Amorphous Magnetic Powder Research Articles

Preparation of low-loss amorphous soft magnetic powder cores by joint coating of resin and ZnO nanoparticles

Preparation of low-loss amorphous soft magnetic powder cores by joint coating of resin and ZnO nanoparticles

Co-hydrolysis of TEOS and DDS to obtain a modified hydrophobic SiO2 insulation layer for FeSiBC amorphous magnetic powder core with low energy loss

The hysteresis effect and eddy currents caused by alternating magnetic fields greatly impede the improvement of the working efficiency and performance stability of soft magnetic powder cores. In this work, modified hydrophobic SiO2 nanoparticles were prepared by tetraethyl orthosilicate (TEOS) and dimethyl-diethoxy-silane (DDS) as co-precursors through sol–gel methods. The effect of different proportions of DDS and TEOS on the amorphous magnetic powder cores performance was studied. It was demonstrated that the insulation layer in DDS and TEOS co-precursors hydrolyzed composite powders exhibited more uniform distribution compared with TEOS hydrolyzed alone counterpart. The introduction of methyl groups reduced the accumulation of hydrolysis intermediates on the surface of FeSiBC powders. Furthermore, the addition of DDS reduced eddy current loss significantly with a low hysteresis loss. The total energy loss of the DDS and TEOS co-hydrolysis powder core were reduced by 16.1 % and 7.7 % at 1 MHz, 0.05 T compared to the uncoated powder core and the TEOS hydrolysis alone counterpart, respectively. The presented results provide insights into improving the application range and energy utilization efficiency for the magnetic powder cores.

Fabrication of FeSiBCr/wollastonite amorphous soft magnetic powder cores with low loss and high-quality factor

In this paper, the best magnetic properties of FeSiBCr/wollastonite soft magnetic composites were explored by adjusting the content of wollastonite powder and annea- ling temperature. FeSiBCr/wollastonite soft magnetic composites with low loss and high quality factor were successfully prepared by adding micron-sized wollastonite po-wder into amorphous magnetic powder. Wollastonite was used as the insulating coating material of amorphous magnetic powder for the first time, which showed good performance in reducing the loss of magnetic powder. The loss change of FeSiBCr/wollastonite magnetic powder cores was studied by B-H analyzer and loss separation analysis model. The results show that the total loss (Pcv) of FeSiBCr/woll- astonite composite cores is lower than that of the pure FeSiBCr cores. With the incre- ase of wollastonite powder content and annealing temperature, the total loss of FeSiBCr/wollastonite composite powder cores shows a trend of first decreasing and then increasing. The composite powder cores containing 0.8 wt% wollastonite powder was heat treated at 678 K for 1 hour under the protection of nitrogen, and its magnetic properties were the best, with a permeability of 28.93 and a loss of 196.2 mW/cm3( f =1 MHz and Bm =20 mT). Wollastonite is a new coating material, which has a good effect of reducing loss. At the same time, this work also provides a new scheme for reducing the total loss of soft magnetic powder cores.

Study on the Magnetic Property of Fe-Si-B Amorphous Magnetic Powder Core Mixed with Carbonyl Iron

Study on the Magnetic Property of Fe-Si-B Amorphous Magnetic Powder Core Mixed with Carbonyl Iron

Inhomogeneity of the Backward Extruded NdFeB Ring Magnet Prepared from Amorphous Powders.

Back extrusion is an important process to prepare radially oriented NdFeB ring magnets. In this work, we fabricate the ring magnets using amorphous magnetic powders as the raw material. The microstructure, magnetic properties, corrosion resistance, and mechanical properties of the backward extruded magnet at different positions along the axial direction have been investigated, and the inhomogeneity of the magnet is clarified. The results showed that the grains in the middle region of the ring magnet exhibit a strong c-axis orientation, whereas the grains at the bottom and top regions are disordered with random orientation. The microstructure variation is related to the distribution of the grain boundary phase and the degree of grain deformation. Due to the microstructure difference, the magnetic properties, temperature stability, corrosion resistance, and mechanical properties in the middle region of the magnet are higher than those in the top and bottom regions. The exchange coupling between grains also varies in different regions, which is related to the grain size and grain boundary thickness. In addition, different Co element segregations were observed in different regions, which has a crucial effect on the Curie temperature and thermal stability of the magnet. The microstructure difference also leads to the variation of corrosion resistance and mechanical properties for the samples from different regions of the magnet. This work suggests that the amorphous powder can be used to directly prepare radially oriented ring magnets, and the inhomogeneity of the magnet should be fully understood.

