Interfacial Surface Research Articles

Anisotropic weak antilocalization in thin films of the Weyl semimetal TaAs

Device applications of topological semimetals await the development of epitaxial films in the ultrathin limit. Weak antilocalization (WAL) has been extensively utilized in the understanding of surface states in topological insulators and shows promise for use in elucidating the properties of thin film topological semimetals. Here, we report insights from WAL in the surface state and interface transport properties of our recently synthesized single-crystal-like thin films of the Weyl semimetal TaAs(001) grown on GaAs(001). We observe robust, anisotropic WAL in the magnetoconductance from 2 to 20 K in films from 10 to 200 nm thick. We link the anisotropic WAL magnetoconductance to anisotropic mobility stemming from film topography. We conclude that WAL in the films likely originates from the antilocalization of topological surface states. The WAL magnetoconductance is impacted by the film thickness and topography, solidifying the useful role of WAL in the study of topological semimetal/semiconductor heterointerfaces. Published by the American Physical Society 2024

Activation of Bi2MoO6/Zn0.5Cd0.5S charge transfer through interface chemical bonds and surface defects for photothermal catalytic CO2 reduction

The photocatalytic reduction of CO2 to high-value fuels has been proposed as a solution to the energy crisis caused by the depletion of energy resources. Despite significant advancements in photocatalytic CO2 reduction catalyst development, there are still limitations such as poor CO2 adsorption/activation and low charge transfer efficiency. In this study, we employed a defect-induced heterojunction strategy to construct atomic-level interface Cd-O bonds and form Bi2MoO6/Zn0.5Cd0.5S heterojunctions. The sulfur vacancies (VS) formed in Bi2MoO6/Zn0.5Cd0.5S acted as activation sites for CO2 adsorption. While the interfacial stability provided by the Cd-O bonds served as an electron transfer channel that facilitated the movement of electrons from the interface to the catalytic site. The VS and Cd-O bonds simultaneously influence the distribution of charge, inducing the creation of an interface electric field that facilitates the upward displacement of the center of the d-band. This enhances the adsorption of reaction intermediates. The optimized Bi2MoO6/Zn0.5Cd0.5S heterostructure exhibited high selectivity and stability of photoelectrochemical properties for CO, generating 42.97 μmol⋅g−1⋅h−1 of CO, which was 16.65-fold higher than Zn0.5Cd0.5S under visible light drive. This research provides valuable insights for designing photocatalyst interfaces with improved CO2 adsorption conversion efficiency.

Role of Electrochemical Activation in Evaluating Oxygen Evolution Activity of Ni-Incorporated Bimetallic Tungstate in Alkaline Media

Hydrogen is considered the future fuel and promising alternative towards carbon neutrality. In this context, water electrolysis using renewable electricity is an environmentally benign approach for clean hydrogen production. In water electrolysis, among the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), OER is the rate-limiting due to slow kinetics, high overpotential, and complex pathways. To catalyze the OER, choice of non-precious electrocatalysts is preferred over the precious platinum group metal (PGM)-based catalysts owing to their relatively higher abundance and cost-effectiveness. The feasibility of using non-precious electrocatalysts in alkaline water electrolysis is also favorable for the low-capital cost compared to the acidic one. In lab scale research, the preliminary evaluation of OER electrocatalysts is usually performed using thin-film rotating disk electrodes (TF-RDEs) in a three-electrode system. In this process, the very first step involves multiple cyclic voltammetry (CV) cycles for better wettability of the catalyst layer to the electrolyte, which is considered as electrochemical activation (EA). Incomplete activation of the catalyst layer would lead to inconsistent OER performance of the electrocatalysts. This is much more pronounced in non-precious electrocatalysts compared to the precious ones in alkaline media. Despite that the importance of EA is overlooked most of the time and rarely studied. In this work, the critical role of EA is systematically investigated for Ni-containing bimetallic tungstate in alkaline OER and also compared with that of monometallic counterparts. This study demonstrates more than 1.2-fold performance improvement in OER for bimetallic tungstate. The corresponding insights on the interfacial structure and oxidative surface reconstruction are also noted by using in-situ electrochemical analysis and ex-situ characterizations. The present study is believed to be beneficial for the precise analysis and development of non-precious alkaline OER electrocatalysts.

