only defects. The spatial frequency filtering under oblique incidence is theoretically explained and defect extraction was investigated in experiments. [ABSTRACT FROM AUTHOR]

We validate a computational setup based on density functional theory to investigate hexagonal boron nitride ( h-BN) monolayers grown on different transition metals exposing hexagonal surfaces. An extended assessment of our approach for the characterization of the geometrical and electronic structure of such systems is performed. Due to the lattice mismatch with the substrate, the monolayers can form Moiré-type superstructures with very long periodicities on the surface. Thus, proper models of these interfaces require very large simulation cells (more than 1,000 atoms) and an accurate description of interactions that are modulated with the specific registry of h-BN on the metal. We demonstrate that efficient and accurate calculations can be performed in such large systems using Gaussian basis sets and dispersion corrections to the (semi-)local density functionals. Four different metallic substrates, Rh(111), Ru(0001), Cu(111), and Ni(111), are explicitly considered, and the results are compared with previous experimental and computational studies. [ABSTRACT FROM AUTHOR]

We demonstrate that reflectance difference spectroscopy (RDS) is sensitive to defects induced by ion bombardment, located either in the topmost layer or in the subsurface region. Most importantly, these two kinds of defects can be spectrally discriminated, since the corresponding signatures in the RD spectrum arise from perturbations of different types of electronic states: The defects in the topmost surface layer mainly lead to a quenching of the optical anisotropy related to surface states, whereas the subsurface defects strongly affect the optical anisotropy originating from transitions between surface-modified bulk electronic states. Consequently, RDS can be used to simultaneously monitor the defects in the topmost surface layer and in the subsurface region in-situ during ion bombardment and thermal annealing. [ABSTRACT FROM AUTHOR]

A chemicurrent is a flux of fast (kinetic energy ≱ 0.5-1.3 eV) metal electrons caused by moderately exothermic (1-3 eV) chemical reactions over high work function (4-6 eV) metal surfaces. In this report, the relation between chemicurrent and surface chemistry is elucidated with a combination of top-down phenomenology and bottom-up atomic-scale modeling. Examination of catalytic CO oxidation, an example which exhibits a chemicurrent, reveals 3 constituents of this relation: The localization of some conduction electrons to the surface via a reduction reaction, 0.5O2 + δe- → Oδ- (Red); the delocalization of some surface electrons into a conduction band in an oxidation reaction, 0δ- + CO → CO → CO2δ- → CO2+ δe- (Ox); and relaxation without charge transfer (Rel). Juxtaposition of Red, Ox, and Rel produces a daunting variety of metal electronic excitations, but only those that originate from CO2 reactive desorption are long-range and fast enough to dominate the chemicurrent. The chemicurrent yield depends on the universality class of the desorption process and the distribution of the desorption thresholds. This analysis implies a power-law relation with exponent 2.66 between the chemicurrent and the heat of ad- sorption, which is consistent with experimental findings for a range of systems. This picture also applies to other oxidation-reduction reactions over high work function metal surfaces. [ABSTRACT FROM AUTHOR]

Combinatorial bio-techniques have demonstrated that proteins can be good and even selective binders for several inorganic surfaces, including metals. However, the understanding of the basic physical mechanisms that govern such interactions did not keep up with the success in these experiments. The comprehension of such mechanisms would greatly benefit from the computational investigation of the problem. Because of the complexity of the system, classical molecular dynamics simulations based on an atomistic description appear to be the best compromise between reliability and feasibility. For proteins interacting with metal surfaces, however, methodological improvements with respect to standard Molecular Dynamics (MD) of proteins are needed, since the polarization of the metal induced by the protein (and the surrounding water) is not generally negligible. In this article, we present a simple approach to introduce metal polarization effects (often termed image effects) in MD simulations by exploiting standard features of bio-oriented MD codes such as the widely used GROMACS and NAMD. Tests to show the reliability of the proposed methods are presented, and the results for a model application showing the importance of image effects are also discussed. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [ABSTRACT FROM AUTHOR]

The present paper analyses the time that wetness sensors on Zn and galvanised steel plates stayed wet in four locations within Australia: two in inland zones, one in a marine zone, and the other in a severe marine zone. All locations are classified as having a temperate climate. At each location, wetness was determined from interdigitated gold grids in thermal contact with plates openly exposed to the atmosphere. Individual periods of wetness were analysed, and it was found that the duration of wetness fell into three modes: short wetness periods of 1–4 h, but centred on <2 h; part day wetness periods of 8–20 h, depending on environmental severity; and multiple day wetness periods of three to five days, but with odd occurrences out to 20 days. The relative occurrence of each mode depended on the severity of the sites. To illustrate the dependence of corrosion events on the duration of wetness, time factors regulating secondary spreading were examined. It was observed that secondary spreading on Zn and galvanised steel only occurred if the duration of a drop on a plate exceeded certain critical limits. Furthermore, the spread of secondary spreading was highly dependent on the time period for which the drop remained stable. The implication of these findings to developing accelerated tests and to modelling atmospheric corrosion are discussed. [ABSTRACT FROM AUTHOR]

