Search Results (2,939)

The development of cost-effective and resource-rich materials is crucial for the practical application of microwave absorbers. This study demonstrates the successful fabrication of core-shell Fe and TiC nanoparticles encapsulated within carbon shells using the arc discharge method. The samples are designated as Fe3Ti1 and Fe1Ti3, where the numbers indicate the Fe-to-Ti mass ratio in the precursor (e.g., Fe1Ti3 = 1:3 by mass). In the arc discharge synthesis mechanism, the mass ratio of Fe to Ti in the raw material was adjusted from 3:1 to 1:3 to optimize the Fe/TiC/C interfaces under a CH₄ forming gas atmosphere. TEM analysis reveals spherical and polyhedral nanoparticles with diameters of 30–50 nm and a uniform carbon shell thickness of 3–4 nm. Raman spectroscopy shows that the Fe1Ti3 sample has a higher defect density (I_D/I_G = 1.13) compared to Fe3Ti1 (0.87), indicating a more disordered carbon structure. Magnetic measurements yield saturation magnetization values of 87 emu/g for Fe3Ti1 and 50 emu/g for Fe1Ti3, with coercivities of 190.72 Oe and 203.65 Oe, respectively. When composited with paraffin at 50 wt% loading, the Fe1Ti3 sample exhibits superior microwave absorption performance, achieving a minimum reflection loss (RL) of −25.22 dB at 8.23 GHz and an effective absorption bandwidth (RL ≤ −10 dB) of 4 GHz (6.5–10.5 GHz) at a thickness of 2.5 mm. This enhanced performance is attributed to the synergistic effect of multiple loss mechanisms, including conduction loss within the three-dimensional core-shell architecture, interfacial polarization at the heterojunctions between the core and the carbon shell, and magnetic loss induced by ferromagnetic behavior associated with defects in both the shell and carbon atomic layers. The magnetic loss in the (Fe/TiC)@C nanocomposites primarily arises from the natural resonance (at ~6.5 GHz) and exchange resonance (at ~12 GHz) of the Fe cores. The dielectric loss is primarily attributed to dipole, interfacial, and space charge polarization from TiC and the carbon shell, as well as multiple scattering effects between nanoparticles. Furthermore, far-field radar cross-section simulations substantiate that the Fe/TiC@C nanocomposite demonstrates excellent radar wave attenuation capability. Further, first principles simulations reveal that introducing Fe at the C/TiC interface induces strong charge redistribution and orbital hybridization, transforming a localized dielectric interface into a highly conductive and electronically coupled C/Fe/TiC system. This interfacial modulation enhances both dielectric loss (via charge transport and polarization) and magnetic loss (via Fe-induced magnetic interactions), thereby enabling optimized dielectric-magnetic synergy for broadband microwave absorption in (Fe/TiC)@C nanocomposites. Full article

A Wedge Shaped T–Type magnetic flux concentrator (MFC) is proposed to improve the magnetic detection capability of tunneling magnetoresistance (TMR) sensors. The TMR chip used in this work integrates a CoFeSiB soft magnetic thin film on-chip and exhibits a sensitivity of 251 mV/Oe with a magnetic noise of 65.3 pT/sqrt(Hz). Based on magnetic circuit analysis and finite-element simulations, the key structural parameters of the Wedge Shaped T–Type MFC were optimized, including the air-gap distance, aspect ratio, and input–output cross-sectional ratio. The optimal parameters were determined as an air gap of 200 μm, an aspect ratio of 2, and a cross-sectional compression ratio exceeding 100. Sixteen MFC structures with different sizes were fabricated and integrated with the TMR sensors for experimental evaluation. The results show that the external flux concentrator does not introduce additional voltage noise while significantly improving the sensor response. With optimized structures, the sensor sensitivity increases from 251 mV/Oe to 17,812 mV/Oe, and the magnetic noise is reduced from 65.3 pT/sqrt(Hz) to 0.92 pT/sqrt(Hz) at 1 Hz. The experimental results demonstrate that the Wedge Shaped T–Type MFC effectively enhances the magnetic field gain and significantly improves the detection limit of TMR sensors. Full article

