Search Results (65)

Van der Waals (vdW) multiferroic tunnel junctions (MFTJs) based on two-dimensional layered materials have emerged as a promising platform for next-generation non-volatile memory devices. In this work, we propose and theoretically investigate a high-performance all-vdW MFTJ consisting of a sliding ferroelectric bilayer GeC barrier sandwiched between asymmetric ferromagnetic metallic electrodes, Fe₃GaTe₂ and Fe₃GeTe₂. Using first-principles calculations combined with the non-equilibrium Green’s function (NEGF) method, we demonstrate that the bilayer GeC possesses robust vertical ferroelectricity switchable by interlayer sliding. By incorporating monolayer graphene as protective layers to mitigate metal-induced gap states, the device preserves the intrinsic ferroelectric polarization of the barrier. Our results reveal that four distinct non-volatile resistance states can be realized by independently manipulating the ferroelectric polarization and magnetization configurations. Remarkably, the device exhibits a giant Tunneling Magnetoresistance (TMR) ratio of up to 750.95% and a large Tunneling Electroresistance (TER) ratio of 322.97%. Furthermore, we observe perfect spin-filtering efficiency and a significant negative differential resistance (NDR) effect under finite bias voltage. These findings suggest that the Fe₃GaTe₂/graphene/bilayer-GeC/graphene/Fe₃GeTe₂ heterostructure is a compelling candidate for multifunctional spintronic applications in the post-Moore era. Full article

This study presents a coupled numerical–experimental investigation into the early-age thermo-mechanical behaviour of 3D-printed concrete (3DPC), with particular emphasis on strength development, interlayer bonding, and thermally induced cracking that govern structural buildability and performance. A coupled multiphysics modelling framework was developed in COMSOL Multiphysics by integrating hydration kinetics, maturity theory, thermo-mechanical coupling, and a cohesive-zone-based interlayer damage formulation through user-defined time-dependent constitutive relationships and domain activation functions. The model simulated the temporal evolution of temperature, stiffness, stress development, and interlayer degradation during the early-age printing process. The model simulates the temporal evolution of temperature, stiffness, and interlayer damage and was validated against experimental results from compression, interlayer bond, and fracture tests conducted under varying printing time gaps and curing temperatures. The results demonstrate that increasing interlayer deposition intervals up to 60 min leads to reductions of approximately 38% in interlayer bond strength and a significant reduction in apparent compressive strength exceeding 80% between 0 and 60 min deposition delay. It should be noted that this reduction primarily reflects interlayer-dominated failure and loss of structural continuity rather than intrinsic degradation of the bulk cementitious matrix, primarily due to hydration discontinuity, moisture loss, and progressive substrate stiffening. Elevated curing temperatures further intensify thermal gradients, resulting in higher residual stresses and increased crack susceptibility at interlayer interfaces. The numerical predictions showed good agreement with the experimental responses, with peak-force prediction errors below 5% and RMSE values of approximately 0.30–0.45 kN along the post-peak softening, confirming the reliability of the proposed modelling approach. The findings highlight the critical importance of printing continuity and thermal control in governing early-age structural performance and provide quantitative guidance for optimising process parameters in extrusion-based 3D concrete printing. Full article

The functional valorization of waste fabrics, particularly their conversion into flexible low-cost, high-performance electrodes, holds significant promise for resource sustainability and the development of advanced energy technologies. Here, a NiB/Cu/polyester fabric (PF) composite electrode was fabricated via two-step electroless plating on waste PF and was demonstrated as a bifunctional electrocatalyst for methanol oxidation (MOR) and urea oxidation (UOR). The morphology, crystal structure, surface chemical state, and wettability of the electrodes were characterized using SEM, TEM, XRD, XPS, and contact angle measurements. The Cu interlayer critically enhanced interfacial wettability, intrinsic catalytic activity and stability. At 0.8 V, the NiB/Cu/PF electrode delivered average current densities of 312 mA·cm⁻² for MOR and 288 mA·cm⁻² for UOR, outperforming NiB/PF by 27.9% and 9.1%, respectively. After 2000 accelerated degradation cycles with electrolyte renewal, MOR and UOR activities were retained at 91.6% and 105.0%, respectively. Remarkably, the Cu interlayer conferred exceptional mechanical–electrochemical robustness: following 100 sequential bending and twisting deformations, current density retention ranged from 84.6% to 96.7% across multiple test configurations. The Cu interlayer acted as a flexible stress buffer during mechanical deformation, effectively improving the adhesion between the coating and the substrate. Full article

