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Graphical abstract Highlights • Pd nanocubes supported on functionalized graphene was synthesized without the use of any surfactant. • PdNCs/fG shows an enhanced electrocatalytic activity towards formic acid oxidation. • The synergistic effect of modified support and shape selectivity plays an important role to the activity. Abstract Direct Formic Acid Fuel Cells (DFAFCs) have been extensively focused and rapidly growing as one of alternative energy systems for portable devices and automobiles. However, power energy requires the active and selective metal nanocatalysts to perform the highest electrochemical activity. Here, we propose a nanocubic shape of palladium nanoparticles (PdNPs) decorated on functionalized graphene (fG), where surface modification is obtained by surfactant free method. The 11 nm and high dispersion of Pd nanocubes (PdNCs), which are majorly enclosed with (1 0 0) indicated by XRD and HRTEM results, are successfully deposited on functionalized graphene (PdNCs/fG) and used as an enhanced electrocatalysts for formic acid oxidation. Our PdNCs/fG catalyst displays a remarkable mass activity towards formic acid oxidation (494.50 A/g, over 100 times) compared to commercial catalysts of Pd/C, and over 20 times to PdNPs on unmodified graphene or reduced graphene oxide (PdNPs/rGO). Moreover, our catalyst exhibits better stability and higher CO resistance. The PdNCs/fG catalyst also generates the superior specific activity towards formic acid oxidation to 20.37 A/m2. The study demonstrates the synergistic effect of high selective site enabled by {1 0 0} facet on PdNCs and a great potential from a support of modified graphene to Pd metal catalyst for the development of electrocatalysts in fuel cell applications. [ABSTRACT FROM AUTHOR]

Highlights • Vapor condensation in nanopores on hydrophilic surface affects AFM contrast inversion. • Use of Si probes may provide AFM contrast inversion of nano-sized surface features. • Use of Pt/C nanowire probes ensures adequate AFM imaging of nano-sized features. • The explanation of the phenomenon is based on the liquid meniscus shape in nanopores. Abstract We found that enhanced vapor condensation in nanopores and nanochannels on hydrophilic surfaces affects contrast and spatial resolution of the atomic force microscopy (AFM) imaging. It was demonstrated, that at ambient conditions the use of conventional Si probes may provide contrast inversion of the topography image of the hydrophilic samples with nano-sized surface features whereas use of the probes modified with hydrophilic Pt/C nanowires ensures adequate AFM imaging. The phenomenon of the AFM contrast inversion and the spatial resolution improvement effect obtained with the probes modified with the nanowires are discussed. The explanation of the phenomenon considering the shape of liquid meniscus in hydrophilic nanopores and nanochannels is proposed. [ABSTRACT FROM AUTHOR]

Graphical abstract The advantages, challenges, interface engineering strategies and surface modification approaches of hierarchical photocatalysts are systematically summarized and addressed. Highlights • The advantages and challenges of hierarchical photocatalysts were highlighted. • The interface engineering strategies of hierarchical photocatalysts were reviewed. • The surface modification approaches of hierarchical photocatalysts were addressed. Abstract In developing efficient heterogeneous photocatalysts, the design and fabrication of hierarchical semiconductors at the micro/nanometer scales have received much attention during the past decade due to their unique advantages in addressing the critical problems during photocatalysis. However, there are still many challenges in designing and constructing highly efficient hierarchical photocatalysts. Thus, in this review, we first systematically summarize and discusse the fundamentals and important interface engineering strategies of designing hierarchical photocatalysts, such as fabricating Z-Scheme heterojunctions, constructing Schottky-based heterojunctions, creating carbon-based heterojunctions and designing multicomponent heterojunctions. Then, especially, the different surface modification approaches of hierarchical porous photocatalysts, including loading cocatalysts, exposing the reactive facets, introducing defects/heteroatoms, adding photosensitizers, are highlighted. Finally, the major conclusions are made regarding this promising class of heterogeneous photocatalysts, and some perspectives are given on its future development. Through studying the important advances on this topic, it may pave a new avenue for fabricating highly effective hierarchical semiconductors for various applications in photocatalysis, electrocatalysis, thermal catalysis and other fields. [ABSTRACT FROM AUTHOR]

Atomistic (binary-collision) simulation is used to study the sputter yield of rippled C and Si surfaces bombarded with Ar and Ga ions in a wide range of incidence angles and energies. This study was motivated by conflicting theoretical predictions of results when the ion energy is varied. Most simulations refer to a sinusoidal ripple topography with h / λ  = 0.05–0.15, where h and λ are the amplitude and wavelength of ripples, respectively. Results are compared with Monte Carlo simulation based on Sigmund’s continuum model of ion sputtering and not tied to a specific ion-target combination. Both types of simulation do not confirm a strong suppression of the angular variation in the sputter yield from rippled surfaces with increasing ion energy, predicted theoretically (Makeev and Barabási, 2004). [ABSTRACT FROM AUTHOR]

Lead(II)-benzohydroxamic acid (lead-BHA) is a metal-organic complex system used as a highly selective collector in the flotation separation of oxide minerals. In the current study, the surface microstructures and adsorption mechanism of lead-BHA on mineral surfaces were comprehensively investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Raman spectroscopy, atomic force microscopy (AFM) and first-principles calculations. The characteristic Raman peak indicated that lead-BHA adsorbs on mica surfaces. The AFM topography of a mica surface (0 0 1) treated with lead-BHA at a ratio of 1:1 showed many local adsorption layers, but no obvious adsorption layer was observed for the same surface treated with lead-BHA at a ratio of 1:2, which suggests that Pb(BHA) + might be the effective species for mineral flotation. First-principles density functional theory (DFT) calculations indicated that the lowest unoccupied molecular orbital (LUMO) of Pb(BHA) + was mainly localized on the lead atom, while the LUMO of Pb(BHA) 2 was distributed over the whole molecule, implying that Pb(BHA) + exhibits better affinity to the mica surface than Pb(BHA) 2 , and further suggesting that Pb(BHA) + might be an effective specie. The further first-principle calculation, from the molecular level on mica surface, showed that the Pb(BHA) + could produce a higher adsorption energy than Pb(BHA) 2 , revealing that the Pb(BHA) + should be an effective specie that can efficiently adsorb onto the mica surface. This work may shed new light on the effective species of metal-organic complex collectors on oxide mineral surfaces in flotation separation. [ABSTRACT FROM AUTHOR]

