Search Results (253)

As a new type of alloy system composed of five or more principal components, high-entropy alloys demonstrate outstanding comprehensive performance in the field of friction and wear through the synergistic effects of the high-entropy effect, lattice distortion effect, hysteresis diffusion effect and cocktail effect. This paper systematically reviews the research progress on the friction and wear properties of high-entropy alloys. The mechanisms of metal elements such as Al, Ti, Cu and Nb through solid solution strengthening, second-phase precipitation and oxide film formation were analyzed emphatically. And non-metallic elements such as C, Si, and B form and strengthen the regulation laws of their tribological properties. The influence of working conditions, such as high temperature, ocean, and hydrogen peroxide on the friction and wear behavior of high-entropy alloys by altering the wear mechanism, was discussed. The influence of test conditions such as load, sliding velocity and friction pair matching on its friction coefficient and wear rate was expounded. It is pointed out that high-entropy alloys have significant application potential in key friction components, providing reference and guidance for the further development and application of high-entropy alloys. Full article

Na₀.₈₉Co_0.90Me_0.10O₂ (Me = Cr, Ni, Mo, W, Pb, and Bi) ceramic samples were prepared using a solid-state reaction method, and their crystal structure, microstructure, and electrical, thermal, and thermoelectric properties were investigated. The effect of the nature of the doping metal (Me = Cr, Ni, Mo, W, and Bi) on the structure and properties of layered sodium cobaltite Na_0.89CoO₂ was analyzed. The largest Seebeck coefficient (616 μV/K at 1073 K) and figure-of-merit (1.74 at 1073 K) values among the samples studied were demonstrated by the Na_0.89Co_0.9Bi_0.1O₂ solid solution, which was also characterized by the lowest value of the dimensionless relative self-compatibility factor of about 8% within the 673–873 K temperature range. The obtained results demonstrate that doping of layered sodium cobaltite by transition and heavy metal oxides improves its microstructure and thermoelectric properties, which shows the prospectiveness of the used doping strategy for the development of new thermoelectric oxides with enhanced thermoelectric characteristics. It was also shown that samples with a higher sodium content (Na:Co = 0.89:1) possessed higher chemical and thermal stability than those with a lower sodium content (Na:Co = 0.55:1), which makes them more suitable for practical applications. Full article

Solid oxide fuel cells (SOFCs) represent a pivotal technology in renewable energy due to their clean and efficient power generation capabilities. Their role in potential carbon mitigation enhances their viability. SOFCs can operate via a variety of alternative fuels, including hydrocarbons, alcohols, solid carbon, and ammonia. However, several solutions have been proposed to overcome various technical issues and to allow for stable operation in dry methane, without coking in the anode layer. To avoid coke formation thermodynamically, methane is typically reformed, contributing to an increased degradation rate through the addition of oxygen-containing gases into the fuel gas to increase the O/C ratio. The performance achieved by reforming catalytic materials, comprising active sites, supports, and electrochemical testing, significantly influences catalyst performance, showing relatively high open-circuit voltages and coking-resistance of the CH₄ reforming catalysts. In the next step, the operating principles and thermodynamics of methane reforming are explored, including their traditional catalyst materials and their accompanying challenges. This work explores the components and functions of SOFCs, particularly focusing on anode materials such as perovskites, Ruddlesden–Popper oxides, and spinels, along with their structure–property relationships, including their ionic and electronic conductivity, thermal expansion coefficients, and acidity/basicity. Mechanistic and kinetic studies of common reforming processes, including steam reforming, partial oxidation, CO₂ reforming, and the mixed steam and dry reforming of methane, are analyzed. Furthermore, this review examines catalyst deactivation mechanisms, specifically carbon and metal sulfide formation, and the performance of methane reforming and partial oxidation catalysts in SOFCs. Single-cell performance, including that of various perovskite and related oxides, activity/stability enhancement by infiltration, and the simulation and modeling of electrochemical performance, is discussed. This review also addresses research challenges in regards to methane reforming and partial oxidation within SOFCs, such as gas composition changes and large thermal gradients in stack systems. Finally, this review investigates the modeling of catalytic and non-catalytic processes using different dimension and segment simulations of steam methane reforming, presenting new engineering designs, material developments, and the latest knowledge to guide the development of and the driving force behind an oxygen concentration gradient through the external circuit to the cathode. Full article

