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Electrochemical activity of composite (100-x) wt% Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ–x wt% Ce_0.8Sm_0.2O_1.9 (x = 10, 20, 30, 40) electrodes in contact with the BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3-δ proton-conducting electrolyte has been studied by impedance spectroscopy depending on temperature, oxygen partial pressure, and the presence of H₂O/D₂O in the atmosphere. An H/D isotope effect in the electrode response has been observed for all the investigated conditions, resulting in an increase in polarization resistance in a D₂O-containing atmosphere. The distribution of relaxation times reveals that the electrode reaction mechanism is similar for all the investigated electrode compositions, with two main rate-determining processes being highlighted. The main contribution to electrode polarization gives the low-frequency stage. Based on the dependencies of the partial resistances on the oxygen partial pressure and the substitution of H₂O by D₂O, the processes were assigned to oxygen reduction and water formation at the triple-phase boundary. The increase in proton conduction in the electrode is a possible way to improve the electrode performance.

The resourceful utilization and harmless disposal of high-iron red mud remain a global challenge. An innovative process for separating iron and aluminum from high-iron red mud via fluidized pre-reduction and electric furnace smelting is proposed. Iron in high-iron red mud from the Bayer process mainly exists as goethite and hematite, while aluminum is primarily present as alumogoethite due to isomorphic Fe substitution, with part of the aluminum as gibbsite. While conventional magnetization roasting converts hematite and goethite into magnetite, it cannot disrupt the isomorphic aluminum-iron lattice, resulting in residual aluminum in the magnetic concentrate that still requires further separation. Building on this, the innovative fluidized pre-reduction and electric furnace smelting process developed in this study effectively breaks the aluminum-iron substitution, disrupting their symbiotic structure and enabling the decoupling of aluminum and iron phases. This process produces high-quality pig iron (TFe > 92 wt%) that meets steelmaking standards, along with an aluminum-rich slag suitable for aluminate cement clinker production. It achieves a high iron recovery rate (> 95%) while ensuring the comprehensive recovery of aluminum resources. These results address the environmental and resource challenges associated with high-iron red mud and offer a technically robust and economically viable solution for its large-scale valorization.

Hydrogen production by electrolysis of water is a clean and efficient green hydrogen production technology. The core of improving hydrogen production efficiency is to obtain electrocatalysts with excellent performance. In this study, CuS/NF material was synthesized by one-step hydrothermal method as a hydrogen evolution catalyst, and its performance was evaluated by physical characterization, electrochemical test, and first-principles calculation. The CuS/NF hydrogen evolution catalyst has a nano-spherical spatial structure. This special structure increases the area of electrocatalytic activity, facilitates electron transfer, and improves HER efficiency. When the current density is 10 mV/cm², the overpotential is 156 mV, the Tafel slope is 121.43 mV/dec, the electrocatalytic activity area is 177.5 cm², the charge transfer resistance is 13.424 Ω, and the material maintains stability over 12 h. The hydrogen evolution performance of the CuS/NF electrode is better than that of the blank nickel foam electrode. This experiment provides new ideas and directions for the application and progress of copper-based catalysts in the field of hydrogen evolution from electrolytic water.

This study focuses on FZG gears made of carburizing steel 20MnCrS5, considering the effects of carburizing hardening. A modified phase transformation kinetics formula and constitutive equation are introduced. Based on the ‘phase − thermal − mechanical’ coupling theory and multi-scale simulation methods, a diffusion − temperature − phase − stress − strain − hardness multi-field coupling model is established. The multi-scale and full-process "visualization" prediction of carburizing and quenching heat treatment under phenomenological phase transformation kinetics has been carried out. The results show that, under the H2 process, the surface carbon content is 0.763%, the residual austenite volume at the surface is 7.7%, the residual compressive stress is 513 MPa, the maximum deformation is 40 μm, the surface hardness is 696 HV, and the carburized layer depth is 1.02 mm. The prediction errors are 1.7%, 9%, 2.1%, 7.5%, 0.14%, and 2.9%, respectively. This confirms the feasibility of the multi-field coupling model. The study analyzes the mechanisms of carburizing diffusion kinetics, iron − carbon phase transformation, and carbide precipitation, revealing the effect of process parameters on microstructure and distortion. It also discusses the impact of surface integrity on gear fatigue contact life, offering new insights for optimizing carburizing heat treatment processes and enhancing macroscopic mechanical properties.