The lamprophyre dikes and multi-generational pyrite and arsenopyrite developed in the Jinshan gold deposit in the West Qinling metallogenic belt provide critical evidence for understanding the role of mantle-derived magmatism in gold mineralization processes. In this study, we conducted zircon U-Pb dating of lamprophyre to constrain the timing of magmatic activity and the mineralization age, and performed EMPA and LA-ICP-MS analyses on sulfides from the main metallogenic stage (Py II–III, Apy II–III) and lamprophyre-hosted pyrite (Py L) to constrain the formation conditions and metal sources of the Jinshan deposit. The results show that the mantle-derived magmatism represented by lamprophyre yields an age of 206 ± 2 Ma, which provides a lower-limit constraint on the timing of gold mineralization, corresponding to the subduction-to-extension transition period in the region. Stage II mineralization occurred at 270–320 °C with logƒS₂ of −9 to −5, dominantly as Au-HS complexes, indicating medium-temperature hydrothermal conditions with low sulfur fugacity, consistent with microscopic mineral assemblages and thermodynamic simulations. Systematic δ³⁴S variations reveal: stage II values (9.24–5‰) indicate granitic/Devonian sedimentary sources; Py L values (2.19–3.6‰) reflect mantle contributions; stage III signatures (−2.3–1.93‰) record late meteoric water mixing. Complementary δ⁵⁶Fe data show that Py II (0.2–0.3‰) and Py L (0.58–0.68‰) preserve magmatic fingerprints, while negative values of Py III (−2.29 to −0.71‰) document increasing sedimentary Fe incorporation. Combined with geochronology, S-Fe isotopes, and physicochemical constraints, we propose that the Jinshan gold deposit formed in a tectonic setting transitioning from compression to extension during the Late Indosinian (ca. 237–201 Ma). Mineralization was initiated by the partial melting of the metasomatized mantle, where hydrous magmas efficiently extracted Au and volatiles. These components ascended through transcrustal faults, with Au partitioning into exsolved fluids that precipitated gold through immiscibility and boiling in secondary structures. Full article

A one-pot strategy was developed for preparing a chitosan/Mg–Fe layered double hydroxide (LDH) composite by alkaline coprecipitation from an acidic chitosan solution containing Mg(II) and Fe(III) precursors, avoiding separate LDH synthesis and subsequent incorporation into chitosan. X-ray diffraction confirmed LDH formation within the chitosan matrix, and ICP analysis indicated an LDH-equivalent content of approximately 4.1 wt.% on an anhydrous basis. The composite exhibited enhanced chromate adsorption compared with both starting components. The experimental plateau adsorption capacity reached 137.4 mg/g, exceeding those of chitosan (92.2 mg/g) and Mg–Fe LDH (53.5 mg/g). Nonlinear isotherm fitting showed that Mg–Fe LDH was better described by the Freundlich model, whereas chitosan and the composite were better described by the Langmuir model. The kinetic behavior followed the pseudo-second-order equation, while Weber–Morris analysis indicated multistep uptake involving surface interaction and diffusion-related processes. In simulated groundwater containing chloride, bicarbonate, and sulfate, the composite removed 82% of Cr(VI) at 1.0 g/L. It also retained complete chromate uptake over five sorption/desorption cycles, although desorption efficiency decreased from 97.3% to 90.3%. A limitation of this study is that performance was evaluated mainly in batch systems and simplified simulated groundwater; validation with real contaminated waters and dynamic flow conditions is still required. Full article

Iron-exchanged bentonites derived from a natural montmorillonite-rich clay (Taganskoe deposit, Kazakhstan) were prepared through a simple aqueous ion-exchange route using Fe(II) or Fe(III) inorganic salt precursors, yielding final Fe contents of ca. 5–7 wt.%, while preserving the smectite layered framework. A mild thermal treatment under air was applied to tune iron coordination without triggering major structural collapse. The resulting materials were characterized by ED-XRF, PXRD, FE-SEM/EDX, DLS/ζ-potential and DR UV–Vis–NIR spectroscopy, revealing predominantly exchanged Fe species with a limited fraction of surface iron-oxide clusters, whose contribution increases after activation. Structure–reactivity relationships were probed under mild conditions in liquid-phase ethyl acetate using dimethyl methylphosphonate (DMMP) and 2-chloroethyl ethyl sulfide (2-CEES) as organophosphorus and organosulfur hazardous chemicals and chemical warfare agent simulants, respectively. Fe(III)-bentonite enabled very fast DMMP removal (ca. 93% within 0.5 h) with a remarkable improved performance with respect to Fe(II)-bentonite and the pristine mineral clay. For 2-CEES, the presence of H₂O₂ markedly enhanced oxidation on Fe-containing clays, reaching quantitative abatement within 24 h (up to >90%), with strong retention of oxidized sulfur products by the clay matrix. These results highlight Fe-exchanged natural bentonites as robust, cheap and multifunctional adsorption/catalytic solids for decontamination and water-treatment applications. Full article