Magnetic properties of phosphoric acid passivated Fe-Si-B amorphous magnetic powder core

The magnetic properties of Fe-Si-B amorphous soft magnetic powder cores (SMCs) passivated by phosphoricacid are investigated in this work. Effects of phosphoric acid content and annealing temperature at different frequencies on permeability and magnetic loss of SMCs have been studied, too. Electronic microscope pictures and results of B-H analyzer show that the surface of Fe-Si-B SMCs is coated with a layer of dense phosphate. Experimental results show that Fe-Si-B SMCs with the best comprehensive magnetic properties (μe = 23.71; Pcv = 470.6 mW•cm−3 measured at 1000 kHz, 20 mT) can be obtained by adding 0.8 wt% phosphoric acid at the annealing temperature of 480 °C.

Fe(81-x-y)Si9B10CxCry amorphous magnetic powder fabricated by gas-water coupled rapid-setting sedimentation atomization

In this study, Fe(81-x-y)Si9B10CxCry (x = 0, 2, and y = 0, 2, at.%) amorphous powders with high sphericity were prepared using a gas-water coupled rapid-setting sedimentation atomization (GWC) device. The morphology and internal structure of the Fe(81-x-y)Si9B10CxCry amorphous powder are analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results show that the alloy composition and particle size have a significant effect on the sphericity and glass forming ability (GFA) of amorphous powders. The Fe79Si9B10C2 and Fe77Si9B10Cr2C2 amorphous powders under 45 μm have formed a completely amorphous structure. However, the Fe81Si9B10 amorphous powders above 30 μm were partially crystallized. Among the three groups of amorphous powder samples, the Fe81Si9B10 amorphous powder with the highest saturation magnetization, the Fe77Si9B10Cr2C2 amorphous powder had the lowest core losses and the Fe79Si9B10C2 amorphous powder exhibited the best comprehensive performance.

Study on the magnetic property of Fe–Si–B amorphous magnetic powder core coated with Al2O3/phosphoric acid–Al2O3 double layer

Study on the magnetic property of Fe–Si–B amorphous magnetic powder core coated with Al2O3/phosphoric acid–Al2O3 double layer

Industrial-scale fabrication of amorphous magnetic powder cores with excellent high-frequency magnetic properties: Optimization for kinds and content of insulating agents

Based on the powder metallurgy method, FeBSiC amorphous powders were produced by a novel gas-water combined atomization process and were co-coated by five kinds of insulating agents (polyamide, aluminum dihydrogen phosphate, calcium phosphate, zinc phosphate and hydrochloric acid) and epoxy resins. The content of each insulating agents was optimized to improve the magnetic properties of the amorphous magnetic powder cores (AMPCs). The results showed that the FeBSiC powders showed extremely high saturation magnetization (171.1 emu·g–1) and low coercivity (6.11 Oe), which could provide excellent raw materials for AMPCs. Among the five insulating agents, the polyamide-coated AMPCs had the worst electrical insulating effect and magnetic properties. Although the AMPCs coated with aluminum dihydrogen, zinc phosphate, calcium phosphate and hydrochloric acid all exhibited low eddy current losses, only the AMPCs coated with calcium phosphate exhibited extremely low hysteresis losses. As the calcium phosphate content increased, the density and resistance of the AMPCs both increased and then decreased, and the core losses decreased and then increased. When the calcium phosphate content was 0.5 wt.%, the FeBSiC@ calcium phosphate + epoxy resins core-shell structured AMPCs had high permeability of 28.1 ± 0.3, high DC bias% of 96.1 ± 0.2 at a DC magnetic field of 5671.5 A·m–1, and low core loss of 18.0 ± 0.8 kW·m–3 at 100 kHz and 0.02 T, which showed excellent magnetic properties at high frequency and confirmed to the current development trend of miniaturization, high-frequency and high-efficiency in electrical and electronic fields.

