Interfacial Properties Research Articles

Role of voltage-controlled magnetic anisotropy in the recent development of magnonics and spintronics

With significant recent progress in the thin film deposition and nanofabrication technology, a number of physical phenomena occur at the interfaces of magnetic thin films, and their heterostructures have been discovered. Consequently, the electric field-induced modulation of those interfacial properties mediated through spin–orbit coupling promises to develop magnetic material based smarter, faster, miniaturized, energy efficient spintronic devices. Among them, the electric field-induced modification of interfacial magnetic anisotropy, popularly termed as voltage-controlled magnetic anisotropy (VCMA), has attracted special attention because of its salient features. This article is devoted to reviewing the recent development of magnonics, which deals with collective precessional motion of ordered magnetic spins, i.e., spin waves (SWs), and skyrmions with chiral spin textures, with VCMA, including the perspectives of this research field. Starting with a broad introduction, the key features of VCMA and its advantages over other electric field-induced methods are highlighted. These are followed by describing the state-of-the-art of VCMA, and various other direct and indirect electric field-induced methods for magnetization reversal; controlling skyrmion dynamics; excitation, manipulation, and channeling of SWs; and tailoring magnonic bands. The critical challenges, their possible solutions, and future perspectives of this field are thoroughly discussed throughout the article.

Density Functional Theory Study of Adhesion Mechanism between Epoxy Resins Cured with 4,4'-Diaminodiphenyl Sulfone and 4,4'-Diaminodiphenylmethane and Carboxyl Functionalized Carbon Fiber.

The molecular mechanism of adhesion of two epoxy resins based on diglycidylether of bisphenol A (DGEBA) cured with 4,4'-diaminodiphenyl sulfone (DDS) and 4,4'-diaminodiphenylmethane (DDM) to the carbon fiber (CF) surface is investigated by employing density functional theory (DFT) calculations. The CF surface was modeled by the armchair-edge structure of graphite functionalized with carboxyl (COOH) groups. Two adhesion interfaces were constructed using the CF surface: one with the DGEBA-DDS molecule (CF/DGEBA-DDS interface) and the other with the DGEBA-DDM molecule (CF/DGEBA-DDM interface). The interfacial properties were analyzed by calculating the maximum adhesion stress (Smax) at the interface. The adhesion stress-displacement curve revealed that Smax is 1160.37 MPa, higher for the CF/DGEBA-DDS interface compared to the CF/DGEBA-DDM interface, which is 1060.48 MPa. The energy decomposition analysis showed a similar DFT contribution to adhesion stress for both interfaces, but the dispersion contribution is more significant at the CF/DGEBA-DDS interface. The crystal orbital Hamilton population (COHP) analysis revealed distinct interfacial interactions despite similar DFT contributions. Hydrogen bonding (H-bonding) between the functional groups at both interfaces including feeble OH-π interactions between the benzene rings of epoxy resins and COOH groups on the CF surface were observed. The orbital interaction energies calculated from integrated COHP, i.e., IpCOHP, revealed that the CF/DGEBA-DDS interface has six H-bonding interactions with large absolute IpCOHP values (>1 eV), whereas the CF/DGEBA-DDM interface has five. The interaction between the amine group of the DGEBA-DDM molecule and the CF surface has a large IpCOHP value among all interactions. The sulfone group being at the center of the DDS molecule and its strong surface interaction positioned the DGEBA-DDS molecule closer to the CF surface than the DGEBA-DDM molecule, enhancing dispersion interaction at the CF/DGEBA-DDS interface. Hence, the CF surface exhibits a stronger affinity toward the DGEBA-DDS molecule than the DGEBA-DDM molecule through dispersion interaction.

Tailoring Interface via Tuning the Phase and Morphology of TiO2 for Efficient Mesoporous Perovskite Solar Cells.

