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.
Journal of Semiconductors (半导体学报 - 中国科学院半导体研究所)•2026•DOI: 10.1088/1674-4926/26020013
Polarization is a defining lever of wurtzite (WZ) III-nitrides, enabling two-dimensional electron and hole gases, polarization doping, and electrostatic control in GaN-based power, RF, and optoelectronic devices. Recent advances, especially ferroelectric nitrides, have pushed polarization to unprecedented magnitudes, elevating it from a static constant to an engineering knob. However, the field has long suffered from ambiguity in polarization magnitude, orientation, and mapping to crystal polarity due to inconsistent sign conventions and reference choices. This mini-review highlights recent progress that rethinks and unifies polarization in wurtzite III-nitrides. It discusses how experimental re-benchmarking of giant polarization is reshaping understanding and enabling predictive polarization engineering. Key issues include the dependence of polarization sign on coordinate choice and magnitude on reference structure, as exemplified by Bernardini et al.'s 1997 predictions (values below 0.1 C/m², downward orientation for metal-polar) and Dreyer et al.'s 2016 refinements. The review emphasizes that consistent benchmarking under a unified convention makes interface bound charge density a quantitative design knob rather than an adjustable fitting parameter, benefiting classical HEMTs, N-polar stacks, polarization-doped structures, and ferroelectric nitride integration. A pragmatic roadmap is proposed: reports should state polarity, sign convention, and reference explicitly to ensure portability and falsifiability.
International Journal of Mining Science and Technology•2026•DOI: 10.1016/j.ijmst.2025.10.009
Investigations into the long-term creep behavior of Beishan granite in uniaxial compression were conducted. Four levels of axial stress (60, 70, 87, and 95 MPa) were applied to rock specimens. Contrasting with earlier research, the long-term creep data in this work present a substantial advancement in the time dimension. Except for the sample subjected to 60 MPa axial loading, which did not fail after a loading duration of 1650 d, the specimens under the other three stresses all failed after sustained constant loading durations of 1204, 1023, and 839 d, respectively. A lower envelope of driving stress-ratio for crystalline rocks was obtained, tending towards approximately 0.45 over an infinite time scale. According to the experimental results, as axial stress increases, both the axial strain accumulated in the transient creep process and the strain rate associated with steady-state creep deformation increase exponentially; however, the share of steady-state creep strain remains nearly constant at about 82.53 %. A novel damage-based creep model was put forward. It provides an enhanced depiction of the comprehensive creep process in rocks, notably improving the accuracy in forecasting the accelerated creep phase, which significantly impacts the long-term stability of engineering structures.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-025-01760-x
Fluoropolymers promise all-solid-state lithium metal batteries (ASLMBs) but suffer from two critical challenges. The first is the trade-off between ionic conductivity (σ) and lithium anode reactions, closely related to high-content residual solvents. The second, usually consciously overlooked, is the fluoropolymer's inherent instability against alkaline lithium anodes. Here, we propose indium-based metal–organic frameworks (In-MOFs) as a multifunctional promoter to simultaneously address these two challenges, using poly(vinylidene fluoride–hexafluoropropylene) (PVH) as the typical fluoropolymer. In-MOF plays a trio: (1) adsorbing and converting free residual solvents into bonded states to prevent their side reactions with lithium anodes while retaining their advantages on Li+ transport; (2) forming inorganic-rich solid electrolyte interphase layers to prevent PVH from reacting with lithium anodes and promote uniform lithium deposition without dendrite growth; (3) reducing PVH crystallinity and promoting Li-salt dissociation. Therefore, the resulting PVH/In-MOF (PVH-IM) showcases excellent electrochemical stability against lithium anodes, delivering a 5550 h cycling at 0.2 mA cm−2 with a remarkable cumulative lithium deposition capacity of 1110 mAh cm−2. It also exhibits an ultrahigh σ of 1.23 × 10−3 S cm−1 at 25 °C. Moreover, all-solid-state LiFePO4|PVH-IM|Li full cells show outstanding rate capability and cyclability (80.0% capacity retention after 280 cycles at 0.5C), demonstrating high potential for practical ASLMBs.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-025-01691-7
Composite solid electrolytes (CSEs) are promising for solid-state Li metal batteries but suffer from inferior room-temperature ionic conductivity due to sluggish ion transport and high cost due to expensive active ceramic fillers. Here, a host–guest inversion engineering strategy is proposed to develop superionic CSEs using cost-effective SiO2 nanoparticles as passive ceramic hosts and poly(vinylidene fluoride-hexafluoropropylene) (PVH) microspheres as polymer guests, forming an unprecedented “polymer guest-in-ceramic host” (i.e., PVH-in-SiO2) architecture differing from the traditional “ceramic guest-in-polymer host”. The PVH-in-SiO2 exhibits excellent Li-salt dissociation, achieving high-concentration free Li+. Owing to the low diffusion energy barriers and high diffusion coefficient, the free Li+ is thermodynamically and kinetically favorable to migrate to and transport at the SiO2/PVH interfaces. Consequently, the PVH-in-SiO2 delivers an exceptional ionic conductivity of 1.32 × 10−3 S cm−1 at 25 °C (vs. typically 10−5–10−4 S cm−1 using high-cost active ceramics), achieved under an ultralow residual solvent content of 2.9 wt% (vs. 8–15 wt% in other CSEs). Additionally, PVH-in-SiO2 is electrochemically stable with Li anode and various cathodes. Therefore, the PVH-in-SiO2 demonstrates excellent high-rate cyclability in LiFePO4|Li full cells (92.9% capacity-retention at 3C after 300 cycles under 25 °C) and outstanding stability with high-mass-loading LiFePO4 (9.2 mg cm−1) and high-voltage NCM622 (147.1 mAh g−1). Furthermore, we verify the versatility of the host–guest inversion engineering strategy by fabricating Na-ion and K-ion-based PVH-in-SiO2 CSEs with similarly excellent promotions in ionic conductivity. Our strategy offers a simple, low-cost approach to fabricating superionic CSEs for large-scale application of solid-state Li metal batteries and beyond.
