Search Results (387)

The spatial distribution of different hard magnetic phases is a key factor affecting the coercivity of dual-main-phase rare-earth permanent magnets. However, the underlying relationship between main-phase distribution and magnetization reversal behavior in Nd₂Fe₁₄B/Dy₂Fe₁₄B magnets remains unclear. In this work, micromagnetic simulations based on MuMax3 and OOMMF are performed to systematically investigate the effects of main-phase spatial arrangement on the magnetic properties and magnetization reversal mechanisms of Nd₂Fe₁₄B/Dy₂Fe₁₄B exchange-coupled magnets. First, single-phase Nd₂Fe₁₄B and Dy₂Fe₁₄B models are constructed to clarify the intrinsic magnetic characteristics of the two phases. The calculated demagnetization curves show that, although the magnetocrystalline anisotropy field H_A of Nd₂Fe₁₄B is lower than that of Dy₂Fe₁₄B, its higher saturation magnetization M_S results in a slightly larger anisotropy constant K, according to K = ${\displaystyle \frac{1}{2}}$µ₀·H_A·M_S. Nevertheless, Dy₂Fe₁₄B exhibits a stronger resistance to magnetization reversal, as reflected by its higher nucleation field H_N and coercivity H_C. This indicates that the resistance to magnetization reversal is more directly associated with H_A than with K alone. Subsequently, three types of exchange-coupled dual-main-phase Nd₂Fe₁₄B/Dy₂Fe₁₄B magnet models, including cubic, cylindrical, and sandwich structures, are constructed with identical size fractions of the two phases to investigate the influence of phase spatial distribution on magnetization reversal behavior. The calculated results demonstrate that placing the Dy₂Fe₁₄B phase in the outer region leads to higher H_Nand H_C than the reverse phase arrangement, owing to its higher H_A, which strengthens the resistance against magnetization reversal. Further analysis of the in-plane magnetic-moments and angular distributions reveals that magnetic-moment deviation is initially activated in the Nd₂Fe₁₄B region with lower H_A, followed by gradual propagation through exchange coupling at the phase interface. This effect of phase spatial distribution is not limited to Nd₂Fe₁₄B/Dy₂Fe₁₄B exchange-coupled magnets. In Nd₂Fe₁₄B/La₂Fe₁₄B and Nd₂Fe₁₄B/SmCo exchange-coupled magnets, placing the phase with the higher H_A in the outer region likewise results in higher H_Nand H_C than the reverse phase arrangement. In addition, for all the dual-main-phase exchange-coupled magnets considered above, the coercive field decreases with increasing magnet size. These findings provide theoretical insights into the regulation of coercivity through spatial phase distribution in dual-main-phase rare-earth permanent magnets. Full article

Antimony (Sb) nanopowder was synthesized using fine Sn powder as a reducing agent. The Sn powder was first produced by the chemical reduction of SnCl₂·2H₂O using commercial Al foil in acidic medium, yielding approximately 89% of the theoretical Sn yield. The resulting Sn powder exhibited a mean particle size of approximately 93 nm and a mean crystallite size of 57 nm, which promoted rapid reduction during Sb synthesis. Prior to synthesis, the composition of the Al foil was examined using SEM/EDS, confirming an Al-rich matrix containing minor Fe and Si impurities. High-purity Sb nanopowder was synthesized by reducing SbCl₃ in acetone at 50 °C under magnetic stirring and ultrasonic agitation, using the produced fine Sn powder as a reducing agent, achieving approximately 97% of the theoretical yield. SEM analysis revealed nearly spherical particles of black Sb nanoscale powder with the most frequent size falling within the 20–40 nm range and a mean particle size of approximately 32 nm. XRD analysis confirmed a trigonal Sb structure with a mean crystallite size of around 23 nm. For comparison, pellets prepared from synthesized Sb nanopowder and commercial Sb powder were compacted and sintered under identical conditions. Vickers microhardness measurements showed that the hardness of the sintered Sb nanopowder pellet was approximately 62% higher than that of the commercial Sb pellet. In addition, UV-Vis-NIR reflectance measurements (240–840 nm) demonstrated that the reflectance of the Sb nanopowder pellet was approximately three times higher than that of the commercial Sb pellet. These results demonstrate that fine Sn powder can serve as an efficient reducing agent for the synthesis of high-purity Sb nanopowder with enhanced mechanical and optical properties. Full article