Polydopamine/polyethyleneimine enhanced Fe-based amorphous powder cores with improved magnetic properties

Coating soft magnetic powders by an insulation layer is an effective way to improve the high-frequency performance of soft magnetic powder cores. The quality of insulation coating is highly dependent of the coating materials and the coating method. In the present work, a commercial amorphous powder (Fe 73 Si 11 B 11 C 3 Cr 2 ) was primarily coated by a PDA/PEI layer by a co-deposition method in alkaline solution. A thick PDA/PEI layer with good homogeneity was co-deposited on the surface of amorphous soft magnetic powders. The high frequency core loss of magnetic powder cores was reduced by up to ~ 44 % at the magnetic induction of 0.1 T and the frequency of 100 kHz by primarily coating the amorphous powders by PDA/PEI. Microscopic images showed that the PDA/PEI coating layer on the amorphous powders does not peel off while being compressed. These results indicates that PDA/PEI insulation coating is a coating method which can effectively improve the comprehensive magnetic properties of magnetic powder cores. • Thick PDA/PEI primary coating layer deposited on amorphous soft magnetic powders. • Coating layer with cross-linked 3D network structure and uniform thickness. • Strong adhesion to powder surface without peeling off. • Excellent soft magnetic properties of powder core in high frequency.

Microstructure evolution and soft magnetic property optimization of core-shell FeSiBCCr@SiO2&ZrO2 amorphous magnetic powder cores

In this study, core-shell structured FeSiBCCr@SiO2&ZrO2 amorphous magnetic powder cores (AMPCs) were successfully prepared by the sol-gel method using tetraethyl orthosilicate (TEOS) and zirconium oxychloride hydrate (ZrOCl2·8H2O) as raw materials. The growth mechanism and potential chemical reactions of the SiO2&ZrO2 mixed insulation layer were analyzed by XRD, XPS and SEM‒EDS. In addition, the effect of the insulation layer content on the soft magnetic properties of FeSiBCCr@SiO2&ZrO2 AMPCs was systematically investigated. The SiO2&ZrO2 insulation layer can significantly increase the resistivity, effectively improve the DC bias performance and reduce the core loss of AMPCs. S2* (1.2 mL TEOS and 1.4 g ZrOCl2·8H2O) had a minimum core loss of 2290 mW/cm3 at high frequency (50 mT, 1 MHz). It had a high effective permeability of 48.2 and a superior direct current (DC) bias performance of 77.9% at 8 kA/m. This study provides a valid method to practically produce SMPCs with high resistivity, low core loss at high frequency and excellent DC bias performance through a novel insulation coating process.

Fe-Based Amorphous Magnetic Powder Cores with Low Core Loss Fabricated by Novel Gas-Water Combined Atomization Powders.

FeSiBCCr amorphous powders were produced by a novel gas–water combined atomization process, and the corresponding MPCs (magnetic powder cores) were subsequently fabricated by phosphating treatment (0.4~1.6 wt.%), cold pressing (550~2350 MPa), and annealing (423~773 K), respectively. The results showed that the powders had high circularity, excellent thermal stability (ΔT = 59 K), and high saturation magnetization (0.83 T), which could provide raw powders for high-performance MPCs. With increasing phosphoric acid concentrations, despite the increase in DC-bias%, the uniformity of the insulation layers deteriorated, which led to a decrease in permeability and an increase in core loss. With increasing compaction pressures, the core loss increased continuously, and the permeability and DC-bias% first increased and then decreased. When annealing below the crystallization temperature, with increasing annealing temperatures, the permeability increased, and the core loss and DC-bias% decreased continuously. Under the optimized process of 0.4 wt.% phosphating concentration, 550 MPa pressure, and 773 K annealing temperature, the MPCs had a permeability of 21.54 ± 1.21, DC-bias% of 90.3 ± 0.2, and a core loss (Bm = 50 mT, f = 100 kHz) of 103.0 ± 26.3 mW cm−3. The MPCs had excellent high-frequency low-loss characteristics and showed great application potential under the development trends of high current, high power, and high frequency of electronic components.

Enhanced high frequency properties of FeSiBPC amorphous soft magnetic powder cores with novel insulating layer

Fe-based amorphous magnetic powder cores (AMPCs) with excellent comprehensive properties were successfully fabricated via using the uniform double insulating layer core-shell structured FeSiBPC/Fe3O4@Epoxy resin (EP). The effects of the in-situ hydrothermal oxidized time on the magnetic properties of the AMPCs have been systematically investigated on the basis of the growth mechanism of the insulating layer of spherical amorphous powder in alkaline environment. The hydrothermal oxidation process could well ensure the uniformity of the oxide layer composed of Fe3O4 nanoparticle. The evolution of the insulating layer is a process of homogeneous nucleation and growth at different hydrothermal oxidation time. After 10 h of hydrothermal oxidation, a thin and dense layer composed of Fe3O4 nanoparticle was formed on the surface of the amorphous powder. As a consequent, the FeSiBPC AMPCs exhibit excellent performance such as stable effective permeability of 49.5 at 2 MHz, a very low core loss of 187 mW/cm3 at 100 kHz@0.05 T and high-quality factor of 160 at 600 kHz. The results indicate that the thickness of the Fe3O4 insulating layer can be completely controlled via the reaction parameters, and can effectively suppress the eddy current loss, which is promising for high-frequency electromagnetic systems.

