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Surface engineering of active materials to generate desired energy state is critical to fabricate high-performance heterogeneous catalysts. However, its realization in a controllable level remains challenging. Using oxygen evolution reaction (OER) as a model reaction, we report a surface-mediated Fe deposition strategy to electronically tailor surface energy states of porous Co3O4 (Fe-pCo3O4) for enhanced activity towards OER. The Fe-pCo3O4 exhibits a low overpotential of 280 mV to reach an OER current density of 100 mA cm−2, and a fast-kinetic behavior with a low Tafel slop of 58.2 mV dec−1, outperforming Co3O4-based OER catalysts recently reported and also the noble IrO2. The engineered material retains 100% of its original activity after operating at an overpotential of 350 mV for 100 h. A combination of theoretical calculations and experimental results finds out that the surface doped Fe promotes a high energy state and desired coordination environment in the near surface region, which enables optimized OER intermediates binding and favorably changes the rate-determining step.

The continuous and isothermal crystallization diagrams of the Pt 42.5 Cu 27 Ni 9.5 P 21 and the Pt 60 Cu 16 Co 2 P 22 bulk glass forming compositions are determined using calorimetric experiments. In the case of the Pt 42.5 Cu 27 Ni 9.5 P 21 bulk metallic glass, the formation of the primary crystalline phase can be prevented by rapid cooling in a conventional DSC. In contrast, for similar cooling conditions, the formation of the primary precipitating compound in Pt 60 Cu 16 Co 2 P 22 cannot be prevented in a conventional DSC as also observed in in-situ synchrotron X-ray scattering experiments. This is attributed to a critical overheating, above which remaining structures dissolve, resulting in a drastic increase of the degree of undercooling, similar to what is observed in Zr-based BMGs. Using the classical nucleation theory, the combined thermodynamic and kinetic data are used to model the isothermal crystallization data for Pt 42.5 Cu 27 Ni 9.5 P 21 , yielding an interfacial energy value of 0.11 J/m 2 between the primary nucleating crystal and the liquid. This value is three times higher than the value for good Zr-based glass-formers, suggesting that the interfacial energy plays a pivotal role in the exceptionally high glass-forming ability of Pt-P-based systems and compensates for the fragile liquid behavior and the large driving force for crystallization.

A new methodology was proposed to determine the dispersive component of the surface energy ${\gamma}_s^d$ of a solid taking into account the effect of the temperature on the surface area of n-alkanes, methylene group (${a}_{- CH2-}$) and polar molecules, thus defeating the method used by Dorris–Gray Schultz et al. We determined the correct ${\gamma}_s^d$ of the surface energy, the specific free energy, enthalpy and entropy of adsorption of polar molecules as well as the acid base constants of silica particles with an excellent accuracy. We confirmed the dependence of the dispersive component of the surface energy on the variations of the surface areas of organic molecules used in IGC technique at infinite dilution. The specific properties of interactions of silica particles were determined. The new proposed model took into account this thermal effect. Obtained results proved that the other used IGC methods gave inaccurate values of the specific parameters of silica surface, except for the vapor pressure method that led to excellent results of the specific free energy, enthalpy and entropy of adsorption, and the acid–base constants of the silica particles.

Microgels are soft colloidal particles constituted by cross-linked polymer networks with a high potential for applications. In particular, after adsorption at a fluid interface, interfacial tension provides two-dimensional (2D) confinement for microgel monolayers and drives the reconfiguration of the particles, enabling their deployment in foam and emulsion stabilization and in surface patterning for lithography, sensing and optical materials. However, most studies focus on systems of fluids with a high interfacial tension, e.g. alkanes/ or air/water interfaces, which imparts similar properties to the assembled monolayers. Here, instead, we compare two organic fluid phases, hexane and methyl tert-butyl ether, which have markedly different interfacial tension () values with water and thus tune the deformation of adsorbed microgels. We rationalize how controls the single-particle morphology, which consequently modulates the structural and mechanical response of the monolayers at varying interfacial compression. Specifically, when is low, the microgels are less deformed within the interface plane and their polymer networks can rearrange more easily upon lateral compression, leading to softer monolayers. Selecting interfaces with different surface energy offers an additional control to customize the 2D assembly of soft particles, from the fine-tuning of particle size and interparticle spacing to the tailoring of mechanical properties., Journal of Colloid and Interface Science, 608 (3), ISSN:0021-9797, ISSN:1095-7103

openaire: EC/H2020/788489/EU//BioELCell Funding Information: The authors acknowledge funding support by JSPS KAKENHI Grant Number JP 1 9 K 2 3 6 8 8 and 2 1 K 0 5 1 5 6 (MA). OJR also acknowledges supported by the Canada Excellence Research Chair initiative, the European Research Council under the European Union’s Horizon 2020 research and innovation program (ERC Advanced Grant No. 788489, “BioElCell”), and the Canada Foundation for Innovation (CFI). The authors are thankful to Ms. Kiyoko Kawashima for operating the EDX in the Collaborative Research Center, Meisei University and we are gratefully acknowledged Prof. Tetsuo Kondo, Kyusyu University for continuous discussions. We also thank Mr. Yutaka Igarashi CEO, Kazu-technica Co.ltd., Drs. Tatsuya Sakurai and Masashi Koyama, Meisei Univeristy for discussions. Publisher Copyright: © 2022, The Author(s), under exclusive licence to Springer Nature B.V. We introduce a simple spray drying method for the scaleup production of spherical organic (lignin) particles with sizes between 0.85 and 1.57 µm. We assess the surface energy of the lignin particles by inverse gas chromatography to reveal their role in composites synthesized with unsaturated polyester. Such nanocomposites are shown to be transparent to electromagnetic irradiation (millimeter wave bands). The permittivity and tanδ of the composite material reached values 3.01 and 0.01 at 28 GHz with 10% lignin content. Vinyl groups were introduced on the surface of the particles to achieve enhanced interfacial adhesion, and resulted in a reduced relative permittivity (2.75). Together with wave interactions, the mechanical and thermal properties of the composites are put in perspective, opening new opportunities in the development of bio-based devices for 5G high-speed communication.

Oil palm trunk (OPT) panel has high potential of being the substitution of wood due to the abundant of its availability in Malaysia and correspondingly resulted an increase in the export of palm oil in recent years. The properties of OPT has widely been studied including improvement on their strength and stability properties. In the present work, a hydrophobic coating was applied on compressed OPT panel prior to improve its surface quality. The hydrophobic properties were determined by water contact angle (WCA) and water sliding angle (WSA). The addition of SiO2 and chlorotrymethylsilane (CTMS) as a hydrophobic agent plays a critical role in enhancing the panel surface by generate roughness at nanoscales and lower its surface free energy which turn to higher WCA and smaller WSA values. Based on mechanical stability of hydrophobic compressed OPT, it shows that the WCAs of the surface panel remained almost constant and the coated surface remain non-wettable with the nanoscales features remain intact after performing scratch test.

