Search Results (1,050)

The impingement of a molten droplet on a solid surface, forming a “splat,” is a fundamental phenomenon observed across numerous industrial surface engineering techniques. For example, thermal spray deposition is widely used to create metal, ceramic, polymer, and composite coatings that are vital for aerospace, biomedical, electronics, and energy applications. Significant progress has been made in understanding droplet impact behavior, largely driven by advancements in high-resolution and high-speed imaging techniques, as well as computational resources. Although droplet impact dynamics, splat morphology, and interfacial bonding mechanisms have been extensively reviewed, a comprehensive overview of the mechanical behaviors of single splats, which are crucial for coating performance, has not been reported. This review bridges that gap by offering an in-depth analysis of bonding strength and residual stress in single splats. The various experimental techniques used to characterize these properties are thoroughly discussed, and a detailed review of the analytical models and numerical simulations developed to predict and understand residual stress evolution is provided. Notably, the complex interplay between bonding strength and residual stress is then discussed, examining how these two critical mechanical attributes are interrelated and mutually influence each other. Subsequently, effective strategies for improving interfacial bonding are explored, and key factors that influence residual stress are identified. Furthermore, the fundamental roles of splat flattening and formation dynamics in determining the final mechanical properties are critically examined, highlighting the challenges in integrating fluid dynamics with mechanical analysis. Thermal spraying serves as the primary context, but other relevant applications are briefly considered. Cold spray splats are excluded because of their distinct bonding and stress generation mechanisms. Finally, promising future research directions are outlined to advance the understanding and control of the mechanical properties in single splats, ultimately supporting the development of more robust and reliable coating technologies. Full article

In this study, aiming to develop novel biocomposites that offer competitive properties while retaining their renewable and biodegradable characteristics, a biodegradable polymer matrix (Mater-Bi^® HF51L2) was reinforced with natural particles extracted from the culm and leaf of Cymbopogon flexuosus (lemongrass). Particles (<500 µm) were incorporated at 10 and 20 wt.% via twin-screw extrusion followed by compression moulding. Morphological analysis via SEM revealed distinct structural differences between culm- and leaf-derived particles, with the latter exhibiting smoother surfaces, higher density, and better dispersion in the matrix, resulting in lower void content. Quasi-static mechanical tests showed increased stiffness with filler content, particularly for leaf-based composites. This material, at 20 wt.% filler loadings, enhanced the tensile and flexural moduli of the neat Mater-Bi approximately three and two times, respectively, a result attributed to enhanced interfacial adhesion. Rheological measurements (rotational and capillary) indicated significant increases in complex viscosity, particularly for leaf-filled systems, confirming restricted polymer chain mobility and good matrix–filler interaction. Dynamic mechanical thermal tests (DMTA) results showed an increased storage modulus and a shift in glass transition temperature (T_g) for all biocomposites in comparison to Mater-Bi matrix. Specifically, the neat matrix had a T_g of −28 °C, which increased to −24 °C and −18 °C for the 20 wt.% culm-reinforced and leaf-reinforced biocomposites, respectively. Overall, the leaf-derived particles demonstrated superior reinforcing potential, effectively improving the mechanical, rheological, and thermal properties of Mater-Bi-based biocomposites. Full article

Viscous fingering is an interfacial instability that occurs when multiple fluids displace each other. This research focuses on the interface instability during immiscible displacement of shear-thinning fluids by CO₂. By controlling velocity and applying heat to the upper and lower walls, the influence of velocity and temperature on viscous fingering during CO₂ displacement is investigated. Moreover, by modifying the geometric conditions of the classical Hele-Shaw cells (HSCs), a novel analytical framework for viscous fingering is proposed. The primary methodology involves implementing a minute depth gradient distribution within the HSC, coupled with the Volume of Fluid (VOF) multiphase model, which systematically reveals the dynamic suppression mechanism of shear-thinning effects on viscous finger bifurcation. The results indicate that temperature elevation leads to increased sweep efficiency, reduced residual non-Newtonian fluid in the displaced zone, and enhanced displacement efficiency. Furthermore, increased velocity leads to reduced sweep efficiency. However, at lower velocities, displacement efficiency remains relatively low due to limited sweep coverage. The direction and magnitude of the depth gradient significantly govern the morphology and extension length of viscous fingering. Both positive and negative depth gradients promote fingering development on their respective sides, as the gradient establishes anisotropic permeability that prioritizes flow pathways in specific orientations, thereby intensifying finger propagation. Full article