The search and discovery of underwater shipwreck sites represent the most arduous and critical phases of underwater archaeology. Wooden shipwrecks, in particular, are characterized by low acoustic impedance contrast and weak magnetic anomalies, coupled with their limited physical dimensions. Consequently, they predominantly exist as shallow-buried, discontinuous small targets scattered within confined areas, making their detection exceptionally challenging. Furthermore, the complexity of the submarine environment—including rugged topography, turbid water columns, and strong currents—poses formidable obstacles to the effective detection of these archaeological remains. Single geophysical methods are often limited by insufficient imaging resolution, interpretation ambiguity, and geological noise, making precise localization and characterization difficult. Focusing on the Nan’ao I Ming Dynasty shipwreck located in waters approximately 24 m deep off the coast of Nan’ao, Guangdong Province, China, this study proposes and validates an “acoustic-magnetic” multi-source data integration detection method. This approach systematically integrates high-resolution multibeam echo sounding (MBES), side-scan sonar (SSS), sub-bottom profiling (SBP), and marine magnetic data to establish a comprehensive framework for identification and integration analysis. The results indicate that the MBES bathymetric data reveal a regular, elongated structure oriented north–south (approximately 34 m × 12 m), closely matching the main hull and deck configuration. The SSS imagery exhibited high backscatter intensity and parallel linear textures, effectively delineating the hard shipwreck structure and the associated rigid protective frame employed for in situ preservation. SBP data confirmed the semi-buried state of the shipwreck (burial depth of approximately 0.6 m). Spatial variations in sediment thickness around the site suggested ongoing modification by strong hydrodynamic processes. Marine magnetic surveys identified localized negative anomalies (−210 nT relative to the ambient magnetic field), contrasting sharply with the positive anomalies of the surrounding natural reefs, thereby indicating an artificial ferromagnetic source. The spatial registration and feature superposition of multi-source data facilitated the characterization of the shipwreck, demonstrating its potential to mitigate environmental interference and enhance detection reliability in this complex environment. Using the Nan’ao I shipwreck site as a case study, this study provides a detailed characterization of the site’s 3D morphology, burial state, and physical properties. The proposed methodology offers a practical and robust technical solution for underwater shipwreck archaeology in complex nearshore environments, providing significant implications for proactive discovery, efficient investigation, and protection of underwater cultural heritage (UCH). Full article

The Co₄₀Fe₄₀B₂₀ alloy is a key magnetic material that combines high saturation magnetization with excellent soft magnetic properties, offering broad application prospects in fields such as spintronic devices, magnetic tunnel junctions, and tunnel magnetoresistive sensors. Hot pressing can be used to produce fine-grained, highly dense CoFeB alloys. However, there is currently a lack of systematic research on the intrinsic mechanisms by which the particle size of gas-atomized CoFeB powders and their non-equilibrium solidification microstructure regulate phase transformations, microstructural evolution, and densification behavior during hot pressing and sintering—particularly regarding the microstructural inheritance effects of powders with different particle sizes. To address this issue, this study used vacuum induction melting and gas atomization technology to prepare Co₄₀Fe₄₀B₂₀ pre-alloyed powders in three particle size ranges: <38 μm, 38–74 μm, and 74–154 μm. Under identical process parameters, corresponding bulk alloys were produced via vacuum hot-press sintering, and the effects of initial powder particle size on phase transformations and microstructural evolution in the sintered bodies were systematically investigated. Microstructural characterization revealed the complete phase evolution of the alloy from the non-equilibrium solidified powder state to the sintered equilibrium state. During hot-press sintering, the metastable (Fe,Co)₃B phase in the powder completely decomposed, transforming into a stable body-centered cubic bcc-(Fe,Co) phase and a bcc-(Fe,Co)₂B second phase. The dispersed (Fe,Co)₂B phase precipitated after sintering strongly inhibits grain boundary migration via the Zener pinning effect, effectively hindering grain growth and resulting in a uniform, fine-grained, equiaxed microstructure. In coarse powders, due to the presence of a portion of the (Fe,Co)₂B phase, this phase aggregates and grows during sintering, weakening the pinning effect and leading to abnormal grain growth. The Hall–Petch fine-grain strengthening effect resulting from grain refinement couples with and offsets the weakening of second-phase strengthening caused by second-phase coarsening, ultimately leading to sintered bodies prepared from powders of different particle sizes exhibiting similar macroscopic density and hardness properties. Full article