Al-V-B master alloy is promising for refining Al-Si alloys, yet its optimal composition with superior efficacy remains to be explored. In this work, the evolution of refining phases in the Al-10Si/Al-V-B system with different V:B ratios was evaluated by thermodynamic calculations, based on which the Al-V-B refiners with V:B = 1:1 and 5:1 were designed. Refining trails demonstrated that they could significantly reduce the grain size of Al-10Si (wt.%) alloy from 1736 to 184–245 μm with industrial addition amount. Detailed examinations results clarify that when V:B ratio is 1:1 the nucleation particle is (V,Al)B2, which has a VB2-AlB2 core-shell structure and therefore presents the nucleation capability as AlB2 particle. When V:B ratio is as high as 5:1, the nucleation particle is pure VB2. Density functional theory (DFT) calculation indicates that (0 0 0 1) VB2/(1 1 1) α-Al interface has the lowest interfacial energy such that highest nucleation potency among other types of diboride/α-Al interfaces under consideration. The outcomes of this work provide fundamental guidance to develop superior V-B based refiners for Al-Si alloys.

Hybrid nanocrystals (NCs) with multiple components and junctions have attracted considerable attention due to their promising synergistic properties. In particular, great attention has been paid to the manipulation of buried multijunction heterointerfaces because they are closely related to the surface energy and carrier transfer of NCs. However, heterointerfaced NCs are usually constructed by sequential step-by-step pathways, and buried interfaces can only be formed along a given direction, resulting in the one and only spatial orientation of multiple interfaces. In this work, we demonstrate two types of Au-Ag2S-Cu2-xS NCs with disparate interfacial features. Specifically, the first type (Type I) is prepared through a routine two-step method and shows that Au domain close to the Ag2S-Cu2-xS interface; another type (Type II) is achieved by a facile one-pot synthesis procedure and contains Au domain with an interphase only with the Ag2S domain, far from the Cu2-xS domain. More importantly, type II NCs could not be formed through other traditional strategies and an underlying mechanism of formation is developed by monitoring the evolution process. Au@Ag core-shell NCs, metastable Au@Ag2S NCs and Janus Au-Ag2S NCs are formed successively before the Cu2-xS domain appears. We speculate that the Au@Ag2S intermediate plays an essential role in building the final complex nanostructure. We expect that such a simple and facile one-pot method will be used to fabricate additional asymmetric multicomponent NCs with distinctive interfacial features and promising potential applications.

Core−sheath electrospinning is a powerful tool for producing composite fibers with one or multiple encapsulated functional materials, but many material combinations are difficult or even impossible to spin together. We show that the key to success is to ensure a well-defined core−sheath interface while also maintaining a constant and minimal interfacial energy across this interface. Using a thermotropic liquid crystal as a model functional core and polyacrylic acid or styrene-butadiene-styrene block copolymer as a sheath polymer, we study the effects of using water, ethanol, or tetrahydrofuran as polymer solvent. We find that the ideal core and sheath materials are partially miscible, with their phase diagram exhibiting an inner miscibility gap. Complete immiscibility yields a relatively high interfacial tension that causes core breakup, even preventing the core from entering the fiber- producing jet, whereas the lack of a well-defined interface in the case of complete miscibility eliminates the core−sheath morphology, and it turns the core into a coagulation bath for the sheath solution, causing premature gelation in the Taylor cone. Moreover, to minimize Marangoni flows in the Taylor cone due to local interfacial tension variations, a small amount of the sheath solvent should be added to the core prior to spinning. Our findings resolve a long-standing confusion regarding guidelines for selecting core and sheath fluids in core−sheath electrospinning. These discoveries can be applied to many other material combinations than those studied here, enabling new functional composites of large interest and application potential.

openaire: EC/H2020/788489/EU//BioELCell Funding Information: The authors acknowledge funding support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 788489, “BioElCell”). The Canada Excellence Research Chair (CERC) program is also gratefully acknowledged as well as Canadian Foundation for Innovation (CFI). M.B. acknowledges financial support from the Austrian Science Fund (FWF) (J4356). Publisher Copyright: © 2021 The Authors. Published by American Chemical Society. Colloids are suitable options to replace surfactants in the formation of multiphase systems while simultaneously achieving performance benefits. We introduce synergetic combination of colloids for the interfacial stabilization of complex fluids that can be converted into lightweight materials. The strong interactions between high aspect ratio and hydrophilic fibrillated cellulose (CNF) with low aspect ratio hydrophobic particles afford superstable Pickering foams. The foams were used as a scaffolding precursor of porous, solid materials. Compared to foams stabilized by the hydrophobic particles alone, the introduction of CNF significantly increased the foamability (by up to 350%) and foam lifetime. These effects are ascribed to the fibrillar network formed by CNF. The CNF solid fraction regulated the interparticle interactions in the wet foam, delaying or preventing drainage, coarsening, and bubble coalescence. Upon drying, such a complex fluid was transformed into lightweight and strong architectures, which displayed properties that depended on the surface energy of the CNF precursor. We show that CNF combined with hydrophobic particles universally forms superstable complex fluids that can be used as a processing route to synthesize strong composites and lightweight structures.

Bulk nanobubbles which are usually observed in pure water have a mean diameter typically around 100 nm. We use a combination of physical and chemical techniques to prove the hypothesis that the nanoentities observed in pure water are stable clusters of much smaller stable nanobubbles. The stability of bulk nanobubble clusters is affected by factors such as ionic strength or internal energy of the system. We show that bulk nanobubbles on the order of 100 nm exist in a stable cluster form in neutral or basic media, and dissociate into tiny primary nanobubbles on the order of 1 nm in acidic media, or in the presence of small amounts of salt. These new findings suggest that bulk nanobubbles which have a high surface energy unsurprisingly tend to behave in a similar manner to solid nanoparticles in terms of their agglomeration tendency, which is confirmed by the DLVO theory. The results will have important implications for our understanding and interpretation of the behaviour of bulk nanobubbles, in particular their interfacial and colloidal stability.

Lithium-sulfur (Li-S) batteries are considered as one of the promising next-generation energy storage systems because of their high energy density. While the low utilization of sulfur and sluggish reaction kinetics would lead to degradation of electrochemical performance and thus hinder the practical application of Li-S batteries. Herein, a double-shelled TiO2-graphene heterostructure (H-TiO2/rGO) with abundant oxygen vacancies (OVs) and highly exposed active plane as advanced host material in Li-S batteries is designed. This rational structure not only provides sufficient active sites and lower bandgap for lithium polysulfides (LiPSs), but also builds smooth adsorption-diffusion-conversion of LiPSs on catalyst, which greatly reduces interfacial energy barrier and promotes the utilization of sulfur through suppressing the devastating shuttling effect. Combining the synergetic merits of strong anchoring ability and catalyzing the of LiPSs, the electrode (S-TiO2/rGO-1) exhibits superior rate performance and long lifespan (1000 cycles at 1C, 0.023% capacity loss per cycle) with high columbic efficiency. This work paves an alternative way to establish smooth adsorption-diffusion-conversion of polysulfides on catalyst in Li-S batteries and provides a new sight to understand catalyst design in energy storage devices.