Understanding the microscopic interaction between agricultural tillage tools and soil is essential for improving wear resistance. In this study, molecular dynamics (MD) simulations are employed to investigate the tribological behavior of the Fe–SiO₂ interface under varying loads and sliding velocities. The results demonstrate that the coefficient of friction increases with both normal load and sliding velocity, accompanied by a clear running-in stage. Under high loads, significant plastic deformation occurs, characterized by asymmetric atomic pile-up, expansion of the strain field, and heterogeneous von Mises strain distribution. Energy analysis reveals intensified kinetic and potential energy variations, indicating enhanced defect accumulation and interfacial non-equilibrium states. Temperature distributions are highly localized at the interface, with thermal saturation observed under high-velocity conditions. Mean square displacement (MSD) results confirm that higher loads and velocities promote atomic migration and plastic flow. This study provides atomic-scale insights into wear mechanisms under extreme mechanical conditions, offering theoretical support for the design of durable soil-engaging components in agricultural machinery. Full article

Graphene, owing to its exceptional mechanical properties and interfacial modulation capability, is considered an ideal material for enhancing the interfacial strength and damage resistance during the fabrication of ultra-thin lithium foils. Although previous studies have demonstrated the reinforcing effects of graphene on lithium metal interfaces, most analyses have been restricted to single-temperature or idealized substrate conditions, lacking systematic investigations under practical, multi-temperature environments. Consequently, the influence of graphene coatings on lithium-ion conductivity and mechanical stability under real thermal conditions remains unclear. To address this gap, we employ LAMMPS-based molecular dynamics simulations to construct atomic-scale models of pristine lithium and graphene-coated lithium (C/Li) interfaces at three representative temperatures. Through comprehensive analyses of dislocation evolution, root-mean-square displacement, frictional response, and lithium-ion diffusion, we find that graphene coatings synergistically alleviate interfacial stress, suppress crack initiation, reduce friction, and enhance ionic conductivity, with these effects being particularly pronounced at elevated temperatures. These findings reveal the coupled mechanical and electrochemical regulation imparted by graphene, providing a theoretical basis for optimizing the structure of next-generation high-performance lithium metal anodes and laying the foundation for advanced interfacial engineering in battery technologies. Full article

Macroscopic fatigue tests, mesoscopic finite element simulations, and microscopic molecular dynamics simulations were composed to study the damage and failure of drainage asphalt mixtures in multiscale. The applicability of the fatigue models fit by strain, stress, and the linear fitting slope of the indirect tensile modulus curves were compared. The mesoscopic damage and failure distribution and evolution characteristics were studied, considering the single or coupling effect of traffic loading, hydrodynamic pressure, mortar aging, and interfacial attenuation. The microscopic molecular mechanism of the interface adhesion failure between the aggregate and mortar under water-containing conditions was analyzed. Results show that the fatigue model based on the linear fitting slopes of the indirect tensile modulus curves has significant applicability for drainage asphalt mixtures with different void rates and gradations. The damage and failure have an obvious leap development when traffic loading increases from 0.7 MPa to 0.8 MPa. The hydrodynamic pressure significantly increases the stress of the mortar around the voids and close to the aggregate, promoting damage development and crack extension, especially when it is greater than 0.3 MPa. With the aging deepening of the mortar, the increase rate of the damage degree gradually decreases from the top to the bottom of the mixture. With the development of interfacial attenuation, the damage and failure of interfaces continue increasing, while that of the mortar increases first and then decreases, which is related to the loading concentration in the interface and the stress decrease in the mortar. Under the coupling effects, whether the cracks mainly generate in the mortar or interface depends on their damage degrees, thus causing the stripping of the aggregate wrapped or not wrapped by the mortar, respectively. The van del Waals force is the main molecular effect of interface adhesion, and both acidic and alkaline aggregate components significantly tend to form hydrogen bonds with water rather than asphalt, thus attenuating the interface adhesion. Full article