Nanocomposite rare-earth permanent magnets composed of exchange-coupled hard magnetic nanoparticles offer a promising route toward high-performance, rare-earth-efficient magnet technologies. In this work, we investigate the structural self-organization and magnetic hysteresis behavior of 40 nm Sm₂Co₁₇/Nd₂Fe₁₄B hybrid nanoparticles using a combined molecular dynamics (MD) and micromagnetic simulation framework. First, MD simulations are employed to study the Brownian motion and field-induced assembly of the hybrid nanoparticles at two particle concentrations (1 and 5 mg/cm³). In the absence of an external magnetic field, the nanoparticles display dispersed configurations governed by thermal fluctuations and interparticle interactions. Upon application of a high magnetic field (500 mT), the particles align into linear chain-like assemblies, with a more pronounced and rapid aggregation at higher concentration. Subsequently, micromagnetic calculations performed using the OOMMF are used to determine the magnetization reversal behavior of the assemblies. Quasi-static hysteresis loops at low field (40 mT) and room temperature reveal enhanced coercivity and remanence for field-aligned chain structures compared to randomly oriented particle ensembles. Additionally, increasing particle concentration amplifies the field-induced collective response due to stronger dipolar coupling. The combined MD–micromagnetic approach provides insight into structure–property relationships in magnetic nanocomposite systems and highlights the critical role of particle arrangement and concentration in determining magnet performance. These results contribute to the design principles for advanced nanostructured permanent magnets with tunable magnetic anisotropy and energy density. Full article

Unrinsed surimi production has emerged as a sustainable alternative to conventional rinsed surimi due to its substantial water savings, reduced nutrient loss, and lower environmental footprint. However, poor gel strength and water-holding capacity remain major bottlenecks limiting its industrial application. This study investigated the effects of κ-carrageenan (κ-CG) on the rheological properties, textural characteristics, water distribution, intermolecular interactions, and microstructure of unrinsed surimi gels. The results showed that κ-CG enhanced gel properties in a concentration-dependent manner. At 0.75% κ-CG, gel strength increased to 47.0 g·cm (a 2.2-fold increase vs. control), water holding capacity (WHC) reached 97.9%, and cooking loss decreased to 4.0%. In contrast, at 1.0% κ-CG, gel strength and hardness further increased, but WHC declined slightly. Low-field nuclear magnetic resonance analysis revealed that κ-CG promoted the conversion of free water to immobilized water, with the relative peak area of T₂₂ (immobilized water) increasing from 85.9% to 88.9% at 0.75% κ-CG. Protein solubility measurements indicated that hydrophobic interactions and disulfide bonds appeared to be the major contributors stabilizing the gel network. FTIR revealed enhanced hydrogen bonding via an O–H red shift and intensification with κ-CG, and amide I deconvolution showed that 0.75% κ-CG maximized β-sheet content while reducing α-helix, indicating ordered protein reorganization during heating. Quantitative SEM analysis further verified that 0.75% κ-CG produced the densest protein network with the maximum fractal dimension and minimum lacunarity, alongside reduced average pore area and porosity. These findings demonstrate that κ-CG at an appropriate level effectively improves the gel properties of unrinsed tilapia surimi by strengthening intermolecular interactions and optimizing water distribution, offering a practical approach for developing high-quality surimi products. Full article