Chromium nitride (CrN) can be used as a coating material deposited via physical vapour deposition (PVD), thereby improving the corrosion and wear resistance of the substrate. However, this level of corrosion protection may not be sufficient in an aggressive corrosion environment. The coatings often contain intrinsic microstructural defects, such as microcraters, which can serve as pathways for the corrosive medium to reach the substrate, thereby initiating and promoting corrosion. In this study, the influence of parameters on the formation of a TiO₂ layer using the ALD technique was investigated. In particular, the work focused on assessing the effectiveness of the TiO₂ layer as a sealing barrier for CrN coatings (PVD) applied to austenitic 316L steel. The TiO₂ ALD coatings were produced at a constant temperature of 200 °C with a varying number of cycles, ranging from 200 to 1000 cycles. Structural investigations were carried out using scanning electron microscopy SEM and atomic force microscopy. Electrochemical properties were investigated using a potentiodynamic test and electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution. SEM observations indicate that the morphology of the hybrid coatings is strongly influenced by the number of ALD cycles. The TiO₂ layer conformally reproduces the underlying PVD topography while progressively sealing the coating by filling intrinsic defects and discontinuities. Hybrid coatings (PVD/ALD) with titanium oxide deposited at 500 ALD cycles were found to have the best corrosion resistance. The polarisation resistance for these coatings was nearly four times higher than that of both the single PVD (CrN) coating and the uncoated stainless steel 316L substrate. At the same time, the corrosion current density was several times lower than that of the reference systems. The corrosion mechanisms were investigated by observing the surfaces of the samples after corrosion testing using SEM. Abrasion resistance tests using the pin-on-disc method and adhesion tests (scratch tests) were also performed, which showed that appropriate optimisation of the layer architecture in the PVD/ALD hybrid system significantly improves its tribological durability, interlayer stability, and adhesion to the substrate. Full article

O3-type layered transition-metal oxides are widely regarded as promising cathode materials for sodium-ion batteries due to their intrinsically high sodium content and favorable energy density. Nevertheless, their practical rate capability is hindered by sluggish Na⁺ transport and relatively high diffusion barriers. To address this issue, elemental substitution has emerged as an effective modification strategy. In this work, fluorine (F), characterized by strong electronegativity and a small ionic radius, is introduced to partially substitute oxygen in the bulk lattice of O3-type NaNi_1/3Fe_1/3Mn_1/3O₂ (NNFM). First-principles calculations demonstrate that F incorporation leads to an expansion of the interlayer spacing along the c-axis and a weakening of Na–O interactions, both of which facilitate Na⁺ migration. Among the considered configurations, Mn-adjacent substitution exhibits the lowest formation energy, indicating enhanced thermodynamic stability. Furthermore, electronic structure analysis reveals a reduced band gap (from 0.515 eV to 0.342–0.356 eV) and strengthened O-2p/Mn-3d orbital hybridization, contributing to improved electronic conductivity. These findings provide atomistic insights into F-induced modulation mechanisms and suggest an effective pathway for optimizing Na⁺ transport in O3-type cathodes. Full article

