Search Results (379)

High-grade non-oriented silicon steel is a critical material for new energy vehicles and energy-efficient appliances due to its superior magnetic properties. However, these properties are significantly degraded by non-metallic inclusions, particularly Ti(C,N). This study employs integrated thermodynamic and kinetic calculations to systematically analyze the formation and growth mechanisms of Ti(C,N) inclusions in high-grade non-oriented silicon steel, trace the sources of [Ti], and propose targeted theoretical control strategies. Results indicate that Ti(C,N) inclusions do not precipitate above the liquidus temperature (1779 K). During solidification, microsegregation enriches Ti, C, and N; however, only TiN precipitates in the final stage as its ion product exceeds the solubility limit, whereas TiC remains undersaturated—findings valid within the present composition window and modeling framework. Inclusion size is governed by cooling rate and initial Ti/N content, where higher cooling rates yield finer inclusions and lower Ti/N content suppresses precipitation. Titanium originates from primary sources (raw materials and alloys) and secondary sources (decomposition or reduction of TiO₂ in slag/refractories). Therefore, mitigating [Ti] requires strictly limiting primary input and suppressing secondary formation through optimized process control, such as reducing BOF slag carryover, lowering refining temperature, and controlling [Al] content. Full article

The present study examined the interactions between the structure, microstructure and mechanical properties of CrMnFeCoNi, CrMnFeCoNiV_0.5 and CrMnFeCoNiMo_0.5 High-Entropy Alloys (HEAs). Starting from elemental powders, the HEAs were obtained by high-energy ball milling, followed by vacuum annealing at 1373 K for 1 h. After milling, a binary FCC-BCC solid solution was formed; the samples showed hardness values ranging from 800 to 973 HV. Evidence shows that annealing HEAs reduced the solubility of V and Mo in the alloys’ FCC structure. Additionally, the Cr content in the FCC phase also decreases. The carbon derived from the decomposition of the process control agent was trapped in the interstices of the HEA structure during mechanical alloying. This amount of carbon is sufficient to form carbides during annealing. The thermodynamic stability of the precursor elements in HEAs is a determining factor in M_xC_y-type formation. The hardness response of HEAs was associated with the HEAs’ structure, while the elastic modulus was affected by their microstructure. Full article

High-phosphorus iron ore is an abundant yet refractory resource whose industrial exploitation is severely constrained by its elevated phosphorus content. Guided by the ore’s reduction characteristics, two process routes were designed and compared: carbon-composite pellet direct reduction followed by melting separation (CCP-DR–MS) and direct reduction–magnetic separation–melting separation (DR–MS–MS). Systematic experiments under simulated industrial conditions evaluated the metallization degree, dephosphorization efficiency, and smelting performance while clarifying the key factors that govern the differences in phosphorus removal between the two processes. The results show that both routes raised the ore’s metallization degree to above 95% during direct reduction, but the DR–MS–MS route delivered markedly better dephosphorization, achieving a maximum phosphorus removal rate of 89.20%. Although the slags produced by the two processes showed comparable phosphorus capacities, the difference in overall dephosphorization efficiency stemmed from their distinct reduction mechanisms: in DR–MS–MS, metallic iron is generated mainly via CO-mediated reduction, which suppresses phosphorus reduction, whereas in CCP-DR–MS, phosphorus and iron are simultaneously reduced by carbon. Consequently, DR–MS–MS attains superior phosphorus removal. Full article

This comparative study investigates binder-free binary WC-TiC and ternary WC-TiC-TaC carbide ceramics as alternatives to cobalt-bonded hard materials. Equimolar compositions were processed via high-energy ball milling (HEBM) and consolidated by spark plasma sintering (SPS) at 1700–2100 °C. X-ray diffraction analysis (XRD) revealed fundamentally different homogenization kinetics: the ternary system achieved a complete single-phase structure at 2000 °C, 100 °C earlier than the binary system. This acceleration correlates with finer initial particle size (2–5 μm vs. 3–10 μm) and near-stoichiometric TaC, facilitating interdiffusion. Lattice parameter evolution confirmed the formation of (W,Ti)C and (W,Ti,Ta)C substitutional solid solutions. Mechanical characterization showed contrasting behaviors: binary WC-TiC exhibits maximum hardness at 1900 °C (1793 HV30, fracture toughness 5.07 MPa·m^1/2), while ternary WC-TiC-TaC peaks at 1700–1800 °C (1947–1782 HV30) with higher toughness (max 5.42 MPa·m^1/2). Optimal processing windows with acceptable property uniformity are 1800–1900 °C (binary) and 1700–1900 °C (ternary). The binary system offers superior toughness and stability; the ternary system enables faster processing and higher initial hardness, defining distinct application domains. Full article

