Search Results (297)

High-performance but expensive neodymium-iron-boron (Nd-Fe-B) magnets are widely used in automotive and electrical applications. Prospective candidates for rare-earth-free magnets include Fe-based magnets such as L1₀-FeNi and α″-Fe₁₆N₂ phase. However, these rare-earth-free magnets cannot replace Nd-Fe-B magnets due to their lower coercivity. Thus, the development of Sm-based magnets, using the relatively abundant rare-earth element Sm, has become a focus of attention. A promising, cheaper alternative with excellent magnetic properties is the Samarium-iron-nitride (Sm-Fe-N) magnet. This paper describes the production and magnetic properties of Sm-Fe-N powders with Th₂Zn₁₇ and TbCu₇ phases. The production process and magnetic properties of Sm-Fe-N bonded magnets prepared from the powders are also described. Current approaches for producing Sm-Fe-N sintered magnets are included. Full article

Considering that soft airbag sensors made from soft materials are limited to detecting only normal forces, a novel PEBA–silicone composite magneto-sensitive airbag sensor is proposed for simultaneously detecting normal contact force and horizontal motion during human–robot interaction. In terms of structural design, the PEBA–silicone composite airbag is manufactured using fused deposition modeling, 3D printing, and silicone casting, achieving a balance between high airtightness and adjustable stiffness. Beneath the airbag, a magneto-sensitive substrate with several NdFeB magnets is embedded, while a fixed Hall sensor detects spatially varying magnetic fields to determine horizontal displacements without contact. The results of contact-force and motion experiments show that the proposed sensor achieves a force resolution of 20 g, a force range of 0 to 1100 g, a fitting sensitivity of 7.54 N/Pa, an average static stiffness of 4.82 N/mm, and a horizontal motion detection range of 0.125 to 1 cm/s. In addition, the prototype of the sensor is lightweight (with the complete assembly weighing 81.25 g and the sensing part weighing 56.13 g) and low-cost, giving it potential application value in exoskeletons and industrial grippers. Full article

The grain boundary diffusion (GBD) process is currently the relatively effective method for utilizing heavy rare earth (HRE) elements in NdFeB magnets, especially for magnetic sheets. However, due to a highly uneven microstructure, the recovery of GBD magnets was considered difficult. In this work, our study prioritized short-loop recycling of GBD NdFeB sheet magnets to prepare block magnets. A comparative investigation was conducted between GBD-processed NdFeB magnets and the conventional sintered magnets, with particular emphasis on their recyclability characteristics. Among them, the Tb content of GBD magnets of 0.4 wt.% was significantly lower than sintered magnets of 1.73 wt.%. When two waste magnets were supplemented with the same amount of rare earth, it was found that the coercivity of the block magnets regenerated from GBD sheet magnets was higher. Microstructural analysis revealed that the core–shell grains originally located in the surface layer of GBD magnets were uniformly mixed and diffused with the ordinary particles originally located inside during the regeneration sintering process. The regenerated GBD magnets exhibited a more uniform core–shell microstructure with submicron shells of Tb elements along with reduced areas of RE-rich phase enrichment which facilitated the formation of a continuous and uniform thin-layer grain boundary, thereby enhancing the magnetic isolation effect. Apart from the significance of recycling, these block magnets regenerated from GBD magnets also provides a new approach to solving the challenge of high coercivity and low HRE elements in bulk magnets. Full article

