Search Results (922)

P2/O3-type Ni/Mn-based layered oxides are regarded as promising cathode materials for sodium-ion batteries (SIBs) because of their high energy density. However, their practical application is limited by low initial Coulombic efficiency, sluggish Na⁺ kinetics, transition-metal dissolution/migration and irreversible phase transitions during cycling. Herein, a controlled P2 phase was achieved through elemental ratio regulation, enabling systematic synthesis of a series of Na_xNi_0.4Co_0.1Mn_0.5O₂(x-NCMO) materials with tailored P2/O3 ratios. The optimized composition (x = 0.8), containing 16.6% P2 and 83.4% O3 phases, achieves an optimal phase equilibrium, thereby maximizing the synergistic coupling between the two layered polymorphs. This biphasic architecture demonstrates significantly enhanced Na⁺ transport kinetics and exceptional electrochemical performance, high initial capacity of 168.65 mAh g⁻¹ and excellent rate performance, maintaining 84.88 mAh g⁻¹ at 10 C, outperforming most reported P2/O3 biphasic cathodes. Structural analysis and electrochemical analysis reveal that elemental ratio regulation modulates the TM–O electronic structure, promotes electronic transport, and accelerates Na⁺ migration. These effects collectively reduce polarization, stabilize the structure, and thereby improve rate capability and long-term cycling capacity retention. This work provides an effective design strategy for designing high-performance layered oxide cathodes with improved structural and interfacial stability. Full article

Copper (Cu) smelting slags are considered secondary reserves of technology metals (TMs) and base metals (BMs), which are crucial for the transition to renewable energy and mechatronic applications. In this study, thermochemical and experimental analyses were conducted to investigate the pyrometallurgical extraction of TMs and BMs from Cu smelting slag. FactSage thermochemical simulations and smelting experiments were carried out at temperatures from 1300 to 1600 °C and with carbon (reductant) additions of 2% to 10% relative to the mass of the feed slag. The results showed that during smelting, gallium (Ga), germanium (Ge), cobalt (Co), and copper (Cu) deported into the iron-based alloy product. Zinc (Zn) and lead (Pb) oxidised to ZnO and PbO, respectively, which were subsequently collected as fumes. The produced alloy mass was more sensitive to carbon addition than to smelting temperature variation. The TM and BM contents in the alloy decreased with increasing carbon addition in the feed; this was attributed to dilution by Fe, Si, and C from the increasing reduction of iron and silicon oxides in the feed slag and dissolution of C in the alloy. High recovery degrees of TMs and BMs in the alloy stream—over 90% for Co and Cu, over 50% for Ga, and over 70% for Ge—were achieved when smelting at 1500 °C with 4% carbon addition. The final alloy comprised 70.5% Fe, 6.6% Co, 23.6% Cu, 0.11% Ga, and 0.13% Ge. The fumes primarily comprised ZnO and, to a lesser extent, PbO, with recovery degrees over 90% for Zn and Pb. These alloy and fume products would be processed following conventional hydrometallurgical separation and purification processes to produce high-purity metals. The pyrometallurgical extraction of TMs and BMs presents an opportunity for the valorisation of Cu smelting slag dumps, especially in Southern Africa, aiming to attain zero-waste industrial processes. Full article

Developing active and robust catalysts for the acidic oxygen evolution reaction (OER) with reduced Ir loading is still a challenge in the industrial production of green H₂. In this work, several catalysts ranging from single metal oxides (e.g., IrO₂) to high-entropy oxides (IrNiMnFeCoCuVO_x) were synthesised through thermal decomposition in air to study the effect of the mixed-oxide composition in terms of activity and stability towards the acidic OER. Catalysts were named MOx-n, with n being the number of metal elements in the mixture. The results show that the activity of rutile IrO₂ can be improved by introducing other elements into the composition. The best performance was obtained for MOx-4 to MOx-5, which delivered a current density of 10 mA cm⁻² at an overpotential (η₁₀) of 279 ± 4 mV; approx. 100 mV lower than IrO₂ at a comparable Ir loading and with better stability. Nevertheless, further increasing the complexity of the mixed oxide resulted in an evident degradation in terms of activity and stability. It is worth noting that surface dissolution and reconstruction occurred with all mixed-oxide catalysts, including high-entropy configurations. Full article

