Magnetic Powder Cores Research Articles

Formation of Fayalite for Insulating Layer of Powder Magnetic Core

Formation of Fayalite for Insulating Layer of Powder Magnetic Core

Significant improving magnetic properties and thermal conductivity of FeBSiPCNbCu nanocrystalline powder cores by designing novel ZnO insulating layer

As the application scenarios of soft magnetic composites (SMCs) tend to be high frequency, reducing their high-frequency core loss (Pcv) and improve the heat-sinking capability to avoiding thermal failure of electronic system are still greatly challenging. In present work, we successfully designed and prepared novel ZnO insulating layers on the surface of FeBSiPCNbCu nanocrystalline powders and discussed their growth processes. In addition, we investigated the effects of the ZnO insulating layers on the magnetic properties and heat-sinking capability of the FeBSiPCNbCu nanocrystalline magnetic powder cores (NMPCs) and explored the related mechanisms. The experimental results show that the hydrolysis of 1.75 wt% zinc acetate dihydrate under the coupling of 1 wt% polyvinylpyrrolidone forms uniform and thin ZnO insulating layers on the powders surface. The FeBSiPCNbCu@ZnO NMPCs annealed at 510 °C for 60 min exhibit excellent magnetic properties and superior heat-sinking capability with a low core loss of 698.4 mW/cm3 (20 mT, 2 MHz), high DC bias permeability of 68.3% (100 Oe) and heat conductivity coefficient of 2.22 W/(m•K) as compared with those of 859.8 mW/cm3, 57.1% and 1.86 W/(m•K), respectively, for the NMPCs without ZnO insulating layer.

Enhanced soft magnetic properties of SiO2-coated FeSiCr magnetic powder cores by particle size effect

Abstract It has been known that metal FeSiCr powders with large average particle sizes have been typically employed to prepare magnetic powder cores (SMCs), with few studies reported on the influence of magnetic properties for original powders with various average particle sizes less than 10 μm. In this work, SiO2-coated FeSiCr SMCs with different small particle sizes were synthesized using the sol–gel process. The contribution of SiO2 coating amount and voids to the soft magnetic properties was elaborated. The mechanism was revealed such that smaller particle sizes with less voids could be beneficial for reducing core loss in the SMCs. By optimizing the core structure, permeability and magnetic loss of 26 and 262 kW/cm3 at 100 kHz and 50 mT were achieved at a particle size of 4.8 μm and ethyl orthosilicate addition of 0.1 mL/g. The best DC stacking performance, reaching 87%, was observed at an ethyl orthosilicate addition rate of 0.25 mL/g under 100 Oe. Compared to other soft magnetic composites (SMCs), the FeSiCr/SiO2 SMCs exhibit significantly reduced magnetic loss. It further reduces the magnetic loss of the powder core, providing a new strategy for applications of SMCs at high frequencies.

Preparation and Magnetic Properties of Low-Loss Soft Magnetic Composites Using MgO-Phenolic Resin Coating.

Optimizing the interface between a magnetic powder matrix and an oxide-insulating layer is an effective method to improve the permeability and lower eddy current loss of iron-based soft magnetic composites. In this study, in order to improve the bonding strength of the substrate and insulation layer, soft magnetic composites were prepared by pressing and heat treating with reduced iron powder as a magnetic matrix, high-temperature MgO nanoparticles as insulating coating, and phenolic resin as an adhesive. The effects of MgO content on the microstructure and magnetic properties of the composites were investigated. The results of a scanning electron microscopy and an energy-dispersive spectrometer analysis corroborate that the results obtained regarding the frequency characteristics and the resistivity of the iron powder agree with the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis and confirm their improvement by the presence of an insulating layer of MgO. The resistivity of the sample coated with 4 wt.% MgO is nearly 45 times higher than that of the uncoated sample under the same conditions. The MgO-insulating film formed on the surface of iron powder makes the coated sample have low effective grain size, high resistivity, and low magnetic loss at a high frequency. At 1 kHz, the magnetic loss of the 4 wt.% MgO-coated sample is reduced by 77.3%, and the magnetic loss is only 5.8% compared with the uncoated sample at 50 kHz. This magnetic loss separation study shows that the addition of MgO insulation material can effectively reduce the eddy current loss of the magnetic powder core. The 4 wt.% MgO-coated sample has the lowest hysteresis loss factor and relatively low eddy current loss factor, so it can be determined that the addition of 4 wt.% MgO is the optimum content to attain a low magnetic loss.

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

Influence of four kinds of organic binders on magnetic properties of FeSiCrC magnetic powder and magnetic powder core

Influence of four kinds of organic binders on magnetic properties of FeSiCrC magnetic powder and magnetic powder core

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.

Optimizing FeSiCr-Based Soft Magnetic Composites Using the Deionized Water as the Phosphating Solvent.

