Fabrication of the novel Fe2+αO3+α–CoFe2O4 composite fibers and their magnetic properties

김효영,박혜경,Ju Young-Wan 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.4

Soft-hard magnetic composites have attracted much attention as magnetic materials for permanent magnets due to high coercivity and saturation magnetization in various fi elds such as motor, storage device and magnetic actuators. Hard magnetic materials with low saturation magnetization improve magnetic properties through exchange coupling eff ect with soft magnetic materials. Rare earth metals, which are used as magnetic materials in permanent magnetic, have issued such as high cost due to resource scarcity. Transition metals have been used for fabricating magnetic material with high magnetic properties due to low cost and abundant in the resource. Spinel magnetic materials with transition metals have excellent chemical, thermal stability, large magnetocrystalline anisotropy and magnetic properties. Composite magnetic materials in one dimensional (1D) morphology are eff ective in improving coercivity. In this work, soft-hard composite fi ber has been fabricated by electrospinning method using iron oxide as soft magnetic material and cobalt ferrite as hard magnetic material. The change in the oxidation state of iron oxide can be controlled with sintering atmosphere and infl uences on the magnetic properties. In comparing with simple CoFe 2 O 4 , the fabricated Fe 3 O 4 –CoFe 2 O 4 exhibits excellent saturation magnetization of 133.63 emu g −1 and enhanced coercivity of 2746.9 Oe.

Preparation and characterization of flaky FeSiAl composite magnetic powder core coated with MnZn ferrite

Zhen Wang,Xiansong Liu,Xucai Kan,Ruiwei Zhu,Wei Yang,Qiuyue Wu,Shengqiang Zhou 한국물리학회 2019 Current Applied Physics Vol.19 No.8

The flattening of FeSiAl soft magnetic powder was achieved by ball milling process, and MnZn/FeSiAl composite magnetic powder core was prepared by press molding. The effect of different coating amount of MnZn ferrite on the soft magnetic properties of FeSiAl was studied. At the same time, the optimal stress-relieving annealing temperature of the composite magnetic powder core is revealed. The results showed that the addition of MnZn ferrite affected the magnetic properties such as saturation magnetization (Ms), initial permeability (μi) and power loss (Pcm) of FeSiAl soft magnetic. With the increase of MnZn ferrite addition content, the saturation magnetization of composites decreased gradually, and the magnetic permeability increased first and then decreased, and the loss decreased first and then increased. When the addition content of MnZn ferrite was 5%, the permeability reached the maximum, which was 28.1% higher than that of the pure FeSiAl magnetic powder core under the same conditions. At the same time, the loss was the lowest, which was 13.3% lower than the pure FeSiAl powder core under the same conditions. When the annealing temperature is around 650 °C, the magnetic powder core has the largest magnetic permeability and the lowest loss.

고에너지효율 연자성 복합 분말 소재의 연구개발 동향

김휘준(HwiJun Kim) 한국자기학회 2011 韓國磁氣學會誌 Vol.21 No.2

The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-toparticle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

Effect of Organic Fuel on High-Frequency Magnetic Properties of Fe–Al₂O₃ Composite Powders Synthesized by a Combustion Method

Choi, Donchul,Choi, Moosung,Kim, Jongryoul IEEE 2015 IEEE transactions on magnetics Vol.51 No.11

<P>Nanocrystalline Fe-Al2O3 soft-magnetic composite powders were synthesized by a conventional combustion method followed by a H-2 reduction process. In this paper, we analyzed the effect of the types and compositions of organic fuel on the dispersive magnetic properties of the composite powders for improving the soft-magnetic properties. To understand the properties, the microstructural and thermal characterization of as-synthesized oxide powders and their reduced powders were analyzed by an X-ray diffractor, a scanning electron microscope, and a thermogravimetric and differential thermal analyzer. In addition, the high-frequency dispersive magnetic simulation using the Landau-Lifshitz-Gilbert (LLG) equation and extended Maxwell-Garnet effective medium theory mixing rule was carried out. As a result, the microstructural and thermal analyses showed that the high-frequency dispersive magnetic behaviors of nanocrystalline Fe-Al2O3 composite powders were dependent on the types and the compositions of fuel by controlling the released heat amount during the combustion redox reaction. In particular, a relative real permeability (u(r)') of 3.6 at 1 GHz was obtained in Fe-Al2O3 (Fe: Al = 95: 5, wt%) composite powders combusted by a mixed fuel composed of a 50 mol% glycine and a 50 mol% urea.</P>

