Search

Pulverization and surface instability have been identified as the main impediments to the application of Si anodes in high-energy lithium-ion batteries (LIBs). In this study, a Si-graphitic carbon hybrid (SiG) is created via embedding Si nanoparticles in between expanding graphite interlayers, thus to be adopted as a model system to unravel structure-properties relations for LIBs applications. We explore the impact of artificial surface coating layers on the lithium cycling performance of SiG particles. In comparison with native SiG and carbon-coated SiG (CC-SiG), we find that the “sticky-carbon” coating, i.e., an epoxy-rich layer on top of the carbon coating, gave rise to superior cycle performance. In the “sticky carbon” coated SiG (SCC-SiG), the surface chemistry appears to have a pivotal role in both alleviating electrode disintegration and forming a favorable SEI rich in fluorine-polymers. These positive findings are examined in electrodes with mass loading ranging from 1.0 to 5.0 mg/cm2, achieving area capacities up to ∼5.0 mAh/cm2. A full cell adopting >6 mg/cm2 LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode and SCC-SiG delivers stable cycling performances. It is hence unraveled that the carbon coating layer with reactive surface groups on the top is an unrecognized key for wide range of Si-based anodes.

The stability of emulsions requires the fast formation of viscoelastic interfaces between water and oil phases. In double emulsions, two surfactant types (hydrophilic and lipophilic) are present and two interfacial films are involved. Understanding cooperative adsorption of these surfactants and its implication on properties of water/oil/water interfacial films will enable replacing the empirical methodologies used in designing double emulsion systems with a knowledge-based approach.The distribution of surfactants between the water/oil interfaces was investigated using single droplet diffusion experiments and simulation of equilibrium surfactant density profiles. The stability of the interfaces against coalescence was characterized by dye transport in a leach cell and coalescence time of single droplets in a model experiment. The conformation of the surfactants at an interface was then examined via surface rheology, sum frequency generation spectroscopy, and dissipative particle dynamics simulation.Two selected hydrophilic surfactants combined with a lipophilic surfactant induce very different properties at water/oil interfaces and different dye release behaviour from their corresponding double emulsions. Competitive adsorption of sodium dodecyl sulfate and lipophilic surfactant results in the improvement of encapsulation efficiency, elasticity of the interface, and resistance against coalescence due to the intercalation of surfactant alkyl chains into the oil chains.

In this work, the corrosion behavior and surface reactivity of as-cast and heat-treated nickel aluminum bronze casting alloy (UNS C95800) in 3.5 wt% NaCl solution is investigated under stagnant and flow conditions. Increasing flow rate conditions are simulated using a rotating disk electrode from 0 to 9000 revolutions per minute (rpm). Optical micrographs confirm the decrease in the phase fraction of corrosion-sensitive β phase in the microstructure of C95800 after annealing, which, in turn, enhances the corrosion resistance of the alloy. Electrochemical studies including open circuit potentiometry, potentiodynamic polarization, and electrochemical impedance spectroscopy are performed to assess the effect of flow rate and heat treatment on the corrosion of samples at 25 and 40 °C in 3.5 wt% NaCl solution. For both as-cast and heat-treated samples, increasing the flow rate (i.e., electrode rotating rate) linearly reduces the corrosion resistance, indicating that the metal dissolution rate is significantly affected by hydrodynamic flow. Increasing the solution temperature negatively impacts the corrosion behavior of the as-cast and heat-treated samples at all flow conditions.