Laser-induced oxidation of metallic surfaces such as titanium is used in many application areas for colour marking due to its selectivity, cleanness and processing speed. However, as the generated colours are permanent this reduces the flexibility and applicability of this laser processing technology. Therefore, a method is reported in this paper to erase selectively the oxide-based colours using laser-induced oxygen reduction. Especially, the colour marks are reprocessed in a low oxygen environment employing a nanosecond laser. A low fluence was used in order to diffuse oxygen out into the atmosphere and yield a lower form of metal oxides or a pure metal. Any cumulative fluence exceeding 25 J/cm 2 was sufficient to erase any laser-induced colours on titanium substrates. The XPS analysis revealed that all fields were mainly comprised of TiO 2 prior to erasing with only small contributions from Ti 2 O 3 and TiO/TiN. Following the proposed laser-induced oxygen reduction, the relative concentration of TiO 2 decreased substantially while the overall amount of Ti in the near surface region increased. The results clearly show that the erasing of oxide-based colour marks is only due to oxygen diffusion back into the atmosphere and there were not any signs of laser ablation. [ABSTRACT FROM AUTHOR]

Reactive potentials are increasingly used to study the properties of glasses and glass water reactions in a reactive molecular dynamics (MD) framework. In this study, we have simulated a ternary sodium aluminosilicate glass and investigated the initial stages of the glass surface-water reactions at 300 K using reactive force field (ReaxFF). On comparison of the simulated glass structures generated using ReaxFF and classical Buckingham potentials, our results show that the atomic density profiles calculated for the surface glass structures indicate a bond-angle distribution dependency. The atomic density profiles also show higher concentrations of non-bridging oxygens (NBOs) and sodium ions at the glass surface. Additionally, we present our results of formation of silanol species and the diffusion of water molecules at the glass surface using ReaxFF. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electro-thermal coupling effect and the thermal–mechanical coupling effect were the basic principles of the coupling field tip enhancement induced with laser irradiated probes. • The thermo-mechanical coupling effect allows an accurate estimation of the probe displacement and avoids mechanical scratching on the sample surface. • Nanostructures with a feature size of approximately λ/20 (23 nm) was obtained. • The essential mechanism of the coupling field tip enhancement interacting with samples is the deposition of total energy on materials. The nanofabrication mechanism of coupling field tip enhancement induced by laser-irradiated probe tip was investigated theoretically and experimentally. The coupling mechanisms and distribution characteristics of the enhanced electric, thermal, and stress fields were studied at wavelengths of 400–800 nm and tip-sample distances of 1–20 nm for 9 material combinations. The simulation results demonstrated that the electro-thermal coupling effect and thermal–mechanical coupling effect are the basic principles of this technique, independent of the materials. It was also demonstrated that probe damage due to mechanical scratching can be avoided through the estimation of probe displacement. The superposition of electromagnetic energy and thermal energy generates an extremely constrained total energy of up to 10–12 orders of magnitude near the tip end. The nano-line structures were processed at each tip-sample distance, and nanostructures with a feature size of approximately λ/20 were obtained. The experimental results and the total energy distribution demonstrated that the interaction of the coupling field tip enhancement with samples is in the form of total energy deposits on materials. The significance of this study will not only enable a refined understanding of the fundamental physics of surface nanostructuring but will also advance the scientific and industrial applications of the technology. [ABSTRACT FROM AUTHOR]

The electronic structure and magnetic properties of relaxed (001) surfaces of the sp -electron half-metallic ferromagnet NaSe in the zinc-blende phase, are calculated on the basis of first principle density functional theory within the framework of self-consistent field plane wave pseudo-potential method, using the generalized gradient approximation for the exchange-correlation functional. The results of this study reveal that both Na- and Se-terminated surfaces retain the robust bulk half-metallic property. The negative value found for the bulk formation energy indicates that this material is stable against phase separation. We also obtain the surface energies and discuss their stability via the calculated bulk formation energy. The Curie temperature is estimated to be 920 K within mean field approximation, which is well above the room temperature. In the light of the above, zinc-blende NaSe appears to be a good candidate for spintronic applications as spin injection material. [ABSTRACT FROM AUTHOR]

The rubber friction coefficient, and the contact area during stationary sliding is calculated, for the contact of a polished rubber block and a concrete surface, when both surfaces are rough. The calculation is based on an extended version of Persson's contact mechanics theory. Compared to only the substrate being rough, when both of the surfaces are rough but their cross correlation is zero, the friction coefficient is larger. Introducing a positive correlation decreases the friction coefficient, while introducing a negative correlation increases the friction coefficient. To support these theoretical arguments, some experiments have been performed. We have produced roughness on the rubber surface, using abrasive paper, and measured the surface topographies for the concrete and the polished rubber surfaces. The auto spectral density functions for the both surfaces have been calculated, and the rubber viscoelastic modulus mastercurve has been obtained. We have measured the rubber friction at different sliding velocities, when the rubber surfaces are rough and smooth, and compared it to the theoretical results. It is seen that when the rubber surface is rough, the rubber friction coefficient is larger compared to the case the rubber surface is smooth. The theoretical results are in good agreement with experimental observation. [ABSTRACT FROM AUTHOR]