The efficiency of mesoporous perovskite solar cells (mp-PSCs) is significantly influenced by favorable charge transport properties across their various interfaces. The interfaces involving compact-TiO2, mesoporous electron transport layer (ETL), and perovskite layer are particularly vital for high-performing devices. Our study presents a combined experimental and computational approach, specifically employing density functional theory, to explore the impact of mesoporous-ETL/perovskite interface properties on carrier transport. These properties are examined in relation to the phases and morphologies of the mesoporous layer. Different phases of TiO2, including anatase, rutile, and brookite, and various morphologies such as nanocubes, nanorods, and disks/clusters, were synthesized using a simple hydrothermal synthesis route. They constitute the mesoporous layer, and Cs0.05FA0.84MA0.14PbI2.55Br0.45 is used as the perovskite absorber in mp-PSCs. The performance of the resulting mesoporous-TiO2 (mp-TiO2) device was investigated in relation to the different phases and morphologies of mp-TiO2. The mp-PSCs with the anatase phase as the mesoporous ETL exhibited the highest device parameters, including power conversion efficiency of 19.15%, short-circuit current density of 22.55 mA/cm2, fill factor of 76.50%, and open-circuit voltage of 1.11 V. The superior performance of the anatase structure is attributed to its promising band edge alignment, which results from a small negative conduction band offset compared to other phases, thereby enhancing carrier transport. This study underscores the potential of interface optimization to improve device performance. By investigating the device performance across different phases and morphologies of the mp-TiO2 layer, we can pave the way for the design of next-generation energy devices.

Shaping the mechanical properties of a gelatin hydrogel interface via amination.

Injuries to musculoskeletal interfaces, such as the tendon-to-bone insertion of the rotator cuff, present significant physiological and clinical challenges for repair due to complex gradients of structure, composition, and cellularity. Advances in interface tissue engineering require stratified biomaterials able to both provide local instructive signals to support multiple tissue phenotypes while also reducing the risk of strain concentrations and failure at the transition between dissimilar materials. Here, we describe adaptation of a thiolated gelatin (Gel-SH) hydrogel via selective amination of carboxylic acid subunits on the gelatin backbone. The magnitude and kinetics of HRP-mediated primary crosslinking and carbodiimide-mediated secondary crosslinking reactions can be tuned through amination and thiolation of carboxylic acid subunits on the gelatin backbone. We also show that a stratified biomaterial comprised of mineralized (bone-mimetic) and non-mineralized (tendon-mimetic) collagen scaffold compartments linked by an aminated Gel-SH hydrogel demonstrate improved mechanical performance and reduced strain concentrations. Together, these results highlight significant mechanical advantages that can be derived from modifying the gelatin macromer via controlled amination and thiolation and suggest an avenue for tuning the mechanical performance of hydrogel interfaces within stratified biomaterials.

Effect of nano-Cu-loaded graphene fillers on tribological properties of PTFE based composite coatings

The Polytetrafluoroethylene(PTFE)-based composite coating has been widely used in the tribology field due to the high strength of graphene(GNS) and the self-lubricating property of PTFE. However, the weak interfacial bonding between GNS and PTFE inhibits the tribological performance of PTFE-based composite coatings. In this study, the composite coating is in situ fabricated by loading Cu nanoparticles on the GNS surface, and the microstructure, bonding, friction, and wear properties of the composite coating were investigated. The results showed that the interfacial bond strength, friction, and wear properties of Cu@GNS-PTFE coating are higher than those of pure PTFE and GNS-PTFE coating. Compared with the PTFE coating, the Cu@GNS-PTFE coating with the optimal ratio(5%) can increase the bond strength by 24.6% and reduce the wear rate by 42.2%. The lubrication mechanism of the Cu@GNS-PTFE coating is the Cu nanoparticle can increase the interfacial bonding property of GNS and PTFE from both mechanical interlocking and chemical activity, which can promote the synergistic lubrication of GNS and PTFE, and provide a theoretical basis for the further application of PTFE and GNS.

Adsorption, Aggregation, and Application Properties of Green Pluronic Aliphatic Alcohol Ether Carboxylic Acids and Nonionic/Amphoteric Surfactants in Water.