The increasing global demand for sustainable water purification technologies has accelerated research on catalytic degradation and advanced oxidation processes for the removal of refractory pollutants. This study provides a comprehensive bibliometric analysis of global research trends in catalytic water and wastewater treatment from 2010 to 2025, combining quantitative mapping with a qualitative synthesis of emerging technological directions. Bibliographic data were retrieved from the Scopus database and screened using the PRISMA framework, followed by analysis using VOSviewer (v1.6.20) and OriginPro (version 2023, OriginLab Corporation, Northampton, MA, USA) to examine publication growth, citation patterns, international collaboration networks, and thematic evolution. A total of 1550 publications, including 1265 research articles and 285 review papers, were analyzed. The results show a significant increase in research output after 2015, reflecting growing global attention to water sustainability and environmental remediation. China, the United States, and India were identified as the leading contributors, with strong international collaboration networks. Keyword co-occurrence analysis revealed three dominant research themes: photocatalytic degradation and semiconductor engineering, Fenton and Fenton-like advanced oxidation processes, and emerging hybrid catalytic systems involving carbon-based materials and metal–organic frameworks. The analysis also indicates a recent shift toward multifunctional hybrid catalysts designed to improve efficiency, stability, and performance in complex wastewater systems. These findings highlight key scientific developments and suggest future research priorities, including green catalyst synthesis, reactor and process scale-up, AI-assisted catalyst design, and life-cycle sustainability assessment to support the transition from laboratory research to practical water treatment applications. Full article

The persistent discharge of refractory toxic organic pollutants poses a severe threat to aquatic environmental safety, driving the urgent demand for high-efficiency water treatment technologies in environmental engineering. Fenton and Fenton-like oxidation processes have garnered extensive attention due to their robust oxidizing capacity and environmental benignity; however, traditional Fenton systems are constrained by inherent limitations, including a narrow applicable pH range, potential secondary pollution, and cumbersome catalyst recovery. To address these challenges, Fenton-like catalysts have evolved progressively from single-metal systems to multi-metal alloy configurations. This review systematically elaborates on the fundamental principles and technical bottlenecks of classical Fenton and Fenton-like reactions, while comprehensively summarizing the research progress of multi-metal alloy catalysts—encompassing binary alloys, multi-component alloys, and high-entropy alloys. Special emphasis is placed on dissecting the core mechanisms through which multi-metal alloys optimize redox cycles and enhance structural stability, leveraging intermetallic synergistic effects, unique electronic structures, and lattice distortion. Furthermore, this work synthesizes key performance enhancement strategies for such catalysts, including co-catalyst synergy, external field assistance, and supported composite modification. Ultimately, this review aims to provide a scientific foundation and technical reference for the rational design, development, and engineering application of high-performance Fenton-like catalysts in sustainable wastewater remediation. Full article

The accelerating transition to low carbon energy systems has intensified the demand for nickel and cobalt from low-grade (<1.5 wt.%) refractory lateritic ores. These low-grade laterites are however not amenable to conventional beneficiation due to their complex mineralogy, eclectic physicochemical properties, and fine Ni–Co dissemination. This review examines recent advances made in the extraction of nickel and cobalt from complex low-grade lateritic ores, emphasizing the interplay between ore mineralogy, chemistry, beneficiation, pretreatment, and processing route selection. Developments in selective ore comminution–classification have led to the generation of Ni-rich fine fractions (undersize) and Co-rich coarse fractions (oversize), enabling differentiated extraction strategies that improve resource utilization, frugal energy use, and process efficiency. Mechanical activation via stirred media milling, thermal calcination-induced structural disorder, and dehydroxylate goethite products, are shown to significantly enhance Ni–Co leaching kinetics under both atmospheric and heap leaching conditions. A critical comparison of pyrometallurgical (rotary-kiln electric furnace) and hydrometallurgical (HPAL, EPAL, heap, atmospheric, bioleaching) routes demonstrates that ore-specific optimization is essential to balance recovery, acid consumption, and greenhouse gas emissions. The novel resin in moist mix (RIMM) process, which integrates ambient leaching and in situ ion exchange selective recovery, is shown to offer potential for sustainable values extraction from sub-economic resources. Furthermore, the review highlights the key innovation challenges and concomitant opportunities for enhanced critical battery metal recovery from complex laterite ores. 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

