Search Results (490)

Energy storage technology is crucial for addressing the intermittency of renewable energy sources and plays a key role in power systems and electronic devices. In the field of energy storage systems, multivalent vanadium-based oxides have attracted widespread attention. Among these, vanadium dioxide (VO₂) is distinguished by its key advantages, including high theoretical capacity, low cost, and strong structural designability. The diverse crystalline structures and plentiful natural reserves of VO₂ offer a favorable foundation for facilitating charge transfer and regulating storage behavior during energy storage processes. This mini review provides an overview of the latest progress in VO₂-based materials for energy storage applications, specifically highlighting their roles in lithium-ion batteries, zinc-ion batteries, photoassisted batteries, and supercapacitors. Particular attention is given to their electrochemical properties, structural integrity, and prospects for development. Additionally, it explores future development directions to offer theoretical insights and strategic guidance for ongoing research and industrial application of VO₂. Full article

There are many advantages of the smelting of vanadium–titanium magnetite pellets by hydrogen-based shaft furnace pre-reduction and electric arc furnace process, including high reduction efficiency, low carbon dioxide emission and high recovery of titanium and so on. However, vanadium–titanium magnetite pellets are highly susceptible to severe reduction disintegration when reduced in the gas-based shaft furnaces. H₂ and CO are the primary reducing gas components in the gas-based shaft furnace process, which significantly influences the reduction behavior of vanadium–titanium magnetite pellets. In this study, the reduction disintegration behavior and reduction kinetics of vanadium–titanium magnetite under mixed H₂–CO atmospheres at low temperatures (450–600 °C) were investigated. The differences in the reduction capacities and rates of H₂ and CO on iron oxides and titanium–iron oxides were revealed, along with their impact on the reduction disintegration behavior of the pellets at low temperatures. At lower temperatures, CO exhibited a greater reducing capability for vanadium–titanium magnetite. As the reduction temperature increased, the reduction capacities of both H₂ and CO improved; however, the reduction capacity of H₂ was more significantly influenced by the temperature. The disparity in the reduction capacities of H₂ and CO for vanadium–titanium magnetite pellets caused an inconsistent expansion rate in different regions of the pellet, increasing internal stress, contributing to a more severe reduction disintegration of vanadium–titanium magnetite pellets in the mixed H₂–CO atmospheres. Full article

The oxygen blast furnace (OBF) process presents a promising low-carbon pathway for the smelting of vanadium–titanium magnetite (VTM). This study develops an innovative mathematical model based on mass and heat balance principles, specifically tailored to the OBF smelting of VTM. The model systematically investigates the effects of key parameters—including pulverized coal injection ratio, recycling gas volume, hydrogen content in the recycling gas, and charge composition—on furnace productivity, hearth activity, and the tuyere raceway zone. The results show that increasing the pulverized coal injection ratio slightly reduces productivity and theoretical flame temperature: for every 25 kg/tHM increase in the coal ratio, the theoretical flame temperature decreases by 21.95 °C; moreover, indirect reduction is enhanced and the heat distribution within the furnace is significantly improved. A higher recycling gas volume markedly increases productivity and optimizes hearth thermal conditions, accompanied by enhanced blast kinetic energy and an expanded tuyere raceway zone, albeit with a notable drop in combustion temperature. Increased hydrogen content in the recycling gas promotes productivity, but may weaken blast kinetic energy and reduce the stability of the raceway zone. Furthermore, a higher titanium content in the charge increases the difficulty of iron oxide reduction, resulting in lower CO utilization and reduced productivity. Full article

This study investigated the radiation attenuation characteristics of commonly used dental implant materials across an energy spectrum relevant to dental radiology. Two titanium implants were examined, with densities of 4.428 g/cm³ and 4.51 g/cm³, respectively. The first consisted of 90.39% titanium, 5.40% aluminum, and 4.21% vanadium, while the second comprised 58% titanium, 33% oxygen, 7% iron, 1% carbon, and 1% nitrogen. The third material was a zirconia implant (5Y form) composed of 94.75% zirconium dioxide, 5.00% yttrium oxide, and 0.25% aluminum oxide, exhibiting a higher density of 6.05 g/cm³. Monte Carlo simulations (MCNP6) and XCOM data were utilized to estimate photon source parameters, geometric configuration, and interactions with biological materials to calculate the half-value layer, mean free path, and tenth-value layer at varying photon energies. The results indicated that titanium alloys are well suited for low-energy imaging modalities such as CBCT and panoramic radiography due to their reduced artifact production. While zirconia implants demonstrated superior attenuation at higher energies (e.g., CT), their higher density may induce beam-hardening artifacts in low-energy systems. Future research should validate these simulation results through in vitro and clinical imaging and further explore the correlation between material-specific attenuation and CBCT image artifacts. Full article