Rubberized concrete is a novel green building material that enhances many features when rubber particles are incorporated into cement mortar, simultaneously yielding economic benefits through the recycling of waste tires. This study applies styrene–butadiene latex (SBL) for toughening treatment. The investigation delves into the mechanism by which SBL improves the interface between rubber and cement, encompassing macroscopic mechanical properties, microscopic structural characteristics, and nano-scale interfacial interactions. Macroscopic mechanical tests reveal a significant increase in flexural strength, shear strength, and compressive strength of the composite concrete upon the introduction of SBL and rubber. Specifically, the compressive strength improved by 8.8%, shear strength by 13.7%, and flexural strength by 18.9% at 28 days. Through electron microscopy observation of corresponding polymer cement concrete sections, observations reveal that SBL reinforces both interfaces and elucidates its bonding impact at the micro-level interface. Molecular dynamics (MD) modeling of SBL/rubber/CSH is employed at the nanoscale to compute and examine the local structure, dynamic behavior, and binding energy of the interface. The findings indicate that SBL mitigates interface impacts, enhances interface hydrogen bonds, van der Waals interactions, $\mathrm{C}\mathrm{a}-\mathrm{H}$ coordination bonds, and stability, consequently improving interfacial adhesion and fortifying the feeble interface bonding between organic polymers (rubber) and inorganic silicates (CSH). Full article

Heavy metal ions (HMIs) threaten ecosystems and human health due to their carcinogenicity, bioaccumulativity, and persistence, demanding highly sensitive, low-cost real-time detection. Electrochemical sensing technology has gained significant attention owing to its rapid response, high sensitivity, and low cost. Molybdenum disulfide (MoS₂), with its layered structure, tunable bandgap, and abundant edge active sites, demonstrates significant potential in the electrochemical detection of heavy metals. This review systematically summarizes the crystal structure characteristics of MoS₂, various preparation strategies, and their mechanisms for regulating electrochemical sensing performance. It particularly explores the cooperative effects of MoS₂ composites with other materials, which effectively enhance the sensitivity, selectivity, and detection limits of electrochemical sensors. Although MoS₂-based materials have made significant progress in theoretical and applied research, practical challenges remain, including fabrication process optimization, interference from complex-matrix ions, slow trace-metal enrichment kinetics, and stability issues in flexible devices. Future work should focus on developing efficient, low-cost synthesis methods, enhancing interference resistance through microfluidic and biomimetic recognition technologies, optimizing composite designs, resolving interfacial reaction dynamics via in situ characterization, and establishing structure–property relationship models using machine learning, ultimately promoting practical applications in environmental monitoring, food safety, and biomedical fields. Full article

This study investigates the interfacial behavior of four phosphate ester ionic liquids (ILs) with contrasting cation hydrophobicity under humid environments. Through tribological tests, surface analysis, and molecular dynamics simulations, we reveal how moisture absorption governs lubricant film organization at metal interfaces. Aromatic ILs (imidazolium/pyridinium cations) exhibit significant degradation in lubrication after moisture exposure, with friction coefficients increasing by 0.03–0.05 and wear volumes scaling with humidity. This deterioration arises from competitive water–cation adsorption, where hydrogen bonding disrupts Fe-cation coordination bonds and destabilizes the protective film. In contrast, aliphatic ILs (tetraalkylammonium/phosphonium cations) maintain robust tribological performance. Their alkyl chains spatially confine water to outer adsorption layers (>17 Å from the surface), preserving a stable core lubricating film (~14 Å thick). Molecular dynamics simulations confirm that water co-adsorbs with aromatic cations (RDF peak: 2.5 Å), weakening interfacial interactions, while aliphatic ILs minimize cation–water affinity (RDF peak: 4 Å). These findings establish cation hydrophobicity as a critical design parameter for humidity-resistant lubricants, providing fundamental insights into water-mediated interfacial phenomena in complex fluid systems. Full article

This study quantifies the effects of freeze–thaw (FT) cycling and dynamic water scouring, and establishes links between mesoscale pore evolution and macroscale strength degradation in cement-stabilized macadam (CSM) bases. The objective is to provide quantitative indicators for durability design and non-destructive evaluation of CSM bases. First, laboratory tests were conducted to simulate alpine service conditions: CSM cylindrical specimens (Ø150 × 150 mm) with 4.5% cement content, cured for 28 days, were exposed to 0, 5, or 20 FT cycles (−18 °C for 16 h ↔ +25 °C for 8 h), followed by dynamic water scouring (0.5 MPa, 10 Hz) for 15, 30, or 60 min. Second, the resulting damage was tracked at two scales. Acoustic emission (AE) sensors monitored internal damage during subsequent splitting tests, while industrial computed tomography (CT) was used to scan selected specimens and quantify porosity, pore number, and average pore diameter. Third, gray relational analysis correlated pore structure parameters with strength loss. The results indicate that under 30 min of scouring, increasing FT cycles from 0 to 20 increased mass loss from 0.33% to 1.27% and reduced splitting strength by 28.8%. AE cumulative ringing count and energy decreased by 97.9% and 98.4%, respectively, indicating severe internal degradation. CT scans revealed porosity and pore count increased monotonically with FT cycles, while average pore diameter decreased (dominated by microcrack formation). Frost-heave pressure and cyclic suction enlarged edge pores and interconnected internal voids, accelerating erosion of cement paste. FT cycles compromise the cement–aggregate interfacial bond, thereby predisposing the matrix to accelerated deterioration under dynamic scouring; the ensuing evolution of pore structure emerges as the pivotal mechanism governing strength degradation. Average pore diameter exhibited the strongest correlation with splitting strength (r = 0.763), and its change was the primary driver of strength loss (r = 0.774). These findings facilitate optimizing cement dosage, validating non-destructive evaluation models for in-service base courses, and erosion durability of road base materials in permafrost regions. Full article