For optical-waveguiding structures composed of uniform segments that are invariant in the longitudinal direction, the Dirichlet-to-Neumann (DtN)-map method is highly competitive. Instead of computing the eigenmodes, it calculates the DtN operators of the uniform segments using an efficient Chebyshev collocation scheme. In this paper, a new formulation of the DtN-map method is developed for periodic piecewise uniform waveguiding structures. The method involves a recursive-doubling process so that the overall required computation time is proportional to log2 N, where N is the number of periods. We illustrate our method by analyzing the scattering of surface plasmon polaritons due to Bragg gratings on metal surfaces and thin metal films. [ABSTRACT FROM PUBLISHER]

This is the seventh paper outlining a holistic model of atmospheric corrosion. Previous papers have outlined how airborne salinity can be estimated at any given location, how salt deposition onto a surface can be modelled and what forms moisture can take on a plate surface. The present paper develops a model for rain induced cleaning of deposited aerosols from metal surfaces. The individual phenomena of splash and wash off are modelled, and then the effect of these processes on salt retention is discussed. The results of the models are compared with data from field exposures and laboratory tests. Simplified rules to allow the process to be incorporated into the holistic model framework are proposed. [ABSTRACT FROM AUTHOR]

First principles periodic density functional theory (DFT) has been applied to simulate the electrochemical interface between water and various (111) metal surfaces. The chemistry of water at these electrified interfaces is simulated and the parameters relevant to the macroscopic behavior of the interface, such as the capacitance and the potential of zero charge (PZC) are examined. In addition, we examine the influence of co-adsorbed CO upon the equilibrium potential for the activation of water over Pt(111). We find that for copper and platinum there is a potential window over which water is inert, but on Ni(111) water is always found in some dissociated form (as adsorbed OH* or H*, depending on the applied potential). Furthermore, the relaxation of water molecules via the flip/flop rotation is an important contribution to the interfacial capacitance. Our calculations for the coadsorbed H2O/CO system indicate that the adsorption of CO affects the binding energy of OH, such that water activation occurs at a higher equilibrium potential. [ABSTRACT FROM AUTHOR]

The paper describes a number of studies relating to the retention of marine salts on atmospheric corrosion test plates and the cleaning of such salts in field exposures. Data from three separate field studies are presented. In each study, instrumented zinc plates were openly exposed to the atmosphere. Plates were exposed in tropical, subtropical and temperate regions of Australia in severe marine, marine, urban and inland exposure conditions. Plates were washed at various times during exposure and, in some cases, they were ultrasonically cleaned after exposure. Ion chromatographic analysis was undertaken to determine the ion contents of the wash-off and ultrasonic cleaning solutions, and thus the salts present on the exposed plates. Sites and plates were also instrumented with rain gauges, salt candles, relative humidity sensors, surface temperature sensors and surface wetness sensors. Changes in the relative humidity at which the surfaces became wet were determined and used as a guide to infer the presence of salts on the surfaces. The effect of rainfall on the presence of salt was then determined. The factors controlling salt retention on surfaces are discussed, including the possibility that the ability of a surface to retain salt changes with time, and that sources of chloride other than crystalline salt may exist. The relevance of the study to atmospheric corrosion is discussed. [ABSTRACT FROM AUTHOR]

The time taken for wetness sensors on zinc plates, openly exposed to the atmosphere, to dry was analysed at four sites in southern Australia. The sites cover a range of environmental conditions from inland to marine. A number of typical drying patterns were observed, and it was found that these patterns could be related to the environmental severity and the probable presence of various salt contaminants. Therefore, at the marine site drying was frequently slow (>4 h) and appeared to be controlled by the presence of salts with a low deliquescent relative humidity (DRH) such as MgCl2. In contrast, at the inland sites drying was generally more rapid, which was consistent with either the drying of a clean surface or that of a surface controlled with salts of high DRH such as NaCl. The present paper presents histograms of drying rate for each site and the relationship between the distributions in drying rate and the environmental conditions is discussed. The relevance of the present study to modelling of atmospheric corrosion and to the design of cyclic tests to duplicate atmospheric corrosion is also discussed. [ABSTRACT FROM AUTHOR]

The present paper sets out the mathematical models that control the surface temperature of metal plates during atmospheric exposure. Heat transfer can be modelled by a series of heat transfer coefficients for different thermal processes, i.e. conduction, natural convection, forced convection, radiative heat losses to the sky, radiative heat transfer to or from the ground, incoming solar radiation, and evaporation and condensation. The model is applied to predict the surface temperature of near horizontal galvanised steel plates. Undercooling of a galvanised plate relative to the ambient air, i.e.the extent to which the temperature of the plate falls below that of its surroundings, is calculated for both clear and cloudy nights, with and without a slight breeze. It is found that breezes and clouds significantly decrease the extent of undercooling. The temperature differences between the plate and the ambient air after sunrise are also calculated. It is found that the prime factors controlling the post-sunrise temperature difference are whether the plate is wet or dry, whether the sky is cloudy or clear, and the wind speed. Under certain conditions, the increase in plate temperature relative to the surrounding air may be substantially suppressed. The time for wetted salts and aerosols to dry on plates post-sunrise is calculated and, under those conditions where the rise in temperature difference is suppressed, it may take a number of hours for aerosols to dry out. Estimates of temperature difference are compared with experimental data, and parametric equations for estimating surface temperature are presented. The relevance of the results to models of atmospheric corrosion is discussed. [ABSTRACT FROM AUTHOR]

