Search Results (236)

Metal–Insulator–Metal (MIM) tunneling diodes are among the most promising rectifying devices for long-wave infrared (LWIR) rectenna systems due to their ultrafast response and zero-bias operation. However, their performance is strongly dependent on the choice of electrode and dielectric materials, making the identification of optimal material combinations a key challenge. To address this issue, this theoretical study presents a numerical investigation of a new class of MIM diodes based on a quantum-mechanical tunneling framework. Novel combinations of transition-metal dichalcogenides (NbS₂, VSe₂, and TaS₂) as anode materials (M1), conductive carbides and nitrides (Mo₂C, VN, and V) as cathode materials (M2), and rare-earth oxide and oxyhalide compounds (Sc₂O₃, LaOF, and LaOBr) as tunnel barriers (I) were selected through an extensive literature survey. These materials were combined to design previously unexplored MIM architectures for LWIR rectification. The electrical transport and rectification properties were evaluated using the Simmons tunneling model by calculating the current density–voltage (J–V) and current–voltage (I–V) characteristics, together with key figures of merit (FOMs), including zero-bias resistance, asymmetry factor, nonlinearity, and responsivity, at room temperature (300 K). The effects of tunnel barrier height and dielectric properties on device performance were systematically investigated. Among all the investigated architectures, the TaS₂/LaOBr/V MIM diode exhibited the most promising overall performance, achieving an asymmetry factor exceeding 2.5 × 10⁵, a nonlinearity factor of 1, and a zero-bias responsivity of 10 V⁻¹ at 300 K. Furthermore, this structure demonstrated the highest current density and the most favorable I–V characteristics among the proposed material combinations. These results identify the TaS₂/LaOBr/V material system as a promising candidate for high-performance LWIR energy harvesting applications, owing to its optimized tunnel barrier height, which promotes efficient electron tunneling while maintaining excellent rectification properties. Full article

The increasing use of electric vehicles has led to a growing demand for rare-earth elements, particularly neodymium (Nd), which is a critical component of Nd–Fe–B permanent magnets used in traction motors. End-of-life electric vehicle motors are therefore considered promising secondary resources for Nd recovery. In this study, a pyrometallurgical process using non-ferrous smelting slag as a flux was proposed for recovering Nd from Nd–Fe–B magnets contained in waste electric vehicle motors. Steel and magnet fractions obtained from a dismantled motor were melted at approximately 1600 °C under an air atmosphere, and Fe₂O₃ was added as an oxidizing agent to promote the selective oxidation of Nd. The oxidized Nd was subsequently partitioned into the slag phase as Nd₂O₃ through metal–slag separation. The effects of the slag flux addition ratio, Fe₂O₃ content, slag flux type, and crucible material on Nd recovery behavior were systematically investigated. Increasing the fayalite-based slag flux addition enhanced Nd transfer into the slag phase, and the highest Nd recovery of approximately 80% was obtained at a slag flux addition ratio of 30 wt%. The addition of 2 wt% Fe₂O₃ was found to be suitable for promoting stable Nd oxidation and efficient slag–metal separation. The non-ferrous smelting slag exhibited chemical and phase characteristics comparable to those of synthetic fayalite slag flux, resulting in similar Nd recovery performance. In addition, the crucible material significantly affected the process stability and Nd recovery behavior. Although a carbon crucible showed relatively high Nd recovery, severe slag foaming and crucible erosion occurred during melting. In contrast, alumina and MgO crucibles provided stable process conditions with comparable Nd recovery behavior, whereas zirconia crucibles caused relatively higher Nd loss. These results demonstrate that non-ferrous smelting slag can be effectively used as a flux for the pyrometallurgical recovery of Nd from end-of-life electric vehicle motors, offering a potential route for sustainable rare-earth recycling. Full article

