Railway Engineering Science (铁道工程科学)•2026•DOI: 10.1007/s40534-025-00379-3
Stick–slip vibration in disc brake systems at low speeds arises from the interaction of multiple factors, posing persistent challenges for high-speed train safety and passenger comfort. This study establishes three- and four-degree-of-freedom (DOF) dynamic models that incorporate wheel–rail adhesion and nonlinear friction, validated through line testing. System stability, stick–slip bifurcation characteristics, and key influencing factors are analyzed via numerical simulation. Results demonstrate that the four-DOF model, by accounting for normal motion, avoids the over-evaluation of system stability inherent in the three-DOF model. In the three-DOF model, tangential stiffness is the primary factor inducing chaotic stick–slip vibration. In the four-DOF model, tangential stiffness predominantly affects vibration amplitude, while normal stiffness governs the onset of chaos. Damping exhibits minimal influence on chaotic stick–slip occurrence. Optimal parameter ranges are identified: brake disc rotational inertia of 5–9 kg·m² and 11–22 kg·m², and friction pad mass of 7–17 kg, which effectively mitigate chaotic stick–slip vibration. These findings provide quantitative guidelines for brake system design, enhancing operational reliability and reducing wear-related failures in high-speed rail applications.
Railway Engineering Science (铁道工程科学)•2026•DOI: 10.1007/s40534-025-00388-2
The escalating traffic density and operational speeds of subway systems have intensified fatigue damage in turnout rails, particularly within the hazardous space of fixed frogs where wheel–rail dynamic interaction is exacerbated. This study addresses the rolling contact fatigue (RCF) crack initiation behavior of a No. 9 turnout fixed frog, a configuration widely deployed in subway networks. A three-dimensional explicit transient rolling contact finite element model was developed to simulate wheel–rail interaction under varying vehicle speeds and fastener vertical stiffness conditions. The analysis focused on crack initiation locations, angles, and fatigue life. Results demonstrate that the 30 mm top width cross-section of the nose rail is the most susceptible to fatigue cracking, with cracks initiating on the rail surface. The angle between the crack initiation surface and the lateral direction ranges from 70° to 95°, while the angle relative to the vertical direction remains difficult to predict. Higher vehicle speeds significantly reduce fatigue life, whereas fastener vertical stiffness exerts a minor influence. The calculated RCF crack initiation life is approximately 24,000 cycles across three stiffness conditions. Simulation outcomes align with field survey findings, validating the model's fidelity. The established methodology provides theoretical support for optimizing fixed frog structures and predicting fatigue life in subway turnouts.
Nano Research•2026•DOI: 10.26599/NR.2026.94908775
Flexible sensors have advanced rapidly to achieve skin-like multisensory capabilities, yet their performance is compromised by strain disturbances and multi-parameter interactions, impeding widespread deployment. Here, we report a flexible fibrous device with a patterned cellular structure enabling anti-strain interference, dual-parameter measurement, and static/dynamic detection. The patterned cellular fibrous structure achieves a heterogenous strain distribution that preserves sensing performance under 10% strain. The sensor integrates a piezoresistive component for low-frequency mechanical stimuli and a thermoelectric response to calibrate temperature-induced resistance changes. A hybrid piezoresistive/piezoelectric sensing platform was experimentally implemented for static pressure persistence and high-frequency acoustic excitation from 0 to 300 Hz. The hybrid tactile sensing achieved the highest material identification accuracy of 98.6%. This work provides valuable proposals to resolve practical constraints in flexible sensor applications, compelling advantages for broader wearable integration.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-025-01787-0
Neuromorphic devices have shown great potential in simulating the function of biological neurons due to their efficient parallel information processing and low energy consumption. MXene-Ti3C2Tx, an emerging two-dimensional material, stands out as an ideal candidate for fabricating neuromorphic devices. Its exceptional electrical performance and robust mechanical properties make it an ideal choice for this purpose. This review aims to uncover the advantages and properties of MXene-Ti3C2Tx in neuromorphic devices and to promote its further development. Firstly, we categorize several core physical mechanisms present in MXene-Ti3C2Tx neuromorphic devices and summarize in detail the reasons for their formation. Then, this work systematically summarizes and classifies advanced techniques for the three main optimization pathways of MXene-Ti3C2Tx, such as doping engineering, interface engineering, and structural engineering. Significantly, this work highlights innovative applications of MXene-Ti3C2Tx neuromorphic devices in cutting-edge computing paradigms, particularly near-sensor computing and in-sensor computing. Finally, this review carefully compiles a table that integrates almost all research results involving MXene-Ti3C2Tx neuromorphic devices and discusses the challenges, development prospects, and feasibility of MXene-Ti3C2Tx-based neuromorphic devices in practical applications, aiming to lay a solid theoretical foundation and provide technical support for further exploration and application of MXene-Ti3C2Tx in the field of neuromorphic devices.