To prepare a soft magnetic powder core, the magnetic powder surface has to be insulated by phosphating treatment. Organic chemicals such as ethanol and acetone are generally used as solvents for phosphoric acid, which may cause serious environmental problems. This work proposed deionized water as the environmentally friendly phosphating solvent for FeSiCr powder. The soft magnetic composites (SMCs) were prepared using phosphoric acid for inorganic coating and modified silicon polymer for organic coating. The effect of different phosphating solvents, including deionized water, ethanol, and acetone, on the structure and magnetic properties of SMCs were investigated. It is found that the solvent affects the phosphating solution's stability and the phosphoric acid's ionization. The phosphoric acid is more stable in deionized water than in ethanol and acetone. The phosphating reaction in deionized water is also more stable in deionized water, resulting in a dense phosphate coating on the particle surface. The effects of phosphoric acid concentration and temperature on the magnetic properties of FeSiCr-based SMCs were further studied. With the increase in phosphoric acid concentration and temperature, the magnetic permeability and saturation magnetization of the powder core decrease, and the core loss decreases, followed by an increase. The optimized combination of properties was obtained for the SMCs phosphated with 0.2 wt.% phosphoric acid in deionized water at 35 °C, including a high effective permeability μe of 25.7, high quality factor Q of 80.2, low core loss Pcv of 709.5 mW/cm3 measured at 0.05 T @ 100 kHz, and high withstanding voltage of 276 V, due to the formation of uniform and dense insulating coating layers. In addition, the SMCs prepared with phosphated powder show good corrosion resistance. The anti-corrosion properties of the SMCs using deionized water as a phosphating solvent are better than those using ethanol and acetone.

Soft magnetic properties, microstructure, and growth mechanism of FeSiAl soft magnetic powder cores fabricated via hexafluozirconic acid passivation

Soft magnetic properties, microstructure, and growth mechanism of FeSiAl soft magnetic powder cores fabricated via hexafluozirconic acid passivation

Finemet nanocrystalline magnetic powder cores: Application of binder and warm compaction process

In this paper, Finemet flake amorphous powder with poor flowability is used as raw material to investigate the effect of the type of silicone resin and compaction method on the density and soft magnetic properties of the magnetic powder cores. The results show that due to the different thermal stability of the three silicone resins 600, S2 and JH, the permeability of the three magnetic powder cores has significant differences. Since the lubricant is in a viscous flow state during the warm compaction and reduces the friction between the particles, the density of the magnetic powder cores is increased, which further improves the soft magnetic properties of the magnetic powder cores. Among them, the density of Finemet magnetic powder cores prepared by warm compaction with the S2 silicone resin as binder is 5.62 g∙cm−3, the permeability is 43.86, the DC bias capability is 66.77 % at 100 Oe, and the total loss is 113.94 mW∙cm−3 (100 kHz, 50 mT), which has excellent comprehensive soft magnetic properties and is a very significant improvement compared with cold compaction. This shows that the warm compaction process is an effective method to further improve the soft magnetic properties of magnetic powder cores.

Industrial-scale fabrication of FeSiBC cores with balanced soft magnetic properties by transverse magnetic field annealing and mixing of carbonyl iron powder

In this study, the effects of transverse magnetic field annealing and mixing fine powder on the soft magnetic properties of FeSiBC soft magnetic powder cores (SMPCs) are investigated. The results show that with the increase of transverse magnetic field intensity, the core loss of FeSiBC SMPCs decreases and then increases with a continuous increase in permeability compared to the zero magnetic field treatment. Wherein, the effective permeability of the powder cores is increased from 58.07 to 59.63 after transverse magnetic field annealing at a magnetic field intensity of 900 Gs and annealing temperature of 430 ℃. It shows that mixing the FeSiBC amorphous crushed powder with fine powder and transverse magnetic field annealing are effective ways to further promote amorphous SMPCs to meet the requirements of the development of electronic devices, and the prepared high-performance SMPCs also have a certain prospect of industrial application.

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.

Development of FeCoMnAl multi-principal element alloys and soft magnetic powder cores with excellent magnetic properties and high temperature magnetic stability

In order to develop a multi-principal element alloy with outstanding soft magnetic properties and high thermal stability, a Fe35Co35Mn30−xAlx (x = 9, 12, 15, 18, 21, 24) alloy system was designed. The findings demonstrated that the optimal Al/Mn content ratio contributes to the formation of a BCC and B2 dual-phase structure, which leads to a significant increase in the saturation magnetic flux density (Bs) and a considerable decrease in the coercivity of the alloy. The as-cast Fe35Co35Mn15Al15 alloy with a co-lattice structure exhibits exceptional soft magnetic properties, with a resistivity of 324 μΩ·cm, a Bs of 1.46 T and a Hc of 167.2 A/m. Corresponding soft magnetic powder cores (SMPCs) were fabricated and the impact of heat treatment temperature on the properties of the SMPCs was examined. The SMPCs after annealing at 660 °C exhibits high stable permeability (μe) of 48 up to 10 MHz, a low core loss (Pcv) of 1208 mW/cm3 (at 1 MHz, 20 mT), and excellent direct current bias performance. In addition, these SMPCs possess excellent high temperature magnetic stability, and the variation of both μe and Pcv at a high frequency (1 MHz) is less than 2 % over a wide temperature range of 25–150 °C.