The scale features of rock art exhibit significant diversity and graduality. Among the existing semantic segmentation methods for rock art, although some models have taken note of the scale differences in rock art patterns and the complexity of directional features, and proposed targeted improvement strategies, most of these methods view scale adaptation and directional representation as unconnected problems. They fail to model the intrinsic correlation between the scale adaptation and directional representation, and particularly overlook the restrictive effect of scale accuracy on the extraction of directional features. This ultimately leads to the problem of “spatial representation misalignment” in the semantic segmentation of rock art. To address the above problems, this paper proposes a Dynamic Fine-tuning Rotation Network (DFTR-Net), which aims to solve the problems of imprecise scale feature extraction and directional misalignment for rock art patterns with arbitrary orientations. The network consists of a dynamic selective convolution structure and a shapeaware spatial feature extraction module. Specifically, the dynamic selective convolution dynamically adjusts the coverage range of the receptive field through inter-layer feature aggregation. It uses stacked small dilated convolution kernels to replace large convolution kernels with the same receptive field for extracting the neighborhood details of patterns. Then, by combining with feature aggregation, it constructs spatial feature differences and realizes intra-layer dynamic weighted fusion, thereby achieving accurate scale feature extraction. After obtaining fine-grained scale features, the shape-aware module first corrects the initial segmentation candidate regions of the patterns to generate directional guide boxes. Subsequently, it drives the rotational sampling of convolution kernels based on the angles of the guide boxes, forming region-constrained deformable convolutions that adapt to the shape of the patterns. These convolution kernels obtain strong supervision based on pixel-level annotations, which enhances the sensitivity to the directional features of the patterns and effectively alleviates the problem of directional misalignment. Extensive experiments show that DFTR-Net can achieve higher performance on the 3D-pitoti and Petroglyph Annotation datasets compared with the existing methods. Full article

Photocatalytic reduction of carbon dioxide (CO₂) into high-value multicarbon products, such as ethylene (C₂H₄), remains a significant challenge due to the difficult C-C coupling process. Potassium poly(heptazine imide) (K-PHI) is a promising photocatalyst, yet efficiently exchanging its interlayer cations to tune catalytic selectivity without causing structural degradation is difficult. Herein, an efficient and green supercritical CO₂ (SC CO₂) assisted ion-exchange strategy was developed to successfully prepare a series of mono-/di-/trivalent cation-doped M-PHI photocatalysts (M = H⁺, Na⁺, Sr⁺, Ca²⁺, Co²⁺, Fe³⁺). Systematic characterizations confirmed that the SC-CO₂ treatment successfully achieved in-depth cation substitution without destroying the intrinsic heptazine framework, effectively regulating the interlayer structure and significantly optimizing the photoelectrochemical charge separation. Among the prepared samples, H-PHI exhibited the optimal photocatalytic CO₂ reduction performance with an outstanding selectivity toward C₂H₄ generation. Under simulated sunlight irradiation for 3 h, the yields of CO, CH₄, and C₂H₄ C₂H₄ C₂H₄ reached 3564.87, 807.32, and 40.00 μmol·g⁻¹, respectively, significantly outperforming pristine K-PHI and other metal-doped samples. Crucially, isotope-tracing experiments utilizing a SC CO₂-DCl treatment detected deuterated CH₄ and C₂H₄ products, providing direct evidence that the hydrogen in the carbon products originates from the introduced protons, thereby elucidating the precise reaction pathway for C-C coupling. This study provides a green and efficient supercritical CO₂ ion exchange strategy for the cation engineering of crystalline carbon nitride, and also offers new ideas and methods for designing high-activity photocatalysts for photocatalytic CO₂ reduction. Full article