In scanning probe microscopy (SPM), the chemical properties and sharpness of the tips of the cantilever greatly influence the scanning of a sample surface. Variation in the chemical properties of the sharp tip apex can induce transformation of the SPM images. In this research, we explore the relationship between the tip and the structure of a sample surface using dynamic atomic force microscopy (AFM) on a Cu(110)-O surface under ultra-high vacuum (UHV) at low temperature (78 K). We observed two different c(6 × 2) phase types in which super-Cu atoms show as a bright spot when the tip apex is of O atoms and O atoms show as a bright spot when the tip apex is of Cu atoms. We also found that the electronic state of the tip has a serious effect on the resolution and stability of the sample surface, and provide an explanation for these phenomena. This technique can be used to identify atom species on sample surfaces, and represents an important development in the SPM technique. [ABSTRACT FROM AUTHOR]

This work describes a Monte Carlo algorithm which appropriately takes into account the stochastic behavior of electron transport in solids and the simulation of the energy distributions of the secondary and backscattered electrons from polymethylmethacrylate irradiated by an electron beam. The simulation of the backscattered and secondary electron spectra also allows calculating the backscattering coefficient and the secondary electron yield of polymethylmethacrylate as a function of the initial energy of the incident electrons. Results of the simulation are compared with the available experimental data. The importance of considering all the electrons emerging form the surface in calculating the secondary electron yield and the backscattering coefficient is highlighted. In particular, we will discuss the importance of taking into account the tail of high energy secondary electrons in the spectrum for the simulation of the backscattering coefficient. [ABSTRACT FROM AUTHOR]

Bronze coins coming from the area of the Mediterranean basin, dated back the II–X Cent. A.D., were analyzed using different physical analytical techniques. Characteristic X-ray fluorescence was used with electrons and photons, in order to investigate the elemental composition of both the surface layers and bulk. Moreover, the quadrupole mass spectrometry coupled to laser ablation (LAMQS technique) in high vacuum was used to analyse typical material compounds from surface contamination. Mass spectrometry, at high resolution and sensitivity, extended up to 300 amu, allowed measuring the 208 Pb/ 206 Pb and 207 Pb/ 206 Pb isotopic ratios into the coins. Quantitative relative analyses of these isotopic ratios identify the coin composition such as a “fingerprint” depending on the mineral used to extract the lead. Isotopic ratios in coins can be compared to those of the possible minerals used to produce the bronze alloy. A comparison between the measured isotope ratios in the analyzed coins and the literature database, related to the mineral containing Pb as a function of its geological and geophysical extraction mine, is presented. The analysis, restricted to old coins and the mines of the Mediterranean basin, indicates a possible correlation between the coin compositions and the possible geological sites of the extracted mineral. [ABSTRACT FROM AUTHOR]

In this paper, chemical and structural studies of medieval wall paintings in Ocre (L’Aquila, Italy) are presented. During the latest restoration campaign, non-destructive (Near-Infrared Reflectography and Infrared Thermography) and micro-invasive (Nuclear Magnetic Resonance, Fourier Transform Infrared Spectroscopy, μ-Raman, Scanning Electron Microscopy with X-ray Microanalysis, X-Ray Diffraction, X-Ray Fluorescence, Optical Microscopy, Mass Spectrometry, Thermogravimetry) analyses were performed in order to determine the detachments of wall surfaces and the characterization of original and restoration materials. Data integration allowed to reconstruct the conservative history, the execution techniques and the conservation problems of the artefact, as well as to assess the effectiveness of restoration activities adopted. The combined use of physical and micro-chemical techniques proved to be effective for an in-depth study of materials stratification of paintings. [ABSTRACT FROM AUTHOR]

Surface modification of nanomaterials with polymers is an effective route to render new functions and improve the performance of the final nanocomposites. Here, a facile method was developed to fabricate polyacrylic acid (PAA)-grafted monodisperse SiO 2 nanoparticles (SiO 2 -PDA-PAA) through a combination of mussel inspired chemistry and Michael addition reaction. To obtain the products, the SiO 2 nanoparticles were first coated with polydopamine (PDA) through self-polymerization of dopamine under rather mild conditions. The PDA thin films can then be further conjugated with amino-terminated PAA, which was synthesized by chain transfer free radical polymerization using cysteamine hydrochloride as a chain transfer agent and acrylic acid as a monomer. The SiO 2 -PDA-PAA nanocomposites were characterized via transmission electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and X-ray photoelectron spectroscopy. The effects of contact time, solution pH, temperature and methylene blue (MB) concentration on the removal of MB were investigated. The results demonstrated that SiO 2 -PDA-PAA showed significant improvement in adsorption efficiency towards MB. The kinetics and isotherm studies showed that pseudo-second-order and Langmuir isotherm models were well fitted the experimental data. The values of thermodynamics parameters such as entropy change ( ΔS 0 ), enthalpy change ( ΔH 0 ) and Gibbs free energy ( ΔG 0 ) were calculated based on the Van’t Hoff equation. The negative values of thermodynamic parameters indicated that the adsorption of MB was a feasible, spontaneous and exothermic process. In summary, we developed a facile method to fabricate SiO 2 -based polymer nanocomposites, which showed obviously enhanced adsorption capability towards MB. [ABSTRACT FROM AUTHOR]

High-quality semi-conducting antimony sulfide (Sb 2 S 3 ) thin films were directly deposited on the indium tin oxide (ITO) substrates by a green and facile one-step approach based on a hydrothermal reaction and post-annealing process without any assistance of complexing agents. The obtained Sb 2 S 3 films possessed a relatively ideal S/Sb atomic ratio and a compact and continuous surface as the grain size of Sb 2 S 3 was increased by high temperature annealing. The Sb 2 S 3 film annealed at 450 °C exhibited the improved optical and electrical performances, with a narrow band gap of 1.63 eV, an electrical resistivity of 1.3 × 10 4 Ω cm, a carrier concentration of 7.3 × 10 13 cm −3 and a carrier mobility of 6.4 cm 2 V −1 s −1 . This environmentally friendly synthetic route is promising for the preparation of high-quality Sb 2 S 3 films to be used as absorber layer materials for high-performance solar cells. [ABSTRACT FROM AUTHOR]