Study on the interface of high specific energy High stability

High nickel terterial oxide, with high specific capacity and low cost advantages, is the preferred positive electrode for high specific energy lithium-ion power batteries at present. However, the high nickel ternary cathode material is easy to have side reactions with the electrolyte in the high delithium state, which can not only lead to the dissolution of transition metal ions and the formation of the surface salt phase, but also cause the lattice oxygen loss and surface interface side reactions, resulting in rapid attenuation of electrode capacity. In this paper, the development history and structural characteristics of high nickel ternary cathode materials are introduced, and the surface interface problems leading to capacity attenuation and structural degradation are comprehensively analyzed. From this perspective, three effective strategies for improving electrochemical performance of high nickel ternary cathode materials are summarized. Finally, by describing the advantages and disadvantages of these layered cathode materials, the challenges faced by these layered cathode materials are discussed, and it is pointed out that in the future, composite modification strategies should be adopted to optimize their structures and improve their properties.

Ultrahigh energy harvesting ability of PVDF incorporated with 2D halide perovskite nanosheets via interface effect

Two-dimensional (2D) perovskites have recently emerged as an new family of ferroelectrics and attracted extensive attention for their specific surface interface characteristics benefitting from the unique structure by inserting hydrophobic organic cations into conventional three-dimensional frameworks. In this study, 2D metal–organic perovskite nanosheets, (C4H9NH3)2CsPb2Br7, ((BA)2CsPb2Br7), were successfully synthesized by facile temperature-cooling method and introduced into poly (vinylidene fluoride) (PVDF) polymer fibers to construct flexible piezoelectric energy harvester (PEH). (BA)2CsPb2Br7/PVDF nanofibers reveal a high piezoelectric coefficient (d33) of 63.3 pm/V, which is 2.9 times of the PVDF polymer (21.7 pm/V). Principally, the PVDF composite with 5 wt% (BA)2CsPb2Br7 nanosheet filler assumes an superior electroactive phase amount of about ∼ 93 % profiting from the interfacial interaction between BA+ cations of (BA)2CsPb2Br7 and the dipoles of PVDF. The PEH based on (BA)2CsPb2Br7 nanosheets embedded in PVDF fibers showed a maximum output voltage, 135 V, which is almost 17 times of the PEH based on neat PVDF fibers. Furthermore, the interfacial interaction between (BA)2CsPb2Br7 and PVDF was analyzed by first principle DFT study which reveals electrons migrate and the interfacial polarization between the interface. Simultaneously, (BA)2CsPb2Br7/PVDF composite fibers based PEH reveals exceptional long-term stabilities and durability. More attractively, the exceptional performance of this fabricated PEH evinces a pressure sensitivity of ∼ 7.3 V/N and bio-mechanical harvesting behavior arising from varied human motions, such as beating, pressing, twisting, walking and running. This cost-effective and high performance of (BA)2CsPb2Br7/PVDF based PEH is favorable for the continuation of 2D halide perovskites for further application in new energy and biomechanical filed.

Photophoresis of a moderately large high-viscosity droplet in slip mode

Purpose of research. To obtain analytical expressions that allow calculating the strength and velocity of a moderately large, highly viscous droplet, taking into account the direct contribution of the evaporation coefficient, linear corrections by the Knudsen number and the reactive effect of a plane wave moving in the field of mono-chromatic radiationMethods. Methods of perturbation theory, gas kinetic methods, mathematical methods for solving linear partial differential equations with variable coefficients (the system of Stokes equations, Laplace and Poisson equations) were used.Results. In a quasi-stationary approximation, a theoretical description of the photophoretic motion of a moderately large evaporating highly viscous spherical droplet (there is no circulation of matter inside the droplet and interfacial surface tension forces) in a viscous binary gas mixture is carried out. A velocity-linearized system of Navi-Stokes equations and heat and mass transfer was solved. Expressions are obtained for the fields of mass velocity, pressure, temperature and the relative numerical concentration of the first component. The strength and speed of photophoresis of a highly viscous droplet was determined by integrating a stress tensor over the surface of the particle. Under boundary conditions on the surface of a highly viscous droplet, linear corrections in terms of the Knudsen number (isothermal, thermal and diffusion slips, temperature and concentration jumps, as well as sliding due to temperature inhomogeneity along the curved surface of the particle), the reactive effect and the contribution of the direct influence of the evaporation coefficient were taken into account. The contributions to the obtained formulas for the photophoresis of a moderately large highly viscous droplet are analyzed and the preliminary transitions to the results known in the literature (moderately large and large solid particles of spherical shape) are considered Conclusion. The obtained formulas based on the hydrodynamic method allow us to evaluate the effect of the direct contribution of the evaporation coefficient and linear corrections by the Knudsen number on the strength and speed of photophoresis of a moderately large evaporating highly viscous droplet in a binary gas mixture.