Hypothesis The self-assembly of amphiphilic molecules onto solid substrates can result both in the formation of monolayers and multilayers. However, on oxidized and non-oxidized copper (Cu), only monolayer formation was reported for phosphonic acids possessing one phosphate head group. Here, the adsorption of octadecylphosphonic acid (ODPA) on Cu substrates through a self-assembly process was investigated with the initial hypothesis of monolayer formation. Experiments The relative amount of ODPA adsorbed on a Cu substrate was determined by infrared reflection/absorption spectroscopy (IRRAS) and by atomic force microscopy (AFM) investigations before and after ODPA deposition. X-ray photoelectron spectroscopy (XPS) with sputtering was used to characterize the nature of the layers. Findings The results show that the thickness of the ODPA layer increased with deposition time, and after 1 h a multilayer film with a thickness of some tens of nm was formed. The film was robust and required long-time sonication for removal. The origin of the film robustness was attributed to the release of Cu ions, resulting in the formation of Cu-ODPA complexes with Cu ions in the form of Cu(I). Preadsorbing a monolayer of octadecylthiol (ODT) onto the Cu resulted in no ODPA adsorption, since the release of Cu(I) ions was abolished.

Bronze surfaces were modified by methyl, carboxyl and amino terminated phosphonic acids films to assess the impact of the terminal group and the film thickness on the corrosion resistance of coated samples. The structure of the adsorbed films was characterized by goniometry, specular IR, and SFG spectroscopy. Corrosion studies were conducted for three weeks of continuous immersion in acid rain solution using polarization measurements and electrochemical impedance spectroscopy. Films formed in 1 mM solutions of phosphonic acids provided better corrosion protection than those formed in 0.1 mM solutions. Carboxyl terminated phosphonic acid films exhibited the least protective film on bronze.

The microscopic scale correlation between microstructure and galvanic corrosion of low alloy steel-A508 and its welded-309/308L stainless steel overlayer is investigated. Microstructural characterization shows that the welding process induces complexities at HAZ of the base metal. The microstructure of HAZ changes from tempered bainite to a non-uniform mixture of martensite and bainite, depending on the heat flow. This change in the microstructure leads to a heterogeneous corrosion attack on the base metal (anode), while the weld metal (cathode) is protected in a galvanic interaction. The extent and rate of corrosion attacks on the surface constituents are quantified by AFM.

Photocatalytic splitting of water into hydrogen and oxygen by utilizing sunlight and a photocatalyst is a promising way of generating clean energy. Here, we report a molecular-level study on heavy water (D2O) interacting with TiO2 as a model photocatalyst. We employed the surface specific technique Sum-Frequency-Generation (SFG) spectroscopy to determine the nature of the hydrogen bonding environment and the orientation of interfacial water molecules using their OD-stretch vibrations as reporters. By examining solutions with various pD-values, we observe an intensity-minimum at around pD 5, corresponding to the balance of protonation and deprotonation of TiO2 (point of zero charge). The majority of water molecules' deuterium atoms point away from the interface when the pD is below 5, and point towards the surface when the pD is higher than 5, with strong hydrogen bonds towards the surface.

The oil/water interface, for instance in emulsions, is often stabilized by surfactants. Hence, the co-existence of oil, water, and surfactant molecules at the buried oil/water interface determines macroscopic properties such as surface tension or emulsion stability. Utilizing an inherently surface sensitive spectroscopic method, sum frequency generation (SFG) spectroscopy, we show that adsorption of an anionic surfactant to the buried oil/water interface increases the magnitude of the interfacial electric field. Meanwhile, the degree of ordering of the interfacial oil molecules increases with the surfactant concentration owing to the intercalation of aliphatic chains of interfacial oil and surfactant molecules. At sufficiently high surfactant concentrations, the interfacial charge reaches a maximum value and the interfacial oil molecules arrange in a fully ordered conformation, a state which coincides with the significant decrease in interfacial tension and increased emulsion stability.