A novel laterally-driven inertial micro-switch with two L-shaped elastic cantilever beams as the movable electrode, which is attached to the proof mass, is proposed in this paper. The advantage of this design is that the contact time of the inertial micro-switch can be prolonged. Meanwhile, the micro-switch can withstand a higher shock than the traditional designs whose cantilever beams are attached to the fixed electrode. The designed inertial micro-switch was simulated and optimized with ANSYS software and fabricated on a quartz substrate by surface micromachining technology. The simulated result demonstrates that the threshold acceleration (a ths ) under stable switch-on state is about 288 g and the contact time is about 198 μs when the pulse width of acceleration loads is 1 ms. At the same time, it indicates that the threshold acceleration, the response time and the contact time of designed micro-switch all increase with the pulse width of acceleration loads. The simulation of impact process in non-sensitive direction shows that the introduced constraint sleeve structure in the novel inertial micro-switch can lower the off-axis sensitivity. The fabricated micro-switch prototype has been tested by a standard dropping hammer system under shock accelerations with various amplitudes and pulse widths. The experimental measurements show that the contact time is about 150 μs when the threshold acceleration is about 288 g. It also indicates that the response time and the contact time both increase with the pulse width, which is consistent with the simulation ones. [ABSTRACT FROM AUTHOR]

In most of the realistic ab initio and model calculations which have appeared on the emission of light from silicon nanocrystals, the role of surface oxygen has been usually ignored, underestimated or completely ruled out. We investigate theoretically, by density functional theory (DFT/B3LYP) possible modes of oxygen bonding in hydrogen terminated silicon quantum dots using as a representative case of the Si 29 nanocrystal. We have considered Bridge-bonded oxygen (BBO), Doubly-bonded oxygen (DBO), hydroxyl (OH) and Mix of these oxidizing agents. Due to stoichiometry, all comparisons performed are unbiased with respect to composition whereas spatial distribution of oxygen species pointed out drastic change in electronic and cohesive characteristics of nanocrytals. From an overall perspective of this study, it is shown that bridge bonded oxygenated Si nanocrystals accompanied by Mix have higher binding energies and large electronic gap compared to nanocrystals with doubly bonded oxygen atoms. In addition, it is observed that the presence of OH along with BBO, DBO and mixed configurations further lowers electronic gaps and binding energies but trends in same fashion. It is also demonstrated that within same composition, oxidizing constituent, along with their spatial distribution substantially alters binding energy, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gap (up to 1.48 eV) and localization of frontier orbitals. [ABSTRACT FROM AUTHOR]

Water molecules can be easily adsorbed on the surface or in the interlayer space of clay minerals. This process is named hydration which plays an important role in various application fields. In order to find how water interacted with surface through minimizing the interaction among multiple waters, the adsorptions of single water molecule on external surfaces of sodium-montmorillonite (Na-MMT), including (001) basal and (010) edge surface, were theoretically investigated based on periodic density functional theory (DFT) method. The adsorption energies and geometries as well as electronic properties were studied in the work. It was found that water molecule was adsorbed on Na-MMT (001) basal surface mainly through electrostatic interaction between water molecule and Na + cation, and was adsorbed on (010) edge surface through hydrogen bonding between water and surface OH or OH 2 groups. The adsorption energy E ads value of water molecule on (010) edge surface was larger than that on (001) basal surface. After adsorption, a part of electron density was transferred from both Na-MMT (001) and (010) surfaces to water molecule. Based on the PDOS, there was the bonding between Na 3s and O w 2p orbitals on (001) basal surface and between H 1s and O 2p orbitals for hydrogen bonds on (010) edge surface. [ABSTRACT FROM AUTHOR]

Precise transportation of liquid microdroplets is a great challenge in the microfluidic field. A sticky superhydrophobic surface with a high static contact angle (CA) and a large contact angle hysteresis (CAH) is recognized as the favorable tool to deal with the challenging job. Some approaches have been proposed to fabricate such surface, such as mimicing the dual-scale hierarchical structure of a natural material, like rose petal. However, the available approaches normally require multiple processing steps or are carried out with great expense. In this study, we report a straightforward and inexpensive method for fabricating the sticky superhydrophobic surfaces. The fabrication relies on electroless galvanic deposition to coat the copper substrates with a textured layer of silver. The whole fabrication process is carried out under ambient conditions by using conventional laboratory materials and equipments, and generally take less than 15 min. Despite the simplicity of this fabrication method, the rose petal-like hierarchical structures and the corresponding sticky superhydrophobic wetting properties were well achieved on the artificial surfaces. For instance, the surface with a deposition time of 10 s exhibits the superhydrophobity with a CA of 151.5°, and the effective stickiness with a CAH of 56.5°. The prepared sticky superhydrophobic surfaces are finally shown in the application of droplet transportation, in which the surface acts as a mechanical hand to grasp and transport the water droplet. [ABSTRACT FROM AUTHOR]

In this study, the mechanism of the photoresist (PR) etching by means of a kHz AC atmospheric pressure plasma jet (APPJ) is investigated. The scanning electron (SEM) and the polarizing microscope are used to perform the surface analysis, and the mechanical profilometry is applied to diagnose the etch rate. The results show that granulated structure with numerous microparticles appears at the substrate surface after APPJ treatment, and the etch rate in the etch center is the fastest and gradually slows down to the edge of etch region. In addition, the pin-ring electrode APPJ has the highest etch rate at but easy to damage the Si wafer, the double-ring APPJ is the most stable but requires long time to achieve the ideal etch result, and the etch rate and the etch result of the multi-electrode APPJ fall in between. Ar APPJ had much higher PR etch rate and more irregular etch trace than He APPJ. It is speculated that Ar APPJ is more energetic and effective in transferring reactive species to the PR surface. It is also observed that the effective etch area initially increases and then decreases as plasma jet outlet to the PR surface distance increases. [ABSTRACT FROM AUTHOR]