Conventional separators for lithium metal batteries suffer from poor thermal stability, flammability, and limited mechanical strength. In this study, we report a self-reinforced aramid separator integrated with Li₇La₃Zr₂O₁₂ (LLZO) via a sodium–naphthalene-based selective dissolution strategy. Controlled partial disruption of hydrogen bonding in copolymerized aramid enables the formation of a hierarchical structure consisting of intact fibers and nanofibrillar networks, thereby providing intrinsic mechanical reinforcement without binders. The separator maintains structural integrity up to ~400 °C and retains over 70% weight at 600 °C, exhibiting self-extinguishing behavior (LOI > 30). Puncture strength is more than three times higher than Celgard^®, while LLZO integration doubles the ionic conductivity along with excellent electrolyte wettability. This synergistic design provides a promising route toward intrinsically safe and high-performance lithium metal battery separators. Full article

The increasing demand for higher energy density in lithium-ion batteries has driven significant interest in layered oxide cathode materials. However, their development is hindered by an inherent trade-off between structural stability and ion transport kinetics. This compromise often manifests as a conflict between achieving high capacity, long cycle life, and excellent rate performance. Consequently, mitigating structural degradation and minimizing interfacial side reactions have emerged as core research priorities. Based on this, this review summarizes the crystal chemistry and key challenges of three main types of layered oxide cathode materials, and critically evaluates two main modification strategies: bulk doping, which enhances performance by regulating the electronic structure and suppressing phase transitions; and surface coating, which builds a protective layer at the particle–electrolyte interface to suppress side reactions and metal dissolution. Looking ahead, in terms of modification, the focus should be on multi-scale co-doping to construct a stable bulk phase structure and multi-functional coating to optimize the interface. Integrating artificial intelligence with high-throughput computation will powerfully enable the pursuit of these advanced modification strategies. This integrated approach may resolve the fundamental contradiction between energy density and stability, thereby paving a new pathway for next-generation lithium-ion batteries. Full article

The long-term accumulation of phosphogypsum (PG) stacks has caused combined pollution of total phosphorus (TP), fluoride (F⁻), metals and metalloids (MMs), posing a severe threat to regional ecological security. To clarify the migration characteristics of pollutants in PG stacks, water leaching experiments and environmental risk assessment were conducted in 21 typical PG stacks in Southwest China. The spatial differentiation and vertical migration characteristics of pollutants under various coverage measures (high-density polyethylene (HDPE) film covering, soil covering, a composite of film–soil covering, and open-air storage) at different pH conditions were systematically analyzed. Results indicated that under open-air stockpiling conditions, the surface accumulation of TP and F⁻ was the most significant among all covering measures, corresponding to the highest environmental risk. In contrast, the membrane–soil composite covering exhibited the optimal inhibitory effect on the surface diffusion of TP and F⁻, but was less effective for metal and metalloid enrichment. Under acidic conditions (pH < 6), the vertical migration capacity of TP, F⁻, and MMs (Cu, Cd, Cr, Pb, and Zn) increased, leading to enrichment in the deep layers of the stack. With the increase in pH, the calcium-mediated precipitation–adsorption effect created a “geochemical barrier”, facilitating the solid-phase fixation of pollutants. A significant positive correlation among pollutants indicates synergistic release and fixation behaviors. In addition, a pH-controlled P-F-MM source-to-sink conceptual model was established, outlining the dissolution, precipitation, adsorption, fixation and re-enrichment pathway from fresh stock to leachate. This work provides insights for optimizing cover designs and pollution control strategies. Full article