Background/Objectives: Magnetic drug targeting (MDT) using polyethene glycol (PEG)-coated magnetoresponsive nanoclusters (MNCs) can localize therapeutics, but washout from high-shear arterial flow limits efficacy. This study assesses how PEG molecular weight influences MNC deposition and washout resistance under a pulsatile flow. Methods: Magnetite MNCs were synthesized via solvothermal polyol reactions and PEGylated with PEG-2000, PEG-6000, or PEG-10,000. Characterization included TEM, DLS, zeta potential, FTIR, TGA, XPS, magnetic analysis, and rheology. In vitro assays used a 3 mm diameter glass phantom with pulsatile flow (0.10–0.45 m/s, 1 Hz) and a rectangular NdFeB (N35) permanent magnet (30 × 20 × 20 mm, 0.45 T) positioned 11 mm from the vessel wall. Washout performance was quantified by obstruction degree (OD), magnet coverage degree (MCd), washout degree (WD), washout rate constant (k_out), and half-life (τ₁/₂). Results: MNC-6000 balanced magnetic responsiveness (Ms = 72 emu/g), colloidal stability (ζ = +13.1 mV), and hydrodynamic size (535 nm), yielding superior retention (MCd = 72.3%, OD = 19.6%, WD = 17.9%, τ₁/₂ = 6.93 min). MNC-2000 exhibited faster loss (k_out = 0.14 min⁻¹, τ₁/₂ = 4.95 min), while MNC-10,000 produced higher OD (≈53%) with embolic risk. Magnetic mapping indicated vessel wall thresholds of B ≥ 0.18 T and ∇B ≥ 10 T/m for stable capture. Limitations: Limitations of this work include the use of a single-magnet geometry, an in vitro phantom model without endothelial biology, and a maximum targeting depth of ~12–14 mm. Conclusions: The PEG molecular weight modulates MDT performance through its effects on nanocluster stability, deposition morphology, and washout kinetics. The proposed OD, MCd, and WD metrics provide clinically relevant endpoints for optimizing MDT nanoparticle design and magnet configurations. Full article

Polymer-bonded Nd–Fe–B and Sm–Fe–N magnets have excellent magnetic properties, but their corrosion resistance is inferior. Polymer-bonded magnets, the binary alloys Nd–Fe and Sm–Fe, and the metals Fe, Nd, and Sm were investigated in electrolytes with a pH range of 1.8 to 12.8. Potentiodynamic polarisation measurements showed that these materials corrode in acidic (H₂SO₄) and near-neutral (Na₂SO₄ and NaCl) electrolytes. Iron passivates at pH > 9, but Nd and Sm passivate only in strongly alkaline electrolytes (pH > 12). The alloys and magnets combine the characteristics of the individual metals. Scanning electron microscopy with energy-dispersive X-ray spectroscopy characterised the surface layers before and after electrochemical measurements. The speciation and the depth distribution of elements in the surface layers were analysed using X-ray photoelectron spectroscopy. In the H₂SO₄, a non-protective layer was formed. In NaCl, the corrosion products were more abundant, consisting of a mixture of oxides, hydroxides, and chlorides, while in NaOH, an oxide/hydroxide layer was formed. The corrosion product layers formed in the H₂SO₄ and NaCl electrolytes were significantly thicker for the Sm–Fe–N magnet than for the Nd–Fe–B magnet. Understanding the differences and similarities in the electrochemical behaviour of magnets in various electrolytes is essential to overcoming corrosion-related problems. Full article

This paper presents the design of a permanent-magnet-assisted synchronous reluctance motor (PMa-SynRM) for compressor applications using Sm-series injection-molded magnets that eliminate heavy rare-earth elements. The high shape flexibility of the injection-molded magnets enables the formation of a curved multi-layer flux-barrier rotor geometry based on the Joukowski airfoil potential, optimizing magnetic flux flow under typical compressor operating conditions. Furthermore, electromagnetic performance, irreversible demagnetization behavior, and rotor stress sensitivity were analyzed with respect to key design variables to derive a model that satisfies the target performance requirements. The validity of the proposed design was confirmed through finite element method (FEM) comparisons with a conventional IPMSM using sintered NdFeB magnets, demonstrating the feasibility of HRE-free PMa-SynRM for high-performance compressor drives. Full article

