Sodium Nitrate Passivation as a Novel Insulation Technology for Soft Magnetic Composites

Sodium nitrate passivation has been developed as a new insulation technology for the production of FeSiAl soft magnetic composites (SMCs). In this work, the evolution of coating layers grown at different pH values is investigated involving analyses on their composition and microstructure. An insulation coating obtained using an acidic NaNO_(3) solution is found to contain Fe2O_(3), SiO_(2), Al2O_(3), and AlO(OH). The Fe2O_(3) transforms into Fe3O4 with weakened oxidizability of the NO_(3)– at an elevated pH, whereas an alkaline NaNO_(3) solution leads to the production of Al2O_(3), AlO(OH), and SiO_(2). Such growth is explained from both thermodynamic and kinetic perspectives and is correlated to the soft magnetic properties of the FeSiAl SMCs. Under tuned passivation conditions, optimal performance with an effective permeability of 97.2 and a core loss of 296.4 mW∙cm−3 is achieved at 50 kHz and 100 mT.

Preparation and characterization of carbonyl iron soft magnetic composites with magnesioferrite insulating coating layer

Spherical carbonyl iron(Fe)powders were coated with magnesioferrite(MgFe2O4)insulating coating layer and then mixed with epoxy-modified silicone resin(ESR).Soft magnetic composites(SMCs)were fabricated by compaction of the coated powders and annealing treatment.Transmission electron microscopy(TEM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and X-ray photoelectron spectroscopy(XPS)revealed that the MgFe2O4 layer was coated on the surface of the iron powders.The magnetic properties of SMCs were determined using a vibrating sample magnetometer and an auto testing system for magnetic materials.The results showed that the SMCs prepared at 800 MPa and 550℃ exhibited a significant core loss of 167.5 W/kg at 100 kHz and 50 mT.

Performance improvement of Fe-6.5Si soft magnetic composites with hybrid phosphate-silica insulation coatings

Fe-6.5Si soft magnetic composites(SMCs)with hybrid phosphate-silica insulation coatings have been designed to improve their comprehensive property via chemical coating combining sol-gel method in this work.The microstructure and magnetic performance of the Fe-6.5Si SMCs with hybrid phosphate-silica insulation coatings were investigated.The hybrid phosphate-silica coatings with high heat resistance and high withstand pressure,formed on the surface of the Fe-6.5Si ferromagnetic powders,were found stable in the composites.Compared with Fe-6.5Si SMCs coated by single phosphate or single silica,Fe-6.5Si SMCs with hybrid phosphate-silica show much higher permeability and lower core loss.The work provides a new way to optimize the magnetic performance of soft magnetic composites.

Hysteresis loss reduction in self-bias FeSi/SrFe_(12)O_(19)soft magnetic composites

The magnetic field provided by magnetized SrFe_(12)O_(19)particles in FeSi/SrFe_(12)O_(19)composites is used to replace the applied transverse magnetic field,which successfully reduces the magnetic loss of the composites with minor reduction of permeability.This magnetic loss reduction mainly comes from the decrease in hysteresis loss,while the eddy current loss is basically unaffected.The hysteresis loss reduction in magnetized composites is believed to be due to the decrease in domain wall displacement caused by the increase in the average magnetic domain size in a DC magnetic field.This is an effective method for reducing the magnetic loss of soft magnetic composites with wide application potential,and there is no problem of increasing the cost and the volume of the magnetic cores.

High permeability and bimodal resonance structure of flaky soft magnetic composite materials

We establish a theoretical bimodal model for the complex permeability of flaky soft magnetic composite materials to explain the variability of their initial permeability.The new model is motivated by finding the two natural resonance peaks to be inconsistent with the combination of the domain wall resonance and the natural resonance.In the derivation of the model,two relationships are explored:the first one is the relationship between the number of magnetic domains and the permeability,and the second one is the relationship between the natural resonance and the domain wall resonance.This reveals that the ball milling causes the number of magnetic domains to increase and the maximum initial permeability to exist after 10 h of ball milling.An experiment is conducted to demonstrate the reliability of the proposed model.The experimental results are in good agreement with the theoretical calculations.This new model is of great significance for studying the mechanism and applications of the resonance loss for soft magnetic composite materials in high frequency fields.