Heavy metals (HMs) and rare earth elements (REEs) increasingly co-occur in environmental waste streams and soils, yet their comparative neurotoxic mechanisms and sublethal effects on invertebrate decomposers remain poorly understood. This study used black soldier fly larvae (BSFL, Hermetia illucens) to perform a comparative behavioral and transcriptomic assessment of 23 HMs and 16 REEs across two acute exposure concentrations. High-throughput video tracking and phenomic analysis showed HMs produced broader disruption than REEs, with low-concentration HMs inducing locomotor suppression, thigmotaxis, reduced fractal dimension and entropy, progressing to severe motor inhibition and rigid low-entropy states. In contrast, REEs showed a biphasic profile, shifting from selective locomotor suppression with preserved organization at low concentrations to hyperactive, fragmented, high-entropy movement with increased thigmotaxis at high concentrations. PCA and hierarchical clustering integrated endpoints into four neurobehavioral fingerprints segregating metal class and concentration, with partial overlap of high-concentration REEs with HMs along a shared high-toxicity axis. Transcriptomic profiling showed that cobalt as a representative HM activated DNA damage and cell-cycle pathways, perturbed energy signaling, and suppressed neuroactive ligand–receptor interaction, whereas samarium as a representative REE downregulated xenobiotic metabolism, oxidative phosphorylation, glutathione metabolism, and synaptic vesicle cycling. These findings demonstrate distinct concentration-dependent neurotoxic modes of action for HMs and REEs and establish BSFL behavioral phenomics integrated with transcriptomics as a mechanistically informative platform for ecological risk assessment in contaminated waste systems. Full article

The growing demand for rare earth elements (REEs), heavy metals (HMs) and precious metals (PMs) has intensified interest in sustainable recovery strategies from secondary resources, including mining residues, industrial effluents and waste electrical and electronic equipment (WEEE). These streams represent exposure interfaces, because soluble and bioavailable metal species may persist, bioaccumulate and contribute to oxidative stress, genotoxicity, carcinogenic outcomes and chronic systemic effects. This systematic review, conducted following PRISMA guidelines, evaluates the thermoacidophilic red microalga Galdieria spp. as an extremophilic platform for metal bioremediation, recovery and upstream risk reduction. Galdieria spp. combines tolerance to low pH, elevated temperature and high metal loads with rapid surface biosorption and, in living biomass, slower intracellular sequestration and detoxification. Its interaction with REEs, PMs and toxic HMs is mediated by cell-wall functional groups, extracellular polymeric substances, redox-active processes and metabolic flexibility shaped partly by horizontal gene transfer (HGT). The review discusses matrix complexity and adsorption–desorption cycles, highlighting their implications for real industrial streams. Overall, Galdieria spp. emerges as a robust extremophilic bio-interface for selective metal recovery, hazardous waste mitigation, circular-economy biorefinery models and prevention of metal-associated risks to environmental and human health, while current scale-up limitations and process-oriented research priorities are identified. Full article

The oxygen-evolving center (OEC) in photosynthesis is a unique biological Mn₄CaO₅-cluster that splits water into electrons, protons, and dioxygen. It is a great challenge for chemists to develop a robust and precise mimic of the OEC in the laboratory. Herein, we report the formation of a rare-earth-element-containing Mn₄YO₄-cluster that represents an excellent and robust model of the OEC. The key synthetic precursor, the Mn₃YO₂-cluster, is reported for the first time, which possesses an identical mixed-valence Mn^III₂Mn^IV metal core and a hydrogen-bonding network coordination sphere. This precursor is very reactive and can convert into various compounds in solution. Importantly, it has been found that the presence of organic bases significantly influences the distribution of intermediates and promotes the formation of the Mn₄YO₄-cluster. Meanwhile, two Mn₄YO₄-clusters are described, which closely mimic the main metal-oxide core and peripheral ligands, as well as the oxidation states of the four Mn ions in the OEC, revealing that both the terminal ligands and a bridging carboxylate are variable. This new Mn₄YO₄-cluster displays a remarkable stability in the presence of water in acetonitrile solution. These findings shed new light on the synthesis of rare-earth-element-containing clusters and the rational design of robust artificial water-splitting catalysts, and provide chemical insights into the dynamic structural changes of both biological and artificial clusters. Full article