In the realm of colloid and interface science, new types of green surfactants, including anionic Pluronic alcohol ether carboxylate (AEC), branched alkyl glucoside (IG), and zwitterionic coconut oil amide propyl betaine (CAB), have been identified and merit further exploration. AEC, characterized by its inclusion of 5 EO and 3.5 PO units, was synthesized, and its behavior in aqueous solutions with IG and CAB was meticulously examined. Their performance in applications such as foam generation, wetting, and the dispersion and stabilization of graphene was also evaluated. At αAE5P3C = 0.5, AE5P3C/CAB exhibited superior surface and interfacial properties compared to AE5P3C/IG. In these hybrid systems, the self-assembly of micelles is predominantly influenced by hydrogen bonding, electrostatic interactions, and hydrophobic forces. Kinetic analysis further confirmed that the driving force for micelle formation in these hybrid systems is enthalpy, with the adsorption process involving a mixed diffusion-kinetic adsorption mechanism. AE5P3C/CAB demonstrated enhanced foaming ability, foam stability, and wetting properties compared to AE5P3C/IG. Intriguingly, the optimal dispersion and stabilization of graphene were achieved with AE5P3C/IG at αAE5P3C = 0.2, providing a foundational basis for its potential application in graphene-based systems. A thorough examination of the synergistic mechanisms and application potential of these three distinct surfactants in aqueous solutions was presented, taking into account various charged ions and the specific hydrophilic and hydrophobic groups of EO and PO. This study not only provides fundamental insights into their intrinsic properties but also offers a fresh perspective for the ongoing exploration of green surfactants.

Mechanism of interface performance enhancement of nano-SiO2 modified polyvinyl alcohol fiber reinforced geopolymer concrete: Experiments, microscopic characterization, and molecular simulation

This study proposes a method utilizing nano-SiO2 modified polyvinyl alcohol fibers to enhance the interface properties of geopolymer concrete. The surface properties of modified polyvinyl alcohol fibers were analyzed through microscopic characterization. The influence of different dosages of modified polyvinyl alcohol fibers on the mechanical properties of geopolymer concrete was investigated. Molecular dynamics simulations revealed the interfacial toughening mechanism between modified polyvinyl alcohol fibers and geopolymer concrete. Results showed that nano-SiO2 modified polyvinyl alcohol fibers increased surface roughness, thereby enhancing interfacial adhesion and mechanical interlocking between fibers and geopolymer concrete, significantly improving compressive, splitting tensile, and flexural strengths of geopolymer concrete with an optimal fiber dosage of 0.2 %. Relative to unmodified PVA fibers, the modified fibers enhance the compressive, splitting tensile, flexural strength, and elastic modulus by 20.19 %, 15.72 %, 22.34 %, and 30.58 % respectively. KH560 serves as an intermediate medium for nano-SiO2 modified polyvinyl alcohol fibers, generating numerous hydrogen bonds at the interface and tightly adhering nano-SiO2 to the surface of polyvinyl alcohol fibers. Additionally, nano-SiO2 can form ionic bonds and stable Si-O-Si bonds with the hydrated sodium aluminosilicate gel.

A perspective on guided electrophoretic transport of particles in liquid crystals

Nonlinear electrophoresis in complex fluids like nematic liquid crystals provides new pathways toward achieving precisely controlled motion and assembly of microscopic objects. The nematic host introduces a paradigm shift in the mechanism of electrophoretic transport by generating unbalanced electro-osmotic flows around the colloidal particle due to symmetry breaking of the medium caused by the induced topological defects. Rationally designed particles, which induce various types of defects and asymmetries, provide new opportunities in this regard. In this Perspective article, we discuss how the asymmetry in the shape and interfacial properties help in piloting the particles using an AC electric field. Finally, we propose some feasible strategies to achieve navigational control using magnetic and photo-responsive particles, guided by orthogonal electric, magnetic fields, and light, respectively.

Revealing Intrinsic Functionalization, Structure, and Photo-Thermal Oxidation in Hexagonal Antimonene.

Antimonene is one of the more exciting members of the post-graphene family with promising applications in optoelectronics, energy storage and conversion, catalysis, sensing or biomedicine. Efforts have been focused on developing a large-scale production route, and indeed, through a colloidal approach, high-quality few-layers antimonene (FLA) hexagons have been recently obtained. However, their oxidation behavior remains unexplored, as well as their interface, inner structure, and photothermal properties. Herein, it is revealed that the hexagons have an intrinsic surface functionalization with alkyl thiols that protects the core of the hexagonal flake against oxidation, and displayed inner defects related to the crystal formation during synthesis, as confirmed by cross-sectional scanning transmission electron microscopy energy dispersive X-ray spectroscopy (STEM-EDX) and temperature-dependent X-ray photoelectron spectroscopy (XPS) and selected area electron diffraction (SAED) analysis. A comprehensive study of temperature and laser power-dependent Raman spectroscopy on varying FLA hexagon thicknesses is carried out. Thinner flakes (<20nm) exhibited a blueshift and intensity decrease, contrasting with thicker ones resembling typical exfoliated flakes with a redshift. This work addresses a literature gap, providing insights into hexagonal FLA structure and characterization, and highlighting the influence of surface functional groups on oxidation behavior. Additionally, it emphasizes the potential of antimonene hexagons as building blocks for 2D heterostructures, including combinations with antimonene oxides and other 2D materials.

