Search Results (1,480)

Tantalum and niobium are critical strategic rare refractory metals; however, most associated tantalum–niobium resources are characterized by ultra-low grade, finely disseminated grains, and severe argillization, which causes pronounced slime coating of gangue mica on valuable mineral surfaces and impedes efficient recovery via gravity separation. In this study, an innovative beneficiation route combining sodium silicate pre-dispersion conditioning with shaking-table gravity separation was proposed to recover a spodumene-dominant pegmatitic lithium ore containing trace associated Nb–Ta minerals, with mica as the major slime-forming gangue. Process mineralogy analysis revealed that the raw ore has a total (Nb,Ta)₂O₅ grade of only 0.019%, with the main valuable minerals being columbite-(Mn), columbite–tantalite, and tantalite, whereas layered mica minerals constitute the primary argillization gangue that readily generates micro-fine slimes smaller than 5 μm. Single-factor tests demonstrated that the optimal grinding fineness was 84.4% passing 200 mesh, and the optimal feed pulp density for gravity separation was 28.6%. Adjusting pulp concentration alone, without a dispersant, yielded a Nb₂O₅ concentrate grade of merely 0.144%, as severe slime coating greatly limited separation selectivity. Following the introduction of sodium silicate for pre-dispersion, the separation performance improved markedly at the optimal dosage of 300 g/t: the concentrate Nb₂O₅ grade reached 1.28% (8-fold higher than the blank test), and the Ta₂O₅ grade increased to 0.47% (85-fold higher than the blank test). Multi-scale characterization, including zeta potential measurements, ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), was employed to elucidate the dispersion mechanism of sodium silicate. The results confirmed that sodium silicate undergoes selective chemisorption on mica surfaces by forming Si–O–Al bonds with surface Al–OH active sites, which substantially increases electrostatic repulsion between mineral particles and eliminates mica slime coating on tantalum–niobium minerals. In contrast, sodium silicate exhibits only weak physical adsorption on tantalum–niobium mineral surfaces, with no evident chemical bonding. This work provides a low-cost, eco-friendly pretreatment–gravity separation coupling technology for the efficient enrichment of argillized ultra-low-grade tantalum–niobium associated ores and offers theoretical guidance for the green utilization of complex tantalum–niobium tailings and low-grade mineral resources. Full article

Butylammonium acetate (BAAc) was investigated as a concentration-dependent precursor additive for inverted triple-cation perovskite solar cells based on FA_0.80Cs_0.07MA_0.13PbI_2.64Br_0.39. BAAc loadings ranging from 0 to 7 mol% were systematically compared to determine how moderate and excessive additive concentrations influence film formation, defect behavior, and device operation. At 3 mol% BAAc, the mean equivalent-circle grain diameter increased from 0.508 to 0.719 μm, and the median increased from 0.495 to 0.688 μm, while cross-sectional SEM confirmed a comparable absorber thickness of 500 ± 20 nm across the series. The PbI₂-to-perovskite diffraction peak height ratio decreased from 0.2691 to 0.0427, and the intensity-weighted photoluminescence lifetime increased from 230.2 to 350.0 ns. Light-intensity-dependent open-circuit voltage, impedance spectroscopy, thermal admittance spectroscopy, and space-charge-limited current measurements consistently indicated reduced trap-assisted recombination and transport loss at this concentration. In the EIS analysis, BAAc-3 showed the lowest transport resistance (222.17 ± 9.52 Ω) and the highest recombination resistance (8.211 ± 0.061 kΩ); all principal resistance parameters had relative standard errors below 10%, although systematic high-frequency residuals limit quantitative interpretation of the transport CPE. The champion BAAc-3 device reached 23.37% efficiency, compared with 20.42% for the control, and the 50-device mean increased from 19.63 ± 0.45% to 22.77 ± 0.30%. At 7 mol%, the morphological and electrical trends reversed and the champion efficiency decreased to 19.34%, which defines an over-treatment boundary. The 30-day dry–dark storage and 120 min maximum-power-point tests provide comparative, short-duration stability evidence. The concentration dependence is consistent with a literature-supported working model of precursor coordination and ammonium–halide interactions, without constituting direct spectroscopic identification of a specific complex. Full article