In this study, we employed microwave irradiation for activating boron concentrate, an abundant but low-grade boron mineral resource in China. The boron concentrate was pretreated by microwave irradiation based on TG-DTG-DSC analysis, and the influence of each parameter on processing efficiency was characterized using chemical analysis, XRD, SEM, FTIR and particle distribution analysis. Subsequently, the surface properties of boron concentrate and the mechanism of microwave irradiation was analyzed. Our results indicate that microwave irradiation decreased the processing temperature and shortened the roasting time by accelerating dehydroxylation and oxidation reactions in the boron concentrate, reducing the particle diameter and damaging the microstructure of the minerals, and it increased the B 2 O 3 activity of boron from 64.68% to 86.73%, greater than the optimal conventional treatment. Compared with the simple thermal field, microwave roasting obviously increased ability of the boron concentrate to absorb OH − in the leachant and promoted boron leaching by expanding the contact area of the mineral exposed to leachant, boosting the amount of Mg 2+ and Fe 3+ on mineral surfaces, and increasing the hydrophilicity of the boron concentrate respectively. It enhanced the γ S V L W and γ S V − of boron concentrate from 29.15 mJ/m 2 and 5.07 mJ/m 2 to 37.07 mJ/m 2 and 12.41 mJ/m 2 . [ABSTRACT FROM AUTHOR]

In case of a severe accident occurring in a nuclear reactor, surfaces of the reactor coolant system (RCS), made of stainless steel (304L) rich in Cr (>10%) and Ni (8–12%), are oxidised. Fission products (FPs) are released from melt fuel and flow through the RCS. A part of them is deposited onto surfaces either by vapour condensation or by aerosol deposition mechanisms. To be able to understand the nature of interactions between these FPs and the RCS surfaces, a preliminary step is to characterize the RSC surface states in steam and air atmosphere at high temperatures. Pieces of 304L stainless steel have been treated in a flow reactor at two different temperatures (750 °C and 950 °C) for two different exposition times (24 h and 72 h). After surfaces analysing by a unique combination of surface analysis techniques (XPS, ToF-SIMS and LEIS), for 304L, the results show a deep oxide scale with multi layers and the outer layer is composed of chromium and manganese oxides. Oxide profiles differ in air or steam atmosphere. Fe 2 O 3 oxide is observed but in minor proportion and in all cases no nickel is detected near the surface. Results obtained are discussed and compared with the literature data. [ABSTRACT FROM AUTHOR]

Durable drag-reduction surfaces have recently received much attention, due to energy-saving and power-consumption issues associated with harsh environment applications, such as those experienced by piping infrastructure, ships, aviation, underwater vehicles, and high-speed ground vehicles. In this study, a durable, metallic surface with highly ordered hierarchical structures was used to enhance drag-reduction properties, by combining two passive drag-reduction strategies: an air-layer effect induced by nanostructures and secondary vortex generation by micro-riblet structures. The nanostructures and micro-riblet structures were designed to increase slip length. The top–down fabrication method used to form the metallic hierarchical structures combined laser interference lithography, photolithography, thermal reflow, nanoimprinting, and pulse-reverse-current electrochemical deposition. The surfaces were formed from nickel, which has high hardness and corrosion resistance, making it suitable for use in harsh environments. The drag-reduction properties of various metal surfaces were investigated based on the surface structure: a bare surface, a nanostructured surface, a micro-riblet surface, and a hierarchically structured surface of nanostructures on micro-riblets. [ABSTRACT FROM AUTHOR]

Single (40.68 MHz) and dual (40.68/2.1 MHz) high radio frequency (RF) argon plasma discharge was employed as a source of a low-temperature treatment mechanism that was used to modify the surface of polypropylene (PP). The effects of argon plasma on the surface chemistry and the surface morphology of PP were studied using X-ray diffraction analyses. In this study, samples were treated under different plasma operation conditions for parameters such as RF power, gas pressure and treatment time. Furthermore, the crystallite size was calculated (using Scherrer equation) from the diffraction pattern of the β fraction (Full Width at Half maximum) for PP samples. The results reveal that the crystallite size strongly increases with RF power and treatment time, but decreases with gas pressure. From the analysis, it was found that the treated samples have higher crystallite sizes in compared to those of the single RF plasma discharge. This happens because the increase of plasma temperature leads to increases in the crystallization of PP sample, so that the crystallite size also increases. Furthermore, because of the advantageous features of the dual-RF plasma mode, the surface modification of PP sample can occur more quickly than is possible via the single-RF plasma discharge. [ABSTRACT FROM AUTHOR]

In this work, a detailed high resolution X-ray photoelectron spectroscopy (XPS) analysis is presented for select MXenes—a recently discovered family of two-dimensional (2D) carbides and carbonitrides. Given their 2D nature, understanding their surface chemistry is paramount. Herein we identify and quantify the surface groups present before, and after, sputter-cleaning as well as freshly prepared vs . aged multi-layered cold pressed discs. The nominal compositions of the MXenes studied here are Ti 3 C 2 T x , Ti 2 CT x , Ti 3 CNT x , Nb 2 CT x and Nb 4 C 3 T x , where T represents surface groups that this work attempts to quantify. In all the cases, the presence of three surface terminations, O, OH and F, in addition to OH-terminations relatively strongly bonded to H 2 O molecules, was confirmed. From XPS peak fits, it was possible to establish the average sum of the negative charges of the terminations for the aforementioned MXenes. Based on this work, it is now possible to quantify the nature of the surface terminations. This information can, in turn, be used to better design and tailor these novel 2D materials for various applications. [ABSTRACT FROM AUTHOR]

