To mitigate thermal damage to diamond induced by Ni-Cr filler alloy and enhance interfacial bonding strength, the Ni-Cr filler alloys with different Nb2O5 additions (0, 0.5, 1, 1.5, 2 and 2.5 wt%) were developed, and the high-temperature brazing between diamond and 45 steel was performed under an argon atmosphere. The effects and underlying mechanisms of Nb2O5 addition on the mechanical properties of the Ni-Cr brazed layer, diamond surface morphology, interfacial bonding, and grinding performance were systematically investigated. The results demonstrate that optimized addition of Nb2O5 markedly enhances the mechanical properties and interfacial bonding of diamond brazed with Ni-Cr filler alloy, with the best overall performance achieved at 1.5 wt% Nb2O5. Compared with the pure Ni-Cr filler alloy, the Ni-Cr + 1.5 wt% Nb2O5 brazed layer exhibits an increase in hardness of approximately 35.3%, along with reductions of 47% in scratch height and 0.29% in wear volume. Meanwhile, the brazed diamond specimens show a uniform morphology, good wettability, crack-free interfaces, and suppressed graphitization. After grinding, the wear behavior is dominated by micro-cutting and micro-fracturing, with significantly reduced spalling and fracture wear.

This study systematically investigates the microstructure, diamond thermal damage and grinding performance of brazed diamond with pure Ni-Cr, Nb-added, and Nb2O5-added Ni-Cr filler alloy, combining high-temperature brazing experiments with the first-principles calculations. The experimental results showed that compared to pure Ni-Cr filler alloy, both Nb and Nb2O5 addition improve the overall performance of brazed diamond, with Nb2O5 showing a more significant modification effect. The Nb2O5-added Ni-Cr filler alloy induces the formation of NbNi and B2O3 in the brazing layer, which effectively inhibit diamond graphitization by mitigating the catalytic effect of Ni at the interface and reducing the formation of hard and brittle phases (e.g., Ni3B, CrB, etc.). This helps to prevent crack initiation at the diamond-brazed filler alloy interface. Furthermore, Nb2O5 enhances chemical reactions between Cr and C at the brazed diamond interface, resulting in the formation of structurally refined Cr-C carbides at the interface, which strengthen the interface bonding. First-principles calculations reveal that the interfacial work of separation for the Nb2O5-added Ni-Cr filler alloy system increases by 2.04 J/ m2 and 0.28 J/m2, compared to the pure Ni-Cr and Nb-added Ni-Cr filler alloy systems, respectively. The coexistence of Nb and O enhances electron cloud overlap between Cr and C atoms at the interface and reduces the peak at the of Fermi level for C layer, indicating the stronger interfacial bonding and the lower graphitization of diamond.

A novel width expansion extrusion method produced high-strength, ductile AZ42 Mg alloy sheets (2#). Compared to conventional extrusion (1#), 2# showed finer grains, enhanced strength-ductility synergy in extrusion (ED) and transverse (TD) directions, reduced anisotropy, and improved 45 degrees direction properties, of-fering a new strategy for the adjustment of mechanical anisotropy.

Due to the high brazing temperature and catalytic action of catalyst element Ni, the brazed diamond with Ni–Cr filler alloy is prone to severe thermal damage, thereby resulting in premature interface failure between diamond and filler alloy. In this work, the interface bonding behavior and mechanism, as well as joint performance of brazed diamond with Ni–Cr filler doped with Cu, are systematically investigated through multiscale simulations and experiments. The results show that the mixing of Cu effectively adjusts the ductility of brazing layer and refines the carbides on diamond surface, thereby reducing the residual stress and thermal damage of diamond. Additionally, the mixing of Cu also facilitates a sufficient reaction between Cr and C at the interface, thus improving the interface bonding strength between Ni–Cr filler and diamond. Notably, the machining performance of brazed diamond samples with Ni–Cr filler doped with 10 wt% Cu–Sn–P alloy is significantly enhanced at the low brazing temperature of 1010 °C. The results provide a novel insight to clarify the interface action mechanism and realize the low‐temperature brazing of diamond through the composition optimization of Ni–Cr filler based on multiscale feature fusion.

