Search Results (73)

Pure Fe soft magnetic composites (SMCs) hold a prominent position in cost-sensitive 10–100 kHz medium-to-low-frequency power devices owing to their low raw-material expenditure and high saturation magnetisation. Nevertheless, the inherently poor interparticle electrical resistivity permits the formation of contiguous conduction paths under alternating magnetic fields, giving rise to marked eddy-current dissipation and localised thermal accumulation. To surmount this limitation, the present work introduces γ-mercaptopropyltriethoxysilane (KH580)-functionalised silicon nitride (Si₃N₄) nanosheets as a multifunctional interfacial regulating layer that simultaneously establishes an electrically insulating barrier and a thermally conductive network on the surface of Fe particles. The structural integrity, surface chemical speciation and deposition behaviour of Si₃N₄-s nanosheets on Fe particles were systematically examined, and correlations among lamellar coverage completeness, interfacial bonding robustness and the coupled electrical–magnetic–thermal response were elucidated. The findings reveal that KH580 silanisation introduces a surface functional layer while preserving the parent α-Si₃N₄ crystal structure, and XPS analysis suggests possible local N–Fe and Fe–S interfacial interactions between Si₃N₄-s and the Fe surface. At a loading of 4 wt.% Si₃N₄-s, a comparatively continuous and uniform lamellar coating develops on the Fe particle surfaces. The corresponding Fe/Si₃N₄ SMCs exhibit the highest volume resistivity and a peak thermal conductivity of approximately 12.1 W·m⁻¹·K⁻¹, while maintaining a core loss of approximately 600.2 kW·m⁻³ at 50 mT and 100 kHz. These results indicate that the 4 wt.% specimen provides the most favourable overall balance among electrical insulation, magnetic response, core-loss suppression and thermal transport within the investigated composition range, furnishing a functionalised lamellar interfacial engineering strategy for performance advancement of low-cost Fe-based SMCs. Full article

This study systematically investigates the effects of varying Ni doping levels (1.0–7.0 wt.%) on the microstructure, static magnetic properties, and high-frequency dynamic magnetic performance of Fe-5.5 wt.% Si soft magnetic composites (SMCs). Toroidal core samples were fabricated using powder metallurgy combined with silicone resin coating and high-temperature annealing. The influence of Ni doping on phase composition, morphology, saturation magnetization, coercivity, effective permeability, quality factor, total core loss and its components, and DC bias characteristics was comprehensively evaluated by XRD, SEM, EDS, hysteresis loop testing, and DC bias measurements. The results indicate that an appropriate Ni content (3.0–5.0 wt.%) promotes the formation of α-Fe(Si,Ni) solid solution and (Fe,Ni)₃Si ordered phases, optimizes grain size and structural ordering, enhances saturation magnetization, and reduces coercivity. In contrast, excessive Ni doping (7.0 wt.%) leads to Ni segregation at grain boundaries, forming strong pinning centers that significantly increase coercivity and hysteresis loss. Within the wide frequency range of 1–100 kHz, Ni doping improves the permeability retention under DC bias but reduces the initial effective permeability. Notably, the sample with 5.0 wt.% Ni exhibits the highest quality factor (Q value) across the entire frequency range, demonstrating the best overall performance. This study provides experimental evidence and theoretical guidance for developing high-saturation-resistance, low-loss soft magnetic composites for medium-to-high-frequency applications. Full article

High-frequency induction (HFI) tube welding is an energy-intensive process in which the impeder plays a critical role in power utilization. Conventional ferrite cores often operate near magnetic saturation in small-diameter applications, which can limit efficiency and process stability, particularly under high production rates. Soft magnetic composites (SMCs) offer higher saturation potential, but their internal behavior under welding conditions is difficult to assess experimentally. To address this challenge, this study proposes a methodology for evaluating impeder performance without relying on industrial-scale trials. The approach combines a three-dimensional electromagnetic–thermal model of the welding process with a reduced two-dimensional model for detailed analysis. The predictive capability of the 3D model was assessed through comparison with experimental measurements, providing an initial experimental validation under the investigated operating conditions. Based on this reference, a 2D model is derived by removing the tube and introducing an equivalent correction factor, obtained through comparison with the 3D results, to account for its influence. The reduced model is then used to investigate the internal thermal behavior of a representative SMC (Fluxtrol 50) impeder. The results reveal a pronounced hotspot in the region corresponding to the inductor position, with significantly higher temperatures than in other areas, indicating a critical thermal limitation for operation. The proposed methodology provides a reliable and efficient framework for analyzing and designing impeder systems, offering a practical alternative to costly industrial testing. Full article