Alumina (Al2O3) and titanium dioxide (TiO2) thin films were deposited by the atomic layer deposition technique on steel substrates used in the polymer injection molding industry. The modified steel...

The 3C–SiC whisker was catalytically synthesized with extended graphite and Si powder firing at 1573K using 1 wt% Fe, 3 wt% Co or 3 wt% Ni as catalysts, respectively. First-principles calculation results show the activities of the reactants of the synthesis of SiC could be increased via dwindling the bonding strength of C C, Si–O and C–O bonds. Furthermore, the performance of self-bonded SiC refractories prepared by the present catalytic method was enhanced including the mechanical properties (Fracture toughness of 1.35 MPa﹒m1/2 for the containing Fe catalysts samples, Fracture surface energy of 114 J﹒m−2 and MOR of 32.2 MPa (1473 K) for the sample with Ni catalysts), as well as the TSR (Residual MOR and Residual MOR percentage of 13.17 MPa and 62% at ΔT = 1075 K, respectively). The results indicate that the incorporation of catalysts decreased the reaction temperature by about 100 K as well as facilitated the in-situ formation of 3C–SiC whiskers, which interlinked and connected each other in the matrix of as-prepared self-bonded refractories and improved the high temperature properties. Among them, the Fe NPs presented the best catalytic activity.

Hypothesis Suspensions of nanoporous particles in non-wetting fluids (lyophobic nanoporous suspensions, LPNPS) are explored as energy absorbing materials for shock absorbers, bumpers, and energy storage. Upon application of pressure, the non-wetting fluid invades the pores transforming the impact energy into the interfacial energy that can be stored and released on demand. Experiments Here, we present a comprehensive experimental study of the dynamics of LPNPS compression within a wide range of shock impact energy for three types of mesoporous materials (Libersorb 23, Polysorb-1, and Silochrome-1.5) with water and Wood alloy as non-wetting fluids. Findings Three different regimes of the LPNPS compression-expansion cycle in response to the shock impact are distinguished as the impact energy increases: without fluid penetration into the pores, with partial penetration, and with complete pore filling. In two latter regimes, the suspension compressibility in the process of rapid compression increases by 2–4 decimal decades. This giant effect is associated with the onset of penetration of the non-wetting fluid into the nanopores upon achievement of a certain threshold pressure. The dynamic threshold pressure exceeds the threshold pressure of quasistatic intrusion and does not depends on the impact pressure, temperature, and suspension composition. A dynamic model of suspension compression is suggested that allows to separate the effects of the fluid intrusion into the pores and the elastic deformation of the system.

In this paper, a novel approach was proposed to achieve the joining of AlN and Cu by nanosecond laser pre-irradiation of AlN. The effects of the speed of laser scanning on the morphology, chemical compositions, and properties of the surface of AlN ceramic and the mechanism of laser-assisted joining of AlN and Cu were investigated. With the increase of the speed of laser scanning, the surface roughness of AlN decreased. After nanosecond laser irradiation, element Al was detected on the surface of AlN. When nanosecond laser irradiation was applied, the hydrophilicity and the surface energy of the ceramic surface were improved. The modified AlN was successfully joined to Cu at the temperature of 620 °C with a speed of laser scanning of 500 or 1000 mm/s. The results of TEM confirmed the presence of Al4Cu9, indicating the metallurgical combination of Cu and AlN. Also, the method presented in this paper was supposed to be of great reference significance for the joining of ceramics and metals.

Segregation of granular materials is often induced by differences in size, density, shape and surface properties. Density and size-induced mixing and segregation of binary mixtures of glass beads and/or resin particles in the FT4 powder rheometer are investigated experimentally using a new FT4 methodology. The proposed methodology allows for quantification of mixing and segregation of components based on a mixing index. It is observed that the mixing index increases with increasing density and size ratio. Variation of flow energy and torque is related to the mixing and segregation of the mixture components, thus demonstrating that the FT4 powder rheometer may be used as a predictive tool for the tendency of mixture components to segregate under various stress conditions. Numerical analysis by DEM shows that for non-cohesive systems mixing and segregation occur by sifting of fines through interstitial gaps formed between coarse particles in the dilated region. For the non-cohesive system, higher blade tip speeds reduce the rate of mixing and minimise the segregation of different-sized components. Increasing the interfacial energy reduces the rate of mixing and alleviates the segregation of particles. For the cohesive systems, mixing occurs by rupture of cohesive fine clusters with the mixing index increasing with increasing blade tip speed owing to the higher shear stresses that break the agglomerates.

The article describes a very simple design philosophy of a coating that responds to temperature-rise by changing its behavior from hydrophilic to superhydrophobic in an instantaneous reversible manner. The material developed can be applied to a variety of surfaces simply by brush or roller, making it highly suitable as the basic ingredient of smart paint. Low surface energy fluoro and amino monomers were introduced to prepare the polymer backbone, which was then used as a binder for achieving a nano-micro dual particle morphology based on nano-silica micro-Titania (pre-functionalized with hydrophobic siloxane) by simple physical blending. The final structure was inspired by the so-called lotus effect. The best designed resulting material shows a water contact angle of 152° with a roll off-angle as low as 2° as a coating in response to elevated temperature, changing its hydrophilic nature. This reversible switching is ascribed to the formation and breaking of hydrogen-bond between amine group (secondary or tertiary) in polymer backbone and water. This bond-breaking introduces a critical change in the roughness of the coating, which was observed using atomic force microscopy. We also show that the response temperature can be tuned, which opens up the possibility of designing country-specific self-cleaning exterior paints.

Wetting behavior between hot metal and carbon brick is the first step to explore the erosion of carbon brick. In order to investigate the wetting behavior, wetting experiments between hot metal (with carbon content 2.87, 3.47, 4.12, 4.51, and 4.96 mass%) and carbon brick were carried out. The wetting angle under different conditions was measured, the reaction interface morphology and carbon structure were analyzed, the mechanism of hot metal wetting carbon brick was clarified based on interfacial energy and scaling law. The results show that: The wetting angle decreased gradually with the increase of wetting time for all initial carbon content experiments, the wetting angle increased with the increase of initial carbon content in hot metal. The dissolution of carbon occurred during the wetting process, which left a concave on carbon brick. The graphitization degree of carbon in carbon brick increased after the wetting behavior. In the initial stage of the wetting reaction, the change of interfacial energy caused by carbon dissolution reaction was the essential reason for the change of wetting angle. In the final stage of the wetting reaction, the wetting angle mainly depended on the concave shape after the concave was formed. The wetting model was established to explore the wetting behavior with dissolution reaction, the scaling relationship between the spreading radius of iron drop and time was obtained, which was convenient to evaluate the wetting behavior between hot metal and carbon brick.