Tungsten nitride (WN) coatings were deposited on copper substrates by reactive direct current magnetron sputtering using deposition times of 15, 30, 45, and 60 min. The influence of deposition time on the structural, morphological, and electrical properties of the coatings was systematically investigated. WN coatings with thicknesses increasing from approximately 0.45 to 1.60 μm were obtained as the deposition time increased. Energy-dispersive X-ray spectroscopy confirmed the presence of W and N in the coating region, while X-ray diffraction showed diffraction features consistent with a crystalline hexagonal δ-WN phase with a dominant {110} preferred orientation for all samples. Increasing deposition time was accompanied by a decrease in the lattice parameter from 2.934 to 2.922 Å and in the relative lattice strain from 0.014 to 0.010. Atomic force microscopy showed that coatings deposited for 15 and 30 min reduced the initial surface roughness, whereas longer deposition times promoted the development of larger surface features and increased roughness. Electrical impedance measurements showed a strong frequency-dependent response. Electrical impedance exhibited a pronounced frequency dependence. At the 1000 kHz range, the impedance magnitude was approximately 0.54 Ω, 0.43 Ω, 0.45 Ω, and 0.43 Ω for coatings deposited for 15, 30, 45, and 60 min, respectively. The electrical response was correlated with the evolution of lattice strain and structural characteristics, although the present data not establish a unique charge-transport mechanism. These findings indicate that deposition time is an important parameter for tailoring the structural and electrical response of WN coatings for conductive and protective applications. Full article

Lithium-ion batteries are widely used in electric mobility, renewable energy integration, portable electronics, and renewable–hydrogen hybrid energy systems. Despite significant advances in battery materials and design, long-term degradation remains a major challenge that affects system reliability, efficiency, and economic viability. In renewable–hydrogen hybrid architectures, battery degradation influences not only energy storage performance but also hydrogen production stability, electrolyzer operation, fuel cell utilization, and overall system efficiency. Major degradation mechanisms include solid electrolyte interphase (SEI) growth, electrolyte decomposition, lithium inventory loss, transition-metal dissolution, particle cracking, and structural phase transformations. This review provides a comprehensive assessment of degradation mechanisms affecting lithium-ion battery components and their implications for renewable–hydrogen hybrid systems. Advanced characterization techniques, including in situ and operando X-ray diffraction, electron microscopy, spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry, and differential capacity analysis, are examined for their ability to reveal chemical, structural, and morphological changes during battery operation. Particular emphasis is placed on the effects of dynamic load variations, partial state-of-charge cycling, temperature fluctuations, and intermittent renewable energy inputs that accelerate degradation in hybrid systems. The review further discusses mitigation strategies such as surface engineering, electrolyte optimization, material doping, thermal management, intelligent energy management systems, predictive maintenance, and machine learning-based prognostics. Key challenges associated with battery–hydrogen integration, including efficiency trade-offs, component ageing, hydrogen production stability, and lifecycle costs, are critically analysed. The adaptability of hybrid systems under varying operating conditions is also explored, highlighting the importance of degradation-aware control strategies, digital twins, and real-time diagnostics. Finally, future research directions are identified, including multiscale characterization, physics-informed machine learning, techno-economic optimization, and life-synergy modelling. These approaches are essential for developing reliable, adaptive, and cost-effective renewable–hydrogen hybrid energy systems capable of supporting long-term decarbonization objectives. Full article