Computational biomechanics has grown substantially alongside imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI), which together enable high-fidelity biomodels of both hard and soft tissues. Most such biomodels, however, are represented as continuous homogeneous solids, limiting their capacity to reproduce the internal architecture of living tissues. Micro-finite element (μFE) analysis has addressed this limitation for bone at sub-millimetric scales using micro-CT data, but its adoption remains constrained by scanner availability, computational cost, and workflow complexity. This work proposes a methodological framework, termed intrabiofidelity, as a taxonomic descriptor complementary to biofidelity that characterizes the degree to which a biomodel reproduces the internal morphology and morphometry of a tissue. A reproducible pipeline based on ScanIP^® segmentation of MRI-derived DICOM data, SolidWorks^® solidification, and ANSYS^® Workbench finite element analysis is presented, through which a macro-scale trabecular representation is extracted from the distal femoral cancellous bone and integrated into a knee biomodel. Two numerical analyses were performed under an equivalent bipodal-standing load with orthotropic material properties for cortical and trabecular bone: one with external biofidelity only (Case 1), and one incorporating macro-scale intrabiofidelity in the trabecular bone (Case 2). The introduction of intrabiofidelity produced a substantial redistribution of peak von Mises stress between compartments. Trabecular peak stress increased from 2.66 to 12.10 MPa (a 4.5-fold elevation), while cortical peak stress decreased from 56.25 to 45.97 MPa (an 18.3% reduction), whereas the volume-averaged stress remained essentially unchanged in both tissues, indicating that intrabiofidelity primarily affects local concentrations rather than the bulk stress state. Principal stress data further revealed that the trabecular region transitions from a low-stress, predominantly compressive state in Case 1 to one in which substantial local tensile and compressive concentrations of comparable magnitude coexist in Case 2. The proposed methodology provides an accessible workflow for macro-scale integration of internal bone architecture using routinely available MRI data and commercial FEA software, and introduces intrabiofidelity as a terminological complement useful for teaching and for systematically documenting the fidelity of computational biomodels. Full article

Corn noodles, as a staple food, suffer from poor processing quality and high starch digestibility due to the lack of a gluten network. Magnetically treated Ganoderma lucidum extracellular polysaccharides (MEPSs) possess excellent water-binding and gel-forming properties. This study aimed to investigate the effects of MEPSs at concentrations of 0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% on the technological quality and functional properties of corn noodles and to elucidate the underlying mechanisms through rheological, microstructural, and molecular analyses. The results showed that 0.6% MEPSs was the optimal concentration. Adding MEPSs enhanced dough viscoelasticity and water-holding capacity and induced a compact, continuous gel network with increased short-range molecular order and disulfide crosslinks. Consequently, the cooking loss and breaking rate of corn noodles decreased by 24.69% and 46.65%, respectively, while the hardness and springiness improved and cohesiveness was reduced. Functionally, adding 0.6% MEPSs inhibited α-amylase and α-glucosidase, slowing starch hydrolysis and reducing the estimated glycemic index from 76.4 to 72.3. It also significantly enhanced antioxidant activities, including DPPH, ABTS, and hydroxyl radical scavenging, as well as FRAP. In conclusion, MEPS is a natural multifunctional ingredient that simultaneously improves technological quality and confers hypoglycemic and antioxidant benefits to corn noodles, providing an efficient strategy for developing healthier staple foods. Full article

This study investigated the effect of MoS₂/graphite lubricant composition on the high-temperature compaction behavior, local mechanical uniformity, and microstructural characteristics of Fe–5.0 wt.%Si SMCs. Nine lubricant compositions were prepared by varying MoS₂ and graphite contents, and their friction behavior, Vickers hardness, and compaction behavior were evaluated experimentally and by FEA. One-way ANOVA confirmed that lubricant composition significantly affected the Vickers hardness response (F = 4.245, p = 0.000273). The measured friction coefficients were applied as interface friction conditions in FEA, and the relative density, effective strain, and absolute hydrostatic stress distributions were compared. Among the investigated compositions, C3, containing 1.0 wt.% MoS₂ and 0.3 wt.% graphite, showed the lowest friction coefficient and Vickers hardness standard deviation. In FEA, C3 also showed balanced relative density, effective strain, and hydrostatic stress distributions. XRD confirmed the α-Fe-based bcc Fe–Si matrix, while SEM-EDS indicated locally distributed lubricant-derived residual regions. Therefore, C3 was selected as the most balanced lubricant composition within the investigated range. Future studies will evaluate electromagnetic properties, including core loss and magnetic permeability. Full article