Numerical Simulation of Vapor Bulk Condensation near the Interfacial Surface under Intensive Evaporation Conditions

Numerical Simulation of Vapor Bulk Condensation near the Interfacial Surface under Intensive Evaporation Conditions

Carbon fiber fabrics functionalized with monoclinic CuO nanostructures using seed-assisted hydrothermal growth treatment

The woven carbon fibers (WCF) fabrics were functionalized by growing copper-oxide (CuO) nanostructures using Seed-assisted hydrothermal technique. The effective growth of CuO on surface hydrolyzed WCF samples were achieved by seeding followed by growth treatment in the prepared precursor solution. The impact of hydrothermal process parameters such as number of seeding cycles, duration of growth treatment and molar concentration of growth solution were studied by performing 96 set of experiments with three repetitions. In this work detailed analysis of structural, morphological, and elemental attributes of the CuO-coated WCF fabrics samples have been done. The WCF fabrics were uniformly coated with monoclinic CuO nanostructures having nanopellets, nanoflakes, nanowires, and nanoflowers morphologies. Different characterization techniques such as field emission scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, FT-IR spectroscopy and thermo-gravimetric analyzer were used to study different attributes of CuO-modified WCF samples. The number of seeding treatments and the length of growth treatment had a significant impact on growth of CuO nanostructures on WCF. The detailed analysis exhibits that the developed CuO-modified WCF samples may enhance interfacial surface area, bonding capacity and reduce void content by allowing nanostructures to cross-link together and with polymer matrix while fabricating composite materials.

The interfacial synergistic catalysis effect within Cu/ZrO2 heterogeneous catalyst for highly efficient and selective electrocatalytic reduction of CO2 to CH4

Highly selective production of valuable methane from electrocatalytic CO2 reduction reaction (ECO2RR) is a highly attractive yet particularly challenging route for CO2 utilization. Constructing Cu/metal-oxide (MOx) heterogeneous interface is a feasible strategy for efficient catalyst design, which can realize the electronic control of the surface interface by utilizing the synergistic effect between Cu and metal-oxide. Here we constructed Cu/ZrO2 heterogeneous interface to synthesize a new Cu2+ catalyst. The XPS measurements confirmed that the appropriate ratio of Cu/ZrO2 can effectively stabilize Cu2+ at Cu-O-Zr interface against reduction. The CO temperature-programmed desorption experiments (CO-TPD) showed that the high relative content of Cu2+ in 0.2Cu/ZrO2 can significantly strengthen the adsorption stability of the *CO, which in turn promotes the protonation of the *CO intermediate instead of dimerization, further favoring the generation of methane. The activity data showed the distinctly superior reactivity of 0.2Cu/ZrO2 catalyst, which exhibits an ultra-high faradaic efficiency (FE) of CH4 of 72.0 % and a low FEC2H4 of 2.9 %. This work unravels the valence state and performance relationship of Cu/ZrO2 catalysts and provides a new insight into the electrosynthesis of CH4 as product.

Device‐Level in‐Sensor Olfactory Perception System Based on Array of PCBM‐MAPbI3 Heterostructure Transistors

AbstractAlthough there are significant advancements in device‐level artificial tactile and visual perception systems based on in‐sensor computing paradigms, the development of hardware‐implemented neuromorphic olfactory system is still in its early stages. One of the primary challenges in this field is that most of the gas sensors lack the capability to fuse the sensing and computing functions in a single sensor. Through surface passivation and interface engineering, this work introduces a device‐level artificial olfactory system utilizing array of PCBM‐MAPbI3 heterostructure transistors. Noteworthly, the formation of metastable intermediate phase NH3PbI3•MA can occur at room temperature and can be used to store gas sensory information. Both gas pulse and electrical pulse can dynamically modulate the amount of this intermediate phase, and then change the channel conductance (weight), realizing the fusion of the sensing and synaptic functions in single device. Based on these excellent properties, the spatiotemporal information of gas diffusion can be encoded and processed simultaneously. As a result, an in‐sensor olfactory perception system is successfully demonstrated based on 5 × 5 PCBM‐MAPbI3 heterostructure transistor array, which can be used for detecting the distance and direction of the hazardous gas. This work paves the way for future application of real‐time and data‐intensive machine‐olfactory system.