Transactions of Nonferrous Metals Society of China (中国有色金属学报)•2025•DOI: 10.1016/S1003-6326(25)67012-9
The electrochemical separation of Mn(II) impurity from molten NaCl−KCl−MgCl2 was systematically investigated to facilitate the electrolytic production of high-purity magnesium. The reduction of Mn(II) to Mn metal on tungsten electrode was a quasi-reversible process controlled by diffusion. The apparent standard potential and exchange current density of Mn(II)/Mn(0) electrode reaction were determined at temperatures ranging from 973 to 1048 K. Solid Mn metal generated during electrolysis aggregated into irregular clumps and adsorbed some needle-like MgO, imposing a detrimental effect on both the aggregation and the purity of magnesium metal. After electrolysis at −1.5 V in molten NaCl−KCl−MgCl2−0.62wt.%MnCl2 for 8 h, the concentration of MnCl2 impurity decreased to 0.037 wt.%, achieving a removal efficiency of 94.14%. When direct electrolysis was performed in molten NaCl−KCl−MgCl2−0.62wt.%MnCl2, the obtained magnesium metal was small blocks with a caviar-like appearance, and the purity was just 98.59%. In contrast, a large globule of magnesium metal was obtained when electrolysis was performed in the purified electrolyte, and its purity was improved to 99.94%. The controlled-potential electrolysis proposed in this work has been verified to be a green and practically effective method to separate the metal ion impurities from molten electrolyte for high purity magnesium extraction.
Journal of Central South University•2025•DOI: 10.1007/s11771-025-6114-0
The AlMgScZr high-strength aluminum alloy fabricated by selective laser melting (SLM) technology exhibits a “bimodal microstructure”, resulting in significant non-uniform deformation during thermal deformation. This study investigates the flow behavior of SLM-processed AlMgScZr aluminum alloy utilizing the Gleeble-1500D thermal simulation machine. The true stress−strain curves were amended based on the friction theory. Through determining the Zener-Hollomon parameters, the correlation between flow stress, deformation temperature, and strain rate during the high-temperature thermoplastic deformation of SLM-processed AlMgScZr aluminum alloy with a “bimodal microstructure” was established. In addition, the microstructural evolution during thermal deformation was analyzed. The results indicated that the predicted flow stress values obtained from the Arrhenius constitutive equation with coupled correction of thermal deformation parameters closely matched the experimental values. The correlation coefficient and the average absolute relative error of the corrected model were 0.999 and 2.766%, respectively, accurately predicting the thermoplastic deformation behavior of SLM-processed high-strength aluminum alloy with a “bimodal microstructure”. Furthermore, hot processing maps at different strains were established, identifying stable and unstable regions under different deformation conditions. Microstructural observations revealed different thermal deformation mechanisms under various deformation temperatures. Specifically, dynamic recrystallization characteristics dominated the microstructure at lower temperatures (300−360 ℃), while dynamic recovery was dominant at higher temperatures (390−500 ℃).
Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报)•2025•DOI: 10.1007/s12613-025-3098-6
Along with the surging demand for energy storage devices, the cost and availability of the materials remain dominant factors in slowing down their industrial application. The repurposing of waste asphalt into high-performance electrode materials is of significant interest, as it holds the potential to circumvent energy and environmental issues. Here, we report the controllable synthesis of asphalt-derived mesoporous carbon as an active material for electrocatalytic hydrogen gas capacitor (EHGC). The hierarchically porous carbon (HPC) with a high surface area of 1943.4 m2·g−1 can operate in pH universal aqueous electrolytes in EHGC. It displays a specific energy and power density of 57 Wh·kg−1 and 554 W·kg−1 in neutral electrolyte as well as 52 Wh·kg−1 and 657 W·kg−1 in acidic electrolyte. Additionally, the charge storage mechanism of HPC–EHGC is studied with the help of Raman spectroscopy and X-ray photoelectron spectroscopy. Furthermore, the assembled HPC–EHGC device displays a discharge capacitance of 170 F·g−1 with an excellent capacitance retention rate of 100% up to 20000 cycles at 10 A·g−1 in acidic electrolyte. This work introduces a novel approach to converting waste asphalt into high-performance carbon for EHGC, achieving superior performance over commercial materials. By simultaneously addressing environmental waste issues and advancing energy storage technology, this study makes a significant contribution to sustainable materials science and next-generation battery development.