Comparative study on the high frequency performances of the easy-plane FeNi@SiO2 powder soft magnetic composite

Wang Guowu,Zhang Junming,Zheng Zuying,Qiao Liang,Wang Tao,Li Fashen 한국물리학회 2022 Current Applied Physics Vol.41 No.-

In this work, an easy-plane FeNi@SiO2 powder soft magnetic composite (SMC) was imitated and fabricated and its high frequency magnetic properties were comparatively investigated with a non-easy-plane composite. Due to the planar distribution of easy magnetization axes, the easy-plane composite exhibits a constant permeability of 38 up to 100 MHz. Moreover, the easy-plane SMC exhibits a lower core loss at higher frequencies. Loss separated results show that the hysteresis loss plays a dominant loss component in the composite, rather than dominant excess loss in the non-easy-plane powder composite. These results indicate that, compared with non-easy-plane powder composite, the easy-plane powder composites exhibit comprehensive advantages of higher permeability, wider effective operating frequencies and lower loss, which suggest that the use of easy-plane ferromagnetic powder is a promising and efficient measure to develop a new generation of soft magnetic composites for higher frequency application.

Effect of Magnetic Field on the Dielectric Properties of Multiferroic Composites

Ravindar Tadi,김용일,류권상,김철기 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.9

Magneto-dielectric materials were a subject of potential interests in terms of basics research and new device applications. In this study, 0.5BaTiO<SUB>3</SUB>-0.5MgFe<SUB>2</SUB>O<SUB>4 </SUB> composites with ferroelectric and soft magnetic properties, synthesized using wet chemical methods were investigated for the possibility of controlling the dielectric properties by application of magnetic field. Composite pellets were thermally treated in air at 950 to 1150 ℃ for 3 h and characterized for structural, magnetic and magnetic-dielectric properties. All the composites showed soft magnetic properties. Magnetic field was applied to composite pellets in the order of 200 to 400 Oe and variation of dielectric constant was observed. Significant findings such as the increase of dielectric constant with increase of magnetic field were observed in the composite pellets. The increase in dielectric constant with respect to applied magnetic field was depicted as an effect of increased magnetostriction of the magnetic phase.

연자성 복합체에서 파우더 크기 분포와 Epoxy Resin에 따른 Packing Density 변화

이창현,오세문,신효순,여동훈,김진호 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.12

There is growing interest in power inductors in which metal soft magnetic powder and epoxy resin arecombined. In this field, the process technology for increasing the packing density of magnetic particles in an injectionmolding process is very important. However, little research has been reported in this regard. In order to improve thepacking density, we investigated and compared the sedimentation heights of pastes for three types of soft magnetic alloypowders as a function of the mixing ratios and the type of resin used. Experimental results showed that the packingdensity was the highest (71.74%) when the mixing ratio was 80:16:4 (Sendust:Fe-Si:CIP) according to the particlesize using an SE-4125 resin. In addition, the packing density was found to be inversely related to the layer separationdistance. As a result, it was confirmed that the dispersion of solid particles in the paste was important for curing;however, the duration of the curing process can greatly affect the packing density of the final composite. 금속 연자성 powder와 epoxy 수지가 복합화된 파워인덕터에 대한 관심이 증대되고 있다. 이를 제조하는 주입성형 공정에서 자성 입자의 packing density를 높이는 공정기술이 매우 중요하다. 그러나 이러한 현상에 대한 연구는 거의 보고되지 않고 있다. 따라서 본 연구에서는 packing density를 향상시키기 위해 크기가 다른 3종의 연자성 합금 분말을 사용하여 혼합비율 변화에 따른 침강 높이를 관찰하였고, 경화된 sample의 단면을 절취하여 층 분리 현상과 packing density를 측정하였다. 또한, resin에 따른 차이를 비교하였다. 실험결과 SE-4125 resin을 사용하고 입자크기에 따라 혼합 비율을 80:16:4로 혼합한 경우 가장 높은 71.74%의 packing density를 나타내었다. 또한, packing density는 층분리 현상과 반비례의 관계가 있음이 확인되었다. 결과적으로 경화 공정을 포함하는 paste의 경우 paste 상태에서 고상입자의 분산성이 중요하지만 경화 과정에서의 시간이 최종 복합체의 packing에 영향을 크게 미칠 수 있음을 확인하였다.