To overcome the problems of poor durability and structural incompatibility inherent in conventional urban traffic monitoring technologies, this study develops a self-sensing asphalt concrete composite incorporating carbon fiber (CF) as a conductive functional filler to construct an internal conductive network. The effects of CF dosage and loading rate on the electrical and dynamic piezoresistive characteristics of the composite were systematically investigated. Furthermore, the evolution mechanism of the micro-conductive network was revealed via electrochemical impedance spectroscopy (EIS) coupled with equivalent circuit modeling. The results demonstrate that the electrical resistivity follows a two-stage percolation behavior (“sharp decline followed by stabilization”) with increasing CF content, yielding a percolation threshold of 0.2 wt%. As CF dosage increases, the Nyquist plots transition from quasi-linear profiles to a fully developed single semicircle, and eventually to an alternating pattern of high-frequency capacitive arcs and low-frequency diffusion impedance. Equivalent circuit analysis reveals that higher CF loadings reduce both contact and tunneling resistances while simultaneously elevating interfacial capacitance. Under monotonic loading, the developed conductive network enables enhanced piezoresistive responses, and the 0.2 wt% group achieves the most pronounced improvement relative to the 0.1 wt% group, with the maximum resistivity change rate and stress sensitivity increasing by 82.05% and 313.59%, respectively. Moreover, the specimens exhibit the optimum piezoresistive response under a dynamic loading rate of 250 N/s. This study clarifies the variable-frequency sensing mechanism of self-sensing asphalt concrete, providing scientific guidance for dynamic speed measurement and weigh-in-motion (WIM) monitoring in smart pavements. Full article

The design of efficient small-scale hydrogen energy storage systems requires balancing hydrogen production rate, electrical efficiency, and system simplicity. This study experimentally investigates the energetic compromise imposed by separator material and electrolyzer architecture through a comparative analysis of finite-gap alkaline, finite-gap acidic, and zero-gap proton exchange membrane (PEM) electrolyzers. Zirfon^® Pearl 500 (Agfa, Mortsel, Belgium) diaphragms were employed in alkaline electrolysis using 25 wt.% KOH, whereas Nafion™ 117 (Chemours, Wilmington, DE, USA) membranes were used in both finite-gap acidic electrolysis (2.55 M H₂SO₄) and a commercial five-cell zero-gap PEM electrolyzer supplied with deionized water. Electrochemical performance was evaluated in terms of polarization behavior, apparent resistance, hydrogen production rate, Faradaic efficiency, and energy conversion efficiency. The zero-gap PEM architecture exhibited the best electrochemical performance, with an apparent resistance of only 0.138 Ω per cell, corresponding to reductions of approximately 43-, 51-, and 64-fold compared with the finite-gap PEM, stainless steel/Zirfon alkaline, and nickel/Zirfon alkaline configurations, respectively. The zero-gap electrolyzer delivered currents from 1.53 to 10.0 A while operating below 2.8 V, demonstrating the benefit of minimizing the ionic transport path. In contrast, the finite-gap acidic configuration achieved higher hydrogen production rates than the alkaline system owing to the superior proton conductivity of Nafion™ 117, whereas the alkaline Ni/Zirfon configuration reached the highest Faradaic efficiency (≈98%) and energy conversion efficiency (≈36%) because of improved gas separation and reduced hydrogen crossover. Electrochemical impedance spectroscopy further revealed that the normalized ohmic resistance of the zero-gap PEM cell was only 0.029 Ω, with charge-transfer processes accounting for approximately 96.2% of the total impedance. These results demonstrate that separator properties and cell architecture govern the trade-off between reaction kinetics and energy efficiency, providing practical guidelines for selecting electrolyzer configurations dedicated to decentralized and small-scale hydrogen energy storage. Full article

The article presents the results of a study of the properties of a new pyrochlore (Bi_2.7Mg_0.46Ni_0.70Sb₂O_10+Δ) using X-ray powder diffraction analysis, high-temperature X-ray powder diffraction and thermal analysis, diffuse reflectance spectroscopy, impedance spectroscopy, and X-ray spectroscopy methods (XPS, NEXAFS). The Ni/Mg codoped bismuth stibate pyrochlore was synthesized using the solid-phase method. The best results of the Rietveld structure refinement were achieved for the disordered pyrochlore model (sp. gr. Fd-3m:2, a = 10.47574(6) Å). The results of modeling the cation distribution over crystallographic positions are presented. The thermal expansion coefficient (TEC) of pyrochlore increases monotonically from 6.8 × 10⁻⁶ °C⁻¹ (30 °C) to 9.8 × 10⁻⁶ °C⁻¹ (810 °C). Above 1080 °C, thermal dissociation of pyrochlore occurs with the formation of (Mg/Ni)Sb₂O₆ and two cubic phases. At temperatures below 200 °C, the sample exhibits primarily capacitive impedance. The sample capacitance (~17 pF) is independent of temperature and frequency up to 200 °C. The high-frequency relative permittivity and dielectric loss tangent are 30.5 and 5 × 10⁻⁴ (24 °C, 5 × 10⁴ Hz). The activation energy for conductivity is 0.99 eV. The analysis of NEXAFS and XPS spectra allowed for the determination of the charge state of the metal cations: Bi + (3-δ), Sb + (5-δ), Ni/Mg + 2. Full article