In recent years, replacing the scarce and expensive rare earth element Nd with the more abundant and lower cost Ce in the production of Nd-Ce-Fe-B permanent magnets has become a focus of both industrial and academic research. A critical challenge is how to design the crystal structure of Nd-Ce-Fe-B magnets to compensate for the decline in magnetic performance caused by the Ce substitution. In this study, based on micromagnetic theory, Nd-Ce-Fe-B magnets with perpendicularly oriented easy axes—in which the two main phases, Nd₂Fe₁₄B and Ce₂Fe₁₄B, have a volume ratio of 1:1 but different spatial arrangements—are modeled and simulated using the MuMax3.11 software. The model is either cubic or spherical. The results from the demagnetization curve analysis indicate that the coercivity mechanism of all magnets is pinning. When the magnet volume is constant but the phase distribution differs, the Nd₂Fe₁₄B/Ce₂Fe₁₄B structure exhibits a higher coercivity and maximum energy product than the Ce₂Fe₁₄B/Nd₂Fe₁₄B structure. Furthermore, for both structural models with the same phase distribution, the coercivity and the maximum energy product decrease with the increasing volume of the main phase. Notably, the coercivity is similar when the magnet volume is very small and stabilizes after reaching a certain threshold. This qualitative conclusion was also observed in Nd-Dy-Fe-B magnets with the same structure and equal volume ratio of the two main phases. This general finding indicates that, in biphasic magnets with equal phase volumes, the phase with the larger anisotropy field located at the grain periphery can achieve a higher coercivity and maximum magnetic energy product. The analysis of the angular distribution reveals that the number of magnetic domains remains fixed at six in the Nd₂Fe₁₄B/Ce₂Fe₁₄B structure and two in the Ce₂Fe₁₄B/Nd₂Fe₁₄B structure. The in-plane magnetic moment analysis of the Ce₂Fe₁₄B/Nd₂Fe₁₄B magnet shows that the magnetic moments at the edges of the Ce₂Fe₁₄B begin to deflect first. Even at the pinning stage, the magnetic moments within the Nd₂Fe₁₄B remain unrotated. Nevertheless, the surface magnetic moments of Ce₂Fe₁₄B, through exchange coupling, drive the deflection of the interfacial and interior moments, completing the entire demagnetization process. These computational results provide theoretical guidance for related experimental studies and industrial applications. Full article

This article investigates the connection between the process parameters of solid hydrogenation, disproportionation (HD), desorption, and recombination (DR) (HDDR) in sintered (Nd,Pr,Gd)-Fe-B magnets, as well as their phase composition and degree of texture (DoT). During HD, hydrogen pressures of 10–50 kPa were applied at temperatures ranging from 700 to 785 °C for reaction times ranging from 3 to 11 h. DR was performed at 750–850 °C. The HD reaction was observed across the full range of hydrogen pressure and temperature. The phase composition of the disproportionation products depends on the depth in the sample. Applying HDDR treatment at a pressure of 10 kPa is an effective way to increase the DoT of magnets. Magnets are anisotropic following the HDDR treatment across the parameter ranges. The dependence of the DoT value on HDDR treatment parameters is complicated, with the main trend being a decline in DoT with increasing hydrogen pressure. The DoT is determined by the disproportionation and recombination temperatures, as well as the depth at 50 kPa pressure. The recombined phase is isotropic near the sample surface and highly anisotropic within the sample after 50 kPa is applied. Full article

To address the critical challenges in pyrometallurgical recycling processes—such as poor feedstock adaptability, high energy consumption during roasting conversion, and the low added value of rare earth products—this study systematically investigated the mechanism and process optimization of ammonium bifluoride (NH₄HF₂) roasting for the recovery of neodymium–iron–boron (NdFeB) waste. Thermodynamic analysis confirmed the feasibility of the conversion reaction between NH₄HF₂ and the rare earth components in NdFeB waste. Single-factor experiments were conducted to examine the effects of roasting temperature, reaction time, and NH₄HF₂ dosage on rare earth recovery. The optimal conditions were a roasting temperature of 600 °C, a reaction time of 120 min, and a NH₄HF₂ dosage of 75 wt%, achieving a rare earth recovery rate of 98.81%. Furthermore, the response surface methodology (RSM) was employed to establish a quantitative model correlating process parameters with recovery efficiency. Variance analysis demonstrated that the model was highly significant (F = 136.94, p < 0.0001), with excellent agreement between actual and predicted values (R² = 0.9944). Factor contribution analysis revealed that NH₄HF₂ dosage had the most pronounced impact on rare earth fluorination, followed by roasting temperature and reaction time. Under optimized conditions, the purified rare earth fluoride obtained after acid leaching reached a purity of 99.43%, providing high-quality raw material for producing high-value-added rare earth products. Full article