This study is dedicated to the determination of the surface energy and stress of nanoparticles and cavities in presence of pressure, and to the evaluation of the accuracy of the Young-Laplace equation for these systems. Procedures are proposed to extract those quantities from classical interatomic potentials calculations, carried out for three distinct materials: aluminum, silicon, and iron. Our investigations first reveal the increase of surface energy and stress of nanoparticles as a function of pressure. On the contrary we find a significant decrease for cavities, which can be correlated to the initiation of plastic deformation at high pressure. We show that the Young-Laplace equation should not be used for quantitative predictions when the Laplace pressure is computed with a constant surface energy value, as usually done in the literature. Instead, a significant improvement is obtained by using the diameter and pressure-dependent surface stress. In that case, the Young-Laplace equation can be used with a reasonable accuracy at low pressures for nanoparticles with diameters as low as 4 nm, and 2 nm for cavities. At lower sizes, or high pressures, a severely limiting factor is the challenge of extracting meaningful surface stress values.

The wettability of materials used in the production of devices employed in various technological domains have attracted significant attentions. Therefore, it is important to design the surfaces of these materials such that they can provide the required surface free energy and simplify the interfacial structure. Herein, various Cu films with a highly controllable surface wettability and a wide range of contact angles ranging from 6° to 152° were fabricated, and the corresponding mechanism was discussed. A wide range of wettability was realized by controlling the surface structure of the Cu film. The nanogap structure of the vertical nanowire-array film led to a high surface free energy. Similarly, the oblique nanowire-array film increased the surface free energy; however, the surface free energy was dependent on the size of the nanowires rather than on the nanogaps owing to the crystallinity of the film. Additionally, cluster-nanowire-array films were designed to realize a wettability transition from hydrophilicity to hydrophobicity with a constant surface free energy. The Cu foam possessed a superhydrophilic surface owing to its high porosity, whereas the cluster-nanoparticle structure possessed a superhydrophobic surface. In addition, we noted that the structure-induced wettability played an important role in tuning the semiconductor and metal interfacial stress and simplifying the interfacial structure. Furthermore, the outstanding electrical conductivity of the Cu films indicates its promising potential as an electrode. The structure-induced wettability proposed in this study can be applied for a wide range of materials, particularly for films used for advanced applications.

Superhydrophobic coatings are increasingly being evaluated as anticorrosion interventions in exceedingly hydrated environments. However, concerns about their long-term durability and amenability to large-area applications in marine environments are still hindering commercial-scale deployment. This study is focused on development of easy-to-apply superhydrophobic coatings, with multifunctional capabilities, in order to extend the integrity and durability of the coatings in harsh marine environments. Here, a set of facile methods involving selective chemical etching using concentrated NaOH, as well as fluorination with perfluoropolyether methyl ester were adopted to fabricate a superhydrophobic surface on basalt scales, having the required rough hierarchical micro-nanotextured and low surface energy. The superhydrophobic basalt scales were subsequently aligned atop a fluorocarbon resin, pre-deposited on a metal substrate, to yield a multifunctional superhydrophobic coating (3 μL water droplet; contact angle = 165.1°, rolling angle = 0.7°), easily amenable to large surface area application and having excellent wear resistance, UV-aging resistance, salt spray resistance, corrosion resistance and antibacterial capabilities.

The possibilities of the precise control of wetting properties of a series of laser-induced graphene (LIG) films consisting of microscale air pockets on top of nano-scale surface roughness using electrowetting are demonstrated. By application of a marginal DC bias (∼2 V), water can efficiently wet as well as can be pumped through the superhydrophobic LIG substrates. Interestingly, the electrowetting phenomenon is strongly dependent on the applied voltage polarity and it causes an abrupt wetting transition from superhydrophobic (contact angle ∼152°) Cassie state to superhydrophilic (contact angle ∼7°) Wenzel state on the LIG films. By analyzing the voltage polarity dependent electrowetting results with an equivalent electrical circuit model at the solid-liquid interface, and considering the hierarchical dual surface roughness (micro-nano scale), the transition between the “slippy” Cassie state and the “sticky” Wenzel states is explained. Furthermore, we demonstrate that the unique structural characteristics of the custom-designed micropatterned LIGs, with precisely tailored surface energy by simple post-annealing treatment, enable easy preparation of superhydrophobic LIG films. The approach to prepare stable superhydrophobic LIG with voltage polarity dependent wetting mode transition is used here to controllably transport of water through 3D porous LIG surfaces.

Silicon carbide surface modification is still a challenging task. Its modification mechanism is also still unclear. This paper provides a study of the surface modification mechanism of KH5X0 (X = 5, 6, 7, 8, 9) on the silicon carbide (111) using density functional theory. The electronic structures and densities of states of KH5X0 (X = 5, 6, 7, 8, 9) on SiC surfaces indicates that the surface modification mechanism is attributed to the electronic effects of the functional groups of KH5X0 (X = 5, 6, 7, 8, 9). From the results the easier it is for a functional group to obtain electrons, the better the modifying performance of silane coupling agent will be. Furthermore, the interface energy results showed that silicon carbide (111) modification performance by KH580 silane and KH590 silane is better than KH550, KH560, and KH570. The present work provides theoretical guidance for the fabrication of SiC heat sink products.

Experimental evidence for ferromagnetic ordering in isotropic atomically thin two-dimensional crystals has been missing until a bilayer Cr2Ge2Te6, and a three-atom thick monolayer CrI3 are shown to retain ferromagnetic ordering at finite temperatures. Here, we demonstrate successful isolation of a non-van der Waals type ultra-thin nanosheet of FeS2 derived from naturally occurring pyrite mineral (FeS2) by means of liquid-phase exfoliation. Structural characterizations imply that (111) oriented sheets are predominant and is supported theoretically by means of density functional theory surface energy calculations. Spin-polarized density theory calculations further predicted that (111) oriented three-atom thick pyrite sheet has a stable ferromagnetic ground state different from its diamagnetic bulk counterpart. This theoretical finding is evaluated experimentally employing low temperature superconducting quantum interference device measurements and observed an anomalous ferromagnetic kind of behavior., 21 pages, 5 figures