Coal combustion residues are increasingly viewed as alternative sources of rare earth elements (REEs), but their heterogeneous composition and post-depositional alteration complicate resource evaluation. This study analyzes 50 coal ash (CA) samples collected from a weathered dumpsite near Almaty, Kazakhstan, originating from power generation using coal from the Ekibastuz Basin. A multi-method approach—comprising bulk chemical characterization, unsupervised clustering, X-ray diffraction (XRD), scanning electron microscopy (SEM), and supervised machine learning (ML)—was applied to identify consistent indicators of REE enrichment. While conventional regression models failed to predict individual REE concentrations accurately, ML algorithms consistently highlighted vanadium (V) as the most robust predictor of ΣREE across Random Forest, XGBoost, and LASSO. This suggests that V may act as a geochemical proxy for REE-bearing phases, potentially due to co-retention in amorphous or ferruginous matrices. Despite compositional similarity among many samples, XRD and SEM revealed marked variability in phase structure and crystallinity, underscoring the limitations of bulk oxide data alone. These findings demonstrate that REE behavior in ash cannot be predicted deterministically, but ML can be used to screen for informative compositional signals. The proposed workflow may support the preliminary classification and valorization of heterogeneous ash materials in secondary resource strategies. Full article

This study explores the development of aluminum-doped MgV₂O₄ spinel cathodes for aqueous zinc-ion batteries (AZIBs), addressing the challenges of poor Zn²⁺ ion diffusion and structural instability. Al³⁺ ions were pre-inserted into the spinel structure using a sol-gel method, which enhanced the material’s structural stability and electrical conductivity. The doping of Al³⁺ mitigates the electrostatic interactions between Zn²⁺ ions and the cathode, thereby improving ion diffusion and facilitating efficient charge/discharge processes. While pseudocapacitive behavior plays a dominant role in fast charge storage, the diffusion of Zn²⁺ within the bulk material remains crucial for long-term performance and stability. Our findings demonstrate that Al-MgV₂O₄ exhibits enhanced Zn²⁺ diffusion kinetics and robust structural integrity under high-rate cycling conditions, contributing to its high electrochemical performance. The Al-MgVO cathode retains a capacity of 254.3 mAh g⁻¹ at a high current density of 10 A g⁻¹ after 1000 cycles (93.6% retention), and 186.8 mAh g⁻¹ at 20 A g⁻¹ after 2000 cycles (90.2% retention). These improvements, driven by enhanced bulk diffusion and the stabilization of the crystal framework through Al³⁺ doping, make it a promising candidate for high-rate energy storage applications. Full article

Lithium-rich layered oxide (LLO) has received extensive attention from researchers due to its high initial discharge capacity (≥250 mAh g⁻¹). However, defects such as its high initial irreversible capacity, voltage decay, and poor rate performance have severely limited its commercialization. These issues arise because the Li₂MnO₃ component in LLO is activated during the initial cycle, leading to the participation of lattice oxygen anions (O²⁻) in redox reactions. This results in irreversible oxygen loss (O₂) and subsequent structural phase transitions. To address these challenges, this study focuses on Li₁.₂Ni₀.₁₃Co₀.₁₃Mn₀.₅₄O₂ as the host material, utilizing abundant exposed (010) plane secondary particles and employing a vanadium (V) doping strategy to enhance electrochemical performance. The V forms strong V-O bonds with the lattice oxygen, effectively suppressing irreversible oxygen loss and improving structural stability. The results demonstrate that the LLO achieves the best electrochemical performance as the doping amount is 1 mol%, and the capacity retention improves from 74.5% (undoped) to 86% (V-doped) after 140 cycles at 0.5 C. Full article

Current research on the synthesis of isonicotinic acid (INA) has focused on the development of catalysts by mixing transition metal oxides such as vanadium, titanium and zirconium in the desired molar ratio. These materials have good catalytic activity (CA) but have drawbacks, including low resistance to deactivation and limited ability to control reaction selectivity. In the present study, two- and three-component catalysts containing vanadium were successfully synthesized and their compositions and properties were studied. The experimental results showed that the efficiency of V-Ti-Mn-O catalyst was superior to V-Ti-O. Selectivity analysis showed that V-Ti-Mn-O was the most efficient catalyst, reaching a maximum value of 67.17% at 320 °C. Scanning electron microscope (SEM), Raman spectroscopy and X-ray diffraction (XRD) were used to characterize the catalysts. The corresponding experimental results showed that the superior performance of the V-Ti-Mn-O catalyst was attributed to both the smaller size of the catalyst particles and their more uniform distribution. In the oxidation of 4-methylpyridine (4-MP), the V-Ti-O catalyst showed lower CA and stability compared to the V-Ti-Mn-O catalyst, which can be attributed to its limited CA and potential deactivation at higher temperatures, probably due to excessive oxidation. Full article