Mechanical and Electrical Conductivity Properties of Graphene/Cu Interfaces: A Theoretical Insight.

For graphene/copper (Gr/Cu) composites, achieving high-quality interfaces between Gr and Cu (strong interfacial bonding strength and excellent electron transport performance) is crucial for enabling their widespread applications in electronic devices. This study employs first-principles calculations and the nonequilibrium Green's function method to systematically investigate the mechanical and electrical conductivity properties of Cu(111)/Gr/Cu(111) interfaces with various stacking sequences and different forms of Gr. For these interface systems, the binding energy, separation work, charge transfer, and electrical conductivity across the interface were obtained. The results show that the top-fcc interface exhibits superior interfacial properties, characterized by relatively high binding energy (-3.00 eV/C atom) and separation work (≥0.78 J/m2), a small interfacial distance (2.85 Å), and enhanced electron transport capacity (2.12 G0/nm2). A bilayer form of Gr significantly reduces electronic conductance across the Gr/Cu interface by nearly 2.46 orders of magnitude. Furthermore, point defects in Gr, especially single-vacancy defects, disrupt the traditional trade-offs between mechanical and electrical performance, simultaneously enhancing mechanical performance by 7.50-124.36% and electrical performance by 33.02%. Additionally, stress mechanisms have been proposed to further enhance the interfacial electrical conductivity of Gr/Cu composites. The present study provides a theoretical basis for exploring the engineering applications of Gr/Cu composite materials.

Analysis of foaming mechanism and adhesion of foam rubberised asphalt from the perspective of molecular scale

ABSTRACT Rubberised asphalt faces challenges such as viscosity and construction energy consumption. These problems can be ameliorated by the use of foaming technology. However, existing studies lack a microscopic-level understanding of the foaming mechanism and interfacial properties of foam rubberised asphalt. Therefore, this study used molecular dynamics simulation methods to establish foam rubberised asphalt models and interface models. The models were analysed from the aspects of model density, energy change, molecular agglomeration behaviour and adhesion work. Results revealed that increased temperature and water consumption caused difficulties in the volumetric compression of the model. The diffusion and aggregation behaviour of water molecules altered the distribution of other molecules in the model, effectively reducing the viscosity of the rubberised asphalt without affecting the chemical structure. In the interfacial model, water molecules contribute to the migration of asphalt molecules to the mineral surface, which exists in two forms: aggregating within asphalt and diffusing to the interface. The interface water molecules enhance the electrostatic interaction between asphalt and minerals. However, due to the random nature of water molecule diffusion, it is difficult to form a regular layer of water molecules at the interface, which leads to failure of the adhesion work.

Thermodynamic properties and structure of interfacial boundaries in nonionic fluids from the multilayer quasichemical model

The interfacial properties and structure of nonuniform fluids containing complex chainlike molecules and associating species are very much needed in a variety of different fields, including enhanced oil recovery, drug delivery, pharmacy, cosmetics, food processing, etc.Recently, we described the Multilayer Quasichemical Model (MQuM) of a nonuniform fluid that provides a remarkably detailed structural information, including the local concentration and orientation of functional groups of the molecules, the orientation profiles of the chemical bonds in molecular chains and the orientation profiles of the hydrogen bonds in the mixture.In this work, we focus on the description of thermodynamic properties with the aid of MQuM, including the interfacial tension and the profiles of normal and transverse pressures. Before proceeding to more complex systems, a test is performed through comparison with the previously known results from the Scheutjens-Fleer theory for the planar liquid–vapor interface and spherical droplet in one-component fluid of nonpolar monomeric molecules. The model is applied then for planar interfaces between the liquid phases in mixtures of water with n-alkanes of different chain length and for spherical drops in model systems that contain an associating solvent, a nonpolar chain and a nonionic amphiphile. Our theoretical results are compared with experiment, predictions from iSAFT and MD simulation data from the literature. For the spherical droplets, we discuss the model description of the dependence of the interfacial tension on the curvature and estimate the Tolman length. For the planar interface between the equilibrium liquid phases in water – n-alkane mixtures, the interfacial tensions predicted from the model are in good agreement with experiment.