Soft magnetic composites (SMCs) are attracting increasing attention for electromagnetic applications owing to their three-dimensional shape flexibility and reduced eddy current loss. In this study, the 2-Pressing 1-Annealing (2P1A) process was applied to Fe–5.0 wt.%Si SMC toroidal cores to investigate the effects of pressing temperature and 1st pressing level on densification behavior, interparticle insulation structure, and frequency-dependent electromagnetic response. DEFORM-3D FEM simulations compared relative density distribution, hydrostatic stress, effective strain, and reaction load under single-press and 2P1A conditions. The 1st pressing stage was conducted at 350 °C with 30%, 50%, and 70% pressing levels, followed by final densification at 550 °C. Increasing compaction temperature reduced reaction load and hydrostatic stress range, while the 1st pressing level affected the final density distribution and stress state after 2nd pressing. TEM-EDS confirmed continuous interparticle insulation layers, and thickness measurements were used to compare local boundary structures. Among the 2P1A conditions, the 50% → 100% condition showed the smallest upper/lower relative density difference and the narrowest insulation-layer thickness range, indicating the most balanced condition in terms of densification uniformity and interparticle boundary structure. Compared with the 550 °C single-press condition, the 2P1A compacts showed higher permeability retention and Q-factor values in the 5–20 kHz range. These results indicate that the 1st pressing level influences staged densification behavior, interparticle boundary structure, and frequency-dependent electromagnetic response in Fe–5.0 wt.%Si SMC cores. Full article

Annealing is a critical step in the fabrication of soft magnetic composites (SMCs), and precise coordination of annealing atmosphere and temperature is essential for optimizing their performance. In this study, FeSiCr SMCs were annealed under three different atmospheres (air, nitrogen, and argon) across a range of temperatures, and the effects of the annealing atmosphere on their microstructure and soft magnetic properties were systematically investigated. The results demonstrate that annealing in an inert atmosphere, particularly argon, within the temperature range of 450–750 °C, yields superior magnetic properties compared with air annealing. After annealing under argon at 550 °C, the effective magnetic permeability (μ_e) reached 47.5, and the power loss (P_cv) was 1457.3 kW/m³ at 1000 kHz and 30 mT. These improvements are primarily attributed to effective stress relaxation and the substantial retention of the polyvinyl butyral (PVB) insulating layer. With further increases in annealing temperature, the magnetic properties deteriorate rapidly due to the complete decomposition of PVB and the formation of conductive chromium carbides. Under such conditions, air annealing exhibits distinct advantages. Selective oxidation of FeSiCr occurs, leading to the formation of a dense chromium oxide insulating layer that enhances magnetic performance (after annealing at 850 °C, μ_e = 47.9, P_cv = 1632.0 kW/m³). Moreover, the mechanical properties were significantly improved, with the radial crush strength increasing from 22.36 N in the unannealed state to 330 N after annealing. These results indicate that the comprehensive performance of SMCs can be effectively tailored through the appropriate selection of annealing atmosphere and temperature, providing valuable guidance for the design and optimization of high-performance SMCs. Full article

The Axial Flux Permanent Magnet Synchronous Motor (AFPMSM) has gained significant attention as a core power source for next-generation industrial sectors, including electric vehicles, wind turbines, robot joints, and drone propulsion motors, due to its high power density from a short axial length and large radial dimensions. Despite these structural advantages, cogging torque caused by magnetic interaction between the stator teeth and permanent magnets remains a critical drawback, inducing noise and vibration. While conventional Soft Magnetic Composite (SMC) core methods facilitate 3D flux paths, they suffer from low magnetic permeability, insufficient mechanical strength, and manufacturing complexity. To address these issues, this study proposes a stepped structure model utilizing electrical steel sheets to effectively reduce cogging torque. This structure features radial stacking of identical electrical steel sheets with varying widths, where each layer’s center is incrementally shifted in the rotational direction. This configuration achieves an effect analogous to continuous skewing without specialized 3D machining. To validate the proposed design, 3D Finite Element Analysis (FEA) was conducted. Results demonstrate that the peak-to-peak cogging torque was reduced to approximately 86% of the conventional model’s value, while maintaining the back-EMF reduction rate within 5%. By presenting a novel skewing technique, this research provides a practical alternative for high-precision and high-power AFPMSM. Full article