Funding Information: Financial support from the German Research Foundation through grant KU1980/14-1, the European Commission through ERC Starting Grant 336679, and the joint program by DAAD (57313835) and National Research Foundation of Korea (NRF-2016K2A9A2A14912842) is gratefully acknowledged. Y.M.J. was supported by the Academy of Finland (project no. 314862). A.S.F. was supported by the World Premier International Research Center Initiative (WPI), MEXT, Japan. Y.M.J. and J.T. acknowledge the use of the computational resources provided by the Aalto Science-IT project and CSC, Helsinki. We thank Hao Lu for the XPS experiments. Publisher Copyright: © 2021 The Authors. Published by American Chemical Society. Mineral-water interfaces play an important role in many natural as well as technological fields. Fundamental properties of these interfaces are governed by the presence of the interfacial water and its specific structure at the surface. Calcite is particularly interesting as a dominant rock-forming mineral in the earth's crust. Here, we combine atomic force microscopy, sum-frequency generation spectroscopy, and molecular dynamics simulations to determine the position and orientation of the water molecules in the hydration layers of the calcite surface with high resolution. While atomic force microscopy provides detailed information about the position of the water molecules at the interface, sum-frequency generation spectroscopy can deduce the orientation of the water molecules. Comparison of the calcite-water interface to the interfaces of magnesite-water, magnesite-ethanol, and calcite-ethanol reveals a comprehensive picture with opposite water orientations in the first and second layer of the interface, which is corroborated by the molecular dynamics simulations.

The synergistic effects of area ratio and microstructure on the galvanic corrosion of A508/309 L/308 L dissimilar metals weld (DMW) are studied by a multi-analytical approach. It was demonstrated that decreasing the anode/cathode surface area ratio obviously enhances the corrosion rate of A508, both locally and globally. Deeper analyses of the AFM results enabled quantitative comparison of the corrosion behaviour of the different surface constituents. It was revealed that in the galvanic interaction of the DMW, the grain refined region corrodes most, followed by the partial grain refined region and base metal matrix of the A508, respectively. The electrochemical localization index (LI) estimation method and AFM analysis both confirmed the presence of a mixed (localized and uniform) corrosion phenomenon occurring on the surface of the A508 anode metal in the galvanic interaction of the dissimilar metals. Finally, the degree of synergism equation was utilized to describe the synergistic effects of anode/cathode area ratio and the microstructure of the samples on the galvanic corrosion of LAS A508/309L/308L SS DMW.

Hypothesis The secondary structure of proteins affects their functionality and performance in physiological environments or industrial applications. Change of the solution pH or the presence of protein denaturants are the main chemical means that can alter the secondary structure of proteins or lead to protein denaturation. Since proteins in the bulk solution and those residing at the solution/air interface experience different local environments, their response to chemical denaturation can be different. Experiments We utilize circular dichroism and chiral/achiral sum frequency generation spectroscopy to study the secondary structure of selected proteins as a function of the solution pH or in the presence of 8 M urea in the bulk solution and at the solution/air interface, respectively. Findings The liquid/air interface can enhance or decrease protein conformation stability. The change in the secondary structure of the surface adsorbed proteins in alkaline solutions occurs at pH values lower than those denaturing the studied proteins in the bulk solution. In contrast, while 8 M urea completely denatures the studied proteins in the bulk solution, the liquid/air interface prevents the urea-induced denaturation of the surface adsorbed proteins by limiting the access of urea to the hydrophobic side chains of proteins protruding to air.

Ni-Co composite coatings reinforced with ZnO particles are prepared by either pulsed current (PC) or direct current (DC) electrodeposition methods. X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and EDX mapping are employed to investigate phase structure, surface morphology, elemental composition, and elemental distribution of coating, respectively. The effects of electrodeposition parameters such as stirring rate, average current density, and ZnO particles concentration on the microhardness of electrodeposited composite coating reinforced with nano and micro ZnO particles are investigated. Optimal values are determined for all of the above-mentioned parameters, which result in the maximum hardness of the coating. Any deviation from the optimal parameters leads to a reduction of the coating’s microhardness. The SEM, atomic force microscopy (AFM), wear test, and electrochemical examinations revealed that changing the electrodeposition method from DC to PC and varying the size of ZnO particles from micro to nano affect the surface morphology from rough to smooth and reduce the surface friction coefficient, both of which enhanced the wear resistance of the coating and improved its corrosion resistance. The SEM results from worn surfaces illustrated that the size of reinforcing ZnO particles and the electroplating method change the wear mechanisms and worn surface morphology.

