Enhancing soft magnetic properties of FeSiBNbCu nanocrystalline powder cores by coating ZrO2 insulation layer

The insulation coating plays a crucial role in minimizing core loss (P_cv) in soft magnetic powder cores (SMPCs). In this work, we prepared ZrO₂ coating layer on FeSiBNbCu spherical powder by the hydrolysis-precipitation method and investigated the magnetic properties of the FeSiBNbCu@ZrO₂ nanocrystalline SMPCs. ZrO₂ coating layer were successfully fabricated on the powder by adding a proper amount of K₂ZrF₆ in alkaline ethyl alcohol solution. The micromorphology and chemical structure of the ZrO₂ coating layer on the surface of FeSiBNbCu nanocrystalline powder, as well as the conversion mechanisms, has been investigated. The presence of the ZrO₂ coating reduces the P_cv by significantly lowers eddy loss (P_e) of the nanocrystalline SMPCs, meanwhile improves DC bias performance and slightly decreases their permeability. When the additive amount of K₂ZrF₆ is 1.0 wt%, the nanocrystalline SMPCs has best comprehensive soft magnetic properties, including stable effective permeability (μ_e) of 57.8 up to 1 MHz, excellent DC bias performance of 59.3 % at a bias field of 100 Oe, and the lowest P_cv of 194.7 mW/cm³ at a frequency (f) of 150 kHz and maximum magnetic induction (B_m) of 50 mT.     

FeNi/Glass Soft Magnetic Composites with High Magnetic Properties

FeNi/glass composites with 0 wt%,1 wt%, and 2 wt% glass content are produced, and their soft magnetic properties are systematically studied. The scanning electron microscope (SEM) results indicate that the FeNi particles are surrounded by glass powder. With the addition of glass powder, the saturation magnetization of the FeNi/glass composites decreases from 170 to 158 emu/g, and the effective permeability decreases from 56.1 to 39.1. With the increase of glass content, the imaginary part μ″ is reduced, indicating that the eddy current loss or excess loss is reduced at high frequency. The magnetic loss measurement results show that the addition of glass powder greatly reduces the eddy current loss. Furthermore, the FeNi/glass composite core with 2 wt% glass content has moderate permeability, higher quality factor Q, and better DC bias characteristics than other cores. The results show that the ideal glass powder content can improve the magnetic properties of FeNi composite materials, and glass powder can be used as an insulator in soft magnetic composites (SCMs).

     

Magnetic properties and loss separation mechanism of FeSi soft magnetic composites with in situ NiZn-ferrite coating

Journal of Materials Science: Materials in Electronics - The soft magnetic performances including frequency-dependent permeability, core loss, and DC-bias properties of the Fe-6.5 wt.%Si (FeSi)...     

Worthwhile effects of salt-matrix reduction on shape, morphology and magnetic properties of FeNi nanoparticles

Modification of hydrogen reduction of mechanically alloyed Ni-ferrite led to well dispersed spherical FeNi nanoparticles with superior magnetic properties. The as-milled powder was reduced in hydrogen atmosphere at 600 °C for 1 h. Salt-matrix utilization during the reduction showed itself as a well barrier to the particle sintering and growth. As the results of the modified process, shape of the particles was changed, their size was decreased and their soft magnetic properties were remarkably improved as evidenced by SEM, TEM, XRD and VSM.     

铁粉纯度和粒径对磷化铁粉软磁复合材料磁性能的影响

研究了铁粉纯度和粒径对磷化铁粉软磁复合材料磁性能的影响。结果表明,铁粉经磷化后,表面成功包覆了完整均匀的磷酸盐绝缘层。铁粉纯度提高,软磁复合材料磁芯的密度和磁导率增大,同时磁滞损耗降低。铁粉粒度增大,磁芯密度和磁导率增加,中高频率下磁损耗明显增加,且频率越高越明显。     

Improved magnetic properties of iron-based soft magnetic composites with a double phosphate-SiO2 shells structure

Herein a double shells structure was proposed to overcome the drawbacks such as poor heat resistance, incomplete insulation and high core loss coating of iron-based soft magnetic composites (SMCs) with single shell structure. The surface of the iron powder was coated with a double shells structure composed of an inner phosphate coating and an outer SiO₂ coating through phosphating and hydrolysis successively. Subsequently, the effects of different SiO₂ addition amount on the microstructure of iron powder and magnetic properties of SMCs were studied. The introduction of SiO₂ in the double shells structure inhibited the decomposition and failure of phosphating layer after being annealed at a high temperature. The iron powder coated with the phosphate-SiO₂ insulating layer was still effective after annealing in a N₂ atmosphere at 570 °C, achieving the purpose of eliminating residual stress and improving magnetic properties. The optimal process parameters were set at 0.2 wt% phosphoric acid and 0.5 wt% tetraethyl orthosilicate to fabricate the phosphate-SiO₂ double shells. The iron-based SMCs presented excellent magnetic properties with B_s of 1.29 T and P_s of 169.2 W/kg (measured at 1 T and 1 kHz). In addition, the core loss of SMCs introduced with SiO₂ is 83% lower than that of SMCs produced by the phosphating process. This paper provides a feasible method for improving the magnetic properties of SMCs.