Binary Relations between Magnitudes of Different Dimensions Used in Material Science Optimization Problems Pseudo-State Equation of Soft Magnetic Composites

New algorithm for optimizing technological parameters of soft magnetic composites has been derived on the base of topological structure of the power loss characteristics. In optimization magnitudes obeying scaling, it happens that one has to consider binary relations between the magnitudes having different dimensions. From mathematical point of view, in general case such a procedure is not permissible. However, in a case of the system obeying the scaling law it is so. It has been shown that in such systems, the binary relations of magnitudes of different dimensions is correct and has mathematical meaning which is important for practical use of scaling in optimization processes. The derived structure of the set of all power loss characteristics in soft magnetic composite enables us to derive a formal pseudo-state equation of Soft Magnetic Composites. This equation constitutes a relation of the hardening temperature, the compaction pressure and a parameter characterizing the power loss characteristic. Finally, the pseudo-state equation improves the algorithm for designing the best values of technological parameters.

Investigation of Thermal Losses in a Soft Magnetic Composite Using Multiphysics Modelling and Coupled Material Properties in an Induction Heating Cell

The complex interaction between material properties in an induction heating circuit was studied by multi physics simulation and by experimental verification in a full-scale laboratory heater. The work aims to illustrate the complexity of the system of interacting materials, but also to propose a method to verify properties of soft magnetic composite materials in an integrated system and to identify which properties are the most critical under different circumstances and load cases. Heat losses at different loads were primarily studied, from DC currents to AC currents at 15, 20 and 25 kHz, respectively. A FE model for magnetic simulation was correlated with a corresponding model for heat simulation. The numerical model, as well as the established input material data, could be verified through the experimental measurements. In this particular study, the current loss in the litz wire was the dominant heat source, thus making the thermal conductivity of the SMC the most important property in this material.

Magnetic properties of soft magnetic composites prepared by gas-atomized glassy powders from a new Fe-based alloy with high glass-forming ability

With a pressing need for high efficiency, low power consumption, and miniaturization of electronics, soft magnetic composites(SMCs) show great potential, especially for applications in key electronic component. However, core loss is still the focused issue for SMCs that hinders their sustainable development and widespread applications. In the present study, high-performance SMCs were fabricated by novel Fe_(74)B_(7)C_(7)P_(7)Si_(3)Mo_(1)Cr_(1) powders with spherical shape and a fully glassy structure, which were successfully prepared by a gas atomization method. The microstructure and high-frequency magnetic properties of these SMCs were studied in detail. To enhance the soft ferromagnetism, the effects of annealing temperature(T_a) and powder size on their performance were clarified. Increasing T_a up to 703 K not only helps to effectively release internal stress in the powders, but also improves the integrity of the insulation layer structure, which is conducive to decreasing the core loss. In addition, reducing the powder size contributes to the overall performance enhancement. Prepared from the powders with the smallest mean particle size and annealed at 703 K, the SMC exhibits optimum property combination of a stable effective permeability of 26.2 up to 1 MHz, a total core loss of 883 kW m^(–3)(100 kHz, 100 mT), and a DC-Bias performance of 79.3% under 100 Oe field, which is even comparable to those of the most prominent SMCs reported so far. These results are meaningful for potentially stimulating the development and application of new low-loss SMCs.