This Tutorial aims to provide a concise yet practical guideline for different scenarios that one may face in a sum frequency generation (SFG) spectroscopy laboratory, especially when it comes to sample alignment. The effort is made to reconstruct the real and often challenging sample alignment conditions for a broad range of liquid or solid samples interfacing solid, liquid, or gas phases, with a pedagogical approach. Both newcomer operators of an SFG setup without a strong experience in nonlinear spectroscopy and the more experienced SFG users can utilize the approaches that are provided in this Tutorial for an easier and more reliable sample alignment in their SFG laboratories.

In this work, response surface method (RSM) is employed to design electrochemical experiments for assessment of a green organic molecule, namely Clopidogrel from cardiovascular drugs class, as a corrosion inhibitor for mild steel in sulfuric acid solution. Mathematical models based on multiple regressions are generated to estimate the influence of the affecting factors like acid concentration, solution temperature and inhibitor concentration on the inhibitive performance of Clopidogrel. The corrosion rates are measured experimentally using potentiodynamic polarization technique. The calculated Langmuir adsorption energy reveals that Clopidogrel adsorbs both physically and chemically onto the mild steel surface and the adsorption type is almost independent of the environmental factors. The adsorption mechanism of Clopidogrel is computed through quantum chemical calculations, confirming that this compound can replace water molecules from the surface upon its adsorption to the metal substrate. The simulation results are approved experimentally using an inherently surface sensitive tool, sum frequency generation spectroscopy (SFG).

This study aims to correlate the microstructure and Volta potential distribution of Ti-Cu welded bimetal to its corrosion initiation sites, using AFM-SKPFM, and SEM-EDS. Local melted zones with Ti-Cu intermetallic precipitates in weld interface and in Cu matrix showed different Volta potential values in comparison with those of Ti and Cu regions. SKPFM revealed that Cu region has a higher Volta potential than that of Ti region. AFM and microstructural images after immersion in corrosive media proved the presence of a galvanic cell. Corrosion mainly extends on Cu side due to the increasing growth of Ti passive film.

Regeneration/reclamation of used oil using active adsorbents with high surface area is considered as one of the most efficient methods for the waste management and treatment of oil pollutants. In this work, we developed a mesoporous active γ-bauxite (DABa) from a low-grade raw boehmite ore (RBa) through a two-stage thermal activation process followed by an acid treatment. Acid leaching in hydrochloric acid resulted in the high specific surface area and optimum pore distribution in γ-bauxite. The surface area of the mesoporous γ-bauxite was as high as 130.66 m2/gr, approximately 11-fold larger than its parent ore. The regeneration performance of developed adsorbents to remove contaminants from used transformer oil was compared with three high-performance commercial adsorbents; Brazilian activated bauxite (BABa), Japanese activated bentonite (JABe), and Iranian activated alumina (IAA). The results showed DABa has the best oil reclamation performance and significantly improves the used oil characteristics such as its color, acidity, interfacial tension, dielectric dissipation factor, dibenzyl disulfide (DBDS) content, and corrosive sulfur.

In this work, we fabricated superhydrophilic aluminum alloy (AA 6063) with a hierarchical labyrinth-like structure using a facile and environmentally benign chemical etching method. The patterned samples were functionalized by stearic acid molecules to obtain superhydrophobic samples with water contact angle (CA) >160°, at optimum conditions. Although the superhydrophobic samples initially exhibited up to two orders of magnitude better corrosion resistance compared to as-received samples, their corrosion performance and CA gradually reduced upon prolonged exposure to 3.5 wt% NaCl solution. Hence, the initial high CA in superhydrophobic surface layers cannot be used as a measure of their long-term corrosion stability.