The disposal of end-of-life fluorescent lamps presents significant environmental challenges due to their mercury (Hg) content and the loss of valuable rare earth elements (REEs) contained in phosphor powders, highlighting the need for sustainable recycling strategies. This study proposes an integrated hydrometallurgical process for simultaneous mercury removal and material recovery from spent fluorescent lamps. Various leaching agents were initially evaluated for mercury dissolution, and 10% NaOCl was identified as the most effective solution. The optimized system was applied to linear T8 lamps using a combined milling–leaching approach, followed by size-based separation of metallic, glass, and phosphor fractions. Dissolved mercury was precipitated at pH 11 using Na₂S, forming crystalline α-HgS (cinnabar), as confirmed by XRD, and reducing the residual mercury concentration to 2.7 µg/L. The metallic fraction was recovered as an aluminum-based alloy containing 20.6 wt.% Cu and 10.9 wt.% Zn with low iron content, while the phosphor-rich fraction yielded approximately 50% REE extraction, followed by oxalate precipitation of yttrium-based compounds. The developed process enables efficient mercury stabilization and selective recovery of valuable materials, supporting environmentally secure and resource-efficient fluorescent lamp recycling. Full article

Liquid metal cathodes, particularly liquid cadmium (Cd), are widely used in molten salt electrorefining and pyrochemical reprocessing of spent nuclear fuel due to their high electrical conductivity, strong affinity for actinides, and favorable alloying characteristics. During electrorefining, reduced metal species enter the liquid Cd phase and may exist as dissolved atoms, liquid alloys, or intermetallic compounds, all of which significantly influence deposition behavior, separation selectivity, and cathode performance. Although numerous experimental and theoretical studies have investigated metal solubility, alloy formation, and diffusion in liquid Cd systems, the current understanding remains fragmented. Thermodynamic phase behavior and mass transport kinetics are often discussed separately, and reported diffusion data show considerable discrepancies owing to variations in experimental techniques and interpretations. In addition, the relationship between phase stability, diffusion mechanisms, and electrochemical conditions in practical electrorefining environments has not yet been systematically clarified. This review aims to present an integrated thermodynamic–kinetic perspective on the behavior of metals in liquid Cd cathodes. Recent progress in dissolution behavior, alloy phase formation, and diffusion-controlled transport processes is critically summarized. The differences in solubility and precipitation behavior of actinides, rare-earth elements, and selected transition metals are analyzed in relation to binary phase diagrams and thermodynamic stability. Furthermore, experimental methods for determining diffusion coefficients, including capillary techniques and electrochemical approaches, are comparatively evaluated. By correlating thermodynamic phase stability with diffusion-driven mass transport, this work provides a coherent framework for understanding metal behavior in liquid Cd cathodes and offers insights for optimizing molten salt electrorefining and advanced nuclear fuel cycle technologies. Full article

Electrochemical machining (ECM) offers precise shaping by material dissolution with negligible mechanical or thermal impact on the workpiece. Metal parts with three-dimensional shapes, such as freeform surfaces or additively manufactured parts, can be addressed by robots with up to six degrees of freedom without significant mechanical impacts on the end-effectors and robots. This study summarizes the state-of-the-art of the use of robots in ECM by assessing the relevant literature. Several investigations were found that implemented or conceptualized the use of robotic arms in ECM sinking, jet-ECM or wire ECM, mainly for effective utilization of the processes. This study includes results of pure ECM, as well as hybrid ECM processes and the use of robots considering their accuracy, degrees of freedom and their application potential. Special emphasis is given to the role of robots in improving machining accessibility and their usability for valuable components in the aerospace, biomedical, and tooling industries. Furthermore, the review provides insights into electrolyte delivery mechanisms and pump configurations that facilitate efficient process performance. Overall, the utilization of robots in ECM not only enhances the process flexibility and surface quality but also aligns well with the aim of intelligent, automated, and high-precision manufacturing. Full article