Preparation of gas-atomised amorphous soft magnetic powders with high saturated magnetisation above 1.25 T realised by senary Fe73Si9−x B10P5C3Mo x alloys with abnormal glass-forming ability

ABSTRACT Micron-scale powdered amorphous soft magnetic materials are highly pursued for miniaturised and high-efficiency power inductors working at high frequencies due to their excellent soft magnetic properties such as extremely low coercivity and high electrical resistivity originated from the disordered atomic structures and zero magnetocrystalline anisotropy. However, the limited glass-forming ability (GFA) of amorphous soft magnetic alloys has hindered the preparation of amorphous soft magnetic powders through gas atomisation. Here, we present the development of amorphous soft magnetic alloys based on Mo-containing alloys with abnormal GFA, and demonstrate preparation of fully amorphous soft magnetic powders fabricated through the conventional medium-cooling-rate gas atomisation process. Our Mo-containing Fe73Si9 −x B10P5C3Mo x alloy showed fully amorphous state in a ribbon form with thickness up to 179 μm. Gas atomisation performed using the alloy produced fully amorphous powder with diameter up to 75 μm, while possessing high saturation magnetisation of 1.25 T.

FeSiBCrC amorphous magnetic powder fabricated by gas-water combined atomization

Amorphous soft magnetic composites have been attracting attention because of its low core loss under high frequency application. It is demanded that the powder for fabricating amorphous soft magnetic composites has amorphous structure and nearly spherical shape, which facilitates the uniform coating of insulator on the surface of powder particles. In this paper, amorphous Fe73.5Si13B11Cr1C1.5 (at%) powder was produced by gas-water combined atomization process which takes advantages of both gas atomization and water atomization, and its properties was compared with powder produced by gas atomization and water atomization. Gas-water combined atomization powder with particle size of −60 μm were found to be amorphous with low coercivity, and the shape of particles was nearly spherical. The permeability of magnetic powder cores prepared with three kinds of powder first increased and then decreased with annealing temperature, and the core loss first decreased and then increased. The cores prepared with gas-water combined atomization powder showed the best overall properties, with an effective permeability of 26.9, a relative permeability of 83.3% under a superimposed DC magnetic field of 7.96 kA/m, a core loss of 258 mW/cm3 under a frequency of 100 kHz, and a magnetization intensity Bm of 0.05 T after annealing at 793 K in nitrogen gas.

Enhancements of preparation efficiency and magnetic properties for Fe-based amorphous magnetic flake powder cores upon the adoption of a novel double-paralleled slits nozzle

The thick and brittle amorphous ribbons with the maximum thickness up to 58 μm were successfully fabricated using melt-spinning method upon the adoption of a novel double-paralleled slits nozzle (DPSN). The magnetic properties of the two magnetic flake powder cores (MFPCs) prepared from the conventional thin ribbon pulverization and the thick ribbon pulverization were analyzed and compared. Hereinto, a coupling model of fluid flow with free surface and surface tension, and heat transfer with phase transform was developed to design the slit spacing for the DPSN, and sol-gel method was employed to create SiO2 insulation layer on the surfaces of the magnetic flake powders to improve electrical resistivity. Results show that a quasi-steady-state can be reached for the puddle with the upstream and downstream menisci in crescent and slope shapes, respectively, by adopting the DPSN with slit spaces of 2.0 mm and 2.5 mm. The embrittlement process for the conventional thin ribbon can be omitted to enhance the efficiency of the powder preparation when using the thick ribbon before the ribbon pulverization. The MFPCs fabricated using the thick amorphous ribbon pulverization exhibit a higher permeability of 65.27, lower total core loss with the frequency being less than 234 kHz for Bm = 0.08 T, and a better DC-bias property of 70.97% as compared to the MFPCs made from the conventional thin amorphous ribbon pulverization. This work provides a promising approach to further development of Fe-based amorphous MFPCs with high preparation efficiency and excellent magnetic properties at the frequency below 234 kHz.