One of the enduring goals in structural materials engineering is the development of lightweight materials that combine high strength with exceptional toughness. Natural composites such as nacre have long served as a source of inspiration, as their outstanding mechanical performance stems not only from their intricate hierarchical architecture but also from the vital role of interfaces in controlling deformation and resisting crack propagation. Here, we present a computational model of a three-dimensional (3D) staggered nacre-mimicking nanocomposite and report parametric studies that investigate the roles of interfacial properties (strength and toughness) in controling the bulk properties and failure behaviors under both tensile and compressive loading conditions. Our findings reveal that under tensile loading, the bulk properties are primarily controlled by the surface normal interfacial properties, and composite failure exhibits normal-mode fracture patterns. In contrast, under compressive loading, interfacial shear properties predominantly control the bulk properties, and composite failure patterns follow shear-mode fracture behavior. These findings provide specific design guidelines for tailoring the interfacial properties of nacre-like bioinspired structural composites under different loading conditions.

Profilometry-based indentation plastometry (PIP) was studied in this research to obtain stress–strain data from a simple indentation test. Five alloys commonly produced by additive manufacturing, Ti6Al4V, Ahead CP1, AlSi10Mg, Ni625, and Ni718, were used to print tensile bars using laser powder bed fusion (L-PBF). The tensile bars were then tested using the ‘gold standard’ of mechanical testing, conventional tensile methods outlined in ASTM E8. The tested tensile specimens were then sectioned through the grip section and polished using standard metallographic preparation techniques and PIP tested. When comparing the two test methods, the average tensile strength between all the materials showed a difference of 3.2% while the yield strength differed by 3.7%. These small differences between testing methods demonstrate that PIP testing is a viable alternative to the tensile test. Particular attention was given to the variation in the PIP-determined properties, and the origins of this variation are discussed. A test method standard is currently being developed for this methodology through the ASTM F42 committee, and therefore independent data to assess the precision and accuracy of the method are required.

WC compact and Cu-WC composites were fabricated via spark plasma sintering, and their arc erosion behavior in vacuum was investigated in detail. When subjected to a vacuum arc, WC demonstrated the combined merits of both metals and ceramics. Micro-protrusions, which are commonly observed within the molten pools of alloy-based cathodes, were found on the surface of WC cathodes. The decomposition of WC into W and carbon was observed on both WC cathodes and WC anodes. In Cu-WC composites, WC particles are more refractory than Cu under vacuum arc erosion. After the first vacuum breakdown, Cu-WC composites with higher WC content exhibit smaller molten pools compared to those with lower WC content. After 100 vacuum breakdowns, the WC particles partially melted, and the resulting molten WC was mixed and redistributed throughout the copper matrix.

Achieving green extraction of gold and copper via electrolytic refining of high-silver anode plates has emerged as a significant development trend in the global copper electrolytic refining industry. However, a high silver content in the anode plate can result in elevated Ag levels in the copper cathode, posing challenges for stable control. To address this issue, a novel method involving the insertion of acid-resistant filter membranes between the anode and cathode was proposed to purify the electrolyte in the cathode region and reduce the silver content in copper cathode. By investigating the migration behavior of silver elements in the electrolyte, the structural characteristics of anode slime and the silver content in the copper cathode, the underlying mechanism by which the filter membrane influences the silver content in the copper cathode produced through electrolytic refining was elucidated. Compared to scenarios without a filter membrane, the addition of a filter membrane promotes the aggregation of silver-containing compounds within the adhered anode slime and enhances the densification and enlargement of anode slime particles at the bottom of the tank. The particle size of suspended anode slime in both the anode and cathode regions of the electrolyte decreases; however, fine anode slime particles that traverse the filter membrane from the anode region into the cathode region undergo aggregation and growth in the cathode region. The filter membrane effectively prevents fine anode slime particles containing Ag from entering the cathode region, reducing the Ag content in the cathode region's electrolyte by 27% and 61%, respectively. The incorporation of a filter membrane significantly diminishes the silver content in the copper cathode, decreasing it from 7.75 g/ton to 4.75 g/ton, representing a reduction of 38.7%.

Upgrading magnesium slag into value-added products provides a significant opportunity to address environmental waste pollution while promoting waste recycling. However, challenges such as the low catalytic activity of the resulting products and limited adsorption of macromolecular organic compounds at surface active sites remain critical engineering hurdles. In this paper, mesoporous g-C₃N₄/TiO₂-MgAl₂O₄ heterojunction photocatalysts were synthesized by a facile combustion method using magnesium slag, titanium dioxide, and carbamide as raw materials. Photocatalytic experiments on methylene blue solution under visible light irradiation at room temperature showed that the g-C₃N₄/TiO₂-MgAl₂O₄ heterojunction photocatalyst achieved a 25.6% higher degradation efficiency compared to traditional photocatalysts. This work provides a theoretical framework and practical experience for the value-added and low-cost preparation of photocatalytic materials derived from magnesium slag. Furthermore, a potential enhanced photocatalytic mechanism of g-C₃N₄/TiO₂-MgAl₂O₄ heterojunction photocatalysts is proposed.