Amorphous Magnetic Powder Cores Research Articles

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.

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.

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.

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.

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.

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.

Strategy to Enhance Magnetic Properties of Fe78Si9B13 Amorphous Powder Cores in the Industrial Condition

In this study, the soft magnetic properties of Fe78Si9B13 amorphous magnetic powder cores (AMPCs) were enhanced by coordinately adjusting the technological parameters, including the particle size distribution, molding pressure, and coating agent content, in the industrial condition. The results show that the optimized comprehensive soft magnetic properties of the Fe78Si9B13 AMPCs could be obtained under the following process conditions: (1) the distribution of particle size is 20 wt.% for 140–170 mesh, 70 wt.% for 170–270 mesh, and 10 wt.% for 270–400 mesh; (2) the molding pressure is in the range of 2.35–2.45 GPa; and (3) the additive amount of sodium silicate is 1.5 wt.%. After the collaborative optimization, the AMPCs’ compact density, ρ, the effective permeability, μe, and the residual effective permeability at the applied magnetizing field of 7.96 kA/m, μe@7.96 kA/m, increased from 5.61 g/cm3 to 5.86 g/cm3, from 58.13 to 77.01, and from 40.36 to 49.57, respectively. The attenuation ratio of the effective permeability, when in the frequency band of 20–100 kHz, was less than 0.85%. The core loss at the 50 kHz for the maximum magnetic flux density of 0.1 T reduced from 380.85 mW/cm3 to 335.23 mW/cm3. This work will encourage the further application of Fe-based AMPCs in the fields of electronics and telecommunication.

Improvement of soft magnetic properties of FeSiBPNb amorphous powder cores by addition of FeSi powder

The effect of FeSi powder with volume fraction of 0–40% on the soft magnetic properties of the FeSiBPNb amorphous powder cores has been systematically investigated in this study. The results shows that the amorphous magnetic powder core mixed with 10% FeSi powders in volume fraction exhibits superior DC-bias properties, constant permeability, low core loss up to a higher frequency range, and excellent soft magnetic properties after appropriate heating treatment. The DC-bias properties of the present amorphous magnetic cores decrease by only 20% as the external field increases to 100 Oe. Meanwhile, it also exhibits a high permeability of 60 at 10 MHz and a low core loss of 159 W/kg at Bm = 0.1 T and f = 50 kHz. The present Fe-based amorphous magnetic powder cores mixed FeSi powders with superior DC-bias properties are a potential candidate for a variety of industrial applications.

Enhanced soft magnetic properties of the Fe-based amorphous powder cores with novel TiO2 insulation coating layer

Abstract The core-shell structured FeSiBCCr@TiO2 amorphous magnetic powder cores (AMPCs) with excellent comprehensive magnetic properties were successfully prepared using spherical amorphous powders with high quality insulating layer. Scanning electron microscopy, Energy dispersive X-ray spectroscopy analysis, X-ray diffraction, and Fourier transform infrared spectroscopy revealed that the surface of the Fe-based amorphous powders was covered by a continuous amorphous TiO2 insulation layer. The performances of the AMPCs can be well tuned by changing the thickness of the insulation coating layer, which can be adjusted by controlling the concentration of tetrabutyl titanate (TBOT) in the hydrolysis and condensation reaction system. After annealing at 480 °C for 1 h, the AMPCs with TBOT concentrations of 0.15 ml/g exhibited excellent comprehensive soft magnetic properties, including the highest quality factor of 104.5 at 560 kHz and lowest core loss of 265 mW/cm3 at f = 100 kHz and Bm = 0.05 T. It also maintained a relatively high permeability of 67 up to 5 MHz and superior DC-bias permeability of 68% at a bias field of 100 Oe. This study demonstrated a modified method to develop a novel insulation coating layer to reduce the core loss and improve the magnetic properties of AMPCs.

Fabrication and magnetic properties of novel Fe-based amorphous powder and corresponding powder cores

In this study, Fe77P6B10Si4Nb2Cr1 amorphous powder in the particle size range below 75 µm was synthesized using industrial raw materials by water atomization. Then the amorphous magnetic powder cores (AMPCs) were prepared from the mixture of the amorphous alloy powder with different contents of epoxy resin as insulation/bonding materials by cold pressing. After annealed at 673 K for 1 h, the evolution of the high-frequency properties for the FePBSiNbCr AMPCs with the epoxy resin contents was studied. The AMPCs showed excellent magnetic properties, including high effective permeability of 62–82 with a high frequency stability up to 10 MHz, low core loss of 308–500 mW/cm3 at 100 kHz under the maximum magnetic flux density of 0.05 T, and superior DC-bias permeability of 62–72% at a bias field of 100 Oe. The development of Fe-based AMPCs with excellent soft magnetic properties is encouraging for future applications as functional materials.