Sensory Nervous System‐Inspired Self‐Classifying, Decoupled, Multifunctional Sensor with Resistive‐Capacitive Operation Using Silver Nanomaterials

AbstractSelf‐classification technology has remarkable potential for autonomously discerning various stimuli without any circuit or software assistance, enabling it to realize electronic skin. In conventional self‐classification systems that rely on complex circuitry for operation, integrating the sensing and algorithm processing units inevitably leads to bulkiness in devices and bottlenecks in signal processing. In this study, the novel double‐sided structure inspired by the human nervous system is newly designed for a self‐classifying sensor (SCS) without the need for additional circuits. The sensor is layered with Ag nanocomposites that have been mechanically enhanced via interface engineering and surface treatment techniques. This structure enables the resistance‐capacitance hybrid operation, facilitating the detection and distinguishment of changes in strain, pressure, and temperature within a single device, which mimics the human sensing recognition process. Moreover, the intensity of the applied stimuli is determined by analyzing the detected signal, and precise localization of the stimuli is achieved by arraying the sensors. With its self‐classification capabilities, SCS opens promising avenues for applications in soft robotics and advanced multifunctional sensor platforms, providing a sensing system characterized by simplicity and efficiency.

Numerical Modeling of Cantilever Retaining Wall Using EPS Geofoam

Earth retaining wall structures are common civil engineering structures. Estimation of magnitude and distribution of earth pressure on retaining structures under different surcharge loading conditions is essential as they influence the design and overall economy of retaining structures. Numerical modeling using finite element code PLAXIS is used static analysis. 7 m height of non-yielding cantilever retaining wall with and without EPS geofoam structure is studied and 20 m backfill width was considered. In the present study backfill was modeled as Mohr-Coulomb yield criteria and EPS geofoam and wall were modeled as Linear-elastic. EPS geofoam densities namely 12 kg/m3 and 15 kg/m3 and two different geofoam thicknesses 0.107H and 0.143H were used for static analysis. Three different surcharge loading namely 10 kPa,30kPa and 50kPa which were kept at a distance of 2.0 m away from the wall face. In the static analysis earth pressure distribution for wall with and without geofoam were analyzed. Approximately 50% isolation efficiency was reported. At lower surcharge loads the effectiveness of EPS is more as compare to higher surcharge load and with increase in surcharge load, isolation efficiency gradually decreases and isolation efficiency decreases with increase in buffer modulus. Apart from these serviceability criteria was also checked. Serviceability criteria comprise of lateral deformation of EPS geofoam at sand-geofoam interface and backfill surface settlement were studied. Lower EPS geofoam density and higher EPS geofoam thickness reduces higher magnitude of earth pressure but in this combination the backfill surface settlement was coming very high.

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In rotating 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He superfluids, the Kelvin–Helmholtz (KH) instability of the AB interface has been found to follow the theoretical model above 0.4Tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.4 \\, T_\ extrm{c}$$\\end{document}. A deviation from this dependence has been assumed possible at the lowest temperatures. Our NMR and thermal bolometer measurements down to 0.2Tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.2 \\, T_\ extrm{c}$$\\end{document} show that the critical KH rotation velocity follows the extrapolation from higher temperatures. We interpret this to mean that the KH instability is a bulk phenomenon and is not compromised by interactions with the wall of the rotating container, although weak pinning of the interface to the wall is observed during slow sweeping of the magnetic field. The KH measurement provides the only so far existing determination of the interfacial surface tension at temperatures down to 0.2Tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.2 \\, T_\ extrm{c}$$\\end{document} as a function of pressure.

Interface construction of Ni(OH)2/Fe3O4 heterostructure decorating in-situ defected graphite felt for enhanced overall water splitting

There is a persistent need to design efficient and cheap electrode materials for water electrolysis. Herein, a hierarchical Ni(OH)2/Fe3O4/graphite felt (GF) (NFGF) heterostructure bifunctional electrocatalyst is tailor-designed to accelerate the water splitting process via boosting the heterostructure interfaces. A facile electrochemical method is probed to synthesize NFGF heterostructure with in-situ GF surface functionalization. Various analyses are used to demonstrate the GF in-situ surface functionalization and interface engineering. Remarkably, NFGF displays boosted hydrogen and oxygen evolution reactions by presenting a low overpotential of −50 mV and 281 mV at a current density of 10 mA cm−2 and 30 mA cm−2, respectively. Thus, NFGF is tested as a bifunctional electrocatalyst in the two-electrode cell and demonstrates a low cell voltage of 1.55 V at a current density of 10 mA cm−2 with outstanding performance over a long time of electrolysis up to 24 h.