Iron-based shape memory alloy (Fe–SMA) rebars can generate internal prestress in cement-based members after restrained thermal activation; however, the temperature actually reached by embedded rebars in cracked UHPFRC is difficult to infer from exposed bar segments. This study investigates electrical resistance activation of 4% prestrained Fe–SMA rebars embedded in pre-cracked UHPFRC beams and clarifies the activation-control problem by combining thermocouple measurements with a calibrated two-dimensional electro-thermal simulator. Twelve beams (150 × 150 × 600 mm) containing either Dramix 3D or Dramix 4D hooked steel fibers were first loaded in three-point bending to a mid-span displacement of 4 mm. The 4D series reached a 9.47% higher average pre-cracking load, confirming that fiber geometry modified the cracked state before heating. During activation, the exposed rebar segment reached 200 °C after approximately 77 s, whereas the embedded working segment reached the same target only after approximately 213 s; at that moment, the exposed segment was already close to 350 °C. The calibrated simulator reproduced the target activation time with an error of approximately 3 s and visualized the localized heat transfer from Fe–SMA to UHPFRC. The results demonstrate that activation control based only on exposed-bar temperature may cause under-activation of the embedded reinforcement, and that direct internal temperature monitoring is required for reliable Fe–SMA activation in cracked UHPFRC members. Full article

The use of hydrogen for smelting reduction ironmaking can effectively reduce the consumption of coke, as well as the CO₂ emission. However, the dynamic mechanism of this process is not clear. In this paper, isothermal thermogravimetric analysis (TGA) was used to study the reduction process of wustite by hydrogen at 1673–1773 K. Results show that wustite can be entirely reduced, and with the increase in temperature, the reduction reaction becomes more intense, and the time required for the entire reduction decreases. The hydrogen reduction of wustite at 1673–1773 K fits the Mampel power model: f(α) = 2α^1/2. When the reactants are molten and the products are solid, the apparent activation energy of the reduction process calculated by the iso-conversional method is 9.15 kJ·mol⁻¹. Molecular dynamics simulation results show that the adsorption of hydrogen molecule on FeO surface is spontaneous. With the increase in temperature, FeO substrate becomes more active, and hydrogen molecules move more violently. The average distance between a certain hydrogen atom and its neighboring atom was analyzed statistically. The increase in temperature will increase the average bond length of hydrogen molecules, reduce their bond energy, and facilitate the adsorption of hydrogen molecules on the FeO surface. Full article

Large-scale disasters can result in chronic pollution of coastal environments with unanticipated and poorly quantified impacts, such as the reshaping of marine connectivity. A recent example is the collapse of the Fundão tailings dam in 2015, which released about 50 million m³ of mine waste into the Doce River, affecting one of Brazil’s largest estuarine–mangrove systems. Here, we combine a high-resolution CROCO hydrodynamic simulation with an individual-based Lagrangian model (Ichthyop) to track the dispersal of mangrove crab (Ucides cordatus) larvae from four estuaries along the southeastern Brazilian margin between 2022 and 2024. Trajectories crossing seasonal msPAF fields derived from in situ water-quality measurements were used to quantify larval exposure to contaminants from mine waste. These fields were based on measured concentrations of As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V, Zn, and Al. Results show that surface shelf flow and mesoscale activity in the vicinity of the Doce River mouth contribute to offshore export of larvae, while the reef-dominated Abrolhos shelf promotes retention. Interannual variability alternates between long-distance export and local retention, associated with regional climate variability. Larval mortality rates caused by offshore advection and lethal temperature are high (65–75%). In addition to these modeled mortality sources, surviving cohorts frequently crossed areas with elevated msPAF values during transport, indicating potential exposure to metal(loid) mixtures. This suggests that the regional connectivity of U. cordatus is under chronic stress that likely compromises the integrity and resilience of coastal populations, since southern estuaries depend strongly on northern larval sources. The integration of Lagrangian simulations with in situ contaminant monitoring and spatially explicit exposure metrics demonstrates that transport pathways regulate not only connectivity among estuaries but also the duration and intensity of larval exposure to pollutants. Full article