Improved permeability of Fe based amorphous magnetic powder cores by adding Permalloy

This paper focuses on improving the permeability of Fe-Si-B based amorphous magnetic powder cores by addition of micron-sized ferromagnetic crystalline metal particles (Permalloy). The effects of Permalloy content, size and the amount of insulation on magnetic properties and density were investigated. The results showed that the Fe based amorphous powder cores prepared with 15wt.% Permalloy (<15μm particle size) have higher permeability and relatively low core loss. Furthermore, compared with Fe-Si-B based amorphous powder, the saturation magnetization of mix powder increases by 60.7%, while the magnetic powder cores coated with 3wt.% coating agent (DC805) have low core loss of 57W/kg at 100kHz for Bm=500Oe.

Fabrication of FeSiBPNb amorphous powder cores with high DC-bias and excellent soft magnetic properties

Fe-based amorphous magnetic alloy powders with a composition of (Fe0.76Si0.09B0.1P0.05)99Nb1 were first prepared by water atomization, and then amorphous magnetic powder cores were produced from a mixture of the amorphous alloy powders with diameters of below 75μm and different volume of insulation and bonding materials by mold compacting with a compact pressure of 2200MPa at room temperature. The amorphous magnetic cores exhibit superior DC-bias properties and excellent soft magnetic properties after appropriate heating treatment. The DC-bias properties of the present amorphous magnetic cores just decrease 15% as the external field increases to 100Oe. Meanwhile, it also exhibits a high permeability of 56 at 1MHz and a low core loss of 451W/kg at Bm=0.1T and f=100kHz. The present Fe-based amorphous magnetic powder cores with superior DC-bias properties are a potential candidate for a variety of industrial applications.

Microstructure and magnetic properties of soft magnetic powder cores of amorphous and nanocrystalline alloys

With the development of modern ferromagnetic technology, soft magnetic powder cores (MPCs) of amorphous and nanocrystalline alloys have been intensively studied for their excellent soft magnetic properties such as high flux density, low coercivity and reduced core loss due to amorphous state and nanocrystalline grains of 10–20nm dispersed in a residual amorphous matrix. In this paper, the microstructures and soft magnetic properties, i.e., maximum magnetic induction Bm, effective permeability μe, DC-bias properties and volume power losses PCV of MPCs made from amorphous powder of gas atomization and nanocrystalline powder of pulverized melt-spun ribbon were investigated and also compared on the basis of the same level of μe. It is found that μe of both kinds of MPC keeps unchanged up to 1MHz. The amorphous MPC has lower PCV at lower frequency range, while the nanocrystalline MPC has lower PCV at high frequency range instead. Also, the nanocrystalline MPC has better DC-bias property. Moreover, the DC magnetic properties and the changes of PCV of both MPCs with frequency and flux density are also studied. Furthermore, the electromagnetic characteristics, the microstructures and the mechanisms accounting for these phenomena of both MPCs are also discussed.

Novel Fe-based amorphous magnetic powder cores with ultra-low core losses

Amorphous magnetic alloy powders were prepared from bulk metallic glasses Fe74Cr2Mo2Sn2P10Si4B4C2 with supercooled liquid region of 32 K by water atomization. Amorphous magnetic powder core precursor was produced from a mixture of the amorphous alloy powder with addition of insulation and bonding materials by mold compacting at room temperature. After annealing the core precursor, the amorphous magnetic core exhibits superior magnetic properties as compared with molypermalloy powder core. The initial permeability up to 1 MHz was about 80, the flux density at 300 Oe was 1.06 T and the core loss at 100 kHz for Bm=0.1 T was only 329 kW/m3. The ultra-low core loss is attributed to the combination of relatively high resistivity and the amorphous structure of the Fe-based amorphous powder. Besides the outstanding magnetic properties, the Fe-based amorphous magnetic powder core had a much lower cost which renders the powder cores a potential candidate for a variety of industrial applications.