Tensile properties of SiC/SiC obtained from epoxy‐encapsulated minicomposites

AbstractThe current study investigates the tensile behavior of SiC/SiC minicomposites, focusing on the efficacy of epoxy encapsulation in extracting the intrinsic fiber bundle response. Three minicomposite types were examined: two with Hi‐Nicalon Type‐S fibers and one with Tyranno ZMI fibers. Tensile tests were performed on minicomposites and fiber tows, both bare and epoxy‐encapsulated, whereas interface properties were measured via fiber push‐in tests. The results demonstrate that epoxy encapsulation partially mitigates non‐uniform loading in minicomposites with discontinuous matrices. Theoretical limits on fiber bundle strength, estimated using micromechanical models based on weakest‐link statistics and shear lag theory, are similar to measured encapsulated tow strengths when failure occurs within the elastic regime of the epoxy. In some cases, microstructural defects such as fiber–fiber contacts and debonded coatings play important roles in limiting composite strengths relative to theoretical values. Although encapsulation does not always directly improve properties, it provides useful context for evaluating composite performance and exposing microstructural limitations unaccounted for in idealized models.

Self-forming Na3P/Na2O interphase on a novel biphasic Na3Zr2Si2PO12/Na3PO4 solid electrolyte for long-cycling solid-state Na-metal batteries

A novel biphasic Na3Zr2Si2PO12/Na3PO4 solid electrolyte is proposed to effectively address critical anode interface challenges for solid-state Na-metal batteries (SSSMBs). The Na3PO4 phase, at an optimal composition of ∼20 mol%, transforms the interface chemistry throughout the NZSP electrolyte, which results in dense electrolytes with high Young's modulus, rapid ion transport (6.2 × 10−4 S cm-1) at low activation barrier (0.19 eV), negligible electronic conductivity, and excellent sodiophilicity. The AIMD/DFT calculations and XPS analysis reveal a self-formed, (electro)chemically stable mixed Na+/electron-conducting interphase, comprising Na3P and Na2O, at the Na anode interface. The interphase not only homogenizes the Na+ flux distribution and accelerates the interfacial charge transport, but prevents continuous interfacial reactions, thereby stabilizing the anode interface against dendrite formation. Benefiting from the low-impedance, dendrite-free anode interface, Na symmetric cells demonstrate a low interface resistance of 12.7 Ω cm2 and exceptional cyclability of 3000 h. Additionally, full cells with Na3V2(PO4)3 cathodes achieve 93 % capacity retention after 550 cycles at 0.5 C. This research comprehensively elucidates and leverages the critical advantages of Na3PO4 in enhancing the bulk and interface properties of Na3Zr2Si2PO12 solid electrolytes. The design strategy of biphasic solid electrolytes presented here offers new insights into the developing high-performance solid electrolytes for advanced SSSMBs.

Effects of oil-water interfacial properties on protein structuring and droplet deformation in high moisture meat analogues containing oil

Adding oil to high moisture meat analogues (HMMA) can increase juiciness, and can be achieved by incorporating emulsion droplets during extrusion. Since these droplets can coalesce when subjected to high shear, selecting appropriate emulsion stabilisers is important. For several commercial plant-protein emulsion stabilisers, it was investigated how oil-water interfacial mechanical properties affect droplet deformation and protein structuring in extrusion of HMMAs. Emulsions with 10 wt% or 15 wt% oil, stabilised by potato protein isolates (POPI-1 (Rich in patatin) and POPI-2 (rich in protease inhibitor)) and pea protein isolate PPI, were used to make extrudates with 5.7 wt% and 8.5 wt% oil, respectively. In 8.5 wt%-extrudates, POPI-2 had the most oil leakage from the cooling die, while PPI had the smallest amount despite having softer and more stretchable interfaces. Blade-cutting tests showed the highest maximum force for 8.5 wt%-extrudates with POPI-1, likely because POPI-1 formed the stiffest interfaces. Tensile stress testing showed the largest fracture strain in 8.5% wt%-extrudates with PPI, corresponding to its longer wedge length. Multiphoton excitation microscopy was used to visualise the extrudates protein structure and oil droplets. This showed that droplets near the surface of the extrudate were less deformed than droplets in the centre. There were only small differences between protein stabilisers regarding oil droplet deformation, indicating droplet deformation was dominated by deformation of the protein matrix. The O/W interfacial properties significantly affected oil leakage, cutting force, and tensile strength of extrudates. These results are important to consider when designing emulsions for HMMAs processed by extruders.