Critical state-induced emergence of superior magnetic performances in an iron-based amorphous soft magnetic composite

Soft magnetic composites(SMCs)play a pivotal role in the development of high-frequency,miniaturization and complex forming of modern electronics.However,they usually suffer from a trade-off between high magnetization and good magnetic softness(high permeability and low core loss).In this work,utilizing the order modulation strategy,a critical state in a FeSiBCCr amorphous soft magnetic composite(ASMC),consisting of massive crystal-like orders(CLOs,∼1 nm in size)with the feature ofα-Fe,is designed.This critical-state structure endows the amorphous powder with the enhanced ferromagnetic exchange interactions and the optimized magnetic domains with uniform orientation and fewer micro-vortex dots.Superior comprehensive soft magnetic properties at high frequency emerge in the ASMC,such as a high saturation magnetization(Ms)of 170 emu g^(-1)and effective permeability(µ_(e))of 65 combined with a core loss(Pcv)as low as 70 mW cm^(-3)(0.01 T,1 MHz).This study provides a new strategy for the development of high-frequency ASMCs,possessing suitable comprehensive soft magnetic performance to match the requirements of the modern magnetic devices used in the third-generation semiconductors and new energy fields.

MHz cut-off frequency and permeability mechanism of iron-based soft magnetic composites

The lack of soft magnetic composites with high power density in MHz frequency range has become an obstacle in the efficient operation of the electrical and electronic equipments.Here,a promising method to increase the cut-off frequency of iron-based soft magnetic composites to hundreds of MHz is reported.The cut-off frequency is increased from 10 MHz to 1 GHz by modulating the height of the ring,the distribution of particles,and the particle size.The mechanism of cut-off frequency and permeability is the coherent rotation of domain modulated by inhomogeneous field due to the eddy current effect.An empirical formula for the cut-off frequency in a magnetic ring composed of iron-based particles is established from experimental data.This work provides an effective approach to fabricate soft magnetic composites with a cut-off frequency in hundreds of MHz.

High-frequency magnetic properties and core loss of carbonyl iron composites with easy plane-like structures

To fully release the potential of wide bandgap(WBG)semiconductors and achieve high energy density and efficiency,a carbonyl iron soft magnetic composite(SMC)with an easy plane-like structure is prepared.Due to this structure,the permeability of the composite increases by 3 times(from 7.5 to 21.5)at 100 MHz compared with to the spherical carbonyl iron SMC,and the permeability changes little at frequencies below 100 MHz.In addition,the natural resonance frequency of the composite shifts to higher frequencies at 1.7 GHz.The total core losses of the composites at 10,20,and 30 m T are80.0,355.3,and 810.7 m W/cm^(3),respectively,at 500 k Hz.Compared with the spherical carbonyl iron SMC,the core loss at500 k Hz is reduced by more than 60%.Therefore,this kind of soft magnetic composite with an easy plane-like structure is a good candidate for unlocking the potential of WBG semiconductors and developing the next-generation power electronics.

Effect of Fe Substitution on Magnetic Properties and Radar Wave Absorption of the Y_(2)Co_(17) Rare Earth Soft Magnetic Alloy

The rapid development of information technology leads a demand for high frequency soft magnetic materials with ex-ceptional radar wave absorption properties.A new magnetic material with superior radar wave absorption is explored in this paper.we explored the preparation of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)alloy powders using yttrium oxide as a raw material by a low-cost and short preparation cycle reduction-diffusion process.The crystal structure,intrinsic magnetic properties,high frequency magnetism and radar wave absorption of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)were investigated.These compounds have a perfect magnetic repair of Y_(2)Co_(17) and enable the improvement of the overall magnetic properties of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)compounds.The Y_(2)Co_(17)-xFex/Polyurethane(PU)(x=0.0,1.0,2.0,3.0)absorbers were divided in detail using the zero-reflection mechanism.The results show that all Y_(2)Co_(17)-xFex/PU(x=0.0,1.0,2.0,3.0)absorbers have excellent absorption performance(reflection loss RL is less than-85 dB);in addition,Y_(2)Co_(15)Fe_(2)/PU absorbers and Y_(2)Co_(14)Fe_(3)/PU absorbers are superior candidates for S-band materials.In particular,the perfectly matched frequency fp of the modulated Y_(2)Co_(14)Fe_(3)/PU absorber is shifted to the L-band(1–2 GHz)where early warning radars are located.The Y_(2)Co_(14)Fe_(3)/PU absorber has an effective absorption bandwidth of 300 MHz(1.5–1.8 GHz)at a thickness of 5.230 mm.It can also absorb the full L-band at-4 dB,which has rarely been reported.