The fracture behavior of the Al₄Cu₉ intermetallic compound at the interface of impact-welded Cu/Al joints remains insufficiently explored through integrated multiscale modeling and experimental validation. In this study, molecular dynamic (MD) simulations, finite element (FE) analysis implemented in ABAQUS (version 2020) and a cohesive zone model (CZM) were combined with optical microscopy (OM) and scanning electron microscopy (SEM) observations of the interface and crack initiation zones in impact-welded Cu/Al specimens to investigate crack propagation mechanisms under different defect configurations. The experimental specimens consisted of 1060 aluminum (Al) and oxygen-free high-conductivity (OFHC) copper, fabricated via impact welding and subsequently annealed at 250 °C for 100 h. The interfacial morphology and crack initiation features obtained from OM and SEM provided direct validation for the traction–separation (T-S) parameters extracted from MD and mapped into the FE model. The results indicate that composite defects (blunt crack + void) cause a significantly greater reduction in fracture energy and stress intensity factor than single defects and that defect effects outweigh temperature effects within the range of 200–500 K. The experimentally observed crack initiation locations were in strong agreement with simulation predictions. This integrated simulation–experiment approach not only elucidates the multiscale fracture mechanisms of the Al₄Cu₉ interface but also provides a physically validated basis for the reliability assessment and optimization of aerospace Cu/Al welded structures. Full article

To improve the processing performance and application potential of Grifola frondosa protein (GFP), this study employed multiple freeze–thaw (F-T) cycles to modify GFP and systematically evaluated the changes in its structure, functional properties, and digestive behavior. The results indicated that F-T treatment induced significant oxidation and structural unfolding in GFP, as evidenced by an increase in carbonyl content from 0.75 ± 0.05 nmol/mg to 1.77 ± 0.04 nmol/mg, a decrease in α-helix content from 40.23% to 36.78%, disruption of the microstructure, and degradation of some low-molecular-weight proteins. In terms of functional properties, F-T treatment significantly enhanced the emulsifying performance of GFP, with the best effect observed after 3 F-T cycles. Emulsifying ability increased from 21.83 ± 1.14 m²/g to 26.11 ± 1.61 m²/g, and emulsifying stability improved from 18.36 ± 1.78% to 25.37 ± 0.84%. This was accompanied by favorable changes in the emulsion’s interfacial properties, including a reduction in average particle size (480.5 ± 30.5 nm) and an increase in absolute ζ-potential (−55.5 ± 0.2 mV). These changes were closely related to the dynamic evolution of free sulfhydryl groups and surface hydrophobicity. In vitro digestion experiments revealed that the protein digestibility and soluble peptide content of GFP peaked after two F-T treatments, reaching 64.88 ± 0.86% and 1.99 ± 0.09118 mg/mL, respectively, and then gradually declined; its antioxidant activity also showed an initial increase followed by a decrease with increasing F-T cycles. In summary, an appropriate number of F-T treatments can effectively enhance the emulsifying properties and digestive characteristics of GFP; this research provides a theoretical basis for the physical modification of GFP and broadens its potential applications in food emulsion products. Full article