Even-integer quantum Hall effect in an oxide caused by a hidden Rashba effect.

In the presence of a high magnetic field, quantum Hall systems usually host both even- and odd-integer quantized states because of lifted band degeneracies. Selective control of these quantized states is challenging but essential to understand the exotic ground states and manipulate the spin textures. Here we demonstrate the quantum Hall effect in Bi2O2Se thin films. In magnetic fields as high as 50 T, we observe only even-integer quantum Hall states, but there is no sign of odd-integer states. However, when reducing the thickness of the epitaxial Bi2O2Se film to one unit cell, we observe both odd- and even-integer states in this Janus (asymmetric) film grown on SrTiO3. By means of a Rashba bilayer model based on the ab initio band structures of Bi2O2Se thin films, we can ascribe the only even-integer states in thicker films to the hidden Rasbha effect, where the local inversion-symmetry breaking in two sectors of the [Bi2O2]2+ layer yields opposite Rashba spin polarizations, which compensate with each other. In the one-unit-cell Bi2O2Se film grown on SrTiO3, the asymmetry introduced by the top surface and bottom interface induces a net polar field. The resulting global Rashba effect lifts the band degeneracies present in the symmetric case of thicker films.

Modeling of Physical-Chemical and Electronic Properties of Lithium-Containing 4H—SiC and Binary Phases of the Si—C–Li System

In the equilibrium model of the solid surface–adatom system, including a three-dimensional interfacial surface, changes in surface properties are considered, taking into account the chemical potential due to the action of surface tension. The relationship between chemical potential and electrochemical potential of the ith component in an electrochemical cell is analyzed. Using the density functional theory (DFT), the adsorption, electronic, and thermodynamic properties of 2 × 2 × 1 and 3 × 3 × 1 supercells of crystalline compounds AmBn, (, where n and m are stoichiometric coefficients) of the boundary binary systems of the ternary phase diagram of Si–C–Li are studied. The stability of phases AmBn and property calculations are carried out with the exchange-correlation functional within the framework of the generalized gradient approximation (GGA PBE). The parameters of the crystal structures of the compounds AmBn, the adsorption energy of the lithium adatom on a 4H–SiC substrate, the electronic structure, and the thermodynamic properties of supercells are calculated. The thermodynamically stable configurations of the 4H–SiC–Liads supercells having different locations Liads are determined. The DFT GGA PBE calculations of the enthalpy of formation of compounds AmBn are carried out in the ternary Si–C–Li system. Taking into account the changes in the Gibbs free energy in the solid-phase exchange reactions between binary compounds, equilibrium sections (connodes) in the concentration triangle of the Si–C–Li phase diagram are established. An isothermal section of the Si–C–Li phase diagram at 298 K is constructed. The patterns of diffusion processes that are related to the movement of particles on the surface layer of the 6H–SiC sample are analyzed. The activation energy of lithium diffusion in 6H–SiC is calculated from the Arrhenius type relation in two temperature ranges (769–973 K) and (1873–2673 K).

Tailored portable electrochemical sensor for dopamine detection in human fluids using heteroatom-doped three-dimensional g-C3N4 hornet nest structure

BackgroundThere is widespread interest in the design of portable electrochemical sensors for the selective monitoring of biomolecules. Dopamine (DA) is one of the neurotransmitter molecules that play a key role in the monitoring of some neuronal disorders such as Alzheimer's and Parkinson's diseases. Facile synthesis of the highly active surface interface to design a portable electrochemical sensor for the sensitive and selective monitoring of biomolecules (i.e., DA) in its resources such as human fluids is highly required. ResultsThe designed sensor is based on a three-dimensional phosphorous and sulfur resembling a g-C3N4 hornet's nest (3D-PS-doped CNHN). The morphological structure of 3D-PS-doped CNHN features multi-open gates and numerous vacant voids, presenting a novel design reminiscent of a hornet's nest. The outer surface exhibits a heterogeneous structure with a wave orientation and rough surface texture. Each gate structure takes on a hexagonal shape with a wall size of approximately 100 nm. These structural characteristics, including high surface area and hierarchical design, facilitate the diffusion of electrolytes and enhance the binding and high loading of DA molecules on both inner and outer surfaces. The multifunctional nature of g-C3N4, incorporating phosphorous and sulfur atoms, contributes to a versatile surface that improves DA binding. Additionally, the phosphate and sulfate groups' functionalities enhance sensing properties, thereby outlining selectivity. The resulting portable 3D-PS-doped CNHN sensor demonstrates high sensitivity with a low limit of detection (7.8 nM) and a broad linear range spanning from 10 to 500 nM. SignificanceThe portable DA sensor based on the 3D-PS-doped CNHN/SPCE exhibits excellent recovery of DA molecules in human fluids, such as human serum and urine samples, demonstrating high stability and good reproducibility. The designed portable DA sensor could find utility in the detection of DA in clinical samples, showcasing its potential for practical applications in medical settings.