Electrodeposited metal matrix composite coatings (MMCs) often exhibit superior surface characteristics including corrosion resistance in a wide range of temperatures, improved physical, mechanical, and tribological properties, tunable surface hydrophobicity, and desirable look. Therefore a wide range of studies has been performed so far to assess the diverse physical, mechanical, chemical, electrochemical, and thermal properties of electrodeposited composite coatings that are fabricated on various substrates, under different electrodeposition conditions. In particular, nickel-based composite coatings reinforced with embedded particles (e.g., oxides, carbides, nitrides, and solid-state lubricants) are among the most studied MMCs because of their industrial applications as protective and corrosion-resistant coatings with desirable wear and friction properties. In this review, we provide an extensive overview of the fabricated electrodeposited nickel-based composite coatings which are assessed for their improved wear resistance. The tribological and wear properties of the composite coatings such as weight loss, wear rate, friction coefficient, surface hardness and roughness, as well as their underlying wear mechanisms, will be discussed as a function of the type, content, size, and distribution of the reinforced particles under different electrodeposition parameters such as type and magnitude of applied current, bath composition, pH, temperature, ultrasonication, and presence of surfactants. The quantitative coating characteristics that are tabulated in this review serve as a reference for the researchers in this field and enable the quick selection of coatings and electrodeposition parameters for the desired application.

In this study, the bactericidal properties of the wing surface of two different Psalmocharias cicada species, Psalmocharias querula (PQ) and Psalmocharias akesensis (PA), are examined based on the organization and nano-topographical characteristics of the wing nanostructure. The bacterial killing capacity of the wings was assessed by counting the colony-forming units (CFU). Atomic force microscopy (AFM), scanning electron microscopy (SEM), and contact angle measurements were utilized to reveal wings nano-topographical structures and their impact on bacterial contact-killing efficiency. The role of surface roughness parameters on bacterial cell attachments and bactericidal properties of the wings was evaluated by analysis of topography results using histogram height distribution and power spectral density (PSD) methods. It was found that the skewness and kurtosis values of the cicada wing nanopillars significantly correlate with their shear-inducing capacity, confirming the higher bactericidal activity for PQ wing surface compared to PA wing surface.

Protein adsorption on the surface of implant materials greatly affects the performance of the implants, such as their stability as well as the release of metal ions from and the adhesion of cells to their surface. In addition, the production of extracellular H2O2 from the activation of inflammatory cells could interfere with protein–metal interactions and/or modify the conformation of adsorbed proteins. In this study, we utilised scanning Kelvin probe force microscopy (SKPFM) to visualise the impact of H2O2 on bovine serum albumin (BSA) adsorption on the positively polarised Ti6Al4V alloy in a phosphate-buffered saline (PBS) solution. We show that the negatively charged BSA adsorbs onto the surface of polished and anodically polarised Ti6Al4V in a dense layer with a continuous network-like morphology or cluster shape and reduces the variation in the total surface potential compared to that of blank Ti6Al4V. However, addition of H2O2 to the PBS solution interferes with the formation of the dense protein network, and only a thin and discontinuous protein layer adsorbs onto the surface of the Ti6Al4V alloy, lowering the total surface potential difference. The information presented in this work provides new insights into the adsorption distribution of proteins on metallic substrates in biomaterials field.

Nanocapsules with a hydrophilic core are particularly interesting for biomedical and anticorrosion applications since these nanocontainers allow encapsulating a wide range of hydrophilic payloads and controlling their release profiles. However, a major challenge associated with the preparation of these nanocapsules is the non-controlled leakage of hydrophilic payloads from the core due to osmotic pressure. Herein, we present an approach for the preparation of polymer nanocapsules that suppress the non-controlled leakage of payloads and respond to chemical reduction that triggers release of encapsulated payloads. The non-controlled leakage of hydrophilic payloads from the nanocapsules is hindered by increasing the shell thickness. These nanocapsules consisting of reduction-responsive units possess a remarkable release property only under reductive condition while cease non-controlled leakage of the payload in the aqueous release medium. The described nanocapsules can be applied for biomedical and anticorrosion applications in which triggered release of hydrophilic payloads is suitable.

Hexane selenol (CH3(CH2)(5)SeH) was adsorbed from gas phase in ultra-high vacuum on polycrystalline Cu and studied with synchrotron radiation based photoelectron spectroscopy (PES) and Near edge X- ...