The bonding properties of adhesives are mainly affected by surface roughness, topography and chemical adsorption. In this paper, we studied the effects of surface pretreatment of Al 2024-T3 (bare) in terms of surface roughness, topography and surface free energy. Surface pre-treatment included solvent cleaning, FPL etching, PAA and CAA treatment. The surface energy and roughness of the aluminum surface were significantly increased by the anodizing treatment. Single lap shear and fatigue tests were performed to investigate bonding properties and durability. The evaluation revealed that the surface energy and surface roughness resulting from the aluminum surface treatment had a significant impact on bonding properties and durability. PAA treated surfaces had the highest bonding strength, and CAA treated surfaces had superior bonding retention performance in hot water or salt spray environments. The results of the fatigue test most clearly demonstrated how the surface pretreatment of the aluminum alloy differently affected bonding performance. (Received March 27, 2021; Accepted May 10, 2021)

Thermoplastic materials like High Density Polyethylene (HDPE) and Polytetrafluoroethylene (PTFE) are promising candidates for specialty industry/aerospace sectors considering their exceptional properties and lower densities. However, the low surface energy leading to poor wetting and reduced adhesion curtails the scope of their wide-spread usage. In this work, we report adhesion promoter primers based on epoxy–catechol with and without fluorinated polymer and investigated their adhesion promotion efficiency on low/high surface energy substrates. The rational design of catechol-fluorine-epoxy hybrid network, mimicking mussel chemistry enabled a non-destructive surface activating approach resulting in profound adhesion promotion. The fluorine containing primer could effectively enhance adhesion between homo and hetero interfaces of Aluminium/HDPE/PTFE owing to the good interface interaction and could outperform common etching methods. A series of molecular level characterizations together with computational and AFM studies provided evidences for the high degree of interaction of the primer between the substrates and epoxy-based adhesives. Bond integrity endurance test using a weight of 10 and 20 kg resulted in ‘no fail’ categorization for the primed substrates during the entire 40 days test duration. The catechol-functionalized primers reported here can be a good overreaching approach to keep non-polar substrates afloat in advanced sectors.

It remains a great challenge to prepare polylactic acid (PLA) composites with excellent mechanical properties, superior anti-bacteria, and highly effective electromagnetic interference (EMI) shielding using ultralow loading of functional fillers. Herein, lignin particles were uniformly nano-sized as the matrix reinforcement and the fillers carrier via green mechanochemistry for improved thermal properties of polymer matrix. Through one-pot approach to a multitasking engineered agent, hybridized ZnO/Ag particles were synthesized for multi-functionalities. Inspired by mussels, the bio-derived dopamine cross-linker was introduced to in-situ synthesize the polypyrrole (PPy-PDa) glutinous nanofibrils as an interfacial modifier and a particles dispersant to regulate surface free energy of nanoparticles and improve filler-matrix interactions. With effective constructed 3D conductive networks by glutinous nanofibrils and hybridized particles, the dramatic improvement in EMI shielding and electrical conductivity was accomplished using an ultralow content of the conductive particles modifier (0.29 vol% Ag). The resulted biobased composites presented outstanding anti-dripping properties, mechanical properties, electrical conductivity (104.2 S/cm), anti-bacteria, joule heating, photothermal conversion ability and EMI shielding effectiveness (48.6 dB at X-band), which are superior to those reported. This work will broaden the application prospects of PLA composites in the fields of wearable electronics, food packaging and medical devices.

Based on the three-dimensional thermodynamic model, the wettability of a superhydrophobic solid surface with a circular truncated cone microstructure has been investigated. The relationship between the microstructure of the circular truncated cone surface and superhydrophobic property is established by introducing the tension of the three-phase contact line in the composite state. The results show that the base angle and base spacing of the circular truncated cone have great influence on the wetting transition of composite and non-composite states. The theoretical expressions of the critical transition criteria are also given. The accuracy of the theoretical results is verified by comparing the theoretical prediction with the existing experimental data in the literature. The model established in this paper provides a theoretical basis and a reference for the optimal geometric parameters for studying the wettability of advanced superhydrophobic materials by using engineering microstructures.

A new regioselective route is introduced for surface modification of biological colloids in the presence of water. Taking the case of cellulose nanofibers (CNFs), we demonstrate a site-specific (93% selective) reaction between the primary surface hydroxyl groups (C6-OH) of cellulose and acyl imidazoles. CNFs bearing C6-acetyl and C6-isobutyryl groups, with a degree of substitution of up to 1 mmol g−1 are obtained upon surface esterification, affording CNFs of adjustable surface energy. The morphological and structural features of the nanofibers remain largely unaffected, but the regioselective surface reactions enable tailoring of their interfacial interactions, as demonstrated in oil/water Pickering emulsions. Our method precludes the need for drying or exchange with organic solvents for surface esterification, otherwise needed in the synthesis of esterified colloids and polysaccharides. Moreover, the method is well suited for application at high-solid content, opening the possibility for implementation in reactive extrusion and compounding. The proposed acylation is introduced as a sustainable approach that benefits from the presence of water and affords a high chemical substitution selectivity., We report a versatile and simple preparation of hydrophobic cellulose nanofibers through a spatially confined modification of the primary surface hydroxyl groups.

International audience; Wetting of polymer-grafted nanoparticles (NPs) in a polymer nanocomposite (PNC) film is driven by a difference in surface energy between components as well as bulk thermodynamics, namely, the value of the interaction parameter, χ. The interplay between these contributions is investigated in a PNC containing 25 wt % polymethyl methacrylate (PMMA)-grafted silica NPs (PMMA-NPs) in poly(styrene-ran-acrylonitrile) (SAN) upon annealing above the lower critical solution temperature (LCST, 160 °C). Atomic force microscopy (AFM) studies show that the areal density of particles increases rapidly and then approaches 80% of that expected for random close-packed hard spheres. A slightly greater areal density is observed at 190 °C compared to 170 °C. The PMMA-NPs are also shown to prevent dewetting of PNC films under conditions where the analogous polymer blend is unstable. Transmission electron microscopy (TEM) imaging shows that PMMANPs symmetrically wet both interfaces and form columns that span the free surface and substrate interface. Using grazingincidence Rutherford backscattering spectrometry (GI-RBS), the PMMA-NP surface excess (Z*) initially increases rapidly with time and then approaches a constant value at longer times. Consistent with the areal density, Z* is slightly greater at deeper quench depths, which is attributed to the more unfavorable interactions between the PMMA brush and SAN segments. The Z* values at early times are used to determine the PMMA-NP diffusion coefficients, which are significantly larger than theoretical predictions. These studies provide insights into the interplay between wetting and phase separation in PNCs and can be utilized in nanotechnology applications where surface-dependent properties, such as wettability, durability, and friction, are important.