The development of effective, cost-efficient, and printable solid-state gas sensors for the detection of volatile organic compounds is of great interest due to their wide range of applications, spanning from real-time indoor monitoring to emerging fields such as non-invasive medical diagnostics. However, gas sensors encounter difficulties in discovering materials that have both good selectivity and sensitivity for numerous volatile organic compounds in both dry and humid settings. To expand the class of sensing materials, the current study investigates the sensing performance of solid solutions based on a rare-earth metal oxide. Pr, Fe, and Ti oxide solid solutions were produced using a solid-state technique, with thermal treatments at varied temperatures to tune their structural and functional properties. The powders were used, for the first time, to produce chemoresistive sensors, which showed promising sensing capabilities vs. ethanol, acetone, and acetaldehyde. The sensors were characterized by varying the concentration of the target gases from 1 to 50 ppm in a controlled environment, with the relative humidity ranging from 2 to 40%. The findings bring a turning point, leading to fruitful paths for the development of Pr-based solid solutions-based chemoresistive gas sensors for the detection of volatile organic compounds. Full article

This work is devoted to the study of the effect of small Bi additives on the functional properties of Pdx:Bi/Al₂O₃ catalysts in the selective oxidation of glucose to gluconic acid. The catalysts obtained by the joint impregnation method were characterized (TEM) by high dispersion of bimetallic nanoparticles with a median diameter of 4–5 nm. The structure of the Pd-Bi solid solution was confirmed via XPS and showed a change in the valence state of Pd and Bi depending on the Bi content, as well as the fraction of the oxidized state of Bi. TPR-H₂ revealed various forms of Pd, including PdO and mixed Pd-O-Bi structures. The Pd10:Bi1/Al₂O₃ catalyst demonstrated the highest efficiency (77.2% glucose conversion, 96% sodium gluconate selectivity), which is due to the optimal ratio between Pd and Bi, ensuring the stabilization of metallic Pd and preventing its oxidation. Full article

Antimony (Sb) is a metalloid widely used in different areas—from the cutting-edge renewable energy technologies to “classical” lead acid batteries. Its availability in primary sources is limited, and these sources are geographically unevenly distributed worldwide. Antimony use will increase in the future. That is why Sb is included in the critical raw material lists of the European Union and the USA. In order to mitigate the future Sb shortage, Sb recovery from industrial residues is worth considering. This paper presents the availability of Sb in nonferrous metals extraction waste and the applicability of the hydrometallurgical route for Sb recovery from such sources. Leaching is emphasized. The use of acidic and alkaline leaching methods, their recent modifications, and the effect of different process parameters (reagents’ type, solid-to-liquid ratio, temperature, and the addition of oxidizing reagents) are highlighted. The use of new leaching systems, such as deep eutectic solvents and non-aqueous solutions, is presented. Initial attempts to apply bioleaching are described. Finally, some proposals for future investigations are given. Full article

Heterobimetallic uranium(V) alkoxides incorporating monovalent alkali metal counterions display remarkable structural versatility, dictated by the steric demands of the alkoxide ligands and the ionic radius of the alkali metal. Compounds of the general formula [UM(O^tBu)₆] (UM-O^tBu-type: M = Na, K, Rb, Cs) were obtained by: (i) reacting [U(O^tBu)₅(py)] with equimolar amounts of alkali metal silylamides in tert-butyl alcohol, and (ii) oxidative transformation of [UM₂(O^tBu)₆] (M = Na, K, Rb, Cs) upon reaction with iodine. Trans-alcoholysis of uranium heterobimetallic tert-butoxides with sterically less demanding iso-propyl alcohol yields oligomeric or polymeric iso-propoxide derivatives of the general formula [UM(OⁱPr)₆]_n, where the nuclearity depends on the alkali metal (n = 2 for M = Li; n = ∞ for M = Na, K, Rb). The capacity of alkali metal ions to adopt flexible coordination geometries results in different structural types ranging from finite clusters to infinite chains, with [ULi(OⁱPr)₆]₂ (ULi-OⁱPr-1) found to be dimeric, whereas [UM(OⁱPr)₆]_∞ (UM-OⁱPr-2-type, M = Na, K) and [URb(OⁱPr)₆]_∞ (URb-OⁱPr-3) exhibit a polymeric architecture. These findings provide fresh insights into the structure-directing influence of alkali metals on actinide coordination chemistry and broaden the chemistry of actinide alkoxides. All compounds were unambiguously characterized in both solution and solid-state through NMR and IR spectroscopic studies, as well as single crystal X-ray diffraction analysis. Full article

Refractory metal-based Mo-Si-B alloys have long been considered the most promising candidates for replacing nickel-based superalloys in the aerospace and energy sector due to their outstanding mechanical properties and good oxidation of the Mo-silicide phases. In general, the addition of vanadium to Mo-Si-B alloys leads to a significant density reduction, while small amounts of titanium provide additional strengthening without changing the phase evolution within the Mo_ss-Mo₃Si-Mo₅SiB₂ phase field. In this work, high-energy ball milling studies on Mo-40V-9Si-8B, substituting both molybdenum and vanadium with 2 and 5 at. % Ti in all constituents, were performed to evaluate the potential milling parameters and investigate the effects of Ti doping on the milling characteristics and phase formation of these multicomponent alloys. After different milling durations, the powders were analysed with regard to their microstructure, particle size, oxygen concentration and microhardness. After heat treatment, the silicide phases (Mo,V)₃Si and (Mo,V)₅SiB₂ precipitated homogeneously within a (Mo,V) solid solution matrix phase. Thermodynamic phase calculations using the CALPHAD method showed good agreement with the experimental phase compositions after annealing, confirming the stability of the observed microstructure. Full article