The influence of vacuum on nanosecond laser-induced damage at the exit surface of fused silica components is investigated at 1064 nm. In the present study, as previously observed in air, ring patterns surrounding laser-induced damage sites are systematically observed on a plane surface when initiated by multiple longitudinal modes laser pulses. Compared to air, the printed pattern is clearly more concentrated. The obtained correlation between the damage morphology and the temporal structure of the pulses suggests a laser-driven ablation mechanism resulting in a thorough imprint of energy deposit. The ablation process is assumed to be subsequent to an activation of the surface by hot electrons related to the diffusive expansion of a plasma formed from silica. This interpretation is strongly reinforced with additional experiments performed on an optical grating in vacuum on which damage sites do not show any ring pattern. Qualitatively, in vacuum, the intensity-dependent ring appearance speed V ∝ I 1/2 is shown to be different than in air where V ∝ I 1/3 . This demonstrates that the mechanisms of formation of ring patterns are different in vacuum than in air. Moreover, the mechanism responsible of the propagation of the activation front in vacuum is shown to be outdone when experiments are performed in air. [ABSTRACT FROM AUTHOR]

Traditional black silicon solar cells show relatively low efficiencies due to the high surface recombination occurring at the front surfaces. In this paper, we present a surface modification process to suppress surface recombination and fabricate highly efficient industrial black silicon solar cells. The Ag-nanoparticle-assisted etching is applied to realize front surface nanostructures on silicon wafers in order to reduce the surface reflectance. Through a further tetramethylammonium hydroxide (TMAH) treatment, the carrier recombination at and near the surface is greatly suppressed, due to a lower surface dopant concentration after the surface modification. This modified surface presents a low reflectivity in a range of 350–1100 nm. Large-area solar cells with an average conversion efficiency of 19.03% are achieved by using the TMAH treatment of 30 s. This efficiency is 0.18% higher than that of standard silicon solar cells with pyramidal surfaces, and also a remarkable improvement compared with black silicon solar cells without TMAH modifications. [ABSTRACT FROM AUTHOR]

Silica nanoparticles have become one of the most promising nanomaterials for a vast of applications. In this work, a novel strategy for surface modification of silica nanoparticles has been developed for the first time via combination of mussel inspired chemistry and Michael addition reaction. In this procedure, thin polydopamine (PDA) films were first coated on the bare silica nanoparticles via self-polymerization of dopamine in alkaline condition. And then amino-containing polymers were introduced onto the PDA coated silica nanoparticles through Michael addition reaction, that are synthesized from free radical polymerization using poly(ethylene glycol) methyl methacrylate (PEGMA) and N -(3-aminopropyl) methacrylamide (NAPAM) as monomers and ammonium persulfate as the initiator. The successful modification of silica nanoparticles was evidenced by a series of characterization techniques. As compared with the bare silica nanoparticles, the polymers modified silica nanoparticles showed remarkable enhanced dispersibility in both aqueous and organic solution. This strategy is rather simple, effective and versatile. Therefore, it should be of specific importance for further applications of silica nanoparticles and will spark great research attention of scientists from different fields. [ABSTRACT FROM AUTHOR]

Detonation nanodiamonds (DND), with low hydrogen content, were exposed to microwave plasma generated in pure H 2 , N 2 , and O 2 gases and their mixtures, and investigated using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Raman, and X-ray photoelectron spectroscopies. Considerable alteration of the DND surface was observed under the plasma conditions for all used gases, but the diamond structure of the DND particle core was preserved in most cases. The stabilizing effect of H 2 in H 2 /N 2 and H 2 /O 2 binary gas plasmas on the DND structure and the temperature-dependent formation of various CNH x surface groups in N 2 and H 2 /N 2 plasmas were observed and discussed for the first time. DND surface oxidation and etching were the main effects of O 2 plasma, whereas the N 2 plasma led to DND surfaces rich in amide groups below 1073 K and nitrile groups at higher temperatures. Noticeable graphitization of the DND core structure was detected only in N 2 plasma when the substrate temperature was above 1103 K. [ABSTRACT FROM AUTHOR]

Surface properties of a thin-film p-on-n silicon solar cell with a subwavelength nanoporous structure fabricated on an emitter layer by using metal-assisted chemical etching (MACE) were investigated through an experiment and simulation. After 10-s MACE processing, the conversion efficiency increased by 43.09% (from 5.64% to 8.07%) was obtained, compared with a reference solar cell without MACE. The simulation result indicated that the surface recombination velocity was an exponential function of the etching time from 0 to 30 s, and showed close agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In this paper we show how condensation on substrates can induce wetting behavior that is quite different from that of deposited or impinging drops. We describe surfaces with the same wettability in ambient conditions presenting different wetting behavior and growth of droplets in condensation. The experimental results show a rapid spread of droplets and formation of the film on the copper surface, while droplets on SU-8 surface remains on the regular shape while they grow within the time, without coalescence, as observed for Cu. Although the heat conductivity of SU-8 is much lower, due to a difference in wetting behavior, the heat transfer coefficient (h) is higher for dropwise condensation on Cu with a thin layer of SU-8 than filmwise on the bare copper. [ABSTRACT FROM AUTHOR]

Electric thrusters use hollow cathodes as the electron source for generating the plasma discharge and for beam neutralization. These cathodes contain porous tungsten emitters impregnated with BaO material to achieve a lower surface work function and are operated with xenon propellant. Oxygen contaminants in the xenon plasma can poison the emitter surface, resulting in a higher work function and increased operating temperature. This could lead directly to cathode failure by preventing discharge ignition or could accelerate evaporation of the BaO material. Exposures over hundreds of hours to very high levels of oxygen can result in increased temperatures, oxidation of the tungsten substrate, and the formation of surface layers of barium tungstates. In this work, we present results of a cathode test in which impregnated tungsten and tungsten–iridium emitters were operated with 100 ppm of oxygen in the xenon plasma for several hundred hours. The chemical and morphological changes were studied using scanning electron microscopy, energy dispersive spectroscopy, and laser profilometry. The results provide strong evidence that high concentrations of oxygen accelerate the formation of tungstate layers in both types of emitters, a phenomenon not inherent to normal cathode operation. Deposits of pure tungsten were observed on the W–Ir emitter, indicating that tungsten is preferentially removed from the surface and transported in the insert plasma. A W–Ir cathode surface will therefore evolve to a pure W composition, eliminating the work function benefit of W–Ir. However, the W–Ir emitter exhibited less erosion and redeposition at the upstream end than the pure W emitter. [ABSTRACT FROM AUTHOR]