The reuse of expired pharmaceuticals as corrosion inhibitors offers a sustainable strategy for reducing pharmaceutical waste while providing environmentally friendly alternatives to conventional inhibitors. In this work, the corrosion inhibition performance of expired ibrutinib (EIB) for P110 carbon steel in 1.0 M HCl was investigated using electrochemical techniques, mass loss measurements, surface characterization, and computational approaches. Electrochemical impedance spectroscopy (EIS) revealed a progressive increase in charge-transfer resistance with increasing inhibitor concentration, while potentiodynamic polarization (PDP) measurements demonstrated that EIB acts as a mixed-type inhibitor with a predominant anodic effect. At 1000 mg L⁻¹, inhibition efficiencies of 88.7%, 96.8%, and 93.3% were obtained from EIS, PDP, and mass loss measurements, respectively. SEM analysis confirmed the formation of a compact and homogeneous protective film on the steel surface, significantly reducing corrosion damage and surface roughness. Density functional theory (DFT), Natural Bond Orbital (NBO), Monte Carlo (MC), and molecular dynamics (MD) simulations demonstrated strong adsorption of EIB on the Fe(110) surface through nitrogen- and oxygen-containing active centers, while radial distribution function analysis confirmed the contribution of chemisorption. The excellent agreement between the experimental and theoretical results demonstrates that expired ibrutinib is an efficient and sustainable corrosion inhibitor for P110 carbon steel in acidic environments and represents a promising approach for the valorization of expired pharmaceutical products. Full article

The intrinsic properties of plants offer numerous opportunities for scientific and technological advancement. Considerable efforts have been directed toward developing plant-on-chip platforms to investigate cellular responses to external stimuli, including chemical, mechanical, and electrical cues. In this study, we present a fluidic platform using polydimethylsiloxane (PDMS) and a printed circuit board (PCB), integrated with electrochemical impedance spectroscopy (EIS) detection. Various experimental conditions were examined, including ionic and pH stimulation, as well as membrane dimensions, with the onion inner membrane treated as a black-box system. The measurement results are presented as Nyquist plots, and a resistance model incorporating multifactorial influences is proposed. Impedance variations in plant cells serve as a basis for electrical modulation. To explore these properties, we converted acoustic signals into electrical inputs and recorded the outputs after being modulated by onion inner epidermal cells. A transfer function analysis was subsequently performed. Our results indicate that the plant cell-on-chip (PCOC) platform holds promise for further investigations into plant cell properties. The impedance results suggest that plant cells can respond to different external stimuli, enabling modulation of the electrical properties. These findings lay the groundwork for future studies on cellular electrical characteristics and the development of preliminary bioelectrical circuits. Full article

Composition-tuned Zn_1−xCu_xO (x = 0.0, 0.1, and 0.2) nanoparticles were synthesized via a facile co-precipitation method and investigated as wurtzite oxide anodes for sodium-ion batteries (SIBs). This work focuses on establishing an electro-optical correlation between optical band-edge modulation and electrochemical charge-transfer kinetics. X-ray diffraction confirmed the formation of the hexagonal wurtzite ZnO phase without detectable secondary phases, while FESEM and particle-size distribution analysis showed that the Zn_0.9Cu_0.1O sample possessed a more refined and uniform particle population than pristine ZnO. Diffuse reflectance spectroscopy (DRS) revealed a non-linear optical response with composition, where the direct optical band gap decreased from 3.08 eV for pristine ZnO to 2.66 eV for Zn_0.9Cu_0.1O, followed by partial recovery to 2.99 eV for Zn_0.8Cu_0.2O. Density functional theory (DFT) calculations supported this trend by showing the appearance of additional electronic states near the Fermi level after Cu incorporation, indicating improved electronic accessibility. Electrochemical impedance spectroscopy further confirmed that Zn_0.9Cu_0.1O exhibited the lowest specific charge-transfer resistance of 185.15 $\mathsf{\Omega }$ cm² and the highest Na⁺ diffusion coefficient of 5.77 × 10⁻¹¹ cm² s⁻¹, compared with pristine ZnO and Zn_0.8Cu_0.2O. The improved sodium storage performance of Zn_0.9Cu_0.1O is, therefore, attributed to the favorable combination of particle uniformity, band-edge modulation, and interfacial charge-transfer kinetics. These findings demonstrate a composition-dependent association between optical band gap modulation and charge-transfer behavior in semiconductor-type oxide anodes for sodium-ion storage. Full article