Ca²⁺-rich brines strongly destabilize bentonite-based drilling fluids by weakening hydration and increasing filter-cake permeability. In this work, raw sodium bentonite (Na-Bt) and a series of cation-exchanged bentonites (Li-, Mg-, Ca-, and K-Bt) were comparatively investigated to clarify how cation-dependent hydration characteristics and interlayer structure govern filtration behavior under saline conditions. XRD, zeta potential, TG–DTG, BET, and SEM were employed to correlate basal spacing, surface electrostatic properties, thermal/water-loss behavior, surface area and pore-structure characteristics, and filter-cake microstructure with API fluid loss. Among the examined 2 wt% brines, CaCl₂ produced the most severe deterioration and was therefore selected as the representative screening condition. Under 2 wt% CaCl₂, Li-Bt exhibited the lowest FL_API (141 mL), which was substantially lower than that of Na-Bt (265 mL), indicating the most favorable intrinsic resistance to Ca²⁺-dominated salinity. The cation-exchange analysis further showed that Li-Bt and Mg-Bt had relatively higher calculated exchange degrees than Ca-Bt and K-Bt under the present preparation conditions. Based on the 2 wt% CaCl₂ dataset, a descriptor-based relation between FL_API, hydrated ionic radius (r_h), and basal spacing (d₀₀₁) was established, and an Al-modified bentonite provided an out-of-sample verification with close agreement between predicted and measured filtration loss. Additional tests in 1–3 wt% CaCl₂ showed that although absolute fluid loss increased with brine severity, the relative ranking of the cation-exchanged bentonites remained broadly unchanged. TG–DTG, BET, and SEM results further provided complementary evidence for the structural and microstructural differences among the samples. Overall, the results demonstrate that hydration-related response, interlayer structure, and surface/pore characteristics jointly govern the filtration behavior of cation-exchanged bentonites, providing a useful basis for screening salt-tolerant clay materials for Ca²⁺-rich brines. Full article

Interlayer bond strength is critical for ensuring the safety and durability of 3D-printed concrete (3DPC) structures. However, there remains a lack of real-time prediction methods addressing interlayer performance under the combined effects of interval time and environmental factors during the in situ printing process. To address this issue, this study conducted experiments considering various printing interval times and environmental conditions, incorporating monitoring of dielectric constant and water evaporation, alongside interlayer splitting tensile tests. By integrating the SHAP interpretability algorithm with nonlinear regression analysis, the results indicate that the printing interval time is the dominant factor inducing interlayer strength decay (with a contribution rate of 68.6%), while relative humidity emerges as the primary environmental variable (with a contribution rate of 21.3%). Mechanism analysis reveals that prolonged printing intervals intensify the hydration of the lower deposited layer, leading to reduced interfacial moisture content and loss of plasticity. Furthermore, environmental evaporation significantly regulates this process, with high-humidity environments notably mitigating the moisture loss and strength reduction caused by time delays. Based on the correlation mechanism between moisture and strength, a dimensionless general prediction model for 3DPC interlayer strength was established, incorporating printing interval time and an evaporation index (goodness of fit, R² = 0.96). Consequently, a digital twin quality inversion scheme based on companion specimen monitoring and printing timestamps was proposed. This study quantifies the intrinsic relationships among printing interval time, environmental conditions, and interlayer strength, offering a novel approach for determining the construction window and achieving non-destructive quality prediction for 3DPC in complex environments. Full article

The Panoma Field in the Hugoton Embayment, Kansas, has produced significant gas resources from thousands of wells perforating the Permian Chase and Council Grove Groups. Variability in gas production from these formations is controlled by facies-influenced petrophysical properties. The use of geological facies data in numerical modeling is often limited to delineating regions of interest without intrinsic use in estimating petrophysical properties. Machine learning provides opportunities to integrate facies data into the numerical model-building process. In this study, we employ facies data in optimizing a numerical model permeability matrix scaling parameter using Monte Carlo Simulation of Markov Switching Dynamic Regression and machine learning. Realizations of the scaling parameter are included in a machine learning facies prediction workflow to identify the parameter that maximizes facies prediction accuracy, with test accuracy as high as 83%. A 3D numerical model was constructed to represent the interlayered carbonate, shale, and non-marine sandstones facies typical of the Council Grove intervals. Multiple field development and completion scenarios were evaluated to maximize cumulative gas recovery and assess the role of facies distribution on reservoir performance. History matching results of historical gas production demonstrate strong coupling between facies distribution and the optimized permeability, emphasizing the importance of facies data integration in reservoir property modeling and gas production estimation in Permian reservoirs. This implies that probabilistically constrained permeability scaling using the Monte Carlo and machine learning workflow produces more realistic modeling compared to traditional approaches. Full article