This study characterizes the physicochemical properties of coal gangue in Huainan, a typical coal resource-based city in China, and evaluates variations in its chemical composition and associated ecological risks. The results show that the coal gangue in the Huainan mining area is composed mainly of quartz and clay minerals, with SiO₂ and Al₂O₃ together accounting for over 86% of the total composition. Rare earth element concentrations are generally higher than background levels, whereas heavy metal concentrations are generally below the risk screening values for soil contamination of agricultural land. Complex associations are observed among the elements in coal gangue. The correlation coefficients between SiO₂ and the other oxides or heavy metals range from −0.750 to −0.993, indicating significant negative correlations and suggesting that the silicate mineral phase occurs independently of other element-enriched phases. The potential ecological risk index (RI) for heavy metals ranges from 33.75 to 300.71 and is driven primarily by Hg and Cd. The RI for rare earth elements ranges from 98.9 to 220.3, with Lu as the key influencing element. The predicted probability of adverse biological effects is 14–15%. Overall, classified management of coal gangue in the Huainan mining area is recommended, together with strengthened continuous monitoring of Hg and Cd and optimization of ecological disposal strategies by integrating potential ecological risk assessment with analysis of adverse biological effects, thereby further supporting the green transition of resource-depleted cities. Full article

Modification of DSSC photoanodes by adding various types of materials is a widely used method to improve the performance of electrochemical devices. In this work, selected rare-earth oxide (RE₂O₃) nanoparticles, such as erbium oxide (Er₂O₃), holmium oxide (Ho₂O₃), neodymium oxide (Nd₂O₃), and ytterbium oxide (Yb₂O₃), were applied for photoanode preparation. A simple method for photoanode fabrication based on the direct mixing of oxide nanoparticles with TiO₂ paste was employed. The effect of variation in the rare-earth oxide content in the photoanode was investigated. The prepared composite photoanodes were characterized by XRD and FE-SEM for structural and morphological studies. XRD verified the anatase polymorph of TiO₂; FE-SEM with EDS mapping validated the uniform morphology of the anode and the distribution of RE₂O₃, as well as its amount. The photovoltaic parameters of modified DSSCs based on the current-voltage measurements were analyzed. Full article

Methane partial oxidation (POM) offers a promising pathway for syngas production, but achieving optimal catalyst performance requires precise control of promoter loading. We systematically investigated cerium (Ce) promotion on nickel-based catalysts supported on aluminum oxide (Ni/Al₂O₃) catalysts across 1–3 wt.% loadings and identified a critical discovery: catalyst performance exhibits a pronounced non-monotonic response to Ce concentration. The 1 wt.% Ce-promoted catalyst (Ni+1Ce/Al) achieved the superior performance with 65% methane conversion and 60% hydrogen yield at 650 °C, maintaining stable output over 275 min time-on-stream. This smaller Ce amount tunes NiO reducibility, oxygen mobility, and metal–support interactions, resulting in improved activity performance of Ni+1Ce/Al. Notably, Ce promotion shifts the H₂/CO ratio from 2.5 to 2.9, with the increased hydrogen yield arising from enhanced water–gas shift chemistry and indirect oxidation pathways. Excess cerium (2–3 wt.%) causes performance deterioration, Ni particle agglomeration, and thus loss of Ni active sites, demonstrating that Ce operates as a structural promoter with a well-defined appropriate concentration window. Moreover, the best performing catalyst (Ni+1Ce/Al) remained stable during 20-h long-term POM. An artificial neural network model achieved exceptional predictive accuracy (R = 0.9758 overall), validating the experimental findings. These results indicate that the best Ce loading for industrial application is 1 wt.% and the traditional alumina supports can be competitive in performance with the advantage of thermal stability and cost-effectiveness when doped with rare-earth elements. Full article