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-025-01790-5
Low ionic conductivity is a major obstacle for polymer solid-state electrolytes. In response to this issue, a design concept of enhanced regional electric potential difference (EREPD) is proposed to modulate the interaction of nanofillers with other components in the composite polymer solid-state electrolytes (CPSEs). While ensuring the periodic structure of the graphdiyne (GDY) backbone, methoxy-substituted GDY (OGDY) is prepared by an asymmetric substitution strategy, which increases the electric potential differences within each repeating unit of GDY. The staggered distributed electron-rich regions and electron-deficient regions on the two-dimensional plane of OGDY increase the free Li+ concentration through Lewis acid–base pair interaction. The adjacent ERRs and EDRs form uniformly distributed EREPDs, creating a continuous potential gradient that synergistically facilitates the efficient migration of Li+. Impressively, the OGDY/poly(ethylene oxide) (PEO) exhibits a high ionic conductivity (1.1 × 10−3 S cm−1) and ion mobility number (0.71). In addition, the accelerated Li+ migration promotes the formation of uniform and dense SEI layers and inhibits the growth of lithium dendrites. As a proof of concept, Li||Li symmetric cell and Li||LiFePO4 full cell and pouch cell assembled with OGDY/PEO exhibit good performance, highlighting the effectiveness of our EREPD design strategy for improving CPSEs performance.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-025-01771-8
Daytime radiative cooling is an eco-friendly and passive cooling technology that operates without external energy input. Materials designed for this purpose are engineered to possess high reflectivity in the solar spectrum and high emissivity within the atmospheric transmission window. Unlike broadband-emissive daytime radiative cooling materials, spectrally selective daytime radiative cooling (SSDRC) materials exhibit predominant mid-infrared emission in the atmospheric transmission window. This selective mid-infrared emission suppresses thermal radiation absorption beyond the atmospheric transmission window range, thereby improving the net cooling power of daytime radiative cooling. This review elucidates the fundamental characteristics of SSDRC materials, including their molecular structures, micro- and nanostructures, optical properties, and thermodynamic principles. It also provides a comprehensive overview of the design and fabrication of SSDRC materials in three typical forms, i.e., fibrous materials, membranes, and particle coatings, highlighting their respective cooling mechanisms and performance. Furthermore, the practical applications of SSDRC in personal thermal management, outdoor building cooling, and energy harvesting are summarized. Finally, the challenges and prospects are discussed to guide researchers in advancing SSDRC materials.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-024-01600-4
Reversible solid oxide cells (RSOCs) are capable of converting various energy resources, between electricity and chemical fuels, with high efficiency and flexibility, making them suitable for grid balancing and renewable energy consumption. However, the practical application of RSOCs is still limited by the insufficient activity and stability of the electrodes in different operating modes. Herein, a highly efficient symmetrical electrode composed of La0.3Sr0.6Ti0.1Co0.2Fe0.7O3−δ (LSTCF) nanofibers and in situ exsolved Co3Fe7 nanoparticles is developed for boosting the performance of RSOCs. The reversible phase transition, high activity and stability of the electrode have been confirmed by a combination of experimental (e.g., transmission electron microscopy and X-ray absorption fine structure) and computational studies. Electrolyte-supported RSOCs with the symmetrical electrode demonstrate excellent catalytic activity and stability, achieving a high peak power density of 0.98 W cm−2 in the fuel cell mode using H2 as the fuel (or 0.53 W cm−2 using CH4 as the fuel) and a high current density of 1.09 A cm−2 at 1.4 V in the CO2 electrolysis mode (or 1.03 A cm−2 at 1.3 V for H2O electrolysis) at 800 °C while maintaining excellent durability for over 100 h.