The interfacial structure of water in contact with TiO2 is the key to understand the mechanism of photocatalytic water dissociation as well as photoinduced superhydrophilicity. We investigate the interfacial molecular structure of water at the surface of anatase TiO2, using phase-sensitive sum frequency generation spectroscopy together with spectra simulation using ab initio molecular dynamic trajectories. We identify two oppositely oriented, weakly and strongly hydrogen-bonded subensembles of O–H groups at the superhydrophilic UV irradiated TiO2 surface. The water molecules with weakly hydrogen-bonded O–H groups are chemisorbed, i.e. form hydroxyl groups, at the TiO2 surface with their hydrogen atoms pointing toward bulk water. The strongly hydrogen-bonded O–H groups interact with the oxygen atom of the chemisorbed water. Their hydrogen atoms point toward the TiO2. This strong interaction between physisorbed and chemisorbed water molecules causes superhydrophilicity.

In the present study, the impact of copper substrate grain size on the structure of the succeeding electrodeposited nickel film and its consequent corrosion resistance in 3.5% NaCl medium were evaluated before and after functionalization with stearic acid. Nickel layers were electrodeposited on two different copper sheets with average grain size of 12 and 25 &micro, m, followed by deposition of stearic acid film through self-assembly. X-ray diffraction analysis of the electrodeposited nickel films revealed that the deposition of nickel film on the Cu substrate with small (12 &micro, m) and large (25 &micro, m) grains is predominantly governed by growth in the (220) and (111) planes, respectively. Both electrodeposited films initially exhibited a hydrophilic nature, with water-contact angles of 56&deg, and &lt, 10&deg, respectively. After functionalization with stearic acid, superhydrophobic films with contact angles of ~150&deg, were obtained on both samples. In a 3.5% NaCl medium, the corrosion resistance of the nickel layer electrodeposited on the copper substrate with 25 &micro, m grains was three times greater than that deposited on the copper substrate with 12 &micro, m grains. After functionalization, the corrosion resistance of both films was greatly improved in both short and long immersion times in 3.5% NaCl medium.

In the present work, we have fabricated a superhydrophobic surface on aluminium alloy 2024 through a simple immersion chemical etching method in hydrochloric acid followed by a functionalization step in stearic acid solution. The impact of etching time on water contact angle was investigated and a contact angle of $$\sim $$ 167 $$^{{\circ }}$$ was reached on the superhydrophobic surface, which was etched for 4 min. Morphology of the surface was evaluated by scanning electron microscopy and the surface chemical analysis was performed by energy-dispersive X-ray spectroscopy and Raman spectroscopy. We show that the fabricated superhydrophobic samples can besides water, also repel other liquids. We also demonstrate the self-cleaning properties of the fabricated samples using graphite particles as contaminants. Ultimately, we assessed the corrosion resistance properties of the fabricated surfaces by the potentiodynamic polarization method. The superhydrophobic surface exhibited increased corrosion potential and polarization resistance along with reduced corrosion current density, all of which are indicative of a significant improvement in corrosion performance of the superhydrophobic surface in comparison with typical aluminium 2024. The cheap and facile superhydrophobic surface fabrication method presented in this study can be applied to large scale samples with no need for electricity or expensive raw materials.

Photocatalytic splitting of water into hydrogen and oxygen by utilizing sunlight and a photocatalyst is a promising way of generating clean energy. Here, we report a molecular-level study on heavy water (D2O) interacting with TiO2 as a model photocatalyst. We employed the surface specific technique Sum-Frequency-Generation (SFG) spectroscopy to determine the nature of the hydrogen bonding environment and the orientation of interfacial water molecules using their OD-stretch vibrations as reporters. By examining solutions with various pD-values, we observe an intensity-minimum at around pD 5, corresponding to the balance of protonation and deprotonation of TiO2 (point of zero charge). The majority of water molecules' deuterium atoms point away from the interface when the pD is below 5, and point towards the surface when the pD is higher than 5, with strong hydrogen bonds towards the surface.