Fuel rods can enhance the heat exchange capacity of small reactors. In this paper, four new arrangements are designed to enhance heat transfer by changing the spiral direction of the ribs around petal-shaped fuel rods. Based on numerical simulations, the flow and heat transfer characteristics of petal-shaped fuel assemblies under different arrangements are compared, and the mechanism of the heat transfer enhanced by the configuration with the strongest comprehensive heat transfer performance is deduced. The study finds that the pressure drops of the four new arrangements are almost the same as those of the original arrangement. Based on the comprehensive performance evaluation index, it is determined that the fuel rod spacer arrangement with clockwise and counterclockwise twist in the diagonal direction has the best performance among the four arrangements. A further comparison of the heat transfer performance within each sub-channel of this staggered arrangement and the original arrangement reveals that the heat transfer coefficients within the four types of sub-channels are significantly enhanced. This is because the fuel rod spacer arrangement with clockwise and counterclockwise twist in the diagonal direction can significantly enhance the coolant flow on the leeward side of fuel rods, thereby reducing the thickness of velocity boundary layer and thermal boundary layer, strengthening the mixing of hot and cold fluids, and thus greatly improving the convective heat transfer performance in the leeward area. The relevant research results have laid a theoretical foundation for the arrangement scheme of the petal-shaped fuel rods within the reactor.

Graphene and its derivatives are widely recognized as effective reinforcements due to their unique mechanical, thermal and lubrication performance. Incorporation of these reinforcements into polyamide-imide (PAI) coating matrix has shown significant potential for improving the tribological performance. Here, the mechanisms underlying the tribological improvement enabled by graphene oxide (GO) are investigated via frictional experiments and molecular dynamics simulations. It was found that the coefficient of friction (COF) of PAI coating is reduced upon the addition of GO over the range of 100–400 MPa and 20–100 mm/s, with a maximum reduction of ~25% achieved at 200 MPa and 60 mm/s. Simulations reveal that the friction reduction arises from strong adhesion interactions between the embedded GO sheets and PAI molecular chains, which inhibit the shear-induced mobility of the chains during the friction process. This mechanism enables a further reduction in the COF of the GO/PAI composite coating by increasing the interfacial adhesion through the tailored modulations of surface morphology and chemistry of the GO sheets. These findings pave the way for advancing the rational design and application of graphene-based composite coatings with highly improved tribological performance.

This study investigates the effects of Nd content and aging treatment on the microstructure and mechanical properties of as-extruded Mg–9Gd–3Y–xNd–0.5Zr (x = 0, 0.8, 1.5 wt

To address the extreme thermal challenges in ultra-high temperature scenarios, a synergistic strategy combining layered toughening and N-doped modification was adopted to enhance the ablation resistance of HfC-based coatings. This study systematically explored the relationship between phase composition, multi-layer structure and anti-ablation performance through a two-stage progressive approach. The results demonstrate that the moderate N-doping (HfN0.25C0.75) significantly improves ablation resistance of HfC coatings. Building upon this foundation, an innovative TaC/HfN0.25C0.75 multilayer coating was successfully constructed, exhibiting 18.2 % and 16.1 % reductions in mass/linear ablation rates respectively compared to monolithic coatings after 120 s ablation. Notably, it maintained low ablation rates of 0.66 mg/s and 0.84 mu m/s even under cyclic ablation environment (30 s x 4). The excellent performance originates from two synergistic mechanisms: 1) Multilayer interfaces effectively release thermal stress through crack deflection, inhibiting through-thickness cracking; 2) In-situ formed Hf-Ta-O self-healing glassy phases combined with stable Hf6Ta2O17 phases provide dual functionality of oxygen barrier and structural stabilization. This work provides new insights into designing advanced thermal protection systems through multi-scale structural engineering and composition optimization.