New Carbon Materials (新型炭材料)•2025•DOI: 10.1016/S1872-5805(NCM2024-39-05-07)
There is an urgent need for lithium-ion capacitors (LICs) that have both high energy and high power densities to meet the continuously growing energy storage demands. LICs effectively balance the high energy density of traditional rechargeable batteries with the superior power density and long life of supercapacitors (SCs). Nevertheless, the development of LICs is still hampered by limited kinetic processes and capacity mismatch between the cathode and anode. Metal-organic frameworks (MOFs) and their derivatives have received significant attention because of their extensive specific surface area, different pore structures and topologies, and customizable functional sites, making them compelling candidate materials for achieving high-performance LICs. MOF-derived carbons, known for their exceptional electronic conductivity and large surface area, provide improved charge storage and rapid ion transport. MOF-derived transition metal oxides contribute to high specific capacities and improved electrochemical stability. Additionally, MOF-derived metal compounds/carbons provide combined effects that increase both the capacitive and Faradaic reactions, leading to a superior overall performance. The review begins with an overview of the fundamental principles of LICs, followed by an exploration of synthesis strategies and ligand selection for MOF-based composite materials. It then analyzes the advantages of original MOFs and their derived materials, such as carbon materials and metal compounds, in enhancing LIC performance. Finally, the review discusses the major challenges faced by MOFs and their derivatives in LIC applications and offers future research directions and recommendations.
New Carbon Materials (新型炭材料)•2025•DOI: 10.1016/S1872-5805(NCM2024-39-04-10)
Polyether ether ketone (PEEK) has good mechanical properties. However, its high viscosity when molten limits its use because it is hard to process. PEEK nanocomposites containing both carbon nanotubes (CNTs) and polyether imide (PEI) were prepared by a direct wet powder blending method using a vertical injection molding machine. The addition of an optimum amount of PEI lowered the viscosity of the molten PEEK by approximately 50% while producing an increase in the toughness of the nanocomposites, whose strain to failure increased by 129%, and fracture energy increased by 97%. The uniformly dispersed CNT/PEI powder reduced the processing difficulty of PEEK nanocomposites without affecting the thermal resistance. This improvement of the strength and viscosity of PEEK facilitate its use in the preparation of thermoplastic composites.
Transactions of Nonferrous Metals Society of China (中国有色金属学报)•2025•DOI: 10.1016/S1003-6326(25)67022-1
Based on the application requirements for porous dental implants, four porous structures of gyroid, RD (rhombic dodecahedron), cubic, and CHC (three identical cylinders hollow cubic) for porous titanium implants have been designed and fabricated using selective laser melting (SLM) technology. Typically, the unit cell dimensions range from 0.5 to 1.6 mm, with pore diameters between 300 and 900 µm, achieving porosities of 60%−80%. The influence of porous structures with small unit cell on scaffold formability and mechanical properties was investigated through compression, torsion tests as well as finite element simulations. Consequently, gyroid scaffolds exhibit optimal formability with the lowest porosity and pore deviation. With the same porosity, gyroid and RD scaffolds exhibit lower compressive strength than cubic and CHC scaffolds, yet their torsional properties show an inverse relationship. Moreover, gyroid scaffolds possess the highest torque but the lowest compressive strength and elastic modulus. The gyroid scaffold with 60% porosity shows a modulus of 3.96 GPa, matching bone modulus of 0−30 GPa. Its compressive strength reaches 176.3 MPa, exceeding that of bone by 100 MPa. Additionally, the torque for the d4.0 mm implant is 2.22 N·m, approaching the FDA safe torque of 2.3 N·m. Therefore, the gyroid represents the most ideal structure for porous dental implants.