Carbon-fiber-reinforced polymer (CFRP) composites possess outstanding specific stiffness and strength but typically exhibit low intrinsic damping, which limits vibration attenuation in lightweight dynamic structures. Herein, a hybrid toughening strategy combining carboxyl-terminated butadiene nitrile rubber (CTBN) and hexagonal boron nitride (h-BN) is developed to enhance the damping of CFRP laminates while preserving cure feasibility and thermomechanical stability. An E51/DICY/accelerator epoxy system (100:6.5:1.2, mass ratio) is used as the baseline matrix. Differential scanning calorimetry shows that both CTBN and h-BN shift the cure peak temperature upward (Tp: 160.6 → 170.3 °C) and reduce the reaction enthalpy (ΔH: 386.5 → 255.1 J/g), indicating dilution/transport effects and altered cure kinetics. Dynamic mechanical analysis (DMA) reveals that CTBN exhibits an optimum damping enhancement at 25 phr (tan δ_max = 0.300), whereas h-BN provides a stronger monotonic increase up to 25 phr (tan δ_max = 0.437). Notably, the CTBN/h-BN hybrid (25/25 phr) delivers a high tan δ_max of 0.468 together with the broadest effective damping window (ΔT_half = 28.6 °C), exceeding 85% of the linear additivity criterion proposed herein. When the materials are transferred into CFRP laminates, free-vibration tests (using the logarithmic decrement method) demonstrate a clear structural damping improvement (ζ: 0.021 → 0.035; δ: 0.132 → 0.221; t₁/₂: 0.48 → 0.27 s). Overall, the results suggest that the damping enhancement arises from a combination of EPBN-mediated ductile energy dissipation and h-BN-related interfacial/interlayer frictional losses, which can be jointly tuned to balance processability, thermal response, and damping performance in CFRPs. Full article

To gain deeper insight into the protective mechanism of tungsten carbide/diamond-like carbon (WC/DLC) duplex coatings, this study employed high-velocity oxygen-fuel (HVOF) combined with linear ion source (LIS) technology to deposit the WC/DLC duplex coating on the Ti₆Al₄V substrate. Their tribocorrosion behaviors were thoroughly investigated. The results show that the dense, uniform, and chemically inert DLC top layer acts as an effective barrier, preventing the corrosive medium from penetrating into the underlying WC cermet layer through pores. Consequently, the duplex coating exhibits a lower I_corr of 3.54 × 10⁻⁸ A/cm², compared with that of the single WC coating (1.08 × 10⁻⁶ A/cm²), demonstrating significantly improved corrosion resistance. Moreover, the DLC coating offers excellent tribological performance owing to the high hardness and self-lubricating characteristics. After depositing the DLC top layer on the HVOF-sprayed WC cermet, the COF is reduced to ~0.08, and the wear rate reaches only 5.64 × 10⁻⁸ mm³/N·m, indicating notably enhanced tribocorrosion resistance. In short, in such HVOF-PVD/CVD duplex coating systems, the PVD/CVD functional layer can improve the tribocorrosion performance of the HVOF interlayer by leveraging its intrinsic advantages, such as high hardness, low friction, dense and uniform microstructure, and chemical inertness. Full article