Solid oxide cells (SOCs) are highly efficient and versatile devices capable of utilizing a variety of fuels, presenting promising solutions for energy conversion and renewable resource utilization. There is an urgent need for the strategic design of robust and high-efficiency materials to enhance both conversion and energy efficiencies before SOCs can be applied for large-scale industrial production. Nanocomposite electrodes, especially those fabricated through infiltration and metal nanoparticle exsolution, have emerged as highly active electrocatalytic materials that significantly improve the performance and durability of SOCs. This review systematically summarizes and analyzes recent advances in the nanoscale architecture of electrode materials fabricated via common nanoengineering strategies, including infiltration and in situ exsolution, with applications in CO₂/H₂O reduction, hydrocarbon electrochemical oxidation, solid oxide fuel cells, and reversible operation. Finally, this review highlights existing bottlenecks and promising breakthroughs in common nanotechnologies, aiming to provide useful references for the rational design of nanomaterials for SOCs. Full article

This review explores hydrogen production via magnesium hydrolysis, emphasizing its role in the energy transition. Articles were selected from the Scopus database based on novelty. Magnesium’s abundance, high reactivity, and potential for recycling industrial waste make it a strong candidate for sustainable hydrogen production. A key advantage is the use of non-potable water, enhancing environmental and economic benefits. A major challenge is the passivating Mg(OH)₂ layer, which limits hydrogen release. Recent advances mitigate this issue through additives (metals, oxides, salts), alloying (Ni, La, Ca), mechanical treatments (ball milling, cold rolling), and diverse reaction media (seawater, acids, saline solutions). These strategies significantly improve hydrogen yields and kinetics, enabling industrial scalability. Magnesium hydrolysis exhibits a wide activation energy range (3.5–102.6 kJ/mol), highlighting the need for optimization in additives, concentration, temperature, and medium composition. Critical factors include additive selection, particle size control, and alloying, while secondary additives have a minimal impact. This review underscores magnesium hydrolysis as a promising, circular, economy-compatible method for hydrogen generation. Despite challenges in balancing efficiency and environmental impact, recent advancements provide a solid foundation for scalable, sustainable hydrogen production. Full article

Our planet is currently facing dual challenges of global warming and energy crisis. The heavy reliance of the energy sector on fossil fuels significantly contributes to the accumulation of greenhouse gases, such as CH₄ and CO₂, in the environment atmosphere, exacerbating global warming. Stabilized zirconia-based material offer a promising solutions to address both challenges. As a catalytic support material, active sites incorporated stabilized-zirconia can facilitate the conversions of greenhouse gases like CH₄ and CO₂ into syngas (H₂ and CO). This reaction is popularly known as dry reforming of methane (DRM). Additionally, stabilized zirconia-based materials act as solid-state electrolyte in fuel cells enabling the electrochemical conversion of H₂ and O₂ to generate electricity. Both processes require high-temperature stability and oxide ionic conductivity, making “Ca, Mg, Sc, Y-stabilized zirconia” an optimal choice. In DRM, the key factors influencing catalytic efficiency include metal–support interaction, reducibility, and basicity. Meanwhile, for solid oxide fuel cells, performance is governed by factors such as size-fit, charge imbalance, dopant miscibility, ion conducting phases, densification, electrolyte thickness, and grain boundary volume. This compressive review explores the dual functionality of “Ca, Mg, Sc, Y-stabilized zirconia” as a catalyst’support for DRM and as an solid electrolyte for fuel cells. The most promising research outcomes are highlighted, and future research directions are outlined. By bringing together the catalytic and fuel cell research communities, this study aims to advance sustainable energy technologies and contribute to mitigating environmental and energy crisis through the development of stabilized zirconia-based materials. Full article