Rare earth has been widely introduced in heat-resistant steel. However, excessive amounts of rare earth should be added due to the low yield rate, and the molten steel in the mold was highly reducible. Severe slag–metal interface reactions occurred when conventional mold fluxes were used. To restrain interfacial reactions during continuous casting of heat-resistant steel containing rare earth, a new method for designing mold flux was proposed, and different flux systems containing rare earth oxide were devised. The properties such as melting temperature, viscosity, and crystalline phase of the different mold fluxes were systematically investigated. Comparisons of properties between the new fluxes and the conventional mold fluxes were conducted. The results show that properties similar to those of the conventional mold flux could be obtained by adopting Li₂O and B₂O₃ as fluxing agents in the newly designed system. The new mold flux with high content of CaO and Al₂O₃ had approximate properties with the conventional mold flux. Cerium oxide could not separate out in the continuous cooling process. The main crystalline phase was LiAlO₂ in the new mold fluxes, which is different from the cuspidine (3CaO∙2SiO₂∙CaF₂) in the conventional mold flux. LiAlO₂ can be a potential substitute for cuspidine. It was entirely feasible to devise and develop a new mold flux containing rare earth with a high content of CaO and Al₂O₃ for rare earth steel continuous casting by further optimizing its properties. Full article

Fresh flotation tailings represent an underutilized archive of mineralogical and geochemical information in which multiple strands of evidence for ore-forming processes and post-depositional modification can be preserved. Detailed characterization of tailings is also vital for assessment of their future potential as a secondary source of recoverable by-products. This study investigates residual mineral speciation and mineral distributions in size fractions of tailings from the Prominent Hill iron oxide–copper–gold (IOCG) deposit, South Australia, with emphasis on rare earth element (REE) minerals and associated phases containing uranium (U). Assemblages of REE minerals can be highly complex at the micron scale and include sequences of mineral replacement, notably monazite → florencite, and monazite → synchysite. Bastnäsite-(Ce) commonly appears paragenetically early and is frequently altered or replaced by synchysite and parisite, supporting episodes of REE remobilization and reconcentration over geological time. Uranium is closely associated with REEs, and U-mineral assemblages are similarly characterized by intricate replacement relationships between uraninite and secondary phases. Uraninite is variably replaced by coffinite and the U-carbonate wyartite, reflecting changes in redox state, silica activity, and fluid composition. Additional replacement pathways from uraninite to Cu–Fe sulphides, including bornite and chalcopyrite, are documented and indicate coupled dissolution–reprecipitation of sulphides and U-minerals during superimposed hydrothermal activity. Preservation of mineralogical relationships within tailings drawn from multiple parts of a large deposit highlights their value as an essentially untapped library of information to reconstruct deposit evolution, complementing traditional study of selected drill core samples. Systematic investigation of tailings from large deposits can improve genetic models for large copper deposits, including but not restricted to IOCGs, and provide essential insights into REE behaviour, uranium remobilization, and critical metal potential. These findings emphasize the scientific and economic value of tailings-based studies for improved resource characterization, refining metallogenic interpretations, guiding future exploration strategies, and assessing opportunities for reprocessing and metal recovery in large ore systems worldwide across diverse geological settings. Full article