The performance of flux-cored Zn-Al filler metal is susceptible to corrosion-induced degradation, thereby impairing its brazability. In this study, flux-cored Zn-2Al filler metals are prepared, and the salt spray test is subsequently carried out on the prepared filler metals. Scanning transmission electron microscope is used to identify the phases in filler metals. An electrochemical workstation was employed to test the electrochemical performance of the filler metals. The corrosion pathways and evolution patterns of filler metals are analyzed. The findings demonstrate that the corrosion type of the filler metals is electrochemical corrosion, characterized primarily by the corrosion modes of pitting corrosion and intergranular corrosion. The cathode is the α-Al phase, which undergoes an oxygen-absorption corrosion reaction, while the anode is the η-Zn phase, which experiences corrosion and subsequent dissolution. The continuously distributed α-Al phase bands and discontinuously distributed large-sized rod-like α-Al phases accelerate the corrosion rate, and the corrosion propagation rate along the extrusion direction is higher than that in the radially inward direction. After 15 days of salt spray corrosion, the tensile strength of filler metals decreases by 16.2%, and the elongation rate decreases to 3.73%. Full article

Modern materials science is focused on the development of steels with a range of performance characteristics, including high strength, wear resistance, corrosion resistance, and long-term performance in various conditions. Special attention is paid to the control of the microstructure of steels at the crystallization stage, which allows for the improvement of metal properties without significantly increasing the cost of the manufacturing process. One of the promising methods of microstructural engineering is the modification of steels with dispersed particles of refractory compounds, such as titanium carbide (TiC), zirconium carbide (ZrC), and tungsten carbide (WC). However, the processes of dissolution, dissociation, and interaction of such ceramic particles with the metal melt, as well as their influence on the formation of the microstructure and properties under the conditions of non-equilibrium crystallization, which is typical for centrifugal casting, are not sufficiently studied for austenitic stainless steels. In this work, the influence of dispersed carbide particles of TiC, ZrC, and WC, which are introduced into the melt of austenitic stainless steel (Cr ≈ 18%, Ni ≈ 10%) during centrifugal casting, on the redistribution of alloying elements, the formation of the microstructure, and the mechanical properties of the material is investigated. Special attention is paid to the kinetic nature of the dissolution and interaction of the carbides with the melt, as well as the directional distribution of elements across the cross-section of the billets. The study includes the analysis of the distribution of Ti, W, and Zr across the cross-section of the centrifugally cast billets, the study of the microstructure and phase composition of the inclusions using SEM/EDS, and mechanical testing. It is found that the implementation of dispersion hardening leads to an increase in the tensile strength by up to ~22% compared to the initial alloy (from 496 to 612 MPa), while the impact strength decreases by 5–25% (from 110 to 82 J/cm²) depending on the type and quantity of the introduced particles. The analysis of microhardness shows the presence of a gradient of local properties across the cross-section of the centrifugally cast billets, with microhardness values ranging from ~110 to 195 HV0.5. For the modified samples, the relative difference between the inner and outer zones is ~5–20%, reflecting the combined effect of non-equilibrium solidification, redistribution of alloying elements, formation and spatial distribution of secondary phases, and local structural heterogeneity. These results confirm the possibility of controlling the distribution of properties within a single billet. Full article

Inorganic magnesium potassium phosphate (MKP) coatings offer rapid, zero-volatile organic compound (VOC) corrosion protection for steel structures. However, their application is impeded by insufficient mechanical strength and limited barrier durability. This study integrates calcium sulfate whiskers (CSWs) into a sprayable MKP matrix. Unlike conventional polymeric or metallic fibers, CSWs demonstrate excellent chemical compatibility with the MKP matrix, enabling a dual-enhancement mechanism. The optimal formulation, containing 15 wt.% CSWs, boosts the 28-day compressive strength by 35% and the bond strength by 39%. Electrochemical analysis shows a 93.6% increase in coating resistance (R_f), indicating an improved physical barrier against corrosive species, along with a 52% reduction in corrosion current density. These improvements result from fiber bridging and a dissolution–reprecipitation process that densifies the whisker–matrix interface. Nevertheless, an excessive amount of CSW (20 wt.%) disrupts the matrix continuity and reduces performance. This work presents a high-strength, zero-VOC, spray-applied coating with a novel dual-enhancement mechanism for durable steel protection in aggressive environments. Full article