Enhancing the performance of titanium biomaterials remains a critical challenge in the development of durable implant materials, particularly under complex physiological conditions where corrosion processes are influenced by interactions with biological species. Electrochemical oxidation has emerged as a promising approach for generating nanostructured titanium dioxide layers, which can improve corrosion resistance. In this study, nanostructured oxide layers were synthesized on additively manufactured 3D titanium scaffolds via anodization in a fluoride-containing ethylene glycol and water electrolyte. Corrosion resistance was systematically evaluated using open-circuit potential measurements, Tafel analysis, and electrochemical impedance spectroscopy, considering the effects of biological medium composition and prolonged exposure to corrosive conditions. The main scientific contribution of this work is the elucidation of the time-dependent corrosion behavior and electrochemical stability of anodized additively manufactured titanium scaffolds under physiological exposure conditions. The results demonstrated that the medium composition significantly influenced the properties of the anodized materials, primarily due to the adsorption of medium species on the nanostructured surface. Prolonged exposure tests further confirmed the superior durability of the coatings, which is attributed to the formation of a protective protein layer that enhances corrosion resistance in aggressive environments. These findings advance the understanding of time-dependent corrosion behavior in complex biological environments and highlight the effectiveness of nanostructured oxide layers in maintaining the electrochemical stability of titanium biomaterials during prolonged exposure. Combined with additive manufacturing, this approach represents a promising route toward the development of patient-specific implants with enhanced durability and long-term functionality for bone regeneration applications. Full article

The reactive transport of hexavalent chromium (Cr(VI)) in anthropogenically disturbed sites (e.g., mine waste rock dumps, chromium salt industrial sites) is critically influenced by physico-chemical heterogeneity, yet the interplay between physical and chemical heterogeneities remains poorly understood. This study employed a series of experiments and numerical modeling to investigate the transport of Cr(VI), focusing on the implications of physical heterogeneity—represented by preferential flow paths—and chemical heterogeneity—characterized by reductive mineral lenses. Key findings indicate that physical heterogeneity accelerates Cr(VI) breakthrough by 1.4 to 2.1 pore volumes (PV) relative to homogeneous columns. The presence of pyrite lenses delays breakthrough by 0.6–1.2 PV under neutral pH and 1.6–2.0 PV under acidic pH. At a flow rate of 3.0 m/day, the apparent sorption capacity decreases by ~62.5% compared to 0.3 m/day, indicating that physical advection largely suppresses chemical retention under high-flux conditions. The above results demonstrate that physical heterogeneity governs flow paths and advection rates, whereas chemical heterogeneity impedes transport through heterogeneous adsorption and reduction in Cr(VI) to Cr(III) along these pathways. Furthermore, the presence of preferential paths leads to greater spatial variability, which subsequently influences the interaction dynamics between Cr(VI) and reactive minerals in the aqueous environment. The dominance shifts between physical/chemical controls based on flow rates and pH. At higher flow rates, the influence of physical heterogeneity becomes more pronounced, diminishing chemical reactions due to insufficient residence time of Cr(VI). Conversely, a lower pH environment enhances pyrite dissolution, which decouples the dependency on physical heterogeneity by promoting homogeneous reactions. Further evidence was obtained through X-ray photoelectron spectroscopy (XPS) analysis. The experimental observations are complemented by TOUGHREACT-based reactive transport simulations, which further reveal that the apparent dominance shifts arise from competing timescales between advection and surface reaction. The insights gained from the study emphasize the necessity of integrating both physical and chemical spatial variability in risk assessments, transport modeling, and designing targeted remediation strategies. Full article