ABSTRACT Hydrogen production via water electrolysis is hindered by the sluggish kinetics of the oxygen evolution reaction (OER). High‐entropy materials (HEMs) show great promise due to their unique compositional tunability, though their performance is closely linked to surface reconstruction processes. This review systematically analyzes the impact of various reconstruction features on the OER performance of HEMs, with particular emphasis on the associated energy consumption. Based on reconstruction behaviors under practical operating conditions, these features are categorized into four types: (i) surface reconstruction leading to the formation of metal (oxy)hydroxide active layers; (ii) construction of crystalline/amorphous heterointerfaces; (iii) oxygen‐vacancy formation coupled with lattice oxygen participation; and (iv) synergistic reconstruction mechanisms. By evaluating the effects of these strategies on catalytic activity and durability, this review elucidates the intrinsic correlations between reconstruction pathways and catalyst performance. Furthermore, through systematic compilation and comparative analysis of reported data, optimal reconstruction strategies are identified from the perspectives of both overpotential and long‐term stability. Finally, design principles informed by reconstruction mechanisms are proposed to guide the development of high‐performance HEM‐based OER catalysts for diverse application scenarios, along with a discussion of current challenges and future opportunities for practical implementation.

The synthesis of FeCoNi1.4Mox (x=0.875-1.375) high-entropy alloys (HEAx) was achieved via arc melting. After dealloying, the micro-porous DHEAx structures with μ phase as the framework were obtained. Then, MgH2-DHEAx hydrogen storage systems were fabricated by ball-milling DHEAx and MgH2 in a 5:95 mass ratio. It is shown that doping DHEAx markedly improves the overall hydrogen storage performance of MgH2. Specifically, the onset desorption temperature decreases from 286.4 °C to 213.7-239.8 °C. At 300 °C, the composites achieve complete desorption within 5-10 min, releasing 5.19-6.2 wt% of H2. Correspondingly, the dehydrogenation activation energy ranges from 92.91 to 106.86 kJ·mol-1. Among them, the MgH2-DHEA1.25 system exhibits the best hydrogen storage performance. At 150 °C, a hydrogen uptake of 2.71 wt% is achieved within 8 min, and maintains more than 95 % of its capacity over 25 cycles at 300 °C. Microstructure analyses indicate that the enhanced hydrogen storage capabilities of MgH2-DHEAx are mainly ascribed to the unique micro-porous structure and high catalytic activity of DHEAx. The interface between the μ phase and MgH2 provides abundant catalytic sites for H2 dissociation and recombination. Concurrently, the micro-pores offer ample pathways for hydrogen diffusion, synergistically accelerating the hydrogen sorption kinetics of MgH2. DFT calculations show that there is obvious charge transfer at the interface between μ phase and MgH2, which reduces the stability of MgH2 and enhances its dehydrogenation ability. These findings provide new insights and a theoretical foundation for tailoring the microstructures of high-entropy alloys and for optimizing the hydrogen storage properties of catalyst-modified Mg-based materials.

Multi-principal element alloys exhibit high catalytic ability for oxygen evolution reaction (OER) and urea oxidation reaction (UOR), holding great promise for high-efficiency hydrogen generation and remediating waste water containing urea. However, high-efficiency and durable bifunctional multi-principal element alloy electrocatalysts remain confronted with substantial obstacles. In this study, the FeCoNi1.4Mo1.25 alloy is synthesized by arc melting method. Through heat treatment with different durations and chemical dealloying, porous FeCoNi1.4Mo1.25 multi-principal element alloy electrocatalysts are successfully prepared, which effectively improved their catalytic proficiency for OER and UOR. Specifically, the best-performing FeCoNi1.4Mo1.25 presents potentials of 1.44 and 1.46 V vs. reversible hydrogen electrode (RHE) at 10 and 100 mA/cm2 toward OER, while achieving 1.34 and 1.38 V (vs. RHE) at the same current densities for UOR. Meanwhile, the catalyst demonstrates outstanding long-term stability. It can operate stably for 250 h in OER and 300 h in UOR at 200 mA/cm2. The study contributes to advancing durable, high-performance, non-precious multi-component alloy electrocatalysts and provides a promising approach for further performance enhancement through optimized heat treatment.