     

Evolution of magnetic domain structure and magnetic properties of Fe-based nanocrystalline powder cores during transverse magnetic field annealing

In this work, transverse magnetic field annealing (TA) was performed to FeSiBNbCu nanocrystalline powder cores (NPCs), and the magnetic properties, microstructure, and magnetic domain structure were in detail studied comparing with those after normal annealing (NA), and the mechanism of the improvement of soft magnetic properties by TA was elucidated. The experimental results show that the core loss of the sample is reduced by 14 % and the coercivity is reduced by 38 % after TA at 450 °C compared to the NA sample. The direct current bias performance of the TA sample is maintained at 67 % under a 100 Oe bias field. TA optimizes the soft magnetic properties of NPCs by optimizing the domain structure, reducing the formation of micro-vortex dots and broadening the size of the domain. These results can provide a good guide for optimizing the performance of NPCs with low core loss at high frequency.     

粉末挤出成型法制备FeSiAl/FeCuNbSiB磁粉芯

采用粉末挤出成型法制备了FeSiAl/Fe-CuNbSiB纳米晶磁粉芯,并讨论了FeSiAl粉复合量、粉胶质量比对磁粉芯磁性能的影响。结果表明粘结剂配方为硬脂酸1%、聚丙烯20%、石蜡79%,挤出成型粉胶质量比10∶1的FeSiAl/FeCuNbSiB纳米晶磁粉芯,磁粉芯密度达到4.69g/cm3。200目FeSiAl粉与300目FeCuNbSiB纳米晶粉复合,当磁粉芯磁粉质量配比为"200目FeSiAl粉30%+300目FeCuNbSiB纳米晶粉70%"、粉胶质量比为10∶1、44℃×0.5h石油醚脱脂、热处理温度160℃×1h时,磁粉芯取得最佳的软磁性能,磁粉芯中心频率f为600kHz,有效磁导率μe达到16.48,品质因数Q值为57.5;频率及温度的变化对磁粉芯的有效磁导率的影响小。     

Structure and magnetic properties of ZrO2-coated Fe powders and Fe/ZrO2 soft magnetic composites

Fe particles were coated with ZrO₂ nanopowders using mechanical milling method combined with high temperature recovery annealing process. The effect of milling time on particle size, phase structure and magnetic properties of the core-shell structure powders was studied. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) revealed that the surfaces of the composite powders comprised thin and uniform layers of ZrO₂ insulating powders after milling. Also, the SEM images showed the morphology of micro-cellular structured compacts with cell-body of Fe particles and indicated that Fe particles were well separated and insulated by thin ZrO₂ layers. The Fe/ZrO₂ soft magnetic composites displayed much higher electrical resistivity, lower core loss than that of the pure Fe powder cores without ZrO₂ layers at medium and high frequencies. The preparation method of ZrO₂-insulated Fe powders provides a promising method to reduce the core loss and improve the magnetic properties for soft magnetic composite materials.     

A comprehensive study of soft magnetic materials based on FeSi spheres and polymeric resin modified by silica nanorods

A novel soft magnetic composite (SMC) based on spherical FeSi particles precisely covered by hybrid phenolic resin was designed. The hybrid resin including silica nano-rods chemically incorporated into the phenolic polymer matrix was prepared by the modified sol–gel method. A chemical bridge connecting silica nano-rods with the base polymeric net was verified by FTIR, ¹³C and ²⁹Si NMR spectroscopy, whereas the shape and size of silica nano-rods were determined by TEM. It is shown that the modification of polymeric resin by silica nano-rods generally leads to the improved thermal and mechanical properties of the final samples. The hybrid resin serves as a perfect insulating coating deposited on FeSi particles and the core–shell particles can be further compacted by standard powder metallurgy methods in order to prepare final samples for mechanical, electric and magnetic testing. SEM images evidence negligible porosity, uniform distribution of the hybrid resin around FeSi particles, as well as, dimensional shape stability of the final samples after thermal treatment. The hardness, flexural strength and density of the final samples are comparable to the sintered SMCs, but they simultaneously exhibit much higher specific resistivity along with only slightly lower coercivity and permeability.     