Electrochemical parameter identification is crucial for evaluating the electrochemical processes in proton exchange membrane water electrolysis (PEMWE). Conventional characterization techniques-including polarization-curve fitting, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and current interruption (CI)-face significant limitations for rapid diagnostics under high-current dynamic operation, arising from constraints in instrument current rating, measurement time, zero-current control, and noise amplification in numerical differentiation. In this study, we present a simple current step (CS) method to accurately identify key electrochemical parameters and perform overpotential breakdown by using a simplified equivalent circuit model with a current source. To address the numerical instability in derivative calculation caused by sampling noise during voltage transient analysis, a physics-informed neural network (PINN) is introduced to enhance signal smoothness while guaranteeing physical consist ency. Compared with standard characterization, the proposed CS-PINN method demonstrates high accuracy, with an error of less than 2% in overpotential breakdown, less than 5.3% in ohmic resistance, and 2.8% in the Tafel slope (at 5 A/cm²). These results confirm that the CS-PINN method provides a fast, accurate, and equipment-friendly route for rapid electrochemical parameter identification in PEMWE. Full article

Skin cancer represents a growing global health burden. Current diagnostic pathways combine clinical examination and dermoscopy with histopathological confirmation; however, overlap between benign and malignant lesions can create diagnostic uncertainty and lead to potentially avoidable biopsies. Electrical impedance spectroscopy (EIS) has emerged as a non-invasive technique with potential for portable and cost-efficient implementation that quantifies the dielectric contrast between malignant and healthy tissue, providing objective information that may support clinical decision-making. This review synthesizes the field across four levels. First, we describe the biophysical origins of the impedance contrast in skin cancer, spanning the cellular, tissue architecture, and molecular scales, together with the equivalent circuit and Cole–Cole frameworks used to interpret it. Second, we examine hardware advances, including electrode–skin interface strategies, flexible and wearable architectures, computational electrode design, and the translation from laboratory prototypes to commercial systems such as Nevisense. Third, we critically appraise clinical evidence from large multicenter trials, focusing on the sensitivity–specificity trade-off and the demonstrated reduction in the number needed to excise. Finally, we discuss emerging frontiers, including artificial intelligence-driven analysis and multimodal fusion with dermoscopy, reflectance confocal microscopy, optical coherence tomography, and near-infrared spectroscopy. We conclude that EIS is most valuable as a complementary component within an integrated, AI-supported multimodal diagnostic framework. Full article

Biodegradable Mg–Ca–Sr alloys are promising candidates for temporary implant applications, but their degradation behavior is strongly influenced by alloy composition and electrolyte chemistry. This comparative short-term study investigated how increasing the Sr content from 0.5 to 1.5 wt.% influences the electrochemical response and surface characteristics of cast Mg–0.5Ca–xSr alloys in 0.9% NaCl and calcium- and magnesium-free Dulbecco’s phosphate-buffered saline (DPBS). Potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, quantitative image analysis, and energy-dispersive X-ray spectroscopy were used. Increasing the Sr content reduced the corrosion-current density from 0.0110 to 0.0039 mA/cm² in NaCl and from 0.297 to 0.169 mA/cm² in DPBS, while the corresponding calculated corrosion rates decreased from 2.51 to 0.886 mm/year and from 6.66 to 3.79 mm/year, respectively. Replicated EIS measurements of both alloys showed that Mg–0.5Ca–1.5Sr exhibited higher charge-transfer resistance than Mg–0.5Ca–0.5Sr in both NaCl (253 ± 15 versus 184 ± 14 Ω·cm²) and DPBS (853 ± 48 versus 615 ± 42 Ω·cm²). NaCl-exposed surfaces showed more porous and discontinuous deposits and a greater number of visible pit-like defects, whereas DPBS produced comparatively continuous P-containing deposits. Overall, increasing the Sr content to 1.5 wt.% was associated with lower polarization-derived global corrosion kinetics and a more resistive interfacial response, whereas electrolyte composition strongly influenced both interfacial impedance and surface-deposit morphology. These findings represent comparative short-term electrochemical and surface-characterization data obtained at 23 ± 1 °C and should not be interpreted as measures of long-term physiological degradation or in vivo performance. Full article