Electromagnetic Performance Analysis of Flux-Switching Permanent Magnet Tubular Machine with Hybrid Cores

The performance of traditional flux switching permanent magnet tubular machine(FSPMTM)are improved by using new material and structure in this paper.The existing silicon steel sheet making for all mover cores or part of stator cores are replaced by soft magnetic composite(SMC)cores,and the lamination direction of the silicon steel sheet in stator cores have be changed.The eddy current loss of the machine with hybrid cores will be reduced greatly as the magnetic flux will not pass through the silicon steel sheet vertically.In order to reduce the influence of end effect,the unequal stator width design method is proposed.With the new design,the symmetry of the permanent magnet flux linkage has been improved greatly and the cogging force caused by the end effect has been reduced.Both 2-D and 3-D finite element methods(FEM)are applied for the quantitative analysis.

High-frequency magnetic properties of biphase Ce_(2)Fe_(17)N_(3)/α-Fe microflakes with easy-plane anisotropy

Soft magnetic composites(SMCs)are effective as magnetic powder cores in an inductor.Due to high saturation magnetization,large magnetocrystalline anisotropy and high operating frequency of M(metal)-RE(rear earth)soft magnetic composites,it is possible to miniaturize inductor cores by reducing total loss,especially eddy current loss and excess loss at high frequencies.In this article,the characteristics of Ce_(2)Fe_(17)N_(3)/α-Fe(CFN/F)loss per volume and effective permeability reaching a high frequency of 3 MHz are investigated.The biphase CFN/F composite exhibits a high permeability of 16 at 70 MHz,which is two times greater than that of pure Ce_(2)Fe_(17)N_(3)(CFN)powders.The total loss is as low as 545 mW/cm^(3)at 3 MHz and 6 mT.The direct current(DC)-bias properties have a percent of permeability exceeding 65% at H=7960 A/m.This phenomenon indicates that our material has a higher working frequency and lower core loss than other materials;the biphase CFN/F structure is a promising and efficient approach for developing the miniaturized radio frequency(RF)inductor core.

Design Optimization of a Novel Axial-radial Flux Permanent Magnet Claw Pole Machine with SMC Cores and Ferrite Magnets

Soft magnetic composite(SMC)material is an ideal soft magnetic material employed for developing 3D magnetic flux electromagnetic equipment,due to its advantages of 3D magnetic isotropy characteristic,low eddy current loss,and simple manufacturing process.The permanent magnet claw pole machine(PMCPM)with SMC cores is a good case that the SMC to be adopted for developing 3D flux electrical machines.In this paper,a novel axial-radial flux permanent magnet claw pole machine(ARPMCPM)with SMC cores and ferrite magnets is proposed.Compared with the traditional PMCPM,the proposed ARPMCPM is designed with only one spoke PM rotor and its whole structure is quite compact.For the performance prediction,the 3D finite element method(FEM)is used.Meanwhile,for the performance evaluation,a previously developed axial flux claw pole permanent magnet machine(AFCPM)is employed as the benchmark machine and all these machines are optimized by using the combined multilevel robust Taguchi method.It can be seen that the proposed ARPMCPM is with higher torque/weight density and operation efficiency.