This study explored the behavior of lead, copper, and iron during the leaching process of flash smelting slag from direct-to-blister copper flash smelting using l-ascorbic acid solutions. Flash smelting slag is generated in considerable quantities by various copper smelters worldwide. One drawback of the single-stage flash smelting technology for copper concentrates is the production of large quantities of metal-rich by-products. However, through appropriate management of postprocess waste, valuable components such as copper or lead can be recovered. In practice, the slag is typically subjected to decoppering processes involving electric and converter furnaces. The hydrometallurgical process proposed in this study is aimed at replacing high-temperature recovery methods. The primary objective of the experiments was to investigate the effects of variations in specific leaching parameters and the addition of auxiliary substances on the leaching efficiency of lead, copper, and iron. Four parameters were adjusted during the tests: concentration of l-ascorbic acid, liquid-to-solid phase ratio, temperature, and time. An oxidizing agent in the form of perhydrol and citric acid with an oxidant were used as additives. Optimal process conditions were determined to achieve maximum lead leaching efficiency while maintaining relatively low leaching of copper and iron. The experiments indicated that leaching in ascorbic acid solutions resulted in lead extraction efficiencies ranging from approximately 68% to more than 88%, depending on the conditions. Conversely, relatively low leaching efficiencies of iron (4–12%) and copper (0–29%) were observed. Full article

Metallosurfactants combine the unique soft-matter properties of surfactants with magnetic functionalities of metal ions. The inclusion of iron-based species, in particular, can further boost the functionality of the material, owing to iron’s ability to adopt multiple oxidation states and form both high-spin and low-spin complexes. Motivated by this, a series of hybrid inorganic-organic dodecylpyridinium metallosurfactants with iron-containing counterions was developed. It was established that using either divalent or trivalent iron halides in a straightforward synthetic procedure yields C₁₂Py-metallosurfactants with distinct complex counterions: (C₁₂Py)₂[Fe₂X₆O] and (C₁₂Py)[FeX₄] (X = Cl or Br), respectively. A combination of techniques—including conductometry, dynamic and electrophoretic light scattering, single-crystal and thermogravimetric analysis, and magnetic measurements—provided in-depth insights into their solution and solid-state properties. The presence of different iron-based counterions significantly influences the crystal structure (interdigitated vs. non-interdigitated bilayers), magnetic properties (paramagnetic vs. nonmagnetic singlet ground state), and self-assembly (vesicles vs. micelles) of the dodecylpyridinium series. To our knowledge, this is the first report on the synthesis and characterization of hybrid organic-inorganic metallosurfactants containing the μ-oxo-hexahalo-diferrate anion. Full article

In pursuing sustainable environmental solutions, the concept of ‘waste to treasure’ has emerged as a promising approach. In this study, a new process is proposed to combine solid copper slag with hydrogen peroxide (H₂O₂) to remove nitrogen oxides (NOx) from acidic exhaust gases, thus effectively utilizing waste materials. Firstly, different smelting slags were screened to determine the catalytic potential of copper slag for hydrogen peroxide. Subsequently, the catalytic activity of the copper slags at various stages of the copper smelting process was thoroughly evaluated and optimized. In addition, a multifactorial evaluation of slow-cooled copper slag catalysts for removing NOx was carried out. Preliminary indications are that the iron phase in the copper slag is identified as the main source of catalytic activity sites. The results suggest that Fe²⁺/Fe³⁺ sites on the surface of the Fe phase in the slow-cooled copper slag may be crucial in improving the NOx removal efficiency. The main reactive oxygen species detected in the system were ·OH, ·O₂⁻, and ¹O₂. In addition, the transformation products, formation pathways, and reaction mechanisms of NO in the liquid phase were initially investigated and determined. This study provides a green and sustainable path for the utilization of solid waste and management of atmospheric fumes in the non-ferrous metal industry and offers new perspectives to address environmental challenges in industrial processes. Full article

Metal-ion capacitors (MICs) have emerged as advanced hybrid energy storage devices that combine the high energy density of batteries with the superior power density and long cycle life of supercapacitors. By leveraging a unique configuration of faradaic and non-faradaic energy storage mechanisms, MICs offer a balanced performance that meets the diverse requirements of modern applications, including renewable energy systems, electric vehicles, and portable electronics. MICs employ diverse ions such as lithium, sodium, and potassium, which provide flexibility in material selection, scalability, and cost-effectiveness. For instance, lithium-ion capacitors (LICs) excel in compact and high-performance applications, while sodium-ion (NICs) and potassium-ion capacitors (KICs) provide sustainable and affordable solutions for large-scale energy storage. This review highlights the advancements in electrode materials, including carbon-based materials, transition metal oxides, and emerging candidates like MXenes and metal–organic frameworks (MOFs), which enhance MIC performance. The role of electrolytes, ranging from organic and aqueous to hybrid and solid-state systems, is also examined, emphasizing their influence on energy density, safety, and operating voltage. Additionally, the article discusses the environmental and economic benefits of MICs, including the use of earth-abundant materials and bio-derived carbons, which align with global sustainability goals. The review concludes with an analysis of practical applications, commercialization challenges, and future research directions, including AI-driven material discovery and integration into decentralized energy systems. As versatile and transformative energy storage devices, MICs are poised to play a critical role in advancing sustainable and efficient energy solutions for the future. Full article