The growing field of nanobiotechnology could provide an alternative platform for the development of new therapeutic agents. A potential means for achieving these goals are nanoparticles of rare-earth metals, for example, nanoceria. According to the results of numerous in vitro and in vivo studies, not only oxide forms of lanthanides can demonstrate a pharmacological effect. A promising nano-object for biomedical application is cerium phosphate, which exhibits both properties characteristic of cerium dioxide and its own unique properties, due to the diversity of morphology. However, at present, a unified methodological approach has not been formulated that would make it possible to formulate principles for obtaining a compound with specified properties. This review was conducted on using the international databases PubMed, PubChem, Scopus and Google Scholar, and included original studies and reviews. The literature describes the preparation of cerium phosphate nanoparticles by the hydrothermal, chemical precipitation, microwave, and sol–gel methods. It was established that reaction temperature, pH value of the medium, use of organic solvents, ratio of reagents, and precursors have a direct influence on the size, shape, and structure of the obtained nano-object, making it possible to synthesize nanospheres, nanorods, and nanoneedles by regulating these parameters. In addition, the strategy of obtaining nano-objects with specified properties can be implemented by using excipients of predominantly polymer nature. The use of auxiliary substances is capable both of exerting a stabilizing effect and improving adherence to the nanoscale range, and of influencing pharmacological activity. The literature describes the possibility of using cerium phosphate as a redox-active, regenerative, antibacterial, sunscreen, and antitumor agent. However, the insufficient amount of data on the toxicological profile, as well as the results of in vivo studies, remains a significant limitation for the introduction of cerium phosphate into clinical practice. Thus, the purpose of the present review is to identify patterns that make it possible to formulate recommendations for the synthesis of cerium phosphate with specified properties, to assess factors affecting its suitability for use in biomedicine, and to consider its prospects and limitations. Full article

The Heilongtai–Maogudui (HM) mafic intrusions are exposed in the southern margin of the North China Craton (SNCC), which are contemporaneous with a variety of strategic metal/non-metal minerals (niobium, uranium, and high-purity quartz) and magmatic hydrothermal REE deposits. New geochronology and geochemistry of these intrusions are examined and interpreted to decipher their petrogenesis and tectonic settings. Zircon LA–ICP–MS data formed a concordant cluster, yielding a mean ²⁰⁶Pb/²³⁸U age of 397.5 ± 3.5 Ma, which is interpreted as an Early Devonian crystallization age. The HM mafic intrusions have similar whole-rock geochemical compositions, containing 48.94–51.51 wt% SiO₂, 1.26–1.61 wt% TiO₂, 5.96–7.13 wt% MgO, and 11.00–12.48 wt% FeO_t. The total alkali contents range from 1.61 wt% to 3.53 wt%, with Mg^# values of 47.23–52.30. The petrographic and geochemical results suggest the fractional crystallization of mainly olivine, clinopyroxene, and minor Fe–Ti oxide in the mafic intrusions. Being of tholeiitic composition, these mafic rocks display relatively flat rare earth element (REE) and trace element patterns, which are similar to those of the normal mid-ocean ridge basalt (N–MORB) and the enriched mid-ocean ridge basalt (E–MORB). The HM mafic intrusions are proposed to originate in the continental extensional environment through 5–10% partial melting of the depleted spinel asthenosphere mantle source. This is attributed to the gravitational delamination of the lithospheric mantle and the upwelling of the hot asthenosphere, marking the end of the Paleozoic Proto–Tethyan orogenic cycle. The Paleozoic strategic mineral deposits are proposed to have formed under this specific tectonic regime. Full article

Lignin is one of the most abundant biopolymers in nature. The major challenge in lignin depolymerization lies in the formation of complex mixtures that require extensive downstream separation. Selective depolymerization strategies aim to overcome this limitation by promoting controlled bond cleavage while suppressing undesired secondary reactions. In this work, a series of rare-earth-free, perovskite-type mixed metal oxides with general compositions Zn_xNi_1–xTiO₃ and Cu_yNi_1–yTiO₃ were synthesized and evaluated as heterogeneous catalysts for the base-catalyzed depolymerization of lignin. Among the investigated materials, CuTiO₃ exhibited superior catalytic performance, enabling the formation of vanillin as the dominant monomer with high selectivity. The selected catalyst was further characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface area analysis. The combined effects of key reaction parameters, including temperature, pressure, lignin-to-catalyst ratio, NaOH concentration, and reaction time, were systematically investigated using response surface methodology (RSM). Under the optimized conditions (154 °C, 0.3 MPa, lignin-to-catalyst ratio of 24.5:1, 10 mL of 0.5 M NaOH, and 12 h reaction time), a monomer yield of 11.5 ± 0.46% with ~81% GC-selectivity toward vanillin was achieved. These findings demonstrate that perovskite-type titanates can serve as robust and reusable catalysts. Full article