Annealing Effect on Magnetic Properties and Electromagnetic Absorption Behaviors for Fe-Cr Alloy Powder-Polymer Composites

Sung Jae Lee,Yoon Bae Kim,Kyung Sub Lee,Sang Woo Kim 한국자기학회 2007 Journal of Magnetics Vol.12 No.1

We investigated annealing effect of microforged powders on magnetic properties and electromagnetic absorption behaviors for ferromagnetic Fe-Cr metal alloy powder-polymer composites. The coercive properties greatly decreased with annealing temperature and the magnetic permeability had significantly increased after microforging and subsequent annealing treatment, due to a reduction in lattice strain of the microforged powders. The power loss in the far field regime also had greatly increased after microforging and subsequent annealing treatment in frequency range from 50 ㎒ to 6 ㎓. As a result, the electromagnetic absorption of ferromagnetic Fe-Cr alloy metal powder-polymer composites was highly improved because of the relaxation of the internal strain during annealing process.

Characteristics of crystalline and amorphous soft magnetic cores from Fe-based soft magnetic powders

Minwoo Lee,Yeonjoo Lee,Dohoon Kwon,Eunji Cha,Sungmin Kim,Daewon Jung,Hwijun Kim 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1

Soft magnetic materials are used in powder generation, transfer, and convertor, and are extensively used in electric machines, power electronics, sensors, and electromagnetic interference shielding. Soft magnetic composites (SMCs) components are normally manufactured by modified powder metallurgy processes which are combined with new techniques, such as compaction, warm compaction, multi-step annealing followed by a heat treatment at relatively low temperature. The recent increase in demand for high-efficiency electric motors, especially for electric vehicles (EVs) is finally starting to make a meaningful push into the global market, so the demand is growing in the global automotive industry. The properties of soft magnets depend on diverse manufacturing technologies and materials. The requirement for new soft magnetic materials in the field of the electric motors, high frequency power conversion parts and telecommunications has significantly caused the improvement of soft magnetic materials in Korea for the past decades. To meet the growing need for energy efficiency in power electronics and electric machines, we have been studying on a number of new soft magnetic composite cores with various structures like crystalline, amorphous and nanocrystalline. Compared to the currently most widely used crystalline SMCs, the amorphous SMCs exhibit more favorable properties, including high electrical resistivity, good saturation magnetization and low coercivity. This presentation will introduce the results on frequency dependence of the soft magnetic cores manufactured from crystalline and amorphous powders by means of conventional powder metallurgy processes. While crystalline SMC cores show useful soft magnetic characteristics in low frequency range (∼1000 Hz), amorphous SMCs cores exhibit valuable properties in high frequency ranges (∼100 kHz). Furthermore, characteristics of SMC cores such as permeability, coercivity and core loss will be estimated in the various frequency ranges.

Improving the Magnetic Properties of FeSiB Soft Magnetic Composites by Adding Untreated or Phosphated Fe Powders

D. N. Chen,L. Huang,H. Y. Yu,X. C. Zhong,Z. W. Liu 한국자기학회 2019 Journal of Magnetics Vol.24 No.3

Soft magnetic composites (SMC) based on FeSiB amorphous alloys have been widely used in various electric devices. However, the amorphous powders are difficult to press, and the prepared cores exhibit low mechanical strength with high porosity. In this work, untreated and phosphated Fe powders with mean particle size of 70μm were added into FeSiB powders with mean size of less than 25μm to improve the performance of the SMC. The FeSiB/Fe SMCs are fabricated by cold pressing. The results show that the amplitude permeability of FeSiB/Fe SMCs increases with the increase of Fe content. However, the addition of untreated Fe powder leads to increased magnetic loss. On the contrary, the addition of phosphated iron powder can not only enhance the amplitude permeability but also effectively reduce the core loss. Hence, the addition of phosphated iron powder provides a good way to modify the soft magnetic properties of FeSiB/Fe SMC for AC application.