Controllable SiO2 coating layer of FeSiBPNb amorphous powder cores with excellent soft magnetic properties

Amorphous powder cores based on spherical （Fe0.76Si0.09B0.1P0.05）99Nb1 amorphous powder and their SiO2 layer prepared by in situ coating insulation process were investigated in detAll. These cores were characterized by scanning electron microscopy and X-ray diffraction analyses, and the results revealed that the surface layer of the amorphous powder was composed of SiO2 with uniform surface coverage. The thickness of the SiO2 insulating layer could be controlled by adjusting the tetraethyl orthosilicate （TEOS） content. By cold-pressing with epoxy resin under a pressure of 1800 MPa, a ring powder core with an outer diameter of 20.3 ram, inner diameter of 12.7 mm, and height of 5.3 mm was prepared. The FeSiBPNb composite core showed its best properties when the TEOS content was 2 mL/g （the volume of TEOS for each gram of （Fe0.76Si0.09B0.1P0.05）99Nb1 amorphous powder, mL/g）, which showed good relative permeability in the high-frequency range of up to 10 MHz and a low core loss of 320 W/kg under the maximum magnetic flux density of 0.1 T and frequency of 100 kHz.

Development of a New Flux Switching Transverse Flux Machine with the Ability of Linear Motion

This paper proposes a new rotary flux switching transverse flux machine with the ability of linear motion(FSTFMaLM),in which both the stator and the rotor cores are made by using soft magnetic composite(SMC)materials.With the special design pattern,for the rotary motion model,the proposed machine can combine both the advantages of the flux switching permanent magnet machine(FSPMM)and the transverse flux machine(TFM).It can output with relatively high torque density,and as there is no windings or the magnets on the rotor cores,the proposed machine can operate in the high speed region to improve the output power.With the adoption of the SMC materials,the manufacturing of this machine can be quite easy.By stacking the rotor core together and prolong it with the determined length in the axial direction,in addition with the special control algorithm,the proposed machine can have the ability of the linear motion.In this paper,the operation principle of this machine has been explained and the design methods are also presented.To seek the better performance,the main dimension of the machine is optimized,and for the performance evaluation,the finite element method(FEM)is adopted.The proposed machine can be used for the electric driving systems,robotic systems or other applications where the linear motion ability is required.

Preparation of Ce_(2)Fe_(17)N_(3-δ)@FePO_(4) composite with excellent microwave absorption performance by reduction-diffusion(R/D)and phosphating processes

Ce_(2)Fe_(17)N_(3-δ)composites have always been focused on electromagnetic wave(EMW)absorbing field because of their high resonance frequency and magnetic loss.However,the issues of preparation cost and impedance mismatching still limit the industrial conversion and practical application of Ce_(2)Fe_(17)N_(3-δ)composites.In this work,the composites of Ce_(2)Fe_(17)N_(3-δ)with a phosphate insulation layer(Ce_(2)Fe_(17)N_(3-δ)@FePO_(4))were prepared by a newly-developed reduction-diffusion(R/D)and phosphating processes using CeO_(2) as raw mate rials,and their microwave absorption properties were investigated.The composite filled with 30 vol%of the Ce_(2)Fe_(17)N_(3-δ)@FePO_(4) has a minimum reflection loss(RL)of-63 dB and an effective absorption bandwidth(EBW,RL<-10 dB)of 3.83 GHz at a thickness of 1.25 mm in the X-band,and the EBW reaches 5 GHz under 0.98 mm in the Ku-band.This study demonstrates that the Ce_(2)Fe_(17)N_(3-δ)@FePO_(4) composite s with low cost and excellent microwave absorption properties have a significant potential for industrial production and practical applications.

Electromagnetic Characteristics and Corrosion Resistance of New Magnetosoft Materials Based on Capsulated Iron Powders

A new method of depositing an insulating multifunctional oxide coating on metal particles was developed.Such coatings increase corrosion resistance and insulate metal particles from each other.On base of capsulated by oxide coating water-atomized iron powder ASC100.29,new composite soft magnetic materials were synthesized,which are able of replacing electrical steel in devices.Structural,electromagnetic properties and corrosion characte-ristics of the obtained composites were studied.It was found that the synthesized composite materials have low elec-tromagnetic losses,high values of magnetic induction(up to 2.1 T)and good corrosion resistance.The results demon-strate that the use of such materials in power supplies,c hokes,transformers,stators and rotors of electric machines and other products ensures their stable operation under various conditions.