Biohydrometallurgical processing of spent lithium-ion batteries offers a low-impact route for critical metal recovery compared with conventional hydrometallurgy. In this work, the iron-oxidizing bacterium Acidithiobacillus ferrooxidans was evaluated for the bioleaching of cobalt (Co), nickel (Ni), lithium (Li) and copper (Cu) from pyrolyzed industrial black mass derived primarily from LiCoO₂-based batteries, containing both LiCoO₂ and LiNiO₂ layered oxide phases. Batch experiments were conducted in 9K medium at 30 °C, varying pulp density (1%–2%, w/v), inoculum volume (10–20 mL in 200 mL medium) and initial pH (with and without adjustment). At 1% pulp density and 10% v/v inoculum, metal recoveries after 6–7 days reached about 64%–70% Co, 57%–72% Ni, 52%–60% Li and 81%–100% Cu, with most dissolution occurring in the first 6 days. Higher inoculum loads without initial pH adjustment increased Li recovery up to 79%, but did not further improve Co and Cu, indicating a trade-off between microbial activity, metal toxicity and ferric iron availability. The temporal evolution of pH and metal dissolution is consistent with indirect redoxolysis by biogenic Fe³⁺ and sulfuric acid generated during ferrous iron and elemental sulfur oxidation. Overall, the results confirm the feasibility of A. ferrooxidans-assisted bioleaching as a green option for Co, Ni, Li and Cu recovery from spent LiCoO₂ batteries and provide operating windows for subsequent process optimization and scale-up. Full article

The depletion of natural resources remains an acute global problem, highlighting the importance of developing sustainable technologies that enable the simultaneous extraction of metals and recycling of waste. This paper describes a study of a technology for recycling aluminum slag from foundries to produce secondary aluminum alloy and regenerated flux. Research and processing methods include X-ray phase and spectral analysis of slag composition, multi-stage grinding in a jaw crusher and planetary mill, screening for fraction separation, and selective dissolution of the oxide–salt phase in water or hydrochloric acid followed by filtration and evaporation; obtaining regenerated flux based on phase diagrams of chloride systems; and briquetting and remelting of the extracted aluminum. The technology ensures the extraction of up to 85% of the metallic aluminum from slag and the production of regenerated flux based on the NaCl–KCl–MgCl₂ system with a low melting point. Full article

High-entropy alloys (HEAs) provide a broad compositional space for tuning phase stability and surface durability. CoCrFeNiMn_x (x = 0.5, 1.0, 1.5, and 2.0) alloys were fabricated by vacuum arc melting and characterized by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), microhardness testing, electrochemical testing in 3.5 wt.% NaCl, and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations and first-principles molecular dynamics were further employed to analyze the Mn-dependent electronic structure and oxygen–metal bonding. The XRD results indicate a transition from a single FCC solid solution at x ≤ 1.0 to an FCC + BCC constitution at x ≥ 1.5. With increasing Mn, microstructures evolve from coarse dendrites toward higher fractions of equiaxed grains. Hardness decreases from 163.6 HV (x = 0.5) to 125.1 HV (x = 1.0) and then increases to 162.6 HV (x = 2.0), indicating competing solid-solution and phase/segregation effects. Electrochemical measurements show enhanced corrosion resistance with Mn addition; the x = 2.0 alloy exhibits the lowest fitted corrosion current density (icorr = 0.3482 × 10⁻⁶ μA·cm⁻²) and the most stable passivation response. XPS reveals passive films dominated by Fe₂O₃ together with Mn³⁺ oxides, whose synergistic formation promotes a denser barrier layer. DFT predicts a monotonic decrease in Fermi level and a narrowed conduction band range as Mn increases, consistent with reduced electron transfer activity during anodic dissolution. Interfacial simulations show that O preferentially bonds with Cr and Mn, while Ni–O bonds have the lowest estimated rupture barrier, rationalizing a tendency toward localized corrosion at Ni-associated sites. Full article