Two-dimensional nanomaterials exhibit excellent physical barrier properties, which can effectively enhance the corrosion resistance of waterborne epoxy coatings. Herein, we report a facile strategy for preparing a multi-component synergistic anti-corrosion coating, where two-dimensional graphitic carbon nitride (g-C₃N₄) and high-entropy layered double hydroxides (HE-LDHs) are integrated into a waterborne epoxy matrix via magnetic-ultrasonic synergistic dispersion. The resulting HE-LDHs/g-C₃N₄-epoxy coating exhibits exceptional corrosion resistance for Q235 steel. Electrochemical impedance spectroscopy (EIS) and polarization curves showed that when the mass ratio of g-C₃N₄ to HE-LDHs was 1:1, the resulting coating (PCN-LDH-1.0) maintained a coating resistance of 5.48 × 10⁵ Ω·m² after 28 days of immersion in 3.5% NaCl solution, which was five orders of magnitude higher than that of pure waterborne epoxy coating. Meanwhile, the corrosion current density was reduced by four orders of magnitude, from 5.83 × 10⁻¹ A·m⁻² to 1.68 × 10⁻⁵ A·m⁻². After 30 days of salt spray testing, no rust, blistering or adhesion loss was observed on the coating surface. These enhanced performances by addition of g-C₃N₄ and HE-LDHs were attributed to the combined effects of the tortuous diffusion pathways. Additionally, the PCN-LDH-1.0 coating retained excellent mechanical properties, including a pencil hardness of 3H and the highest adhesion grade. This study provides a facile method for preparing high-performance waterborne anti-corrosion coatings. Full article

Polymer-based composites with magnetic properties are promising materials that are able to combine the usual polymer features (low density, high electrical resistance, enhanced flexibility, and processability, etc.) with magnetic properties typically associated with ferro- or ferrimagnetic metals, alloys or metal oxide. The combination of recycled NdFeB powders with additive manufacturing techniques based on material extrusion enables the production of magnetic composites. The novelty of this approach lies in the use of 3D printing supported by an external magnetic field, which is used to align the particles during the printing process and thus improve the final magnetic properties. This approach represents a sustainable strategy for the recovery of electronic waste, converting it into high-value-added magnetic materials intended for additive manufacturing applications. Micrometric particles made of a Neodymium–Iron–Boron (NdFeB) alloy are compounded with a flexible thermoplastic matrix made of polybutylene adipate-co-terephthalate (PBAT). The NdFeB alloy is recovered from permanent magnets of obsolete hard drives and is demagnetized, ground to powder under an inert atmosphere, and finally sieved to a particle size below 50 µm. The obtained powder is mixed with the polymer using a twin-screw extruder. The composite material containing the NdFeB particles is then processed to obtain a calibrated filament, used for the fused deposition modeling (FDM) three-dimensional (3D) printing of magnetic composites. To improve the composite’s ferromagnetic behavior, the particles were aligned along the stacking direction of the layers during the 3D FDM process by printing directly onto a permanent magnet placed on the build plate. Composites containing up to 50% by weight of recycled NdFeB powder were successfully processed using FDM technology, exhibiting increased stiffness, with the storage modulus rising from 123 to 178 MPa at 20 °C, while magnetic field-assisted printing increased the remanence from 11 to 28 emu/g and improved the reduced remanence from 0.21 to 0.49, corresponding to an estimated fourfold improvement in the magnetic energy product. Full article

The optimization of the energy product in permanent magnets presents a complicated multi-parametric problem that encompasses a large variety of intrinsic and microstructural properties. As both high remanent magnetization and coercivity are required, the main concern in optimizing a given material is often how to deal with the trade-off between these two properties. A promising approach is to combine high-anisotropy with high-magnetization phases in chemically synthesized magnetically hard–soft nanoparticles. The magnetization reversal in such systems has been studied by micromagnetics, but most of the solutions are given for a magnetically hard shell surrounding a magnetically soft core, although the inverse configuration may be more accessible from a fabrication perspective and can even help induce tetragonicity in phases such as CoFe. Here we summarize the basic general design rules for such systems, and we present specific calculations for the FePt/CoFe system. Though in larger particles complex reversal modes that are scientifically interesting occur, these are not relevant to the problem of achieving high energy products. Optimal energy products are achieved in small particles in the homogeneous exchange spring regime. Therefore, the optimal size and phase content must be determined under the contradictory requirements of achieving homogeneous reversal and avoiding thermal fluctuations. Full article