The amphiphilic segments on polypropylene nonwoven (PP nonwoven) surface were constructed using the ultraviolet (UV) irradiation graft polymerization for the removal of endocrine disrupting compounds (EDCs) with different polarity from aqueous solution. The stearyl acrylate (SA) as hydrophobic functional monomer was introduced onto the surface of PP nonwoven fabric at first stage and then the hydroxyethyl acrylate (HEA) as hydrophilic functional monomer was introduced subsequently. The effect of functional monomer concentration and UV irradiation time on grafting ratio was studied and discussed. The novel amphiphilic structure was designed and constructed based on adsorption capacity for the target micropollutants. The structure and composition of the amphiphilic adsorption materials were characterized by Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and contact angle (CA). The adsorption behaviors for EDCs of the amphiphilic adsorption materials were studied and the results indicated that the adsorption capacity and adsorption rate were superior to single SA grafted PP nonwoven (PP- g -SA) and single HEA grafted PP nonwoven (PP- g -HEA). The novel amphiphilic adsorption material was efficient for the removal of EDCs with different polarity and could be utilized as a potential adsorption material for removing EDCs from aqueous solution. [ABSTRACT FROM AUTHOR]

We report for the first time hydrophobic properties on cotton fabric successfully achieved by grafting graphene oxide on the fabric surface, using a dyeing method. Graphite oxide synthesized by oxidizing natural flake graphite employing improved Hummer's method showed an inter layer spacing of ∼1 nm from XRD. Synthesized graphite oxide was exfoliated in water using ultrasound energy to obtain graphene oxide (GO). AFM data obtained for the graphene oxide dispersed in an aqueous medium revealed a non-uniform size distribution. FTIR characterization of the synthesized GO sheets showed both hydrophilic and hydrophobic functional groups present on the nano sheets giving them an amphiphilic property. GO flakes of different sizes were successfully grafted on to a cotton fabric surface using a dip dry method. Loading different amounts of graphene oxide on the cotton fiber surface allowed the fabric to demonstrate different degrees of hydrophobicity. The highest observed water contact angle was at 143° with the highest loading of graphene oxide. The fabric surfaces grafted with GO also exhibits adhesive type hydrophobicity. Microscopic characterization of the fiber surface using SEM and AFM reveals the deposition of GO sheets on the fiber surface as a conformal coating. Analysis of the fabric surface using UV–vis absorption allowed identification of the ratio of hydrophobic to hydrophilic domains present on the GO coated cotton fabric surface. Hydrophobic properties on cotton fabric are ascribed to two dimensional amphiphilic properties of deposited GO nano sheets, which successfully lower the interfacial energy of the fabric surface. [ABSTRACT FROM AUTHOR]

The influences that the spacer chain length of Gemini surfactants and clay layer charge have on the structures and sorption characteristics of organoclays have been investigated. Organoclays were obtained by modifying a series of reduced charge montmorillonites (RCMs) using three Gemini surfactants with different spacer length. And their structures and sorption characteristics for methyl orange (MO) were examined. It was suggested that the amount, spacer length of Gemini surfactant and clay layer charge had significant effects on the microstructure of the organoclays. The adsorption experiments results claimed that the uptake of MO onto organoclays was in the order: 16-4-16-Mt > 16-8-16-Mt > 16-6-16-Mt, while it increased with increasing clay layer charge. The adsorption isotherms of MO onto the organoclays could be best described by Langmuir equation, and the adsorption kinetic was in good agreement with the pseudo-second-order model. Thermodynamic parameters demonstrated that the sorption process was spontaneous and endothermic in nature. This work will provide a deep insight into the interaction of Gemini-modified clays and MO, which pave the way for their practical applications in anionic dye adsorption. [ABSTRACT FROM AUTHOR]

A model poly-epoxy surface formed by the reaction of DGEBA and EDA is studied by the combination of experiments and DFT calculations. A special synthesis protocol is presented leading to the formation of a surface that is smooth ( S a < 1 nm), chemically homogeneous, and that presents a low-defect density (0.21 μm −2 ), as shown by AFM characterizations. Then, XPS is used for the determination of the elemental and functional groups’ surface composition. DFT allows the identification and assignment of individual bonds contributions to the experimental 1s core-level peaks. Overall, we demonstrate that such a model sample is perfectly suitable for a use as a template for the study of poly-epoxy surface functionalization. [ABSTRACT FROM AUTHOR]

Photoelectron diffraction is proposed to determine nondestructively the polarity of wurtzite crystals with polar surfaces ( c -plane). Small segments of polar plots of photoemission from anion core levels in the ( 1 0 1 ¯ 0 ) azimuthal plane are qualitatively different for two polarities around the polar angle 20°. The magnitude of the ratio of electron photoemission intensities at two polar angles I 20 / I 23 can be utilized as a simple criterion determining the crystal polarity. [ABSTRACT FROM AUTHOR]

Dispersible coal powder (Cp) particles were prepared by surface modification. Coupling agents such as γ-methacryloxypropyltrimethoxysilane (KH-570), vinyltrimethoxysilane (SG-Si171), and di(dioctylpyrophosphato) ethylene titanate (NDZ-311) were used as modifiers to increase the Cp surface activity. The pristine Cp particles are poorly dispersed in anhydrous ethanol. Compared with the pristine Cp particles, the modified Cp particles, especially the NDZ-311 coupled particles, show good dispersions in anhydrous ethanol. It is suggested that the improvement of hydrophobicity on the modified Cp is mainly ascribed to the forming of coupling agents coating layer onto the surface of Cp particles, and the surface properties of the Cp particles are changed, which show more stable colloidal dispersions in organic media. Cp particles modified by NDZ-311 can be used for rubber, plastic, etc. with better performance and longer life cycle. [ABSTRACT FROM AUTHOR]