Powder composition plays a critical role in determining the phase constitution and microstructural characteristics of coatings, thereby providing an effective approach for improving the wear resistance of rail materials. In this study, 15–5PH, Co21, and Ni35 alloy coatings were fabricated on U75V rail steel by laser cladding, and their phase constitution, microstructural evolution, and tribological performance were systematically investigated. The results indicate that the 15–5PH coating is primarily composed of martensite and retained austenite, exhibiting a mixed microstructure of equiaxed and columnar grains. The Co21 coating consists of γ-Co and ε-Co phases, with dense equiaxed grains dominating most regions and columnar grains appearing locally. The Ni35 coating is composed of a γ-(Fe, Ni) solid solution with Fe3B and Ni3B phases, and its microstructure is characterized by fine cellular crystals. In terms of wear behavior, the 15–5PH coating exhibits the best wear resistance due to work hardening and strain-induced martensitic transformation, with a wear loss of 0.88 × 106 mm3, which is 42.5% lower than that of the U75V substrate (1.53 × 106 mm3), and an average friction coefficient of 0.53. In contrast, the Co21 and Ni35 coatings show higher wear losses of 8.16 × 106 mm3 and 16.32 × 106 mm3, with average friction coefficients of 0.30 and 0.60, respectively. The Co21 coating shows the lowest friction coefficient. In contrast, the Ni35 coating displays the poorest wear resistance, as fragmentation of hard phases promotes combined abrasive and adhesive wear. These results demonstrate that powder composition plays a decisive role in governing microstructural stability and wear performance of laser-cladded rail coatings.

In this study, the hydrogen embrittlement (HE) behavior of an equiatomic CoNiV multicomponent alloy (MCA) fabricated via laser powder bed fusion (LPBF) is systematically investigated, with a focus on the effect of medium-temperature aging on microstructural evolution and HE susceptibility. Aging at 500 °C for 100 h introduces local chemical orders (LCOs) without altering grain size or phase constitution and induced a noticeable increase in strength. However, The HE resistance deteriorates markedly after aging, as reflected by the increase in hydrogen-induced ductility loss from 19.8% to 55.8%, despite a substantial reduction in bulk hydrogen content from 67.9 ppm to 27.2 ppm. This result indicates that HE susceptibility is not governed by the total hydrogen content. LCOs act as effective hydrogen prohibitor and promote planar slip of dislocations, facilitating dislocation-mediated hydrogen transport and hydrogen accumulation at grain boundaries (GBs). Moreover, the increased strength further intensifies stress concentration at GBs, accelerating crack initiation and propagation. As a result, the fracture mode shifted from transgranular (TG) cracking in the as-printed state to predominantly intergranular (IG) cracking in the aged state. These findings provide essential guidance for the estimating the HE behaviors of components serviced at intermediate temperature and designing HE-resistant additively manufactured alloys.

Radially graded porous implants mimic natural bone's multi-level structure by precisely tailoring porosity distributions to address complex mechanical demands in bone grafting. This study thus designed three types of radially graded bio-inspired porous Ti-6Al-4 V (TC4) implants (i.e.: Gyroid, Diamond, and Schwarz structures) with approximately 63% average porosity based on triply periodic minimal surfaces (TPMS), and fabricated via selective laser melting (SLM). Their deformation behaviors, mechanical properties, and corrosion resistance were systematically investigated using finite element analysis (FEA), compression testing, and electrochemical measurements. FEA results revealed that under compression, Gyroid and Diamond structures undergo cyclic deformation involving elastic yielding followed by progressive layer-by-layer fracture, whereas the Schwarz structure behaved similarly to brittle lattices, exhibiting a cycle of elastic yielding and bulk fracture of entire layers, eventually leading to gradual densification. These findings aligned with experimental observations: Gyroid suppressed delamination fracture through diagonal struts, Diamond showed progressive layer-by-layer compaction, and Schwarz underwent brittle collapse. The straight-through channels formed in Schwarz's orthogonal strut network (compared to the spiral/oblique channels of Gyroid/Diamond) facilitated uniform simulated body fluid (SBF) permeation and full surface coverage. This promoted the homogeneous formation of passive film, yielding superior long-term corrosion resistance (Rct of 351.2 k Omega & sdot;cm2 after 12 days immersion). In contrast, Diamond's high pore connectivity led to weakened corrosion resistance. Overall, the Schwarz structure demonstrated the closest elastic modulus to natural bone (2.25 GPa), the highest yield strength (203 MPa), and the lowest corrosion rate (1.62 x 10-5 mm & sdot;year- 1), satisfying both mechanical and corrosion resistance requirements for bone implants.