Mechanisms of Controllable Growth and Ohmic Contact of Two-Dimensional Molybdenum Disulfide: Insight from Atomistic Simulations.

ConspectusTwo-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), in particular molybdenum disulfide (MoS2), have recently attracted huge interest due to their proper bandgap, high mobility at 2D limit, and easy-to-integrate planar structure, which are very promising for extending Moore's law in postsilicon electronics technology. Great effort has been devoted toward such a goal since the demonstration of protype MoS2 devices with high room-temperature on/off current ratios, ultralow standby power consumption, and atomic level scaling capacity down to sub-1-nm technology node. However, there are still several key challenges that need to be addressed prior to the real application of MoS2-based electronics technology. The controllable growth of wafer-scale single-crystal MoS2 on industry-compatible insulating substrates is the prerequisite of application while the currently synthesized MoS2 films mostly are polycrystalline with limited sizes of single-crystal domains and may involve metal substrates. The precise layer-control is also very important for MoS2 growth since its electronic properties are layer-dependent, whereas the layer-by-layer growth of multilayer MoS2 dominated by the van der Waals (vdW) epitaxy leads to poor thickness uniformity and noncontinuously distributed domains. High density up to 1013 cm-2 of sulfur vacancies (SVs) in grown MoS2 can cause unfavorable carrier scatting and electronic properties variations and will inevitably disturb the device performance. The dangling-bond-free surface of MoS2 gives rise to an inherent vdW gap at metal-semiconductor (M-S) contact, which leads to high electrical resistance and poor current-delivery capability at the contact interface and thereby substantially limits the performances of MoS2 devices.In this Account, we briefly review recent experimental and theoretical attempts for addressing the aforementioned challenges and present our own insights from atomistic simulations. We theoretically revealed the vital role of substrate steps for guiding unidirectional nucleation of monolayer MoS2 and uniform nucleation and edge-aligned growth of bilayer MoS2 by advanced simulations. The established thermodynamic mechanisms have successfully directed the experimental works on the controllable growth of 2 in. single-crystal monolayer and centimeter-scale uniform bilayer MoS2. The postgrowth repair mechanism of SV defect in MoS2 via thiol chemistry treatment has been theoretically explored with the consideration of side reaction of surface functionalization to help experimentally reduce SV defect density by 75%. Beyond the atomic level understanding, theoretical simulations proposed the electronic states hybridization mechanism across the semimetal-MoS2 vdW interface, thereby guiding experimental effort for realizing Ohmic contact at the MoS2-Sb(0112) vdW interface with record-low contact resistance.These advances provide a sound basis with an atomic-level understanding for addressing the related issues. However, there are still notable gaps in terms of system size and time scale of dynamics between atomistic simulations and experimental observations for the studies of MoS2 growth and interfaces. The combination of multiscale simulations and artificial intelligence technology is expected to narrow these gaps and provide a more insightful understanding of the controllable growth and interfacial properties modulation of MoS2. We conclude the Account with the standing challenges and outlook on future research directions from the theoretical perspective.

Combined effect of self-stressing and confinement on GFRP-LC3 interface bond

The load capacity, failure mode and durability of reinforced concrete members are strongly affected by the bond strength between the concrete and the reinforcement. This work presents a physics-based approach to improve the bond strength based on self-stressing effect. Combination of limestone calcined clay cement (LC3) and calcium sulphoaluminate cement (CSA) with different ratios was employed to develop self-stressing function. The addition of CSA induces a remarkable volume expansion of matrix due to the formation of ettringite, it however leads to a decreased compressive strength because of the reduced Portlandite content and increased porosity. A push-out test was conducted to evaluate the interface properties between glass fiber reinforced polymer (GFRP) and LC3-based matrix. The results show that the interface bond strength is highly dependent on the matrix strength under unconfined condition. On the contrary, under confined condition, the interface bond strength increases linearly with the expansion value regardless of matrix strength, attributed to that the self-stressing effect can effectively refine the matrix pores and densify the interface transition zone. The findings from this work demonstrate that the self-stressing effect holds promise to be a plausible method to strengthen the overall properties of reinforced concrete without creating additional carbon emission.