Integrating diamond with GaN provides an effective pathway to mitigate self-heating. However, the thermal boundary resistance (TBR) remains a persistent bottleneck for further heat dissipation. While carbon (C) diffusion into the SiNx interlayer is known to reduce TBR, the associated stress evolution and its impact on device performance remain underexplored. In this work, the synergistic regulation of heat transport and electrical performance induced by C diffusion was systematically investigated. Transmission electron microscopy (TEM) was employed to characterize the interfacial microstructure and the influence of C diffusion on the interface. To further assess the resulting impact on heat dissipation, transient thermoreflectance was utilized to precisely quantify the thermal transport within the heterostructures. Classical molecular dynamics (MD) simulations were then performed to analyze the underlying physical mechanisms, revealing that intensifying C diffusion increases the phonon density of states overlap and effectively reduces the TBR. Furthermore, the intrinsic stress was quantified through geometric phase analysis (GPA) based on TEM images, demonstrating that the stress induced during the diffusion process propagates to the AlGaN/GaN heterostructure. Crucially, this stress modulation enhances the piezoelectric polarization by approximately 32%, resulting in a 5% increase in the two-dimensional electron gas (2DEG) sheet density. These findings provide a comprehensive strategy for optimizing the thermal management and mechanical reliability of high-power GaN devices. Full article

Fiber-reinforced polymer (FRP) composites are increasingly used in civil, marine, offshore, and energy infrastructure, where components routinely experience temperatures above ambient conditions. While the design of these components is largely driven by fiber-dominated characteristics, the deterioration of shear properties can lead to premature weakening and even failure. Thus, the performance and reliability of these systems depend intrinsically on the response of interlaminar shear characteristics, in-plane shear characteristics, and flexure-based shear characteristics to thermal loads ranging from uniform and monotonically increasing to cyclic and spike exposures. This paper presents a critical review of current knowledge of shear response in the presence of thermal exposure, with emphasis on temperature regimes that are below T_g in the vicinity of T_g and approaching T_d. Results show that thermal exposures cause matrix softening and microcracking, interphase degradation, and thermally induced residual stress redistribution that significantly reduces shear-based performance. Cyclic and short-duration spike/flash exposures result in accelerated damage through thermal fatigue; steep thermal gradients, including through the thickness; and localized interfacial failure loading to the onset of delamination or interlayer separation. Aspects such as layup/ply orientation, fiber volume fraction, degree of cure, and the availability and permeation of oxygen through the thickness can have significant effects. The review identifies key contradictions and ambiguities, pinpoints and prioritizes areas of critically needed research, and emphasizes the need for the development of true mechanistic models capable of predicting changes in shear performance characteristics over a range of thermal loading regimes. Full article

Hard carbon is widely recognized as a viable anode candidate for sodium-ion batteries (SIBs) owing to its electrochemical advantages, yet simultaneously enhancing specific capacity and rate capability, arising from insufficient plateau capacity, remains a long-standing challenge. Herein, we present a strategy for fabricating ZnCl₂-modified hard carbon (HCMZ-X) using waste macadamia shells and ZnCl₂ as a multifunctional structural modifier through a facile high-temperature carbonization. This approach effectively expands the graphite interlayer spacing to 0.394 nm, reduces microcrystalline size, and induces abundant closed pores, synergistically improving sodium-ion storage kinetics within the hard carbon framework. Mechanistic investigations confirm an “adsorption-intercalation-filling” storage mechanism. Hence, the optimized HCMZ-3 delivers a high reversible capacity of 382.05 mAh g⁻¹ at 0.05 A g⁻¹, with the plateau region contributing approximately 70%, significantly outperforming that of unmodified hard carbon (262.64 mAh g⁻¹). Remarkably, it achieves stable rate performance, delivering 190 mAh g⁻¹ at 1 A g⁻¹, along with excellent cycling stability, retaining over 90% after 500 cycles. By rational pore-structure modulation rather than excessive surface activation, this cost-effective method utilizing agricultural waste and ZnCl₂ dual-functional modification partially alleviates the intrinsic energy-density limitation of hard carbon anodes, advancing the development of high-performance, eco-friendly anodes for scalable energy storage systems. Full article