We propose a low cost and simple method to prepare a paper-based supercapacitor in this study. Multi-walled carbon nanotubes (MWCNTs) were dispersed with a pectin solution under an ultrasonic homogenizer. Carbon nanotube suspension was prepared using a centrifuge to eliminate impurities. The dispersed MWCNTs suspension was dropped and dried onto the shallow surface of commercial copy paper. A paper-based conductive paper was formed as the electrodes. The electrical conductivity and dispersed morphology of the paper-based conductive paper were examined by four probes, atomic force microscope (AFM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The solid-state electrolyte was prepared by casting a solution of phosphoric acid and polyvinyl alcohol onto a glass plate. The paper-based supercapacitor was constructed with one solid-state electrolyte inserted between two electrodes, which were assembled into a sandwich structure by hot press. The specific capacitance and cycle-life stability of the paper-based supercapacitor was investigated by cyclic voltammetry analysis. [ABSTRACT FROM AUTHOR]

Gear backlash has an import influence on gear dynamics and due it has a strong non-linear character, so its effect on the gear dynamics is very complex. In order to get reasonable and precise dynamic analytic result, the fractal theory is employed here to express the backlash instead of the existed way of setting backlash as a fixed value or a steady random number that meets the normal distribution. Though the simulation and comparison of three methods: fractal method, fixed value and normal distribution, it is clearly concluded that fractal method is better than the two latter ways which both have the weakness of being unable to reveal the influence when backlash is changing in a small scope; also the normal distribution method cannot get the unique answer when average backlash is set. Furthermore, the results also show that it is advantageous to improve gear dynamics with decreasing fractal dimension, reducing time-variant stiffness and increasing damping ratio. The theory in this paper shows a new method to analyze the gear dynamics in respect of the changing backlash and as well as builds an indirect relationship between gear dynamic performance and tooth surface characters, which can be utilized to improve gear dynamics characters through guiding gear surface design and manufacture in the future. [ABSTRACT FROM AUTHOR]

In spite of the unique combination of properties of Re-based alloys and the use of electroless plating in many relevant industries, the early stages of electroless plating of Re-based thin films have not been reported before. This paper is focused on the study of the early stages of growth of ultrathin (<20 nm) Re-Ni films with high Re-content by electroless plating on a functionalized-SiO2 substrate. Each step, from the modification of the substrate to the formation of a continuous film, is characterized. Moreover, the effect of the addition of Ni2+ ions to the bath is analyzed. The addition of a low concentration of Ni2+ ions to the electrolyte is found necessary to obtain full surface coverage and thicker deposits. The as-deposited Re-Ni films consist of both amorphous Ni-Re and H0.57ReO3 phases. The Re-content is not uniform along the thickness of the deposit, and has a maximal value at the percolation point. The deposition process is found to consist of sequential reduction reactions, from ReO4- to lower valence oxides, to metallic Re. [ABSTRACT FROM AUTHOR]

Highlights: [•] The thermodynamic stability of the Mg(0001) surfaces doped by transition metals are investigated. [•] The results of hydrogen's dissociation and diffusion on Mg(0001) surface compare with Pozzo et al. in first layer. [•] The effects of hydrogen's dissociation and diffusion on Mg(0001) surface with transition metals in the subsurface. [•] The investigation of interfacial electronic interaction. [Copyright &y& Elsevier]

Highlights: [•] A screening of chemical non-ionic surfactants against pathogenic microbial biofilms is proposed. [•] Pluronic F127 presented anti-adhesion characteristics due its conformation on hydrophobic surface. [•] A simple Pluronic F127 coating remains retained at the surface after extensive washes. [•] We report interesting results in the field of biomaterials and hospital infections. [ABSTRACT FROM AUTHOR]

Highlights: [•] Wettability and blood compatibility of PMPC-grafted UHMWPE were improved. [•] The friction properties including the short and long term under high contact stress were investigated. [•] The PMPC brushes were sheared off from the surface with the increase of sliding cycles. [Copyright &y& Elsevier]

Highlights: [•] Density functional theory study of water adsorption on K1−y Na y Ta1−x Nb x O3 surface terminations. [•] Water monomer prefers to adsorb at the K–Na bridge site on the K(Na)O-termination and the Nb top site on the Ta(Nb)O2-termination. [•] The surface geometry becomes more roughness with the coverage increasing. [•] The strong interaction between water and substrate results in a band gap increase of KNTN surface. [Copyright &y& Elsevier]

Highlights: [•] Comparing 4 approaches to immobilize biotinylated oligonucleotide using streptavidin. [•] Pre-adsorbed biotinylated BSA provides higher oligonucleotide surface density. [•] ToF-SIMS reveals multi-molecular composition of organic overlayer on silicon surface. [•] Composition accords with molecular coverage (ARXPS) and average height (AFM). [ABSTRACT FROM AUTHOR]

Highlights: [•] Copper selenide thin films on polymer were synthesized and characterized. [•] XRD analysis showed several crystalline phases changing with exposure. [•] Bulk and surface elemental analysis showed CuSe with surface enriched Cu. [•] Electrical conductivity decreased with the selenization time to 150Ω/□. [Copyright &y& Elsevier]

Highlights: [•] A facile “dip & rinse” method for nickel (Ni) electroless deposition on hydrophobic polymer surfaces is reported. [•] Hydrophobic interaction is used for surface pretreatment for metal electroless plating. [•] Various hydrophobic polymer surfaces with different geometries and dimensions (i.e., thin sheets and pellets) such as PAH, LDPE, HDPE, PP, PS, PE pellets are tested. [Copyright &y& Elsevier]

Highlights: [•] Comprehensive investigation of all three primary surfaces of an orthorhombic complex metallic alloy. [•] Localised oxidation tracked by scanning tunneling microscopy. [•] Oxidation resistance found using X-ray photoelectron spectroscopy. [Copyright &y& Elsevier]