In this paper, we report on the electrophoretic deposition and characterisation of pure sodium alginate coatings on titanium biomaterials, the commercially pure titanium CP-Ti1 and Ti–13Nb–13Zr titanium alloy. Various solutions differing in the distilled water to ethanol volume ratio and sodium alginate concentration were used for coating deposition. Uniform, dense and continuous coatings with a thickness up to 1 µm were deposited. The effect of surface topography and morphology, wettability and surface free energy as well as surface chemistry on the coating adhesion to the titanium biomaterials were investigated. The coatings exhibited very good adhesion to the polished and then chemically treated alloy. The adhesion mechanisms were identified. The chemical bonding and interfacial adhesion mechanisms are plausible. The coatings exhibited low surface development, dependent on the applied substrate roughness. Sodium alginate coatings on both substrates showed moderate hydrophilicity and relatively high surface free energy, on average 30 pct higher in comparison with that of the substrate materials. The obtained results will be useful for the further development of composite sodium alginate coatings for enhancing the biological performance of titanium biomaterials.

The research aim was to analyse the changes in the air permeability, waterproofness, surface, mechanical and thermal properties of the polyamide 6.6 fabric with a polyurethane coating before and after 1, 5, and 10 washes in the same conditions using specialized (V1) and universal (V2) laundry detergent. A new approach based on SEM and DSC techniques and assessment of surface free energy combined with standard methods was proposed to explain the nature of observed changes in waterproof and breathable material after washing treatment. SEM analysis indicated that after 10 washes the porosity of the polyurethane coating increased from 8.94% to 14.56% and 18.75% for V1 and V2, respectively. The air permeability increased from 0.747 mm/s for the reference sample to 0.766 mm/s and 0.774 mm/s after 10 washes for V1 and V2, respectively. The waterproofness of the reference sample of 992 mbar decreased with the increasing number of washes to 246 mbar and 122 mbar for V1 and V2, respectively. After 10 washes the surface free energy (γS) decreased by 18.8% and 24.3% for V1 and V2, respectively. The average tensile strength amounted to 833 N and decreased by 13.5% for V1 and by 20% for V2 after 10 washes. The glass transition temperature of the reference fabric was 47.6°C. After 10 washes it increased by 7.2°C and 8.8°C for V1 and V2, respectively. The temperatures of thermal degradation increased by 24.6°C and 22.2°C and the heat of thermal decomposition decreased by 23.6% and 15.8% after 10 washes for V1 and V2, respectively.

In this work, a high-entropy alloy and CrZrTiNiCu coating were synthesized by mechanical alloying. It is shown that the microhardness of the CrZrTiNiCu coating is not inferior to and in most cases exceeds the hardness of high-entropy equiatomic alloys. The wear resistance of such a coating is 3·10-4 g/min, which also corresponds to special steels in terms of wear resistance. The high-entropy coating has a low coefficient of friction. It turns out to be antifrictional, which obviously leads to energy savings. For the first time, the surface energy, contact potential difference and work function of electrons for CrZrTiNiCu coating were determined.

Atomic force microscopy (AFM) measurements of dihedral angles are conducted for the first time to characterize the ratio of the twin-boundary energy (γΤ) to the surface free energy (γS). In plane, twin morphology is measured with AFM, verified by scanning electron microscopy, optical microscopy, and found to be consistent. The chemical composition and homogeneity of annealed Cu10 wt%Zn sample are confirmed by energy-dispersive spectroscopy. AFM data indicate that the average depth and height of the grooves and peaks are 118 ± 45 and 158 ± 45 nm, respectively. Surface roughness parameters, Sq and Sa, are measured by a factor of two to four less than the depth and height of the twin boundaries. Both surface roughness parameters are less with no planar defects present compared with selected areas containing twin boundaries. The average dihedral angle is found to be 167 ± 5° for the grooves and 193 ± 4° for the peaks. The twin to surface interfacial free energy ratio, γT/γS, is 0.0018. The comparison of AFM-based results to the other method-based results obtained on pure metals is discussed.

By considering the surface free energy effect, an analytical investigation on the fracture behaviors of nanoparticle-reinforced composites was performed in this study. The plastic zones ahead of the crack tips based on the Irwin model were introduced in our analysis, which has a significant influence on the fracture toughness of inelastic structures, especially for polymer and metal matrix composites. Take copper and aluminum nanoparticles as examples, comprehensive parametric studies were conducted to investigate the interaction between a Griffith crack and the nearby nanoparticle. It was found that for nanoparticles with the radius of less than 10 nm, apart from the mechanical property of the nanoparticle, the surface free energy effect plays a dominant role in determining the fracture behaviors of the nanoparticle-reinforced composites. Moreover, taking the surface free energy into account, a decrease in the plastic zone size is obtained, particularly for the crack tip nearer the nanoparticle.

Li2ZnTi3O8@α-Fe2O3 composites have been successfully prepared by a facile hydrothermal process. Li2ZnTi3O8/α-Fe2O3 composites show similar irregular spherical morphologies like Li2ZnTi3O8 and relatively smaller particle sizes than pristine Li2ZnTi3O8. Among all Li2ZnTi3O8/α-Fe2O3 composites, Li2ZnTi3O8/α-Fe2O3 composite (5 wt%) exhibits the best electrochemical properties. Li2ZnTi3O8/α-Fe2O3 composite (5 wt%) delivers a reversible charge capacity of 184.8 mAh g−1 even at 1000 mA g−1 after 500 cycles, while pristine Li2ZnTi3O8 only delivers a reversible charge capacity of 110.7 mAh g−1. The strong covalent bonds between Li2ZnTi3O8 and α-Fe2O3 will be formed, which is beneficial for the reduction of interfacial energy and thus helpful for the stabilization of the composite. Because of the special synergistic effect of the multi-phase interface, Li2ZnTi3O8/α-Fe2O3 composites not only possess the advantages of single components but also show novel and attractive performances, such as the enhanced ionic conductivity, reduced interfacial charge transfer impedance, improved migration rate of lithium ions, and the enhancement of the rate performance and reversible capacity. The as-prepared Li2ZnTi3O8/α-Fe2O3 composites reveal important potentials as anode materials for next-generation rechargeable Li-ion batteries, and this work also offers an effective strategy to design high performance lithium storage materials for advanced lithium-ion batteries.