Hydrogen-based reduction followed by the electric furnace smelting of vanadium–titanium magnetite pellets offers notable advantages, including high reduction efficiency, reduced energy consumption, lower CO₂ emissions, and improved titanium recovery. However, the disintegration of pellets during the reduction process presents a major barrier to industrial application. In this study, the reduction disintegration behavior and underlying mechanisms under hydrogen-based conditions were systematically investigated. The most severe disintegration was observed at 500 °C in an atmosphere of H₂/(H₂ + CO) = 0.25, where titano–magnetite [(Fe,Ti)₃O₄] was identified as the dominant phase. The complete transformation from titano–hematite [(Fe,Ti)₂O₃] to titano–magnetite occurred within 30 min of reduction. Extended reduction (60 min) further intensified disintegration (RDI_−0.5mm = 81.75%) without the formation of metallic iron. Microstructural analysis revealed that the disintegration was primarily driven by volumetric expansion resulting from the significant increase in the titanium–iron oxide unit cell volume. Raising the reduction temperature facilitated the formation of metallic iron and suppressed disintegration. These findings provide essential guidance for optimizing reduction parameters to minimize structural degradation during the hydrogen-based reduction of vanadium–titanium magnetite pellets. Full article

The selective catalytic reduction (SCR) of NO_x emissions by hydrocarbons (HCs) using a silver (Ag)-based catalyst offers significant advantages over conventional SCR systems that rely on ammonia reductants and vanadium-based catalysts. However, the conversion rate of SCR is influenced by several factors, among which catalyst poisoning is a major concern. Toxic metals such as sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) can degrade catalyst activity and lead to deactivation. Poisoned catalysts suffer from reduced conversion rates and premature deactivation before reaching their intended operational lifespan. In particular, calcium poisoning results in the formation of CaO (calcium oxide), which reacts to produce a CaWO₄ compound that severely impairs SCR performance. This study investigates the role of antimony (Sb) in mitigating Ca-induced deactivation in HC-SCR of NO_x. Five catalysts with varying Sb loadings were prepared and tested to evaluate Sb’s effect on NO_x conversion rate at a space velocity of 30,000 h⁻¹. The results demonstrate that Sb effectively suppresses Ca deactivation, enhancing the conversion rate across all engine test conditions. The highest NO_x conversion rate (95.88%) was achieved using a catalyst with 3% Sb. Full article

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory loss and limited therapeutic options. Metal-based drugs have emerged as promising alternatives in the search for effective treatments, and vanadium coordination complexes have shown significant potential due to their neuroprotective and anti-aggregant properties. This review explores the advances in the development of vanadium-based metallodrugs for AD, focusing on their ability to modulate amyloid-beta (Aβ) aggregation, oxidative stress, and neuroinflammation. Recent in vitro and in vivo studies highlight the efficacy of oxovanadium (IV) and peroxovanadium (V) complexes in inhibiting Aβ fibril formation and reducing neuronal toxicity. Additionally, the interaction of vanadium complexes with key biological targets, such as peroxisome proliferator-activated receptor gamma (PPARγ) and protein-tyrosine phosphatase 1B (PTP1B), suggests a multifaceted therapeutic approach. While these findings underscore the potential of vanadium compounds as innovative treatments for AD, further research is needed to optimize their bioavailability, selectivity, and safety for clinical applications. Full article

Catechol-like compounds are found throughout biology in the form of both redox-active and metal-binding functional groups. Within the marine environment, catechol groups are known to coordinate strongly with vanadate and ferric ions, and this binding is regulated through redox mechanisms. While investigating marine melanin formation in vitro, we found that DOPA, a catechol-containing amino acid, reacts with both metals differently when provided with sulfite, a weak reductant, and selenite, a weak oxidant. Both compounds interacted with the DOPA–vanadium complex, but only selenite, the more redox-labile chalcogenide, led to the creation of melanin particulates. When DOPA, vanadate, and selenite are present together, a metal-binding spectra shift and a melanin variant are rapidly observed. This variant was found to form large, elongated filaments with a low carboxylic acid content and a unique electron paramagnetic resonance signature. When compared to enzymatically produced melanin, this chemically synthesized variant was more thermally and biologically inert, exhibiting a lower redox activity. The results demonstrate that the regulation of the redox environment from metal–catechol interactions can help to control both the chemical and physical properties of melanin aggregates, suggesting a scalable and cell- and enzyme-free synthesis pathway for applications that may require inert materials of strict composition. Full article