Modulating surface characteristics via metal ions has proven to be a successful approach to enhance the flotation efficiency of carbonates. Consequently, this research thoroughly examines how ferrous ions (Fe²⁺) influence the selective separation of rhodochrosite from calcite. Flotation experiments revealed that at pH 9.0, Fe²⁺ strongly depressed calcite flotation (recovery < 20%) while exerting a negligible influence on the floatability of rhodochrosite (recovery > 75%), enabling effective selective separation. To elucidate the underlying mechanism, contact angle measurements, zeta potential analysis, ToF-SIMS, SEM-EDS, XPS and Visual MINTEQ solution chemistry calculations were employed to characterize mineral surface properties. The results demonstrate that Fe²⁺ undergoes chemisorption onto the calcite surface, inducing the formation of a dense, uniform iron hydroxide layer. This layer creates a stable hydrophilic barrier that inhibits collector adsorption. In contrast, only a thin, discontinuous layer forms on the rhodochrosite surface, which is insufficient to hinder collector interaction. These findings reveal the intrinsic mechanism of selective interfacial regulation by ferrous ions, providing a new theoretical basis for the flotation separation of refractory carbonate minerals. Full article

The incorporation of recycled metallurgical slags into refractory materials constitutes a promising approach to enhancing sustainability in the refractory industry. This study investigates the effect of vanadium-bearing slag aggregates as partial replacements for tabular alumina in castables and compares their behaviour with high-alumina and bauxite-based castables. Two vanadium-bearing slags with different mineralogical compositions were introduced in the 1–3 mm aggregate fraction with substitution up to 25 wt.%. Their effects on microstructure, thermo-mechanical performance, and corrosion resistance were evaluated. The introduction of vanadium-bearing slag significantly alters the microstructure of the castables, affecting their performance. Both slags displayed grains with higher porosity, microcracking, and heterogeneity compared with tabular alumina, but showed similarities to bauxite grains. Slag 1, enriched in calcium aluminate phases, provides limited mechanical strength but improved corrosion resistance due to improved bonding with the matrix. Slag 2, containing a higher spinel content, enhances mechanical strength, showing behaviour comparable with bauxite-based castables, particularly at 10 wt.% replacement. Vanadium is mainly present in metallic form and as Mg(Al,V)₂O₄ spinels in both slags. Upon firing, vanadium migrates toward the grain boundaries and reacts with the surrounding calcium aluminate phases to be incorporated in Ca(Al,V)₂O₄ and Ca(Al,V)₄O₇, while the spinel phase remains stable. Full article

The design and fabrication of metal matrix materials (MMCs), as well as the densification and joining of ceramic matrix composites (CMC), are still very challenging. For SiC- and C-based composites, liquid-assisted processing routes, such as the spontaneous infiltration process, emerge among the most cost-effective processes. To succeed in Ir-Si/SiC refractory composite fabrication by spontaneous infiltration, the wetting characteristics of the Ir-Si/SiC system, the surface and transport properties (surface tension and viscosity) of liquid Ir-Si alloys, and microstructural evolution at the interfaces formed between solid SiC (or C) with Ir-Si melt, have been carefully examined. Specifically, the wettability and interaction phenomena occurring at the Si-Ir eutectics/SiC interface as a function of temperature were investigated in the temperature range of T = 1350–1400 °C by the sessile drop method under an inert atmosphere with reduced oxygen content, and the results are presented and discussed in this paper. Taking into account the thermodynamics of the Si-C-Ir system, the interfacial phenomena and subsequent microstructural evolution are well-related to the process parameters, and the properties and characteristics of the as-produced interfaces may be predicted accordingly. The experimental conditions and results of wetting experiments, together with thermodynamic-based models predicting thermophysical property values of liquid Ir-Si alloys, are valuable key input data that are now available for the numerical study of infiltration processes. Full article

The existence of continually increasing refractory organic pollutants in water has always been a serious potential threat to human and environmental health due to their toxicity and persistence. Conventional water treatment technologies suffer from inherent limitations, including low degradation efficiency, secondary pollution issues, and high operational costs. Recently, molecular oxygen (O₂)-based advanced oxidation processes (O₂-AOPs) have attracted increasing attention as sustainable and efficient wastewater treatment technologies, as the abundant and environmentally benign oxidant in nature can be activated into reactive oxygen species (ROS), such as superoxide anions ($·{\mathrm{O}}_2^{-}$), hydroxyl radicals (·OH), and singlet oxygen (¹O₂), enabling the effective mineralization of refractory organic pollutants. This review presents a comprehensive summary of O₂-AOPs for water purification, specifically focusing on photocatalytic, electrocatalytic, thermocatalytic, and mechanocatalytic systems. Furthermore, we conduct a comprehensive analysis of the intrinsic reaction mechanisms associated with both free radical pathways and non-free radical pathways, which include processes involving singlet oxygen and high-valent metal-oxygen intermediates. Finally, we discuss the challenges and prospects associated with the degradation of typical organic pollutants, such as phenolic compounds, pharmaceuticals and personal care products (PPCPs), and organic dyes. Despite significant advancements in O₂-AOPs, several core challenges persist, including low efficiency in utilizing dissolved oxygen, insufficient catalyst stability, and unclear mechanisms of interfacial electron transfer. Future research should prioritize the precise regulation of material structures, a thorough analysis of reaction mechanisms, and the tailored development of reactors to facilitate the industrial application of this technology in water treatment. Overall, this review systematically outlines the current progress in technologies for removing organic pollutants using molecular oxygen, offering novel insights for mitigating organic pollution in water. Full article