Sintering additives play a decisive role in the densification behavior, mechanical properties, and thermal conductivity of silicon nitride ceramics. In this study, Mg₂Si and YH₂ were used as sintering additives for gas pressure sintering of silicon nitride based on the synergistic mechanism of “silicide silicon extraction-hydride dehydrogenation”. The regulation rules of the additives on ceramic densification, mechanical properties, and thermal conductivity were systematically investigated. Two optimization strategies were proposed for the technical route of replacing traditional oxide additives with non-oxide systems. (i) Rare-earth hydride YH₂ was used to replace traditional rare-earth oxides. It reacts with SiO₂ to achieve strong deoxidation and precisely regulate the liquid phase composition. (ii) Metal silicide Mg₂Si was used to replace metal oxides. It promotes the preferred growth of β-Si₃N₄ grains, consumes oxygen in the system, and reduces lattice defects. Mg₂Si introduces Si into the liquid phase, increasing the Si/O ratio, which lowers lattice oxygen content and supports higher thermal conductivity. YH₂ consumes SiO₂ on the Si₃N₄ surface, which reduces liquid phase oxygen content and inhibits lattice oxygen incorporation, promoting a liquid phase with a high N/O ratio. Compared with traditional Y₂O₃, YH₂ increases the Y₂O₃/SiO₂ ratio in the liquid phase. It promotes grain growth, reduces SiO₂ activity, and further improves the thermal conductivity of ceramics. Silicon nitride ceramics prepared by gas pressure sintering at 1750 °C with 3 wt.% Mg₂Si and 4 wt.% YH₂ composite additives exhibit the highest thermal conductivity of 87 W/(m·K), with a Vickers hardness of 14.36 GPa and a flexural strength of 643.15 MPa. This study provides an innovative idea for the preparation of high-performance silicon nitride heat dissipation substrates. Full article

The Judd–Ofelt (J–O) intensity parameters and oscillator strengths are key to understanding the optical transition properties of rare-earth-doped glasses. However, the scarcity of experimental samples and the complex nonlinear relationship between composition and spectral properties pose significant challenges to accurate predictions. To address this, we propose a generalizable framework that integrates conditional generative adversarial network (cGAN)-based data augmentation with an attention-embedded artificial neural network (ANN)–support vector regression (SVR) hybrid model. The cGAN generates physically plausible virtual samples to enrich data distribution and enhance generalization in sparse compositional regions. The attention mechanism in the ANN identifies critical compositional features, which are then leveraged by SVR for robust regression of parameter trends. The framework demonstrates high predictive accuracy for Er³⁺-doped glasses, achieving R² values above 0.93 for Ω₂, Ω₄, and Ω₆, and exhibits strong generalization performance on independent Dy³⁺- and Nd³⁺-doped datasets without task-specific retraining, confirming its practical applicability across multiple rare-earth ions. The model maintains consistency across diverse glass host systems (tellurite, borate, phosphate, silicate/germanate, heavy-metal oxide), and the attention analysis reveals feature importance aligned with established glass chemistry principles. Demonstrated on Er³⁺, Dy³⁺, and Nd³⁺, with potential for a broader range of rare-earth ions through transfer learning and future dataset extensions, this approach offers a data-driven, physics-informed tool for the targeted design of rare-earth optical materials in next-generation optical sensors. Full article