Ultrathin ferrimagnetic heterostructures have emerged as promising platforms for next-generation spintronic devices, yet the role of two-dimensional substrates in modulating their magnetic properties remains underexplored. Here, we report a comprehensive study of the thickness- and temperature-dependent magnetic behavior of amorphous Fe₇₃Co₈Gd₁₉ films (4–32 nm) deposited on Si, WSe₂ bilayer, and WSe₂ monolayer substrates. Structural integrity and stoichiometry were confirmed via X-Ray Diffraction (XRD), X-Ray Reflectivity (XRR), Raman spectroscopy, and Energy-Dispersive Spectroscopy (EDS) analysis. In-plane magnetometry from 10–300 K reveals that monolayer WSe₂ promotes stronger interfacial spin alignment, with the 4 nm film exhibiting a sharp increase in coercivity below 50 K, where $H_c$ exceeds 23 mT and even surpasses thicker counterparts, alongside enhanced saturation magnetization (∼790 kA/m at 100 K). This dramatic enhancement of coercivity is the most significant result of this work, underscoring the dominant role of interfacial coupling in governing low-temperature magnetic hardness. Conversely, films on bilayer exhibit suppressed magnetization and soft magnetic behavior ($H_c$ < 10 mT) across all temperatures, making them attractive for ultralow-power and high-speed spintronic applications. These findings demonstrate that atomically thin WSe₂ interfaces can modulate coercivity, magnetization, and squareness through proximity effects, establishing a tunable and thermally stable platform for spintronic device applications. Full article

This study investigates the removal of Cd²⁺ ions from aqueous solutions using hard magnetic strontium hexaferrite (SrFe₁₂O₁₉) nanoparticles synthesized via the Pechini method, with an average particle size of 116 nm. The material was successfully obtained at a relatively low calcination temperature of 900 °C. The crystalline structure of the hexaferrite particles was investigated by X-ray diffraction, confirming SrFe₁₂O₁₉ crystalline structure. The powder samples were also characterized by Fourier transform infrared spectroscopy (FTIR). The morphology and size distribution were studied using scanning electron microscopy (SEM). Furthermore, the magnetic properties of strontium hexaferrite contribute significantly to adsorption and removal processes, primarily by acting as a recoverable magnetic adsorbent. The ferromagnetic material, with its high saturation magnetization and coercivity, responds rapidly to external magnets, facilitating the removal of contaminants and maintaining its magnetic characteristics even in complex chemical environments. For this purpose, its magnetic behavior was also studied using vibrating sample magnetometry (VSM). The experimental adsorption results were successfully modeled using PFO (pseudo—first—order) and PSO (pseudo—second—order) along with Freundlich and Langmuir isotherms, to fit the experimental adsorption data of the Cd(II) salt from the 0.1 and 0.2 mg samples at room temperature for two quantities of strontium hexaferrite at times ranging from 2.5 to 60 min. The results indicate that the strontium hexaferrite nanoparticles exhibited a 90% removal efficiency, which was the highest value. Additionally, the strontium hexaferrite can be magnetically recovered along with the adsorbed cadmium, representing a more efficient way to remediate water. Full article

While hydroxypropyl methylcellulose (HPMC) is a promising plant-based alternative to gelatin, its industrial application is limited by poor mechanical properties and high production costs. In this study, high-performance HPMC-based hard capsules were developed using an HPMC/gellan gum/ι-carrageenan ternary system. The formulation and preparation process were optimized via single-factor experiments, response surface methodology, and low-field nuclear magnetic resonance analysis. Scanning electron microscopy was applied to characterize the microstructural evolution during disintegration. The optimized capsules exhibited rapid disintegration within 15 min across four pH media and satisfied the requirements of the Chinese Pharmacopoeia (2025). Drug dissolution profiles using cefradine and ranitidine hydrochloride showed over 85% cumulative release within 30 min, with similarity factors higher than 50 relative to commercial gelatin capsules under the tested conditions. This work provides a feasible and low-cost strategy for the industrial production of plant-based capsules and promotes the high-value utilization of polysaccharide-based capsule materials. Full article