ZnO modified carbon fiber-matrix interfacial evaluation via nanoscale digital image correlation and nanoindentation

Improving the adherence of the fiber-matrix interface is an important step for enhancing the capabilities of polymer composites. In this study, carbon fibers were modified by growing zinc oxide (ZnO) nanorods on the fiber surface using a hydrothermal approach, with the aim of increasing the interfacial area and enhancing the friction between the fiber and the matrix. To fully understand the deformation mechanisms at the interface, a microscale evaluation combining nanoindentation with digital image correlation (DIC) for mapping the deformations by using nanoscale speckles is developed in this work. The main objective of this research was to develop a protocol for speckling the modified single fiber composite and show that DIC can be used in microscopic level and to evaluate the fiber-matrix interface by means of nano indentation. The speckle pattern was created using Ti nano powder and used to generate the strain maps in the fiber-matrix interface region. A comparative analysis of DIC results from ZnO modified carbon fibers has shown that shear strains around the interfacial boundary are 60 % reduced on average, as compared to neat carbon fibers, across all nano indentations from 8mN to 65mN of peak load. Results used direct strain measurements to confirm that modification by ZnO growth on the surface of individual fibers has a significant benefit to the interfacial mechanical properties of fiber-matrix composites.

Preparation of glass fiber-reinforced polyphenylene sulfide/magnesium hybrid based on micro-arc oxidation by hot pressing molding

ABSTRACT The construction of surface structures and joining technology has become a key technology for the preparation of polymer-metal hybrid(PMH) materials in recent years. The magnesium alloy surface was subjected to micro-arc oxidation(MAO) to create a micro-nanopore structure, and the Glass fiber-reinforced polyphenylene sulfide/magnesium alloy(GFRPPS/Mg) hybrid joints were prepared by hot pressing molding. The joining mechanism of the GFRPPS/Mg hybrid joints was explored, and the interfacial disruption forms, crystalline properties, embedding depths, and interfacial chemistry of the GFRPPS/Mg hybrids were investigated at different hot pressing temperatures. The results demonstrate that the mechanical strength of the GFRPPS/Mg hybrid joints is a consequence of the interplay between micromechanical interlocking and chemical bonding, and the optimal tensile shear strength is 18.51 MPa. The tensile shear failure of the hybrids can be attributed to a combination of cohesive and interfacial failure. The crystalline properties of the failed surface of GFRPPS were also analyzed by X-ray diffraction (XRD), which revealed that the crystallinity also affects the mechanical properties of the GFRPPS/Mg hybrid joints.

Structure, orientation, and dynamics of per- and polyfluoroalkyl substance (PFAS) surfactants at the air-water interface: Molecular-level insights

HypothesisUnderstanding the intricate molecular-level details of toxic per- and polyfluoroalkyl substances (PFAS) partitioning to the air–water interface holds paramount importance in evaluating their fate and transport, as well as for finding safer alternatives for various applications, including aqueous film forming foams. The behavior of these substances at interfaces strongly depends on molecular architecture, chemistry, and concentration, which define molecular packing, self-assembly, interfacial diffusion, and the surface tension. SimulationsModeling of three PFAS surfactants, namely, longer-tail (perfluorooctanoate (PFOA)) and shorter-tail (perfluorobutanoate (PFBA) and 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy) propanoate (GenX)) has been conducted using atomistic molecular dynamics simulations. A systematic comparison between these representative PFAS of different sizes and structure reveals factors influencing their association behavior, mechanism of surface tension reduction, and interfacial mobility as a function of surface coverage. FindingsShorter-chain PFAS surfactants (GenX or PFBA) require lower surface coverage compared to longer chain (PFOA) PFAS to achieve the same decrease in surface tension. However, a higher concentration of GenX and PFBA is necessary in the bulk aqueous solution to achieve the same surface coverage as PFOA, due to their higher solubility in water. The PFAS molecular orientation and mobility at the interface are found to be vastly influenced by the length and architecture of the hydrophobic fluorocarbon tail. A significant ordering of the water dipole moment near the anionic headgroup is apparent at high surface concentration. A direct correlation is established between the PFAS interfacial properties and PFAS-PFAS, PFAS-counterion, and PFAS-water interactions.