Tubular flux-switching permanent-magnet linear machines (TFSPMLMs) are difficult to optimize using a single core material because conventional axial laminations suffer from severe in-plane eddy-current loss, whereas soft magnetic composites (SMCs) exhibit lower permeability and higher hysteresis loss. To address this trade-off, three hybrid SMC–laminated steel core configurations were investigated: H1, with radially laminated steel in the yoke; H2, with axially laminated steel in the tooth; and H3, with circumferential laminated steel segments. A reference SMC model (R1) and the three hybrid models were comparatively evaluated using three-dimensional finite element analysis (3D FEA). H1 and H2 showed degraded performance due to an interfacial micro-gap along the main flux path and additional in-plane eddy currents in the laminated steel regions. To mitigate these limitations, circumferential segmentation was applied to the laminated steel parts. With eight segments, H2 achieved a thrust force of 278.8 N, comparable to that of R1, while reducing iron loss by 22.5%; even a two-segment structure provided noticeable improvement. Among the investigated models, H3 showed the best overall performance by avoiding a micro-gap on the main flux path, achieving 285.5 N, and 3.9% higher thrust force and 18% lower iron loss than R1. These results indicate that H3 is the most effective hybrid-core configuration for maximizing both thrust force and loss reduction, whereas segmented H2 is an attractive practical option when manufacturability and low-loss operation are considered. Full article

This paper presents the design, optimization, and validation of a dual three-phase yokeless and segmented armature (YASA) axial flux permanent magnet (AFPM) machine for aerospace actuators. The proposed 12-slot, 10-pole topology employs segmented soft magnetic composite (SMC) stator teeth integrated into an additively manufactured aluminium holder, combining modularity, weight reduction, and improved thermal conduction. A multi-objective optimization process based on 3D finite element analysis (FEA) was applied to balance torque capability and losses. The manufacturable design achieved a peak torque of 28.3 Nm at 1400 rpm and a peak output power of 3.5 kW with an efficiency of 81.6%, while limiting short-circuit currents to 14 Arms. Transient structural simulations revealed that three-phase short circuits induce unbalanced axial forces, exciting rotor wobbling—a phenomenon not previously reported for YASA machines. A prototype was fabricated and tested, with static torque measurements deviating by 8.6% from FEA predictions. By contrast, line-to-line back-EMF and generator-mode power output exhibited larger discrepancies (up to 20%), attributed to the frequency-dependent permeability and localized eddy currents of the SMC stator material introduced during EDM machining. These results demonstrate both the feasibility and the limitations of YASA AFPM machines for aerospace applications. Full article

This study examined the effects of phosphoric acid (H₃PO₄), polyimide (PI), and lubricants (MoS₂, graphite) on the phase stability, microstructure, and magnetic performance of Fe-5.0 wt.%Si soft magnetic composites (SMCs). Warm compaction (≤550 °C) and annealing at 700 °C were applied to samples prepared under a full factorial design. X-ray diffraction confirmed stable α-Fe(Si) phases without secondary phases. SEM and TEM–EDS revealed interfacial insulating layers mainly composed of Si-O, with localized phosphorus and carbon. Additive composition strongly influenced magnetic and physical properties. Increasing H₃PO₄ and PI reduced the density from 7.50 to 7.27 g/cm³ and lowered the permeability (from 189 at 1 kHz to 156), due to thicker interparticle layers that restricted metallic contact and domain wall motion. In contrast, Q-values rose significantly with frequency: for H₃PO₄ 0.25 wt.% + PI 0.25 wt.% + graphite 0.3 wt.%, Q increased from 0.39 (1 kHz) to 2.91 (10 kHz), reflecting effective eddy current suppression. Lubricant type further influenced performance: graphite consistently outperformed MoS₂, with 0.3 wt.% graphite providing the best balance of high density, permeability, and a frequency-stable Q-value. Overall, Fe-5.0 wt.%Si performance is governed not by bulk phase changes but by the trade-off between densification and insulation at particle interfaces. The optimal combination of low H₃PO₄ and PI with 0.3 wt.% graphite offers practical guidelines for designing high-frequency, high-efficiency motor materials. Full article