Surface Reduction of Li2CO3 on LLZTO Solid-State Electrolyte via Scalable Open-Air Plasma Treatment

We report on the use of an atmospheric pressure, open-air plasma treatment to remove Li2CO3 species from the surface of garnet-type tantalum-doped lithium lanthanum zirconium oxide (Li6.4La3Zr1.4Ta0.6O12, LLZTO) solid-state electrolyte pellets. The Li2CO3 layer, which we show forms on the surface of garnets within 3 min of exposure to ambient moisture and CO2, increases the interface (surface) resistance of LLZTO. The plasma treatment is carried out entirely in ambient and is enabled by use of a custom-built metal shroud that is placed around the plasma nozzle to prevent moisture and CO2 from reacting with the sample. After the plasma treatment, N2 compressed gas is flowed through the shroud to cool the sample and prevent atmospheric species from reacting with the LLZTO. We demonstrate that this approach is effective for removing the Li2CO3 from the surface of LLZTO. The surface chemistry is characterized with X-ray photoelectron spectroscopy to evaluate the effect of process parameters (plasma exposure time and shroud gas chemistry) on removal of the surface species. We also show that the open-air plasma treatment can significantly reduce the interface resistance. This platform demonstrates a path towards open-air processed solid-state batteries.

Structural integrity assessment and optimization of control surfaces in coaxial unmanned aerial vehicles: A case study of a micro coaxial UAV

Unmanned aerial vehicles (UAVs) play a pivotal role in modern society which requires lightweight yet robust structures to fulfill increasingly complex tasks. This study presents a cost-effective prototyping approach to assess the structural integrity of control surfaces within the innovative Coaxial Unmanned Aerial Vehicle version 3.0 (MCR UAV v3.0). Integrating a hybrid design with coaxial propulsion for vertical stabilization and yaw control, the MCR UAV v3.0 incorporates control surfaces (ailerons) to manage roll and pitch movements during flight. The design process relies on a comprehensive understanding of material mechanical properties, particularly polylactic acid (PLA) specimens fabricated via fused deposition modeling (FDM) with varying infill percentages and building angles. A novel fluid-structure interaction method is developed in order to analyze four control surface topologies: concave (A), optimized concave (B), convex (C), and optimized convex (D). Findings reveal that the optimized design significantly improves stress distribution in the fuselage-control surface interface while reducing aileron weight by approximately 70%. Subsequently, a functional UAV prototype incorporating optimized ailerons is manufactured. Flight tests affirm the efficacy of the ailerons in controlling roll and pitch motions. This work significantly contributes by introducing the novel MCR UAV v3.0 and conducting a comprehensive assessment of fuselage-control surface structural stability, offering insights into enhanced UAV design and performance for diverse applications.

Determining interfacial tension and critical micelle concentrations of surfactants from atomistic molecular simulations

HypothesisAtomistically-detailed models of surfactants provide quantitative information on the molecular interactions and spatial distributions at fluid interfaces. Hence, it should be possible to extract from this information, macroscopical thermophysical properties such as interfacial tension, critical micelle concentrations and the relationship between these properties and the bulk fluid surfactant concentrations.Simulations and ExperimentsMolecular-scale interfacial of systems containing n-dodecyl β-glucoside (APG12) are simulated using classical molecular dynamics. The bulk phases and the corresponding interfacial regions are all explicitly detailed using an all-atom force field (PCFF+). During the simulation, the behaviour of the interface is analyzed geometrically to obtain an approximated value of the critical micelle concentration (CMC) in terms of the surfactant area number density and the interfacial tension is assessed through the analysis of the forces amongst molecules.New experimental determinations are reported for the surface tension of APG12 at the water/air and at the water/n-decane interfaces.FindingsWe showcase the application of a thermodynamic framework that inter-relates interfacial tensions, surface densities, CMCs and bulk surfactant concentrations, which allows the in silico quantitative prediction of interfacial tension isotherms.