A new solvent extraction system for the removal of 4f ions (Ln³⁺) from water by use of chelating ligands (HLn, n = 5, 6, 7, and 8) composed of heterocyclic receptors and one β-dicarbonyl fragment is reported. The covalent attachment of a β-dicarbonyl unit to a saturated N-heterocycle with variable ring size resulted in a cooperative interaction within the receptor for Ln³⁺ transfer, which remarkably enhanced the efficiency of the process. The intramolecular cooperative effect was observed only in the ionic liquid (IL) solvent system, providing a several-fold increase in extraction performance for Ln³⁺ ions (La, Nd, Eu and Dy) over chloroform. Thus, it is not possible to confirm that an identical reaction mechanism operated in both liquid systems: IL or CHCl₃. The existence of neutral chelates of the type LnL₃ or anionic lanthanoid complexes [LnL₄⁻] in an ionic medium during the solvent extraction process applying various solvent systems has been established hitherto. Consequently, the Ln³⁺ ion was held by HLn molecules more rigidly in an IL medium ([C₁C_nim⁺]/[C₁C₄pyr⁺]/[C₁C₄pip⁺][Tf₂N⁻], n = 4, 6, 8, 10) than in chloroform, representing an important factor dominating the magnitude of the intramolecular cooperative effect of the chelating ligands for Ln³⁺ ions. The effect of the diluent’s chemical nature on the metal extraction and separation has been studied and discussed thoroughly. Furthermore, competitive solvent extraction and separation studies with various s-, p-, d-, and f-ions of the periodic table revealed that the magnitude of the intramolecular cooperative effect depends on the suitability between the metal ion size and the cavity size or flexibility of the HLn compounds. In addition, the solvent extraction process of 12 refractory metals and 8 platinum group metals with the synthesized chelating extractants is also investigated in different organic liquid media. Full article

Molybdenum (Mo) finds extensive applications in the steel industry, and the recycling of secondary molybdenum resources is crucial for the green development of the molybdenum sector. Meanwhile, the large-scale stockpiling of copper slag, a bulk industrial solid waste, poses severe environmental and resource-related challenges. Addressing the common issues of the refractory nature of waste molybdenum disilicide (MoSi₂) and the underutilization of iron resources in copper slag, this study proposes a synergistic smelting approach using copper slag and waste MoSi₂, aiming to realize the coordinated treatment of these two solid wastes and the simultaneous, efficient recovery of valuable metals (Mo and Fe). Under non-isothermal conditions, this work elucidates the phase evolution of copper slag and the decomposition–reduction behavior of MoSi₂; clarifies the dual role of coke as the primary reductant at the initial reaction stage and as a maintainer of a reducing atmosphere during smelting; and systematically investigates the effects of smelting temperature, slag basicity, and coke dosage on metal recovery. The results demonstrate that, under optimized process conditions, the recovery efficiencies of molybdenum and iron can reach 98.97% and 98.46%, respectively. This study provides a new strategy for the enrichment and extraction of metallic elements from waste MoSi₂ and copper slag. Full article

Platinum group metals (PGMs)—comprising platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os)—are indispensable strategic materials for key industries, including automotive manufacturing, petrochemical engineering, and the new energy sector. Given the uneven global distribution of primary PGM reserves and the widening supply–demand gap, recovering PGMs from secondary sources—primarily metallurgical by-products and spent catalysts—has become a strategic priority. synergistic smelting, leveraging “multi-feedstock complementarity” and “multi-technology coupling,” offers an efficient approach to overcoming challenges associated with secondary resources, such as low grades, complex matrices, and refractory separation. This paper systematically reviews the technological evolution of synergistic smelting for PGMs recovery, focusing on three aspects: the characteristics and processing bottlenecks of PGMs-bearing secondary resources, the development trajectory of traditional metallurgical technologies, and innovative breakthroughs in microwave-assisted synergistic smelting. A comparative analysis between traditional and microwave-based technologies is conducted across four dimensions: resource adaptability, technical performance, environmental sustainability, and industrial maturity. Finally, the core challenges currently confronting microwave-assisted synergistic smelting and future directions for industrial demonstration are elaborated on. This study serves as a comprehensive reference for the efficient and sustainable recovery of PGMs, with significant implications for the circular economy and strategic resource security. Full article