Supported metals are well-recognized commercial catalysts for important industrial selective hydrogenation. Intrinsic catalysis based on structure-function relationship has traditionally been regarded as a main factor to determine hydrogenation selectivity, while the intense heat release in a strong exothermic reaction also inevitably deteriorates the selectivity by causing coke deposition and/or over-hydrogenation. Herein, this work demonstrates a distribution effect by homogeneously dispersing catalytically-active metal particles on oxide support to enhance the selectivity of exothermic hydrogenation. The catalytically-active metal particles with varied dispersion homogeneity, NiCu here, exhibit similar intrinsic catalysis in the intensely exothermic hydrogenation of alpha-methylstyrene to cumene. However, a distribution effect is found that the increase in metal dispersion homogeneity leads to enhanced cumene selectivity while decreased isopropylcyclohexane (IPCH) selectivity, with a cumene selectivity of > 99 % achieved at a alpha-methylstyrene conversion of > 99 %. The high selectivity is attributed to the in-situ thermal dissipation caused decrease in temperature increment detected at the catalyst bed, while even a slight temperature increase at catalyst bed could be induced by a large temperature rise at catalytic sites. Benefiting from the lowered temperature increment, the over-hydrogenation to IPCH with a higher activation energy has been inhibited.

Although iron-based composite coatings are widely used to improve the surface performance of structural steels, simultaneously achieving high hardness, wear resistance, and impact toughness remains a considerable challenge due to inherent strength-toughness trade-offs. In this work, a Fe-Mo-V-B-C alloy powder was designed and synthesized by gas atomization, and subsequently deposited on Q235 steel substrates via plasma spraying to fabricate iron-based composite coatings. Microstructural characterization indicates that the coating is composed of a martensitic matrix reinforced by petal-like VC and blocky to skeleton Mo2B eutectic phases, with volume fractions of 16.5 and 41.6

The effects of Zn content on the microstructure, texture evolution, and mechanical properties at both cryogenic and elevated temperatures of the Mg-9Y-xZn (x = 1, 2, and 3 wt%, abbreviated as WZ91, WZ92, and WZ93) extruded alloys were systematically investigated. The abnormal C texture (i.e. <0001>(alpha)//ED (extrusion direction)) formed in the WZ91 and WZ92 alloys, which should result from the preferential growth of the grains with specific orientations and the lattice rotation induced by the non-basal slip. Tensile tests conducted at the cryogenic (-100 degrees C) and elevated temperatures (100 degrees C and 300 degrees C) revealed the simultaneous low-temperature plasticizing and high-temperature strengthening in the alloys containing C texture after peak ageing at 200 degrees C. When tensile tested at -100 degrees C, the C texture promoted the activation of tensile twinning and non-basal slip in the WZ91 and WZ92 alloy respectively, leading to the higher elongation than that tested at room temperature. The higher strength at 300 degrees C for the WZ91 alloy resulted from the combined strengthening effect of the rare earth (RE) atoms and beta ' precipitates instead of the LPSO phases. In addition, the C texture in the WZ91 and WZ92 alloys underwent weakening and transformation during tensile tests, accompanied by the emergence of the basal texture component.