Effects of annealing on the magnetic properties of Fe-based amorphous powder cores with inorganic-organic hybrid insulating layer

In order to improve the magnetic properties of soft magnetic composites (SMCs), the Fe-based amorphous powder cores (AMPCs) based on spherical FeSiBCCr amorphous magnetic powders coated with inorganic-organic (TiO2-epoxy resin) hybrid insulating layer were prepared. The influence of annealing temperature on the soft magnetic properties of the AMPCs has been systematically researched in this work. It was found that the reasonable annealing temperature could increase the permeability and decrease the core loss of the AMPCs. The AMPCs annealed at 480 °C showed a constant permeability of 81.5 up to 10 MHz, and low total core loss of 275 mW/cm3. This study demonstrated that the present Fe-based AMPCs with inorganic-organic hybrid insulating layer have a great promising future in the field of medium and high frequency for the various electronic components.

High filling alumina/epoxy nanocomposite as coating layer for Fe-based amorphous powder cores with enhanced magnetic performance

A high-filling alumina/epoxy nanocomposite with improved thermal stability and insulation performance has been successfully designed as an organic–inorganic coating layer for the toroid-shaped FeSiBPNbCr amorphous magnetic powder cores (AMPCs). Unlike the organic coating, the organic–inorganic hybrid coating cores exhibited superior magnetic properties without compromising on saturation magnetization and permeability. The core loss declined by 40%, and the quality factor was 13% higher as half alumina was introduced into the epoxy resin matrix. A thin and uniform-coating layer of alumina/epoxy nanocomposite led to better high-frequency characteristics than those obtained with direct coating of the cores with alumina. Besides the outstanding magnetic properties, the Fe-based AMPCs with a convenient insulation-coating process cost lesser than Fe–Ni magnetic powder cores, thereby rendering the Fe-based AMPCs a potential candidate for a variety of industrial applications.

Improving Power-Inductor Performance by Mixing Sub-micro Fe Powder with Amorphous Soft Magnetic Composites

Amorphous soft magnetic powder is one of the most favorable materials for power applications working in the MHz range. In order to induce high permeability, DC bias characteristics, and low core loss in the working frequency range, the core must achieve high packing density. Sub-micro-sized α-Fe powder has been applied to inductors because of its high saturation magnetization and low intra-particle eddy-current loss. In this study, we investigated the magnetic properties of amorphous Fe alloy/sub-micro-sized α-Fe powder composites. We prepared composites as a bimodal toroid core with various mixing ratios of amorphous Fe alloy and sub-micro α-Fe, whose average particle sizes are approximately 35μm and 3.3μm, respectively. As the amounts of sub-micro α-Fe contents increase, the packing ratio and density of the core maximize at the cores, which have a sub-micro α-Fe content of 30 wt.%. The measurement results of the magnetic relative permeability (μ) and quality (Q) at 1 MHz revealed similar behaviors with the packing ratio and density; both μ and Q are a maximum of 35.5 and 47 in the core with 30 wt.% sub-micro α-Fe contents. The total evaluated core-loss (Pcv) under a driven magnetic flux 200 mT in the MHz range gradually decreased as the sub-micro α-Fe content increased up to 30 wt.%, and the minimum core-loss was 562.2 mW/cm3 at 1 MHz. Based on the experimental results, the improved magnetic performance of the core can be obtained not only by the intrinsic properties of material but also by the microstructure of the core body.

The core-shell structured Fe-based amorphous magnetic powder cores with excellent magnetic properties

The Fe-based soft magnetic amorphous powder cores (AMPCs) with excellent comprehensive magnetic properties were successfully designed and fabricated using the core-shell structured FeSiBCCr/TiO2 composite powders. The influence of the concentration of water (H2O) for the magnetic performance of the AMPCs has been systematically studied based on careful analysis of the process of nucleation and growth of TiO2 under different H2O concentration in the reaction system. The growth process for the TiO2 coating layer with the H2O concentration in the range of 0.01–0.02 ml/g corresponds to the heterogeneous nucleation phase, while the mixing phase of heterogeneous and homogeneous nucleation occurs when the concentration of H2O increases to 0.03 ml/g. Optimized soft magnetic properties have been achieved for the AMPCs with H2O concentration of 0.02 ml/g, including high permeability of 81.5 with a high frequency stability up to 10 MHz, high quality factor of 102 at 530 kHz, low core loss of 42 mW/cm3 at 500 kHz for Bm = 0.01 T, and better DC-bias property of 52% at a bias field of 100 Oe due to the uniform and proper thickness insulation coating layer, which can be used to produce miniature magnetic components for applications in medium and high-frequency fields.