Formation of Fayalite for Insulating Layer of Powder Magnetic Core

Formation of Fayalite for Insulating Layer of Powder Magnetic Core

Research on the soft magnetic properties of iron–nickel magnetic powder core composite with carbonyl iron powder

Research on the soft magnetic properties of iron–nickel magnetic powder core composite with carbonyl iron powder

NiCoCrFeY High Entropy Alloy Nanopowders and Their Soft Magnetic Properties.

High entropy alloy nanopowders were successfully prepared by liquid-phase reduction methods and their applications were preliminarily discussed. The prepared high entropy alloy nanopowders consisted of FeNi alloy spherical powders and NiFeCoCrY alloy spherical powders with a particle size of about 100 nm. The powders have soft magnetic properties, the saturation magnetization field strength were up to 5000 Qe and the saturation magnetization strength Ms was about 17.3 emu/g. The powders have the excellent property of low high-frequency loss in the frequency range of 0.3-8.5 GHz. When the thickness of the powders coating was 5 mm, the powders showed excellent absorption performance in the Ku band; and when the thickness of the powders coating was 10 mm; the powders showed good wave-absorbing performance in the X band. The powders have good moulding, and the powders have large specific surface area, so that the magnetic powder core composites could be prepared under low pressure and without coating insulators, and the magnetic powder cores showed excellent frequency-constant magnetization and magnetic field-constant magnetization characteristics. In the frequency range of 1~100 KHz; the μm of the magnetic powder core heat-treated at 800 °C reached 359, the μe was about 4.6 and the change rate of μe with frequency was less than 1%, meanwhile; the magnetic powder core still maintains constant μe value under the action of the external magnetic field from 0 to 12,000 A/m. The high entropy alloy nanopowders have a broad application prospect in soft magnetic composites.

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

Improved Anti-Saturation Performance of Fe-Si-Al Soft Magnetic Powder Core via Adjusting the Alloy Composition

Ball-milled Fe-Si-Al soft magnetic powder cores with the particle compositions away from the classical Sendust point were prepared in this work. The influences of alloy composition on the metallographic structure, density, hardness, and resistivity of Fe-Si-Al alloy, as well as the frequency-dependent permeability, loss, and the anti-saturation performance of Fe-Si-Al powder cores, were investigated systematically. It was found that the hardness of Fe-Si-Al alloy increases with the Si mass ratio and the saturation magnetization (Ms) increases with the Fe mass ratio. The alloy hardness affects the particle size after the ball-milling process and, thus, influences the porosity of the powder core. Together with adjusting the demagnetization field by controlling the particle size and the core’s porosity, changing the alloy composition to drive K and λ deviating from zero can effectively improve the anti-saturation performance of Fe-Si-Al powder cores at the expense of hysteresis loss, to some extent. In this work, good comprehensive magnetic properties were obtained in the Fe85.5-Si12-Al2.5 powder core. Its effective permeability percentage at 100 Oe and Ms were 59.12% and 132.23 emu/g, respectively, which are higher than those of the classical Sendust core. This work provides a feasible idea for optimizing the overall performance of the high-power magnetic device.

Development of High-Density and Low-Loss Powder Magnetic Core for Reactor in Hybrid Vehicles

Development of High-Density and Low-Loss Powder Magnetic Core for Reactor in Hybrid Vehicles

The effect of phosphate/TiO2 composite insulating layer on the high frequency magnetic properties of FeSiBPCNbCu nanocrystalline soft magnetic powder cores

Currently, power electronic devices are developing to meet the requirement of miniaturization, high-frequency and low-power consumption, reducing the high-frequency loss of soft magnetic powder cores (SMPCs) is one of the popular research topics. The construction of multilayer insulating structures can reduce the core loss (Pcv) of SMPCs by increasing the resistivity. In this work, a composite inorganic insulating layer of phosphate and TiO2 was successfully synthesized on the powder surface by phosphating and then sol-gel method. At last a nanocrystaline SMPCs with excellent soft magnetic properties were prepared with epoxy resin as the binder. The cores were heat-treated at 510 ℃ for 1 h to achieve optimum soft magnetic properties, with a low Pcv of 854 mW/cm3 at 20 mT and 2 MHz, an effective permeability (μe) of 40 at 10 MHz and excellent DC bias with a percent permeability of 74% of the initial value at 100 Oe. The synergistic effect of the epoxy - TiO2 - phosphate - nanocrystalline powder multilayer interface effectively reduces inter-particle eddy current loss, resulting in a significant reduction in the Pcv of the SMPCs.