Int. Journal of Mining Science and Technology (采矿与安全工程)•2025•DOI: 10.1016/j.ijmst.2025.08.010
The spatiotemporal characterization of plume sedimentation and microorganisms is critical for developing plume ecological monitoring models. To address the limitations of traditional methods in obtaining high-quality sediment, a novel sampling system with 6000 m operational capability and three-month endurance was developed. It is equipped with three sediment samplers and a set of formaldehyde preservation solution injection devices. The system is controlled by a low-power, timing-triggered controller. To investigate low-disturbance rheological mechanisms, gap-controlled rheological tests were conducted to optimize the structural design of the sampling and sealing assembly. Stress-controlled shear rheological tests were employed to investigate the mechanisms governing yield stress in sediments under varying temperature conditions and boundary roughness. Additionally, the coupled Eulerian-Lagrangian (CEL) method and sediment rheological constitutive models were employed to simulate tube-soil interaction dynamics and sediment disturbance. The radial heterogeneity of sediment disturbance and friction variation of the sampling tube were revealed. The tube was completely "plugged" at a penetration depth of 261 mm, providing critical data support for penetration depth parameters. The deep-sea pressure test and South China Sea field trials demonstrated the system's capability to collect and preserve quantitative time-series sediment samples with high fidelity.
China Foundry•2025•DOI: 10.1007/s41230-025-4207-x
The GH3536 (Hastelloy-X) nickel-based superalloy is increasingly applied in the aerospace industry due to its exceptional combination of excellent oxidation resistance and high-temperature strength. Laser powder bed fusion (LPBF) is an additive manufacturing (AM) technology for producing metallic components with complex shapes using layer-by-layer manufacture principle. The debate has long prevailed as to research on eliminating anisotropy in the forming of GH3536 alloy through LPBF technology. In this study, the anisotropy of microstructure and mechanical properties of GH3536 alloy formed by LPBF was investigated using different scanning strategies (0°, 90°, 67°, checkerboard, and contour). The scanning strategy was optimized to reduce the weaving differences between the horizontal and vertical directions of the microstructure of the LPBF formed GH3536 alloy, which in turn reduces the anisotropy of the properties in both directions. The results of the tensile specimens indicate that except for the horizontal specimens produced using the contour scanning strategy, the strength of all other specimens exceeds that of the vertical specimens. Additionally, differences in elongation are observed, demonstrating that the GH3536 alloy fabricated via laser powder bed fusion exhibits anisotropic properties. According to electron backscatter diffraction (EBSD) analysis, the grain boundary strengthening and geometrically necessary dislocations (GNDs) impede dislocation motion during tensile deformation along the horizontal direction. Consequently, this mechanism negatively affects both the tensile strength and ductility in that orientation. The anisotropy in tensile strength and plasticity is attributed to the different crack sensitivities in the two tensile directions. In addition, specimens molded using different scanning strategies exhibit varying degrees of anisotropy, strength, and elongation due to different degrees of texture strengthening, grain boundary strengthening, and dislocation strengthening effects. Regardless of the stretching direction, the combined tensile properties of the 0° and contoured specimens are the worst under the room temperature and 815 °C stretching conditions. The 67° specimens exhibit the best combined tensile properties. Therefore, the anisotropy of the mechanical properties of the LPBF formed GH3536 alloy can be positively mitigated by modulating the scanning strategy.
Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报)•2025•DOI: 10.1007/s12613-024-3058-6
In-situ TiB2/Al–Cu composite was processed by multidirectional forging (MDF) for six passes. The microstructure evolution of the forged workpiece was examined across various regions. The mechanical properties of the as-cast and MDFed composites were compared, and their strengthening mechanisms were analyzed. Results indicate that the grain refinement achieved through the MDF process is mainly due to the subdivision of the original grains through mechanical geometric fragmentation and the occurrence of dynamic recrystallization (DRX). DRX grains are formed through discontinuous DRX, continuous DRX, and recrystallization induced by particle-stimulated nucleation. A rise in accumulated equivalent strain results in finer α-Al grains and a more uniform distribution of TiB2 particles, which enhance the Vickers hardness of the composite. In addition, the tensile properties of the MDFed composite significantly improve compared with those of the as-cast composites, with ultimate tensile strength and yield strength increasing by 51.2% and 54%, respectively. This enhancement is primarily due to grain refinement strengthening and dislocation strengthening achieved by the MDF process.
Chinese Journal of Mechanical Engineering•2025•DOI: 10.1186/s10033-025-01352-1
The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains. This study focused on the fluid-solid coupling effect of airflow and HST, and proposed a co-simulation (CS) approach between computational fluid dynamics and multi-body dynamics. Firstly, the aerodynamic model was developed by employing overset mesh technology and the finite volume method, and the detailed train-track coupled dynamic model was established. Then the User Data Protocol was adopted to build data communication channels. Moreover, the proposed CS method was validated by comparison with a reported field test result. Finally, a case study of the HST exiting a tunnel subjected to crosswind was conducted to compare differences between CS and offline simulation (OS) methods. In terms of the presented case, the changing trends of aerodynamic forces and car-body displacements calculated by the two methods were similar. Differences mainly lie in aerodynamic moments and transient wheel-rail impacts. Maximum pitching and yawing moments on the head vehicle in the two methods differ by 21.1 kN∙m and 29.6 kN∙m, respectively. And wheel-rail impacts caused by sudden changes in aerodynamic loads are significantly severer in CS. Wheel-rail safety indices obtained by CS are slightly greater than those by OS. This research proposes a CS method for aerodynamic characteristics and dynamic performance of the HST in complex scenarios, which has superiority in computational efficiency and stability.
Journal of Central South University•2025•DOI: 10.1007/s11771-025-6049-5
The influence of train height on aerodynamic characteristics of high-speed train (HST) is significant in crosswind environments. This study employed the improved delayed detached eddy simulation (IDDES) turbulence model to analyze the aerodynamic characteristics of trains with three different heights under a crosswind of 20 m/s. The numerical model was validated through comparison with wind tunnel experimental data. A comprehensive analysis was conducted on the characteristics of the flow field around trains, surface pressure distribution, and aerodynamic loads for trains with different heights. Results indicate that the side force coefficient increased by up to 61.54% with an increase in train height from 3.89 to 4.19 m. Compared with the 3.89 m case, the roll moment coefficient on the head, middle, and tail cars for 4.19 m cases increased by 18.11%, 24.78% and 34.23%, respectively. The increase in train height widens the impact width of the leading car’s front vortex on the leeward side and intensifies the helical shedding and coupling interactions of two vortices in the wake, leading to an increase in the intensity and extent of wake flow in both vertical and longitudinal directions. Additionally, the increase in height shifted the flow separation point on the leeward side, moving vortices farther from the train, expanding the back-flow region, and intensifying Reynolds stress and turbulent fluctuations on the leeward side, which adversely impacted train stability and safety. The research findings can provide a reference for the design of train configurations and the assessment of dynamic performance in crosswind environments.
Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报)•2025•DOI: 10.1007/s12613-024-2993-6
Hypoeutectoid steel, a crucial metal structural material, is characterized by the coexisting microstructure of ferrite and pearlite. Driven by multiphase competition and multicomponent characteristics, the intricate interplay among its composition, processing conditions, and microstructure substantially complicates the understanding of austenite decomposition kinetics and elemental diffusion mechanisms during phase transformations. The present study explores the effects of cooling rate, prior austenite grain size, and C content on the component distribution and microstructure evolution during the austenite decomposition of hypoeutectoid steels to address the aforementioned complexities. Results of a multiphase field model reveal that an increase in the cooling rate from 1.0 to 7.0°C/s leads to a reduction in the ferrite proportion and fine pearlite lamellae spacing from 52vol% to 22vol% at 400°C and from 1.01 to 0.67 μm at 660°C, respectively. Concurrently, a decreased prior austenite grain size from 25.23 to 8.92 μm enhances the phase transformation driving force, resulting in small average grain sizes of pearlite clusters and proeutectoid ferrite. Moreover, increasing the C content from 0.22wt% to 0.37wt% decreases the phase transition temperature from 795 to 750°C and enhances the proportion of pearlite phases from 27vol% to 61vol% at 500°C, concurrently refining the spacing of pearlite layers from 1.25 to 0.87 μm at 600°C. Overall, this work aims to elucidate the complex dynamics governing the microstructural transformations of hypoeutectoid steels, thereby facilitating their wide application across different industrial scenes.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-024-01613-z
Organic additives with multiple functional groups have shown great promise in improving the performance and stability of perovskite solar cells. The functional groups can passivate undercoordinated ions to reduce nonradiative recombination losses. However, how these groups synergistically affect the enhancement beyond passivation is still unclear. Specifically, isomeric molecules with different substitution patterns or molecular shapes remain elusive in designing new organic additives. Here, we report two isomeric carbazolyl bisphosphonate additives, 2,7-CzBP and 3,6-CzBP. The isomerism effect on passivation and charge transport process was studied. The two molecules have similar passivation effects through multiple interactions, e.g., P=O···Pb, P=O···H–N and N–H···I. 2,7-CzBP can further bridge the perovskite crystallites to facilitates charge transport. Power conversion efficiencies (PCEs) of 25.88% and 21.04% were achieved for 0.09 cm2 devices and 14 cm2 modules after 2,7-CzBP treatment, respectively. The devices exhibited enhanced operational stability maintaining 95% of initial PCE after 1000 h of continuous maximum power point tracking. This study of isomerism effect hints at the importance of tuning substitution positions and molecular shapes for organic additives, which paves the way for innovation of next-generation multifunctional aromatic additives.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-024-01564-5
Formamidinium lead bromide (FAPbBr3) perovskite nanocrystals (NCs) are promising for display and lighting due to their ultra-pure green emission. However, the thermal quenching will exacerbate their performance degradation in practical applications, which is a common issue for halide perovskites. Here, we reported the heat-resistant FAPbBr3 NCs prepared by a ligand-engineered room-temperature synthesis strategy. An aromatic amine, specifically β-phenylethylamine (PEA) or 3-fluorophenylethylamine (3-F-PEA), was incorporated as the short-chain ligand to expedite the crystallization rate and control the size distribution of FAPbBr3 NCs. Employing this ligand engineering approach, we synthesized high quality FAPbBr3 NCs with uniform grain size and reduced long-chain alkyl ligands, resulting in substantially suppressed thermal quenching and enhanced carrier transportation in the perovskite NCs films. Most notably, more than 90% of the room temperature PL intensity in the 3-F-PEA modified FAPbBr3 NCs film was preserved at 380 K. Consequently, we fabricated ultra-pure green EL devices with a room temperature external quantum efficiency (EQE) as high as 21.9% at the luminance of above 1,000 cd m−2, and demonstrated less than 10% loss in EQE at 343 K. This study introduces a novel room temperature method to synthesize efficient FAPbBr3 NCs with exceptional thermal stability, paving the way for advanced optoelectronic device applications.