This study systematically benchmarks the performance of four single soft magnetic powders—water-atomized Fe–Si–Cr (FeSiCr), silica-coated reduced iron powder (RIP), silica-coated carbonyl iron powder (CIP), and phosphate-coated CIP (CIP-P)—to establish quantitative relationships between powder attributes, deformation substructure, and high-frequency loss for molded power inductors (100 kHz–1 MHz). We prepared toroidal compacts at 200 MPa and characterized them by initial permeability (μ_i), core-loss (P_cv(f)), partitioning (P_cv(f) = K_hf + K_ef², K_h, $K_{\mathrm{e}}$: hysteresis and eddy-current loss coefficients), and EBSD (electron backscatter diffraction)-derived microstrain metrics (Kernel Average Misorientation, KAM; low-/high-angle grain-boundary fractions). Corrosion robustness was assessed using a 5 wt% NaCl, 35 °C, 24 h salt-spray protocol. Our findings reveal that FeSiCr achieves the highest μ_i across the frequency band, despite its lowest compaction density. This is attributed to its coarse particle size (D₅₀ ≈ 18 µm) and the resulting lower intragranular pinning. The loss spectra are dominated by hysteresis over this frequency range, with FeSiCr exhibiting the largest K_h, while the fine, silica-insulated Fe powders (RIP/CIP) most effectively suppress K_e. EBSD analysis shows that the high coercivity and hysteresis loss in CIP (and, to a lesser extent, RIP) are correlated with dense, deformation-induced subgrain networks, as evidenced by higher mean KAM and a lower low-angle grain boundary fraction. In contrast, FeSiCr exhibits the lowest KAM, with strain confined primarily to particle contact regions. Corrosion testing ranked durability as FeSiCr ≳ CIP ≈ RIP ≫ CIP-P, which is consistent with the Cr-rich passivation of FeSiCr and the superior barrier properties of the SiO₂ shells compared to low-dose phosphate. At 15 A, inductance retention ranks CIP (67.9%) > RIP (55.7%) > CIP-P (48.8%) > FeSiCr (33.2%), tracking a rise in effective anisotropy and—for FeSiCr—lower M_s that precipitate earlier roll-off. Collectively, these results provide a microstructure-informed selection map for single-powder formulations. We demonstrate that particle size and shell chemistry are the primary factors governing eddy currents (K_e), while the KAM-indexed substructure dictates hysteresis loss (K_h) and DC-bias superposition characteristics. This framework enables rational trade-offs between magnetic permeability, core loss, and environmental durability. Full article

Herein, we address the challenge of high core losses in soft magnetic composites (SMCs) at high frequencies by developing a FeSiAl/WS₂ composite system processed under a transverse magnetic field (TMF). In this study, 200- and 600-mesh FeSiAl powders were used as base materials and combined with 2.25 wt.% two-dimensional tungsten disulfide (WS₂; an insulating agent) to prepare FeSiAl/2.25 wt.%WS₂ soft magnetic composites via ultrasonic mixing. The evolution of soft magnetic properties under a transverse magnetic field (TMF) was systematically investigated. The novelty of this work lies in the synergistic combination of fine FeSiAl particles and WS₂ nanosheets as an interparticle insulator and the application of a TMF to simultaneously suppress eddy current and hysteresis losses—a challenge that is difficult to address using conventional approaches. Morphological analysis confirmed a uniform and continuous organic coating of WS₂ nanosheets on FeSiAl particle surfaces. Permeability measurements revealed a slight decrease in effective permeability after the TMF treatment; however, the high-frequency performance was markedly enhanced. Magnetic loss analysis revealed a substantial reduction in the hysteresis loss and an increase in the quality factor under the TMF. Notably, the FeSiAl (600 mesh)/2.25 wt.% WS₂ composite achieved a total magnetic loss of 234 kW/m³ under a TMF of 140 kA/m, magnetic induction of 20 mT, and frequency of 1 MHz, representing a 69% reduction compared with conventional SMCs. These results not only validate the effectiveness of the proposed synergistic approach but also highlight the potential of FeSiAl (600 mesh)/2.25 wt.% WS₂ for use in high-power, high-frequency magnetic devices, with improved energy efficiency and thermal performance. Full article