The present study reports on an investigation into the dependence of the surface temperature of metal plates on environmental parameters. Monitored plates were exposed at three locations (one coastal and two inland) in southern Australia. The following parameters were monitored: surface temperature, surface wetness, wind speed, ambient relative humidity, air temperature and lifting condensation level. (The lifting condensation level is the height at which a parcel of air rising from the ground will reach saturation.) An analysis was undertaken of the temperature difference between the exposed plate surfaces and ambient air. It was found that the maximum temperature difference during the day depended on season, wind speed and, to a lesser extent, the lifting condensation level. The maximum undercooling during the night showed a relatively limited range and a weak dependence on wind speed. The rate of rise in temperature difference after sunrise was found to be only slightly dependent on season, but highly dependent on whether the surface was wet or dry. If the surface was dry, the rise in temperature difference depended on the wind speed and lifting condensation level. The relevance of these findings to moisture formation and evaporation from surfaces, and thus to corrosion processes, is discussed. [ABSTRACT FROM AUTHOR]

This paper outlines an experimental programme aimed at determining the mechanisms of salt removal from metallic surfaces by wind and rain. The paper provides data and process understanding that will be integrated into a holistic model of atmospheric corrosion. Experiments are reported in which fine salt crystals were deposited either wet (as fine droplets of seawater) or dry onto a surface. The surfaces were then placed in a wind tunnel and salt loss was determined as a function of wind speed. In another experiment, the motion of simulated raindrops falling onto metal plates was determined. Finally, in a third series of experiments, video footage of simulated rain on metal surfaces was studied in order to determine both the subsequent motion of rain and its cleaning efficiency. The efficiency of surface cleaning by wind and rain, as determined by these experiments, was then related to Australian climatic conditions. A future paper will present mathematical models of the processes defined in this paper. [ABSTRACT FROM AUTHOR]

This paper is the sixth paper outlining a holistic model of atmospheric corrosion. Previous papers outline how airborne salinity could be estimated at any given location and how the deposition onto a surface could be modelled. This paper investigates the initial reactions of raindrops or deposited marine aerosols on metal surfaces (zinc, galvanised steel, aluminium and gold). It combines short term field exposures with a series of controlled laboratory experiments. Surface changes to the metal upon field exposure are characterised by the nature and distribution of corrosion nodules, oxide films and retained salts. Eleven distinct forms of surface change are observed. The conditions promoting each pattern of surface changes were estimated by comparison with laboratory tests with a variety of deposition modes. Laboratory tests included deposition of saline droplets in three size ranges. A strategy to use the results in a holistic model of corrosion is proposed. [ABSTRACT FROM AUTHOR]

It is known that the exchange-correlation (XC) potential vXC obtained using the nonlocal weighted density approximation (WDA) does not yield the image behavior −1/4z outside a metal surface. This limitation might be due to the fact that the WDA is based on an isotropic scaling of the electron pair correlation function. In this work we present a WDA scheme based on an anisotropic scaling for the pair correlation function showing that, in this case, the potential vXC has the correct imagelike decay. This new scheme does not entail a significant additional effort if compared with the standard WDA method. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are used to investigate the rheological behavior of confined linear alkane chains under shear flow conditions. The simulated fluids are contained between atomistic, pure titanium walls, coupled to an external bath to maintain the temperature at a constant value. Shear flow conditions are imparted by moving the metal walls in opposite directions, and the corresponding density, velocity, and temperature profiles of the systems are calculated. For the shear rates investigated, all linear alkane chains exhibit a tendency for slip at the walls, evidenced by density profiles divided into two distinct regions and small discontinuities in the velocity and temperature profiles at the wall/fluid interface. Compared to equilibrium, alkane chains show higher mean-square end-to-end distances, characterized by higher components along the shear flow direction. [ABSTRACT FROM AUTHOR]

In this paper we discuss aspects of the concept described by Somorjai as the “flexible surface”, and whether some surfaces can be considered to be inflexible, or rigid. We present STM results which appear to manifest both types of behaviour for surfaces, depending on their oxidation state. Copper metal surfaces can be classed as flexible, showing facile reconstruction in the presence of oxygen, whereas an oxidised Pd(110) surface shows no apparent diffusivity, even at 500 K. We go on to show data for a bulk oxide which indicates that sub-stoichiometry in the sample induces an element of flexibility in the surface, especially during reaction with oxygen. Finally, this is related to the direct observation of spillover on model catalysts of Pd nanoparticles supported on TiO2. It must be recognised that flexibility relates to surface diffusivity and hence length- and time-scales. Surfaces which appear inflexible at short times may be flexible at long times. In relation to catalysis then, surface flexibility depends on the relationship between the time-scale of diffusive events on the surface and the catalytic turnover number. [ABSTRACT FROM AUTHOR]