Against the global carbon neutrality backdrop, amine-based CO₂ capture technology is critical for industrial greenhouse gas emission reduction. However, mixed amine absorbents can cause severe corrosion of Q235B carbon steel, restricting the stable operation of carbon capture, utilization, and storage (CCUS) projects. This study systematically investigated the corrosion behavior of Q235B carbon steel in a novel mixed amine system under simulated industrial conditions using weight loss tests, electrochemical measurements (EIS, potentiodynamic polarization), and advanced characterizations (FT-IR, ¹³C NMR, SEM-EDS, XRD). The temperature was the dominant factor: corrosion rate increased significantly with rising temperature. Under CO₂-saturated conditions, 15–30% absorbent concentrations showed no significant effect on corrosion rate owing to similar molar loading and pH. At 60 °C and 30% concentration, the corrosion rate peaked at 30 L/L CO₂ loading. Carbamate accumulation promoted corrosion at low loading, while increased bicarbonate inhibited corrosion at high loading. The main corrosion products (Fe₃O₄, Fe₂O₃) formed loose, porous films with poor protectiveness. This work clarifies the electrochemical corrosion mechanism and provides data support for corrosion prevention in CCUS equipment. Full article

Photocatalytic reduction of CO₂ to produce high-value chemical fuels is a research hotspot for sustainable development, yet its integration into undergraduate experimental teaching is hindered by a high risk, high cost, and shortage of large-scale instruments. Herein, a Fe₂TiO₅–polydopamine (PDA) S-scheme heterojunction photocatalyst was fabricated via in situ self-polymerization, and its structure, photoelectric properties, and CO₂ reduction mechanism were systematically characterized. Under visible light, the heterojunction delivers a CO production rate of 14.1 μmol·g⁻¹·h⁻¹ (6.6 times that of pure Fe₂TiO₅) with 94.2% cyclic stability. More importantly, this work constructs a virtual–real hybrid experimental teaching mode (virtual simulation pre-training + offline practical verification) for inorganic and environmental chemistry experiments, developing a virtual simulation platform with six modules (laboratory safety, instrument introduction, experimental principle, 3D simulation, virtual assessment, and after-school thinking). This mode solves the teaching bottlenecks of high-risk operation and inaccessible large-scale characterization (in situ XPS and CO₂-BET), standardizes experimental operations, and deepens students’ understanding of photocatalytic mechanisms. This study not only provides a high-efficiency photocatalyst for CO₂ reduction but also offers a replicable virtual–real integration paradigm for inorganic chemistry experimental teaching reform. Full article

This study employs molecular dynamics simulations to investigate hydrogen diffusion and deformation mechanisms in FeCrNi-based austenitic stainless steels, with a focus on the effects of alloying composition, temperature, and hydrogen concentration. Arrhenius analysis reveals that Cr increases, while Ni decreases, the activation energy for hydrogen migration. Alloys with low Cr and Ni contents (6 wt.%) promote FCC→BCC→HCP martensitic transformations, accompanied by stress drops, whereas high Cr or Ni levels (24 wt.%) suppress these transformations and favour dislocation plasticity dominated by cross-slip. High hydrogen concentrations reduce stacking-fault energy, activating dense Shockley partial dislocations in agreement with hydrogen-enhanced localised plasticity. Elevated temperatures and high hydrogen concentrations synergistically promote dislocation-mediated plasticity and facilitate vacancy formation, which can cluster into hydrogen–vacancy complexes and proto-nanovoids, accelerating material failure. These findings advance our understanding of the coupled effects of composition, hydrogen, and temperature on degradation in austenitic stainless steels and provide guidance for tailoring Cr/Ni ratios, controlling hydrogen content, and optimising service temperatures in the design of hydrogen-related structural alloys. Full article

Reinforced concrete (RC) slabs with internal voids are increasingly used to improve material efficiency; however, their residual structural performance after fire exposure remains insufficiently understood. This study presents a numerical investigation of RC slabs with different void geometries using a three-dimensional nonlinear Finite Element (FE) model. A sequential thermal–structural approach was adopted, in which fire exposure was simulated through transient thermal analysis, and the resulting spatial distribution of maximum temperatures was used to assign residual material properties to each FE based on its local peak temperature, followed by structural analysis under ambient conditions. A parametric study was conducted on seven slab configurations, including two solid slabs and five voided slabs with spherical, elliptical, ellipsoidal, capsule, and biaxial capsule geometries. To ensure a consistent evaluation, two reference solid slabs were considered: a 230 mm thick slab to enable comparison under identical geometric conditions, and a 160 mm thick slab representing equivalent concrete volume to assess material efficiency. Fire exposure was applied according to the ISO 834 standard fire curve for durations of 30, 60, and 90 min. The results indicate that voided slabs exhibit higher deflections than the solid slab of identical thickness due to reduced stiffness, while achieving comparable performance relative to the solid slab with equivalent concrete volume. These findings highlight the trade-off between structural stiffness and material efficiency under increasing fire exposure time. Full article