This study investigates the comparative applicability of Somaloy 700HR 5P and Fe-5.0 wt.%Si powders for axial flux permanent magnet (AFPM) motor cores in low-speed electric vehicles. Optimal forming conditions were derived through Taguchi-based simulations, considering corner radius, forming temperature, and forming speed, followed by prototype fabrication and validation. Simulation and SEM-EDS analyses confirmed consistent density distribution trends, and XRD verified phase stability during forming. While Fe-5.0 wt.%Si exhibited ~10% ± 2 superior electromagnetic performance in the powder state, its motor dynamo performance decreased by 19–25% (n = 1) compared to Somaloy 700HR 5P. This discrepancy was attributed to its ~4% lower target density (7.19 ± 0.02 g/cm³ vs. 7.51 ± 0.01 g/cm³, n = 3), assembly-induced mechanical losses, and non-uniform insulation layer caused by residual H₃PO₄ and Mo segregation. Somaloy 700HR 5P, despite a higher relative density variation (0.084 ± 0.002 g/cm³ vs. 0.063 ± 0.003 g/cm³ for Fe-5.0 wt.%Si), achieved an average density close to 7.5 g/cm³ and delivered more stable motor performance. Overall, Somaloy 700HR 5P was identified as a more suitable candidate for AFPM motor cores in low-speed EV applications, balancing formability and electromagnetic performance. Full article

This study aimed to determine optimal forming conditions by comparing the compaction behavior and microstructural characteristics of two Fe-based Soft Magnetic Composite (SMC) powders, Somaloy 700HR 5P and Somaloy 130i 5P. A full factorial design was employed with powder type, compaction temperature, and punch speed as variables. Finite element modeling (FEM) using experimentally derived properties predicted density and stress distributions in toroidal geometries. 700HR 5P exhibited higher stress under most conditions, while both powders showed similar axial density gradients. Experimental results validated the simulations. SEM analysis revealed that 130i 5P had fewer microvoids and clearer particle boundaries. As revealed by TEM-EDS analyses, after heat treatment, both powders exhibited a tendency for the insulation layers to become more uniform and continuous. The insulation layer of 700HR 5P was relatively thicker but retained some pores, whereas that of 130i 5P was thinner yet exhibited smoother and more continuous coverage. XRD analysis indicated that both powders retained an α-Fe solid solution. These results demonstrate that powder properties, composition, and insulation stability significantly influence compaction and microstructural evolution. This work systematically compares the formability and insulation stability of two commercial Somaloy powders and elucidates process–structure–property relationships through an application-oriented evaluation integrating experimental design, FEM, and microstructural characterization, providing practical insights for optimal process design. Full article

MnFe₂O₄/Fe soft magnetic composites (SMCs) were designed by the surface oxidation method, and the MnFe₂O₄ layer was utilized as the insulation coating. The microstructure of SMCs and the chemical composition of the insulation layer were observed using scanning electron microscopy and energy-dispersive spectroscopy. The surface phase composition of SMCs was characterized using X-ray diffraction, X-ray photoelectron spectrometry, and Raman spectroscopy. The effect of annealing temperature on the insulation layer was investigated, and its relationship with the magnetic properties of the MnFe₂O₄/Fe SMCs was explored. The best overall performances were obtained at 50 mT and 100 kHz with saturation magnetization M_s = 205 emu/g, amplitude permeability μ_a = 100, and a core loss of 234.9 W/kg. Therefore, this work can provide a method to develop a novel insulating coating to reduce core loss, which is of great significance to the investigation of other Fe-based soft magnetic composites for applications in high-frequency magnetic fields. Full article

Magnetic gears (MGs) are attracting increasing attention in power transmission systems due to their contactless operation principles, low frictional losses, and high efficiency. However, the broad application potential of these technologies requires a comprehensive evaluation of engineering parameters, such as material selection, energy efficiency, and structural design. This review focuses solely on solid-core magnetic gear systems designed using laminated electrical steels, soft magnetic composites (SMCs), and high-saturation alloys. This review systematically examines the topological diversity, torque transmission principles, and the impact of various core materials, such as electrical steels, soft magnetic composites (SMCs), and cobalt-based alloys, on the performance of magnetic gear systems. Literature-based comparative analyses are structured around topological classifications, evaluation of material properties, and performance analyses based on losses. Additionally, the study highlights that aligning material properties with appropriate manufacturing methods, such as powder metallurgy, wire electrical discharge machining (EDM), and precision casting, is essential for the practical scalability of magnetic gear systems. The findings reveal that coaxial magnetic gears (CMGs) offer a favorable balance between high torque density and compactness, while soft magnetic composites provide significant advantages in loss reduction, particularly at high frequencies. Additionally, application trends in fields such as renewable energy, electric vehicles (EVs), aerospace, and robotics are highlighted. Full article