This study presents a molecular dynamics (MD) investigation of water evaporation in copper nanochannels, with a focus on accurately modeling copper–water interactions through forcefield calibration. The TIP4P/2005 water model was coupled with the Modified Embedded Atom Method (MEAM) for copper, and the oxygen–copper Lennard–Jones (LJ) parameters were systematically tuned to match experimentally reported water contact angles (WCAs) on Cu (111) surfaces. Contact angles were extracted from simulation trajectories using a robust five-step protocol involving 2D kernel density estimation, adaptive thresholding, circle fitting, and mean squared error (MSE) validation. The optimized forcefield demonstrated strong agreement with experimental WCA values (50.2°–82.3°), enabling predictive control of wetting behavior by varying ε in the range 0.20–0.28 kcal/mol. Using this validated parameterization, we explored nanoscale evaporation in copper channels under varying thermal loads (300–600 K). The results reveal a clear temperature-dependent transition from interfacial-layer evaporation to bulk-phase vaporization, with evaporation onset and rate governed by the interplay between copper–water adhesion and thermal disruption of hydrogen bonding. These findings provide atomistically resolved insights into wetting and evaporation in metallic nanochannels, offering a calibrated framework for simulating phase-change heat transfer in advanced thermal management systems. Full article

Carbon dioxide (CO₂), a major greenhouse gas, contributes significantly to global warming and environmental degradation. Carbon Capture, Utilization, and Storage (CCUS) is a promising strategy to mitigate atmospheric CO₂ levels. One widely applied utilization approach involves injecting captured CO₂ into depleted oil reservoirs to enhance oil recovery—a technique known as CO₂-Enhanced Oil Recovery (CO₂-EOR). The effectiveness of CO₂-EOR largely depends on complex rock–fluid interactions, including mass transfer, wettability alteration, capillary pressure, and interfacial tension (IFT). Various factors, such as the presence of asphaltenes, salinity, pressure, temperature, and rock type, influence these interactions. This review explores the impact of these parameters on the IFT between CO₂ and oil/water systems, drawing on findings from both experimental studies and molecular dynamics (MD) simulations. The literature indicates that increased temperature, reduced pressure, lower salinity, and the presence of asphaltenes tend to reduce IFT at the oil–water interface. Similarly, elevated temperature and pressure, along with asphaltene content, also lower the surface tension between CO₂ and oil. Most MD simulations employ synthetic oil mixtures of various alkanes and use tools such as LAMMPS and GROMACS. Experimentally, the pendant drop method is most commonly used with crude oil and brine samples. Future research employing actual reservoir fluids and alternative measurement techniques may yield more accurate and representative IFT data, further advancing the application of CO₂-EOR. Full article

Deicing salt effectively melts ice and snow to maintain traffic flow in seasonal freezing zones, but its erosion effect compromises the water stability and structural integrity of asphalt pavements. To comprehensively explore the impacts of salt erosion on the interfacial behaviors of rubber asphalt–aggregate systems, this study developed a multiscale characterization method integrating a macroscopic mechanical test, microscopic tests, and molecular dynamics (MD) simulations. Firstly, laboratory-controlled salt–freeze–thaw cycles were employed to simulate field conditions, followed by quantitative evaluation of interfacial bonding properties through pull-out tests. Subsequently, the atomic force microscopy (AFM) and Fourier transform infrared spectrometer (FTIR) tests were conducted to characterize the microscopic morphology evolution and chemical functional group transformations, respectively. Moreover, by combining the diffusion coefficients of water molecules, salt solution ions, and asphalt components, the mechanism of interfacial salt erosion was elucidated. The results demonstrate that increasing NaCl concentration and freeze–thaw cycles progressively reduces interfacial pull-out strength and fracture energy, with NaCl-induced damage becoming limited after twelve salt–freeze–thaw cycles. In detail, with exposure to 15 freeze–thaw cycles in 6% NaCl solution, the pull-out strength and fracture energy of the rubber asphalt–limestone aggregate decrease by 50.47% and 51.57%, respectively. At this stage, rubber asphalt exhibits 65.42% and 52.34% increases in carbonyl and sulfoxide indexes, respectively, contrasted by 49.24% and 42.5% decreases in aromatic and aliphatic indexes. Long-term exposure to salt–freeze–thaw conditions promotes phase homogenization, ultimately reducing surface roughness and causing rubber asphalt to resemble matrix asphalt morphologically. At the rubber asphalt–NaCl solution–aggregate interface, the diffusion of Na⁺ is faster than that of Cl⁻. Meanwhile, compared with other asphalt components, saturates exhibit notably enhanced mobility under salt erosion conditions. The synergistic effects of accelerated aging, salt crystallization pressure, and enhanced ionic diffusion jointly induce the deterioration of interfacial bonding, which accounts for the decrease in macroscopic pull-out strength. This multiscale investigation advances understanding of salt-induced deterioration while providing practical insights for developing durable asphalt mixtures in cold regions. Full article