In this paper, we propose a multi-mode switchable ultra-wideband terahertz absorber based on patterned graphene and VO₂ by designing a graphene pattern composed of a large rectangle rotated 45° in the center and four identical small rectangles in the periphery, as well as a VO₂ layer pattern composed of four identical rectangular boxes and small rectangles embedded in the dielectric layer. VO₂ can regulate conductivity via temperature, the Fermi level of graphene depends on the external voltage, and the graphene layer and VO₂ layer produce resonance responses at different frequencies, resulting in high absorption. The proposed absorption microdevices have three modes: Mode 1 (2.52–4.52 THz), Mode 2 (3.91–9.66 THz), and Mode 3 (2.14–10 THz), which are low-band absorption, high-band absorption, and ultra-wideband absorption. At 2.96 THz in Mode 1, the absorption rate reaches 99.98%; at 8.04 THz in Mode 2, the absorption rate reaches 99.76%; at 5.04 THz in Mode 3, the absorption rate reaches 99.85%; and at 8.4 THz, the absorption rate reaches 99.76%. We explain the absorption mechanism by analyzing the electric field distribution and local plasma resonance, and reveal the high-performance absorption mechanism by using the relative impedance theory. In addition, absorption microdevices have the advantages of polarization insensitivity, incident angle insensitivity, multi-mode switching, ultra-wideband absorption, large manufacturing tolerance, etc., and have potential research and application value in electromagnetic stealth devices, filters and optical switches. Full article

Exploring advanced sulfur cathode materials is important for the development of lithium-sulfur batteries (LSBs), but they still present challenges. Herein, zinc oxide dots-modified vanadium nitride flower-like heterojunctions (Zn-QDs-VN) as sulfur hosts are prepared by a phase separation strategy. Characterizations confirm that the flower structure with high specific surface area and pores improves active site exposure and electron/mass transfer. In situ phase separation enriches the Zn-QDs-VN interface, addressing the issues of uneven distribution and interface reduction of Zn-QDs-VN. Further theoretical computations reveal that ZnO-QDs-VN with optimized intermediate spin states can constitute a stable LiS* bond sequence, which can conspicuously facilitate the adsorption and conversion of LiPSs and reduce the battery reaction energy barrier. Therefore, the ZnO-QDs-VN@S cathode shows a high initial specific capacity of 1109.6 mAh g⁻¹ at 1.0 C and long cycle stability (maintaining 984.2 mAh g⁻¹ after 500 cycles). Under high S loading (8.5 mg cm⁻²) and lean electrolyte conditions (E/S = 6.5 μL mg⁻¹), it also exhibits a high initial area capacity (10.26 mAh cm⁻²) at 0.2 C. The interfacial synergistic effect accelerates the adsorption and conversion of LiPSs and reduces the energy barriers in cell reactions. The study provides a new method for designing heterojunctions to achieve high-performance LSBs. Full article

In this study, the effects of reduction temperature and time on the reduction rates of iron and vanadium oxides in low-grade vanadium–titanium magnetite (VTM) were investigated. Based on the results of physical experiments, both the response surface method (RSM) and central composite design (CCD) were used to fit the prediction model of the reduction rate of iron and vanadium oxides in low-grade VTM. The results of the RSM prediction model show that under the condition of a sufficient reducing medium, affected by the high-temperature products, such as silicates and magnesium aluminates, the reduction rate of iron and vanadium oxides in low-grade VTM will first increase and then decrease. This indicates that a single factor cannot maximize the reduction efficiency of metal oxides. The results of the RSM prediction model show that the correlation fitting coefficient and correction fitting coefficient of the model are greater than 99% and 98%, respectively. The F-value is 150.05 and 176.19, respectively, and the p-value is less than 0.0001. This indicates that the RSM prediction model has high accuracy and reliability. After parameter optimization of the RSM prediction model, when the reduction temperature is 1446 °C~1498 °C and the reduction time is 43 min~60 min, the maximum reduction rates of iron oxide and vanadium oxide in iron ore can reach 92.93% and 69.20%, respectively. The study of reaction kinetics shows that the reduction processes of iron and vanadium oxides in VTM are controlled by three-dimensional diffusion conditions. The apparent activation energies of the reactions are 86.76 kJ/mol and 90.30 kJ/mol, respectively. Full article