Electrostatic interactions play essential roles in determining the function, colloidal stability, and adsorption of proteins on different surfaces and interfaces. Therefore, a molecular-level understanding of the charge state of the proteins under different conditions is required to explain their macroscopic properties. In this study, we have employed an inherently surface-sensitive spectroscopic tool, sum frequency generation spectroscopy, to determine the charge state of a wide range of proteins as a function of pH at the air/liquid interface via measurement of the degree of orientation of water molecules. We compared the isoelectric point (IEP) of the 12 investigated proteins at the air/liquid interface with that in the bulk solution obtained through zeta potential measurements. Ellipsometry is performed to determine the film thickness at the air/liquid interface at different charge states. In particular, protein aggregation at the IEP is reflected by increased film thickness. For all proteins, the interfacial point of zero charge is close (with less than 1 pH unit variation) to that in the bulk solution.

Nickel-ZnO nanocomposite coatings were fabricated by pulse electrodeposition in an alkaline bath. The effect of different deposition parameters such as current density, duty cycle, and pulse frequency as well as the impact of addition of 10 g/l ZnO nanoparticles into the nickel matrix on the friction behavior of fabricated coatings were investigated. X-ray diffraction, atomic force microscopy, scanning electron microscopy, microhardness test, and pin-on-disk wear test were utilized to assess the coatings characteristics, mechanical behavior, and wear resistance and a thorough comparison was performed between the pure nickel coating and its reinforced composite counterpart, with respect to their surface morphology, surface topography, and wear resistance properties. Our results indicate that by ZnO incorporation into the coating, the number of nucleation sites for nickel crystals increases, the crystal growth is retarded, and a nanocomposite coating with smaller grains can be fabricated. The incorporation of ZnO led to significantly increase in microhardness, changed the wear mechanism from adhesion to abrasion, and improved the wear rate. By increasing the electrodeposition current density (from 4 to 10 A/dm2), the wear rate was noticeably decreased while the friction coefficient was significantly enhanced. As the electrodeposition duty cycle and pulse frequency were increased to 75% and 100 Hz, respectively, wear rate of the composite coating increased noticeably as a consequence of the changes in the coating properties. The optimum electrodeposition condition for Ni–ZnO nanocomposite coatings was achieved at 10 A/dm2, γ = 50% and f = 10 Hz resulting in a coating with the lowest wear rate (3.2539 × 10−4 mm3/Nm), minimum weight loss (0.0014 gr), highest microhardness (290 Hv), maximum ZnO incorporation rate (4.04 vol% ZnO), and highest friction coefficient (0.972) among all investigated coatings. It was concluded that increasing current density improved the wear resistance while the enhancement of duty cycle and pulse frequency led to worsen it.

In this article results from earlier studies have been compiled in order to compare the protection efficiency of self-assembled monolayers (SAM) of alkanethiols for copper, zinc, and copper–zinc alloys exposed to accelerated indoor atmospheric corrosion conditions. The results are based on a combination of surface spectroscopy and microscopy techniques. The protection efficiency of investigated SAMs increases with chain length which is attributed to transport hindrance of the corrosion stimulators in the atmospheric environment, water, oxygen and formic acid, towards the copper surface. The transport hindrance is selective and results in different corrosion products on bare and on protected copper. Initially the molecular structure of SAMs on copper is well ordered, but the ordering is reduced with exposure time. Octadecanethiol (ODT), the longest alkanethiol investigated, protects copper significantly better than zinc, which may be attributed to the higher bond strength of Cu–S than of Zn–S. Despite these differences, the corrosion protection efficiency of ODT for the single phase Cu20Zn brass alloy is equally efficient as for copper, but significantly less for the heterogeneous double phase Cu40Zn brass alloy.