This study investigates the sustainable production of NdFeB permanent magnets using powder extrusion molding (PEM) with in situ magnetic alignment, utilizing recycled powder from an end-of-life (Eol) wind turbine magnet obtained via hydrogen processing of magnetic scrap (HPMS). Finite Element Method (FEM) simulations were conducted to design and optimize alignment tool geometries and magnetic field parameters. A key challenge in the PEM process is achieving effective particle alignment while the continuous strand moves through the magnetic field during extrusion. To address this, extrusion experiments were performed using three different alignment tool geometries and varying magnetic field strengths to determine the optimal configuration for particle alignment. The experimental results demonstrate a high degree of alignment (B_r/J_s = 0.95), exceeding the values obtained with PEM without an external magnetic field (0.78). The study confirms that optimizing the alignment tool geometry and applying sufficiently strong magnetic fields during extrusion enable the production of anisotropic NdFeB permanent magnets without post-machining, providing a scalable route for permanent magnet recycling and manufacturing. Moreover, PEM with in situ magnetic particle alignment allows for the continuous fabrication of near-net-shape strands with customizable cross-sections, making it a scalable approach for permanent magnet recycling and industrial manufacturing. Full article

The present work was performed in greenhouse conditions, and 10 ppm Se, 10 ppm B, and 100 mM salinity treatments were used. The results showed significant variations in the agronomic traits of oregano among the treatments and harvests. The 10 ppm Se×10 ppm B treatment showed improvements over other properties for morphological and yield properties with protein, essential oil, and Zn contents, and B×salinity outperformed other treatments, with variations in branch number enhancement. The analysis revealed that salinity treatment could effectively enhance Na and Ca contents. B treatment significantly improved Mn (12,443.51–18,739.77 ppm), Mg (406.85–632.79 ppm), Fe (61.43–885.06 ppm), Cu (5.02–9.32 ppm), and B (37.67–114.28 ppm) element contents. The highest K content was found from Se treatment. The effects of the Se, B, and salinity treatments showed effectively after second and third harvests of the oregano for the many examined properties. Fresh and dry weight values showed variability between 1.60–6.00 g/plant and 0.54–2.42 g/plant, respectively. Principal coordinate analysis indicated that most of the properties took place in the groups 1 (1st harvests of plant height and protein content, 2nd harvests of protein content and fresh and dry weight, 3rd harvest of fresh weight and total fresh and dry weight values) and 2 (branch number and essential oil contents, Na, and Zn). The heat-map analysis divided into two main clusters as A and B. A2, A4, and A5 treatments took place in the B group. Treatment of 10 ppm Se×10 ppm B showed better values compared to other treatments. Thus, this treatment may be beneficial for oregano cultivation under non-saline conditions. Full article

TbCu₇-type Sm-based compounds can be produced in bulk and potentially surpass Nd₂Fe₁₄B as permanent magnets. However, as the processes to prepare anisotropic magnetic particles are limited, the full potential of TbCu₇-type Sm-based compounds cannot be exploited. In this study, metastable TbCu₇-type phases of anisotropic Sm–Fe–N ultrafine particles were prepared using the low-oxygen induction thermal plasma (LO-ITP) process. X-ray diffraction analysis revealed that the obtained TbCu₇-type Sm–Fe alloy nanoparticles exhibited a c/a value of 0.8419, with an Fe/Sm atomic ratio of ~8.5. After nitrogenation, the obtained Sm–Fe–N nanoparticles were aligned under an external magnetic field, indicating that each alloy particle exhibited anisotropic magnetic properties. A substantially high degree of alignment of 91 ± 2% was achieved, quantitatively estimated via pole figure measurements. Numerical analysis following Sm–Fe nanoparticle formation showed that, compared with Fe condensation, Sm condensation persisted even at low temperatures, because of a significant difference in vapor pressure between Sm and Fe. Though this led to a relatively large compositional distribution of Sm within particles with a Sm concentration of 9–12 at%, the preparation of single-phase TbCu₇-type Sm–Fe–N particles could be facilitated by optimizing several parameters during the LO-ITP process. Full article