The FeCoNi1.4Mox (x = 0.875-1.375) high-entropy alloys (HEAx) were prepared by arc melting and then ball-milled with MgH2 at a mass ratio of 5: 95 to form MgH2-HEAx hydrogen storage composites. XRD and SEM results indicate that the FeCoNi1.4Mox alloys are mainly composed of FCC and & micro; phases, among which the & micro; phase is characterized by the rhombohedral structure of (Fe, Co, Ni)7Mo6, and the proportion of & micro; phase gradually increases with increasing Mo content. After mixture, the HEAx alloys are uniformly distributed within the MgH2 matrix, forming a stable interface, thereby significantly improving the hydrogen sorption performance of MgH2. The initial dehydrogenation temperature of MgH2-HEAx composites decrease to 203.2-232.4 degrees C, representing a decrease of nearly 80 degrees C compared to that of the ball-milled pure MgH2. At 250-275 degrees C within 1 min, the hydrogen absorption capacity can reach 3.79-5.51 wt%. Subsequently, the hydrogen desorption capacity can reach 1.34-5.53 wt% within 20 min, both values being distinctly greater than those of ball-milled pure MgH2. The dehydrogenation activation energy of the composites decreases to 89.7-98.7 kJ & sdot;mol-1 . Among them, the MgH2-HEA1 presents the most excellent hydrogen storage performance at low temperatures, and its hydrogen storage capacity remains above 90 % after 25 cycles. First-principles calculations show that the weakening of the chemical bond strength of H 2 and MgH2 is attributed to the synergistic effect of FCC and & micro; phases, with both phases inducing substantial elongation. This research provides a novel method for the design and optimization of high-performance magnesium-based hydrogen storage materials catalyzed by multi-component high-entropy alloys.

The poor interfacial bonding and severe stress concentration between diamond reinforcements and metal matrices significantly limit the mechanical and tribological performance of diamond-reinforced composite coatings. In this work, a novel strategy employing porous diamond as a reinforcement for Ni-based composite coatings is proposed. The microstructures, mechanical properties, and wear behavior of the composite coatings were characterized systematically, and finite element simulations were conducted to elucidate the underlying interfacial stress distribution. The results demonstrate that metal-assisted etching uniformly distributed micropores on the diamond surface, markedly increasing surface roughness and specific surface area. This porous surface significantly enhances interfacial mechanical interlocking and promotes metallurgical reactions between diamond and the NiCrBSi alloy. Compared with coatings reinforced by conventional diamond particles, the porous diamond-reinforced coating exhibits a higher density of Cr-C carbides with well-defined prismatic and lamellar morphologies. As a result, it achieves a hardness of 68.58 HRC of about 1.4 times higher than the conventional coating along with a lower and more stable friction coefficient (similar to 0.18) and shallower, more uniform wear scars. Finite element simulations reveal that the porous diamond surface effectively redistributes interfacial residual stresses, alleviating severe stress concentration at diamond surface. The synergistically enhanced interface, governed by a combined "mechanical interlocking-metallurgical reactions" bonding mechanism and reduced residual stress, provides a fundamental basis for the improved mechanical and tribological performance of the composite coating. This work offers a feasible interfacial design strategy for the development of high-performance diamond-reinforced metal matrix composite coatings for demanding wear-resistant applications.

In this study, diamond particles were introduced into a Ni-Cr brazing alloy to improve its wear resistance, and CeO2 was employed as a modifying additive to fabricate high-performance diamond-reinforced Ni-based composite coatings through brazing. The results show that the addition of 1 wt% CeO2 significantly enhances the mechanical and tribological properties of Ni-Cr coating. The microhardness increases from 638.3 HV0.5 to 734.8 HV0.5, while the friction coefficient decreases by approximately 10% and the wear loss is reduced from 11 mg to 8.8 mg. This improvement is mainly attributed to microstructural modification of Ni-Cr alloy induced by CeO2 addition. Furthermore, in the diamond/Ni-Cr composite coating, the introduction of 1 wt% CeO2 leads to a refinement of carbide layer formed on the diamond surface, resulting in improved interfacial bonding. Consequently, the friction coefficient decreases by approximately 17%, and the wear loss is reduced from 2.2 mg to 1.3 mg compared with the coating without CeO2 addition. The enhanced tribological performance is attributed to the synergistic effects of microstructural modification of Ni-Cr alloy, interfacial carbide optimization, and improved load transfer capability. This study demonstrates that the addition of a small amount of CeO2 can effectively improve the performance of diamond-reinforced Ni-based brazed coatings.