Increased temperature of electronic devices during their performance results in the decline of their performance and reduces their lifetime due to the increased thermal damage, a problem which is very substantial in miniaturized electronic components. Here, we present an innovative, cost-efficient, simple, and environmentally benign chemical method for creating micro/nano roughened structure on the conventional aluminum heat sinks to increase their cooling capability. The surface structures of the roughened heat sinks were examined using scanning electron microscopy and atomic force microscopy. The performance of conventional and micro/nano roughened aluminum heat sinks was analyzed for thermal management of a printed circuit board (PCB) producing heat fluxes equivalent to those of a Core i7-1068NG7 processor. At forced air convection condition and under heat fluxes of 8000, 10,000 and 12,000 W/m2, the temperature of PCBs cooled with roughened heat sinks were found to be lower than those cooled with the conventional heat sinks by impressive values of 9.2 °C, 11.0 °C, and 12.8 °C, respectively. The thermal resistance of the novel heat sink decreased by 38.01%, 39.14%, and 39.96%, respectively, compared to that of the conventional heat sink. In free convection, employing the roughened heat sink improved the PCB cooling effectiveness by roughly 14% at heat fluxes of 8000 W/m2 at cutoff temperature. The proposed simple method in this study opens up the possibility of reducing the size (or mass) of aluminum heat sinks or employing a heat sink of a certain size for the thermal management of a system with higher heat flux.

The synergestic role of boric acid, as a crystal modifier, and screw dislocation step defects on the crystal growth and formation mechanism of nickel micro-nanocones during electrocrystallization is explained using density functional theory (DFT) and Monte Carlo (MC) calculations. Earlier atomic force microscopy (AFM) studies provided direct evidences on the effect of boric acid on morphology distribution of nickel micro-nanocones and confirmed the presence of terraces and steps due to the spiral growth of screw dislocation. In the presence of boric acid, the formation of nickel-borate complex leads to a decrease in the system’s supersaturation and in turn provides an appropriate condition for screw dislocation driven-growth. DFT and MC simulations reveal that the nickel-borate complex primarily adsorb in the step edges with the lowest adsorption energy barrier, after which the crystal growth is inhibited on these edges resulting in the formation of nanocone structures.

In this study, we report on a combined microscopic, analytical and electrochemical characterization of the nanoscopic passive layer on a tungsten‑molybdenum-containing super duplex stainless steel. We used scanning transmission electron microscopy/energy dispersive X-ray spectroscopy, scanning Kelvin probe force microscopy, scanning tunneling spectroscopy, and Mott–Schottky electrochemical impedance spectroscopy analysis to correlate the local chemical composition and electronic properties of passive layers on austenite and ferrite phases. The passive layer on the ferrite phase contains a higher amount of Mo, W, and Cr, which accommodates a higher nobility of ferrite and a higher local energy of the band gap compared to those on the austenite. The two aforementioned phases exhibit a different composition and semi-conductive properties of their passive layers leading to dissimilar local corrosion susceptibility. These findings are of pivotal importance in further studies of austenite and ferrite phase resolved corrosion resistance of duplex stainless steel demanding a dedicated alloying strategy.

Self-assembled mono- and multilayers of stearic acid have been examined as corrosion protection systems for copper-nickel alloy in 3% sodium chloride solution. We found that self-assembled multilayers of stearic acid provide more efficient and durable corrosion protection to copper- nickel alloy than just a single monolayer. Electrochemical techniques, such as potentiodynamic polarization and electrochemical impedance spectroscopy, were used to determine the protective properties of the stearic acids films. Sum frequency generation spectroscopy, atomic force microscopy, contact angle measurements and ellipsometry were used to evaluate structural properties and thickness of the surface layers. It was found that the increase of corrosion protection from mono- to multilayer films depends on the number of layers that are formed but also on their homogeneity.

Self-assembled monolayers of octadecanethiol (ODT) have previously shown to provide excellent corrosion inhibition on copper exposed to humidified air containing formic acid, mimicking indoor atmospheric corrosion. ODT layers are, however, much less efficient corrosion inhibitors for zinc. In this work, we elucidate the possibility of using ODT monolayers to inhibit corrosion of brass. Based on a quantitative analysis of corrosion products, we found that ODT provides equally good corrosion inhibition of single-phase Cu20Zn as of pure copper, retarding the transportation of corrosion stimulators to the brass surface. On double-phase Cu40Zn, however, local galvanic effects led to less efficient corrosion inhibition and more corrosion products than on Cu20Zn.