Carbon–oxygen (C–O) shell mergers in the final evolutionary stages of massive stars play a critical role in shaping the pre-supernova structure and the resulting nucleosynthesis. In this work, we investigate the impact of such a merger on the production of elements beyond the Iron peak, focusing on an extremely metal-poor ($[\mathrm{Fe}/\mathrm{H}]=-5$) rotating 15 ${\mathrm{M}}_{\odot }$ stellar model. The results show that the merger favors the synthesis of weak s-process seeds and light p-nuclei, such as ⁸⁸Sr, ⁹⁴Mo, and ⁹⁸Ru, via photodisintegration of heavier nuclei previously produced by rotational-induced nucleosynthesis. By simulating the subsequent core-collapse supernova explosion with a thermal bomb approach, we demonstrate that these chemical signatures are largely preserved, as the expanded structure of the merged shells significantly modifies the impact of the shock wave. These findings suggest that C–O shell mergers in early-generation stars could provide a primary-like source for intermediate and heavy elements, with important implications for the chemical evolution of the early Universe. Full article

Hypersonic aircraft represent a cutting-edge technology in aerospace engineering. Coupled heat transfer is a critical physical phenomenon in such aircraft. However, existing studies face challenges in predicting aerothermal behavior. Based on a specific geometric configuration, an axisymmetric model and the ideal gas assumption, this study establishes a numerical simulation model for coupled heat transfer in hypersonic wide-speed-range cruise aircraft. Through numerical simulations, the heat transfer characteristics of the aircraft under Mach numbers of 6, 7, 8 and 9 are analyzed, revealing the evolution of the temperatures at characteristic points and surfaces as the Mach number increases. Additionally, this study analyzes the heat transfer characteristics of metallic materials such as Inconel 718, 17-4PH, 93WNiFe and TA19, revealing differences in thermal protection performance among aircraft made of different materials under hypersonic conditions. Correlation functions relating nose temperature to time and surface temperatures to Mach number are fitted. The results indicate that as the Mach number increases, the aerodynamic heating temperature of the aircraft rises, and the aerodynamic heating effect at the stagnation point becomes more pronounced. Among the materials studied, 17-4PH exhibits the best overall thermal protection performance. This study provides methodological support for thermal prediction of hypersonic aircraft. Full article

Phthalate acid esters (PAEs) are persistent organic pollutants (POPs) widely prevalent in industrial wastewater, posing significant threats to both ecological environments and human health. Although Advanced Oxidation Processes (AOPs) are recognized as efficient technologies for PAE degradation, conventional synergistic systems typically employ a simultaneous dosing mode. This approach often leads to the instantaneous quenching of excess radicals, low oxidant utilization, and imbalanced degradation kinetics. Despite its critical role in determining efficiency and costs, the dosing strategy remains an overlooked factor in current research. In this study, dimethyl phthalate (DMP) was selected as the target pollutant to evaluate a synergistic FeSO₄/H₂O₂/K₂S₂O₈ system. An innovative continuous dosing strategy was implemented to optimize radical utilization. A laboratory-scale continuous flow apparatus was developed to simulate industrial onsite conditions, enabling a systematic comparison of degradation kinetics, mineralization characteristics, and radical evolution between the two dosing modes. Results indicated that the degradation rate constant for the continuous dosing system reached 0.659 h⁻¹, representing a 21.1% increase over the simultaneous dosing system (0.544 h⁻¹). Electron Paramagnetic Resonance (EPR) analysis confirmed that the continuous dosing mode maintains a sustained and stable radical flux (^•OH and SO₄^•−) during the critical mid-stage of the degradation, effectively mitigating radical–radical quenching. When applied to real industrial wastewater (salinity: 2083 mg/L), the continuous dosing system achieved a Total Organic Carbon (TOC) removal efficiency of 86.0% at ambient temperature and initial raw water pH, outperforming the simultaneous dosing system (82.0%). GC-MS analysis further confirmed the thorough mineralization of complex organic compounds, especially those containing ester groups and aromatic rings. This research addresses a critical gap in dosing strategy studies, providing an efficient, cost-effective, and industrially viable solution for recalcitrant wastewater treatment while establishing a theoretical foundation for large-scale continuous dosing applications. Full article