Development of P/M Fe–P soft magnetic materials

Phosphorous is treated as an impurity in conventional steels owing to segregation of phosphorous and formation of brittle phosphides along the grain boundaries. It is responsible for cold and hot shortness in wrought steels. In conventional powder metallurgy, involving compaction and sintering, high phosphorous content (up to 0·7%) in Fe-based alloys exhibit attractive set of mechanical and magnetic properties. These powder-processed alloys suffer from increasing volumetric shrinkage during sintering as phosphorous is increased beyond 0·6%. Thus both cast as well as conventional powder metallurgy routes have their own limitations in dealing with iron?Cphosphorous alloys. Hot-powder forging was used in the present investigation for the development of high-density soft magnetic materials containing 0·3?C0·8% phosphorous to overcome these difficulties. It was observed that phosphorous addition improves the final density of the resulting product. It was further observed that hot-forged iron?Cphosphorous alloys have excellent hot/cold workability and could be easily shaped to thin strips (0·5?C1·0?mm thick) and wires (0·5?C1·0?mm diameter). The powder hot-forged alloys were characterized in terms of microstructure, porosity content/densification, hardness, soft magnetic properties and electrical resistivity. Magnetic properties such as coercivity 0·35?C1·24?Oe, saturation magnetization 14145?C17490 G and retentivity 6402?C10836 G were observed. The obtained results were discussed based on the microstructures evolved.     

Fe78Si9B13非晶合金磁芯封装及其软磁性能

研究了Fe78Si9B13非晶合金磁芯进行环氧封装及封装后对非晶合金磁芯软磁性能的影响。结果表明对磁芯进行环氧封装,有效改善磁芯的机械强度同时,能改善带材表面的平整度,在带材表面形成一层绝缘层,显著降低了非晶合金磁芯高频下的损耗值,封装后的非晶合金磁芯在Bm=1T,f=1kHz下,损耗值比封装前下降了14%。综合考虑机械强度大小、磁化难易、损耗高低等因素,封装胶浓度为2%时封装效果最佳。     

大高度的非晶变压器磁芯制备及其性能研究

研究了一种制备非晶变压器磁芯的新方法,该方法首先将高度低的铁基非晶磁芯热处理后在两侧面用树脂封装,然后将多个封装后的磁芯叠加成高度能满足非晶变压器需求的组合磁芯。研究结果表明,采用宽度为(50±0.2)mm、厚度(33±2)μm的Fe78Si9B13非晶带材,经过420℃×2h退火处理后,制备成高度为200mm的电力变压器磁芯,该磁芯的磁性能与高度为50mm的原装磁芯的磁性能相近,在f=1kHz,组合磁芯的矩形比为0.5～0.7,最大饱和磁感应强度1.4～1.5T。组合磁芯表现出良好的软磁性能,可以满足电力变压器要求。     

软磁复合材料铁芯电机特性的仿真研究

为了发挥软磁复合材料的高电阻率,低损耗,易于再利用的特点,仿真模拟将其应用在永磁电机的铁芯上.以12槽4极直流电机为仿真对象,把三维计算问题转化成二维模型,用JMAG软件对电机进行建模,阐述SMC与硅钢片铁芯差异,先用两种材料进行仿真,结果说明只靠替换铁芯材料对电机性能改进并不会产生很大改善,改进模型,得出不同延伸高度铁芯延伸长度增加引起的电流和转矩特性与功率变化的关系.利用所建模型将Somaloy500的软磁复合材料与50CS800的硅钢片制备的铁芯进行模拟实验,结果表明:相同条件下软磁复合材料铁芯的效率要更高一些.最低转速时效率增加5%,最高转速时效率增加10%;软磁复合材料铁芯模型抑制电流输出,各向同性的优势明显.结论为SMC材料在低转速电机的开发中依旧能够发挥优势,实现电机性能的提高.     

Effect of magnetic properties in FeSi soft magnetic composites by low melting glass powder as adhesive and insulating agent

Journal of Materials Science: Materials in Electronics - FeSi/1wt% glass soft magnetic composites are prepared by mechanically mixing, compacting, and annealing, their morphology is examined by...     