This research aimed to evaluate the effects of different concentrations of neodymium (Nd: 0, 2.885, 5.770, and 8.655 mg L⁻¹, referred to as Nd0, Nd1, Nd2, and Nd3, respectively) and zinc (Zn: 0.1, 0.2, and 0.3 mg L⁻¹, designated as Zn1, Zn2, and Zn3, respectively), as well as their combined interaction, on the nutritional content of lettuce (Lactuca sativa) cv. Ruby Sky. The seedlings were grown in a floating hydroponic system under greenhouse conditions. After 48 days of treatment, leaf samples were collected to determine their nutrient content. Leaf contents of N, P, Ca, Mg, S, Fe, Mn, B, and Nd were higher with the Nd1 (2.885 mg Nd L⁻¹ + Zn1 (0.1 mg Zn L⁻¹) treatment. The Nd3 (8.655 mg Nd L⁻¹) + Zn3 (0.3 mg Zn L⁻¹) treatment significantly increased the leaf contents of Cu and Zn. The K content was higher in leaves treated with Nd2 (5.770 mg Nd L⁻¹) + Zn3 (0.3 mg Zn L⁻¹). The joint application of Nd and Zn had positive effects on the nutrition of hydroponic lettuce, and Nd promoted the biofortification of lettuce by increasing leaf Zn content. Full article

During the sintering process of NdFeB bulks, temperature changes and significant temperature differences between the bulk interior and the surface region will produce high residual stress. Temperature field and stress field prediction during the sintering process is one of the key techniques for analyzing residual stress. Therefore, the sintering process simulation and residual stress prediction of NdFeB bulks under different sintering temperatures were conducted based on the modified Drucker–Prager cap (DPC) model in ABAQUS (ABAQUS 2024). The calculated field cloud charts were analyzed against the microstructure of the bulks observed by scanning electron microscope (SEM). The finite element analysis (FEA) results of the sintering process and the residual stress show good agreement with SEM morphologies, which validates the accuracy and predictability of the model. The results indicate that cracks predominantly formed in edge regions. As the sintering temperature increased, longitudinal compressive stress at the edge of the cross-section transitioned into tensile stress. These results indicate that the developed simulation framework effectively identifies crack-prone areas, enabling data-driven optimization to reduce experimental trial-and-error costs in engineering applications. Full article

This study examines how the frequency of an innovative energy harvester is tuned and how it behaves. This harvester transforms thermal energy into mechanical oscillations of two polyvinylidene fluoride (PVDF) piezoelectric beams, which produce electrical energy via a shape memory alloy (SMA) thread. The oscillation frequency is modified by two magnetic weights that are positioned symmetrically on the SMA thread and interact with stationary NdFeB permanent magnets. The SMA thread shifts laterally due to longitudinal thermal contraction and expansion induced by a constant-temperature heater. Temperature gradients above the heater trigger cyclical variations in the length of the SMA thread, leading to autonomous vibrations of the masses in both the vertical and horizontal planes. An experimental apparatus was constructed to analyze the harvester by tracking the motions of the masses and the voltages produced by the piezoelectric beams. Information was gathered regarding the correlation between output voltage and power with the consumer’s load resistance. These outcomes were confirmed using a multiphysics dynamic simulation that incorporated the interconnections among mechanical, thermal, magnetic, and electrical systems. The findings indicate that the use of permanent magnets increases the bending vibration frequency from 8.3 Hz to 9.2 Hz. For a heater maintained at 70 °C, this boosts the output power from 1.9 µW to 8.18 µW. A notable property of the considered energy harvester configuration is its ability to operate at cryogenic temperatures. Full article