Fluorinated polyhedral oligomeric silsesquioxane (F-POSS) is one of the most popular candidates at present for superhydrophobic coating. Because of its ultralow surface energy, F-POSS has usually been dissolved with expensive fluoro-solvents, and the melting temperature of F-POSS is not high (122–140 °C), which will cause its loss during use. So trying to polymerize/crosslink F-POSS molecules and/or directly graft F-POSS to substrate is important. In this work, we report the SI-eATRP grafting of methacryl POSS (MA-POSS) on cotton and the subsequent amine catalyzed thiol-methacrylate Michael addition reaction of poly(MA-POSS) with 1H, 1H, 2H, 2H-perfluorododecyl-1-thiol (PFDT) for the fabrication of a durable poly(MA-POSS)-PFDT coating. The cotton fabric coated with poly(MA-POSS) was nearly superhydrophobic after 4 h of SI-eATRP process under potentiostatic condition of −0.40 V. Although the water contact angle (WCA) was ~148°, water droplets tended to adhere to the cotton fabric surface even when the fabric was turned upside down. After fluorination, WCA was increased to ~160°, and water drops could slide off when the fabric was slightly tilted. The sliding angle (SA) was ~10°. The as-prepared poly(MA-POSS)-PFDT coating was durable against repeated washing and physical abrasion. After 30 accelerated washing cycles (equals to 150 home laundering cycles), the coated fabric still showed superhydrophobicity. After 800 abrasion cycles over sandpaper, the WCA was still as high as 149°. In addition, the coated fabric had self-healing ability and could restore its superhydrophobicity after plasma etching through heat treatment. After 10 cycles of plasma etching and heat-induced healing process, the WCA of the coated fabric kept at ~154°. Such a durable superhydrophobic fabric coating may find applications in the development of functional clothing for a variety of purposes.

For SiCp/Al matrix composites, nano SiC particles (SiCp) show more obvious strengthening effect than micro ones. In general, nano SiCp are added into Al matrix by ex-situ method, during which interfacial and agglomerating problems often generate. In-situ method is considered an effective way to solve above problems, but the in-situ synthesis of nano SiCp hasn't been reported. In this research, nano SiCp were in-situ synthesized in Al–Si–C system via a liquid–solid reaction method at relative low temperature (750 °C). Microstructure observation shows that the obtained nano SiCp have 3C polytype and show hexagonal plate morphology, with average size under 100 nm. In order to lower its surface energy, nano SiCp tend to connect with each other and form a coherent interface with stacking faults. Further research reveals that nano SiCp are formed via a two-step reaction. Nano SiCp can be introduced into Al–Si alloy and elevate its strength both at room and high temperature.

Assessment of powder segregation is essential in most powder-based industries when homogeneity of the powder is a concern. This study focuses on exploring correlations between segregation possibilities of the powders with a wide size range and some common material properties such as particle size, size ratio and adhesion, so that a simple method for assessing segregation intensity of a powder just based on the material properties can be developed, although the current study is designed for surface rolling segregation only.\ud \ud In this study, eight blends were made from different grades of calcium carbonate, which were selected based on different particle size ranges and particle adhesions. Segregation of a sample was determined by measuring segregation index, which was defined as a ratio of fines concentration change between segregated samples at the top and bottom sections of a surface segregation tester and the averaged concentration. Particle size distributions of the blended samples were measured before segregation tests and then the segregation tests were completed for the same blends. Powder adhesion of the virgin blends was also examined and represented by measuring the “bond number” using a mechanical surface energy tester developed at the Wolfson Centre.\ud \ud The experimental results showed correlations between the segregation index and the material properties such as particle size, size ratio and bond numbers, and was fitted to multiple empirical functions. With the correlations determined, novel methods for assessing surface segregation have been developed; one method considers just the particle sizes and the other one considers both particle sizes and particle adhesion identified by the bond number.

Designing materials surfaces for reducing the reflection of light is imperative towards enhancing the performance of optical and optoelectronic devices. We show that ion implantation under specific experimental conditions is a single step and controllable process to minimize reflection over a large wavelength range by growth of surface nanostructure in a self-organized fashion. For instance, we show a strong reduction in optical reflectance in the ultraviolet–visible-infrared wavelength range (300–3000 nm) for Ge with the evolution of nanoscale self-organized patterns under energetic ion bombardment at oblique angles. As pattern coarsening takes place with increasing ion fluence (for subtle incident angles), the optical reflectance reduces to a significant extent. The evolution of saw-tooth-like structures on Ge surface, at an oblique incidence of 60° to the fluence of 3 × 1018 ions cm−2, leads to a huge reduction in optical reflectance (below 4% over a wide spectral range) and makes it behave effectively like a black-Ge specimen. The huge reduction in the optical reflectance is found to be related to the dimension of the surface features evolved under ion implantation at room temperature. The observed surface morphology gives rise to an effective gradient in refractive index from the top toward the bottom of the patterned surface. Thus, the reduction in refractive index is calculated and correlated with the respective surface morphology. We have also studied change in the wetting property of ion-induced patterned surfaces and correlated it with the reduction in surface free energy due to the presence of oxygen.

The fast exploration of low energy configuration by surface atoms is believed to favor the formation of ultrastable metallic glasses, prepared by physical vapor deposition. Here, we find that the rearrangement of surface atoms is collective, rather than being dominated by individual atoms. Specifically, we experimentally observe the growth process of ultrastable metallic glasses at monolayer resolution, which follows a periodic island-layer-island pattern with morphology variation between islands and flat surfaces. The estimated surface diffusion coefficient is orders of magnitude higher than that for bulk diffusion. The fast surface dynamics allow the newly deposited clusters on the flat surface to form local islands with spherical shape, which substantially reduces the surface free energy in each island-layer-island growth cycle. Our findings are helpful for understanding the growth mechanisms of ultrastable metallic glasses and potentially for tailoring their properties. Ultrastable metallic glasses form by surface diffusion on a substrate during deposition. Here, this process is shown to involve the collective diffusion of atoms in a cyclic process, involving the formation of islands, their coalescence into a layer, followed by further island formation.

A non-thermal plasma treatment generated in air at atmospheric pressure was used for surface modification of medium density fiberboard (MDF) substrate. Untreated and plasma-treated substrates were coated with a waterborne acrylic coating and exposed to accelerated artificial weathering (AAW) in interior mode. Plasma treatment increased the surface free energy of MDF by about 50%, which positively influenced on the wettability of the MDF with the coating. Weathering of the coated MDF caused a decrease in surface gloss and color changes, which were less pronounced for plasma-treated samples. Attenuated total reflection Fourier transform infrared spectra and microscopic analysis revealed degradation of the acrylic resin on the coated MDF due to light irradiation during weathering. After 250 h of weathering, the surface roughness of the coated MDF increased by about 3 μm. The coated MDF surfaces started to lose their hydrophobic character after 50 h of weathering. Finally, the determination of mechanical properties showed that coated MDF became more resistant to scratching during AAW, while the adhesion of the coating film to the MDF substrate was not affected in a significant trend with time of AAW. In both cases, no influence of plasma treatment was detected.