Fe<Subscript>78</Subscript>Si<Subscript>9</Subscript>B<Subscript>13</Subscript> amorphous powder core with improved magnetic properties

The effects of pre-annealing treatments on the soft magnetic properties of the corresponding Fe₇₈Si₉B₁₃ amorphous powder cores were investigated. The amorphous powder cores prepared from pre-annealed powder have better soft magnetic properties compared with unpretreated powder core in the as-cast state. The result shows that the powder after pre-annealing in a magnetic field presents a regular domain structure and the soft magnetic properties of the corresponding powder cores are greatly improved. As the result, the magnetic-field annealed powder core has the highest effective permeability (μ _e) of 37, which is 23 % higher than the as-cast one and 7 % than only vacuum-annealed one. The total core loss (P _cv) for the core annealed in magnetic field is only 141 W/kg (100 kHz, 50 mT) and as low as 36 % of the P _cv for the powder core in the as-cast state. The one annealed in magnetic field also exhibits the best DC bias properties of 92 %. This work provides a novel approach to realizing low P _cv and high μ _e for Fe₇₈Si₉B₁₃ powder cores and also validates the application prospect of powder cores in the work condition of different ripple currents, different loads and a wide frequency (f) range (10 kHz–10 MHz).     

高性能软磁合金的研究进展EI北大核心CSCD

软磁材料是一种极为重要且应用十分广泛的能源材料,近年来,随着磁性元件的日益高频化和小型化,以及节能环保的号召,开发和研究高性能软磁材料具有重要意义。本工作概述了软磁合金的发展历史,重点归纳出各类软磁合金(包括传统软磁合金、非晶/纳米晶软磁合金、高熵软磁合金)的成分、微观组织、磁性能以及应用范围,并总结出不同软磁合金的优、缺点;指出典型合金的微观组织对合金软磁性能(尤其矫顽力)具有关键性的主导作用,进而探讨了影响软磁合金矫顽力的因素及其微观机制,发现控制晶粒尺寸(或纳米粒子尺寸)是获得低矫顽力的关键,并描述了矫顽力的微观影响机制在高熵软磁合金中的发展;最后,展望了高熵软磁合金因多主元混合的成分特性带来的组织多样化,更有利于实现对合金性能的调控,并有望作为新一代高温软磁体材料。     

Synthesis and characterization of ultra-small magnetic FeNi/G and NiCo/G nanoparticles

Ultra-small magnetic nanoparticles consisting of NiCo and FeNi alloys enclosed within graphitic shells (NiCo/G and FeNi/G) have been synthesized. The particles, which retained the face centered cubic (fcc) symmetry of the original bulk metals, together with the graphitic coating were characterized by means of aberration corrected scanning transmission electron microscopy (STEM), obtaining mean particle sizes of 2.6?nm and 6.2?nm for NiCo/G and FeNi/G, respectively. Due to the enhancement of the thermal stability by the graphite shell, the graphite coated FeNi and NiCo were stable under oxygen atmosphere up to 170?°C. The effectiveness of the graphite shell was confirmed when unprotected bimetallic FeNi and NiCo were prepared and chemical characterization revealed that more than 60?at.% of the samples was oxygen due to the massive oxidation of the bimetallic nanoparticles.     

Exchange-coupled magnetic nanoparticles for efficient heat induction

The conversion of electromagnetic energy into heat by nanoparticles has the potential to be a powerful, non-invasive technique for biotechnology applications such as drug release, disease treatment and remote control of single cell functions, but poor conversion efficiencies have hindered practical applications so far. In this Letter, we demonstrate a significant increase in the efficiency of magnetic thermal induction by nanoparticles. We take advantage of the exchange coupling between a magnetically hard core and magnetically soft shell to tune the magnetic properties of the nanoparticle and maximize the specific loss power, which is a gauge of the conversion efficiency. The optimized core-shell magnetic nanoparticles have specific loss power values that are an order of magnitude larger than conventional iron-oxide nanoparticles. We also perform an antitumour study in mice, and find that the therapeutic efficacy of these nanoparticles is superior to that of a common anticancer drug.     

磁控溅射制备Cu/FeNi复合丝的巨磁阻抗效应

采用磁控溅射法制备了Cu/FeNi复合结构丝,并对其结构及巨磁阻抗(GMI)效应进行了研究.结果表明,Cu/FeNi复合结构丝具有良好的GMI效应,在较低频率下观察到的最大磁阻抗变化可达247.4%,同时发现FeNi铁磁层厚度对复合结构丝的软磁性能有重要影响,找到了复合结构丝铁磁层最佳厚度的范围,当厚度达到一定值时铁磁层内磁矩方向由环向分布转向复合丝长轴方向,表现出不同的GMI行为.