Diamond-like carbon (DLC) films directly deposited on rubber substrate is undoubtedly one optimal option to improve the tribological properties due to its ultralow friction, high-hardness as well as good chemical compatibility with rubber. Investigating the relationship between film structure and tribological performance is vital for protecting rubber. In this study it was demonstrated that the etching effect induced by hydrogen incorporation played positive roles in reducing surface roughness of DLC films. In addition, the water contact angle (CA) of DLC-coated nitrile butadiene rubber (NBR) was sensitive to the surface energy and sp2 carbon clustering of DLC films. Most importantly, the optimum tribological performance was obtained at the 29 at% H-containing DLC film coated on NBR, which mainly depended on the following key factors: (1) the DLC film with appropriate roughness matched the counterpart surface; (2) the contact area and surface energy controlled interface adhesive force; (3) the microstructure of DLC films impacted load-bearing capacity; and (4) the generation of graphitic phase acted as a solid lubricant. This understanding may draw inspiration for the fabrication of DLC films on rubber to achieve low friction coefficient.

Laser surface texturing is a widely accepted technique to alter the surface properties of different biomaterials. The present work investigates the influence of texture shape and texture area fraction on the wettability and bacterial adhesion properties of a metallic (Ti–6Al–4V), ceramic (hydroxyapatite, HAp), and polymeric (polymethyl methacrylate, PMMA) surfaces. A fiber laser (1040 nm wavelength) was utilized to generate patterns on Ti–6Al–4V, whereas a CO2 laser (1062 nm wavelength) was employed for patterning HAp, and PMMA surface. The average surface roughness (~ 10 s of µm) of textured surfaces have elicited corresponding enhancement in the feature of base wettability. A decreased surface energy of textured surfaces commensurate with decreased E. coli bacterial density (~ 30.1% in HAp, and by 53.7% in PMMA) in contrast to that of untextured samples. From the comparative study conducted in this work, among all the textured samples the triangular patterned HAp having 50.6% textured area, contact angle and surface energy of 103.2 ± 3° and 15.1 mN.m−2, respectively, showcased a significant decrease in E. coli adhesion (~ 1.67 ± 0.15 × 105 bacteria per mm2). Thus, laser surface texturing of scaffolds can potentially allow restricting the bacterial adhesion on various biosurfaces for bone replacement applications.

PurposeIn this work, with a goal to ultimately forward the advancement of additive manufacturing research, the author applies the Wheeler-Boettinger-McFadden model through a progressive series of increasingly complex solidification problems illustrating the evolution of both dendritic as well as columnar growth morphologies. For purposes of convenience, the author assumes idyllic solutions (i.e. the excess energies associated with mixing solid and liquid phases can be neglected).Design/methodology/approachIn this work, the author applied the phase-field model through a progressive series of increasingly complex solidification problems, illustrating the evolution of both dendritic as well as columnar growth morphologies. Beginning with a non-isothermal treatment of pure Ni, the author further examined the isothermal and directional solidification of Cu–Ni binary alloys.Findings(1) Consistent with previous simulation results, solidification simulations from each of the three cases revealed the presence of parabolic, dendrite tips evolving along directions of maximum interface energy. (2) For pure Ni simulations, changes in the anisotropy and noise magnitudes resulted in an increase of secondary dendritic branches and changes in the direction of propagation. The overall shape of the primary structure tended also to elongate with increased anisotropy. (3) For simulations of isothermal solidification of Ni–Cu binary alloys, the development of primary and secondary dendrite arm formation followed similar patterns associated with a pure substance. Calculations of dendrite tip velocity tended to increase monotonically with increasing anisotropy in accordance with previous research. (4) Simulations of directional solidification of Ni–Cu binary alloys with a linear temperature profile demonstrated the presence of cellular dendrites with relatively weak side-branching. The occurrence of solute trapping was also apparent between the primary dendrite columns. Dendrite tip velocities increased with increasing cooling rate.Originality/valueThis research, particularly the section devoted to directional solidification of binary alloys, describes a novel numerical framework and platform for the parametric analysis of various microstructural related quantities, including the effects due to changes in temperature gradient and cooling rate. Both the evolution of the phase and concentration are resolved.

Hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) was deposited onto hydrophobic polytetrafluoroethylene (PTFE) surfaces using initiated chemical vapor deposition. By tuning the reactor conditions, the reaction kinetics were varied to achieve a wide range of deposition rates that spanned over 2 orders of magnitude (∼0.1-10 nm/min). Depositions rates at >1 nm/min were successful in overcoming the interfacial energy and wettability barriers between the hydrophobic and hydrophilic polymers and were found to achieve both conformal and ultrathin coatings. PHEMA coatings as thin as ∼10 nm over PTFE were able to transform a hydrophobic surface with a water contact angle of ∼110° to a hydrophilic one with an angle of ∼20°.

A high-entropy alloy coating of AlCoCrFeNi was prepared by plasma spraying and then remelted via laser remelting. The effect of laser remelting on the microstructure, mechanical properties and wear resistance of the AlCoCrFeNi coating was investigated. Particularly, the effect of surface free energy on the wear resistance of the coatings before and after remelting was explored. The results showed that the remelted AlCoCrFeNi coating retained the same single BCC solid solution structure as the as-sprayed AlCoCrFeNi coating. Besides, the defects in the coating were basically eliminated by laser remelting, leading to the porosity of the coating decreased from 4.8 to only 0.3%. Consequently, the hardness, elastic modulus and fracture toughness of the coating were enhanced by 38%, and the wear loss of the remelted AlCoCrFeNi coating was only 22% of that of the as-sprayed one. Therefore, laser remelting is a feasible method to improve the microstructure and enhance the wear resistance of the AlCoCrFeNi high-entropy alloy coating.

Here, we compare the electrochemical oxidation potential of 15 nm diameter citrate-stabilized Au NPs aggregated by acid (low pH) to those aggregated by tetrakis(hydroxymethyl) phosphonium chloride (THPC). For acid-induced aggregation, the solution changes to a blue-violet color, the localized surface plasmon resonance (LSPR) band of Au NPs at 520 nm decreases along with an increase in absorbance at higher wavelengths (600-800 nm), and the peak oxidation potential (Ep) in anodic stripping voltammetry (ASV) obtained in bromide has a positive shift by as large as 200 mV. For THPC-induced aggregation (Au/THPC mole ratio = 62.5), the solution changes to a blue color as the LSPR band at 520 nm decreases and a new distinct peak at 700 nm appears, but the Ep does not exhibit a positive shift. Scanning transmission electron microscopy (STEM) images reveal that acid-induced aggregates are three-dimensional with strongly fused Au NP-Au NP contacts, while THPC-induced aggregates are linear or two-dimensional with ∼1 nm separation between Au NPs. The surface area-to-volume ratio (SA/V) decreases for acid-aggregated Au NPs due to strong Au NP-Au NP contacts, which leads to lower surface free energy and a higher Ep. The SA/V does not change for THPC-aggregated Au NPs since space remains between them and their SA is fully accessible. These findings show that metal NP oxidative stability, as determined by ASV, is highly sensitive to the details of the aggregate structure.

This research aims at detecting the hydrophobicity change in Samama (Anthocephalus macrophyllus) wood surface after hydro-thermo-mechanical modification. The modification started by soaking the tes...