Behavior of Medium-frequency Core Loss in Fe-based Nanocrystalline Soft Magnetic Alloys

The dependences of the power loss per cycle on frequency have been investigated in the ranges of 100 Hz<= f<=25000 Hz and 0.1 T< =Bm <=1.0 T for three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys. The measured and calculated results showed that the total power loss per cycle clearly exhibited a nonlinear behavior in the range below 3 kHz～5 kHz depending on both the magnetic state and the value of Dm, whereas it showed a quasi-linear behavior above this range. The total loss was decomposed into hysteresis loss, classical eddy current loss and excess loss, the obvious nonlinear behavior has been confirmed to be completely determined by the dependence of the excess loss on frequency. It has been indicated that the change rate of the excess loss per cycle with respect to frequency sharp decreases with increasing frequency in the range below about 3 kHz～5 kHz, wherease the rate of change slowly varies above this range, thus leading to the quasilinear behavior of the total loss per cycle. In this paper, some linear expressions of the total loss per cycle has been given in a wider medium-frequency segment, which can be used for roughly estimating the total loss.

General Properties of Low-frequency Power Losses in Fe-based Nanocrystalline Soft Magnetic Alloys

The dependences of the power loss per cycle on frequency f and amplitude flux density Bm have been investigated for the three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys in the ranges of 10 Hz<=f<=1000 Hz and 0.4 T<= Bm <=1.0 T. The total loss P is decomposed into the sum of the hysteresis loss Physt, the classical eddy current loss Pel and the excess loss Pexc. Physt has been found to be proportional to Bm^2 and f. The behavior of Pexc/f vs f being equivalent to P/f vs f clearly exhibits nonlinearity in the range not more than about 120 Hz, whereas the behavior of P/f vs f roughly shows linearity in the range far above 100 Hz and not more than 1000 Hz. In the range up to 1000 Hz, Physt is dominant in the original high permeability state and the state of low residual flux density, whereas Pexc in the state of high residual flux density is dominant in the wider range above about 100 Hz. The framework of the statistical theory of power loss has been used for representing the behavior of Pexc/f vs f. It has been found that the number n of the simultaneously active 'Magnetic Objects' linearly varies as n = n0 + Hexc/H0 as a function of the dynamic field Hexc in the range below about 120 Hz, whereas n approximately follows a law of the form n = n0 + (Hexc/H0)^m with 1 < m < 2 in the range far above 100 Hz and not more than 1000 Hz. The values of the field HO in principle related to the microstructure and the domain structure have been calculated for the three states.

Effect of the Partial Substitution of V for Nb on the Magnetic Properties of Fe-based Nanocrystalline Alloy

The variation of the magnetic properties of the nanocrystalline alloys for the partial substitution of V for Nb with crystallizing treatment temperature and time was investigated. The variation law of the magnetic properties with the annealing temperature and time is essentially the same. The magnetic properties of the Fe-based nanocrystalline alloys for the partial substitution of V for Nb reduce, and the crystallizing treatment temperature of the alloys increases. The optimum properties of Fe74Cu1Nb3Si13B9 nanocrystalline alloys crystallized at 550℃x60 min are μ0=9.2xl0^4, μm=54.8xl0^4, Hc=1.14 A/m and Bs=1.26 T. The best properties for Fe74Cu1Nb3Si13B9 alloys annealed at 560℃x60 min are μ0=8.79x10^4, μm=50.18xl0^4, Hc=1.26 A/m and Bs=1.24 T.

Long-term corrosion behavior of HVOF sprayed FeCrSiBMn amorphous/nanocrystalline coating

A FeCrSiBMn amorphous/nanocrystalline coating with 700 μm in thickness and 0.65% in porosity, was prepared by high velocity oxygen fuel(HVOF) spraying process. The long-term corrosion behavior of the FeCrSiBMn coating was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) tests in a 3.5% NaCl solution with a hard chromium coating as a reference. The FeCrSiBMn coating exhibited higher corrosion potential and lower corrosion current density than the hard chromium coating. The pore resistance(Rp) and charge transfer resistance(Rct) of FeCrSiBMn coating were higher than those of the hard chromium coating. In addition, after immersion in the Na Cl solution for 28 d, only small pores in the FeCrSiBMn coating were observed. All the results indicated that the FeCrSiBMn coating held superior corrosion resistance to the hard chromium coating. This could be attributed to the dense structure, low porosity and amorphous/nanocrystalline phases of the FeCrSiBMn coating.

Formation and crystallization behavior of Fe-based amorphous precursors with pre-existingα-Fe nanoparticles-Structure and magnetic properties of high-Cu-content Fe-Si-B-Cu-Nb nanocrystalline alloys

Structure,crystallization behavior,and magnetic properties of as-quenched and annealed Fe_(81.3)Si_(4)O_(13)Cu_(1.7)(Cu1.7)alloy ribbons and effects of Nb alloying have been studied.Three-dimensional atom probe and transmission electron microscopy analyses reveal that high-number-density Cu-clusters and Pre-existing Nano-sized a-Fe Particles(PN-a-Fe)are coexistence in the melt-spun Cu1.7 amorphous matrix,and the PN-α-Fe form by manners of one-direction adjoining and enveloping the Cu-clusters.Two-step crystallization behavior associated with growth of the PN-a-Fe and subsequent nucleation and growth of newly-formedα-Fe is found in the primary crystallization stage of the Cu1.7 alloy.The number densities of the Cu-clusters and PN-a-Fe in melt-spun Fe8_(1.3-x)Si_(4)B_(13)Cu_(1.7)Nb_(x)alloys are gradually reduced with enriching of Nb,and a fully amorphous structure forms at 4 at.%Nb,although smaller Cu-clusters still exist.After annealing,2 at.%Nb coarsens the average size(D_(α-F)e)of theα-Fe grains from 14.0 nm of the Nb-free alloy to 21.6 nm,and 4 at.%Nb refines the D_(α-Fe)to 8.9 nm.The mechanisms of theα-Fe nucleation and growth during quenching and annealing for the alloys with large quantities of PN-α-Fe as well as after Nb alloying have been discussed,and an annealing-induced oc-Fe growth mechanism in term of the barrier co-contributed by competitive growth among the PN-a-Fe and diffusion-suppression effect of Nb atoms has been proposed.A coercivity(HC)αDα-Fe^(3)correlation has been found for the nanocrystalline alloys,and the permeability is inverse with the H_(C).

Magneto-impedance effect in soft Fe-based nanocrystalline alloys

IN recent years, giant magneto-resistance (GMR) effects have been observed in some binary composite systems such as multi-layered and granular films of Fe, Co, Ni and Cr, Ag, Cu and attracted considerable interest due to their potential applications in magnetic recording heads and field sensors. However, a notable GMR effect in these films always requires a strong external magnetic field at low temperature. More recently, Mohri et al. have discovered

Decomposition of pre-existing Au-P clusters induced in situ a-Fe grains uniformization in Fe-P-based nanocrystalline alloys

In Fe-based amorphous-/nanocrystalline ribbons,the uniformization and refinement of a-Fe grains are key aspects for optimizing their soft magnetic and mechanical properties.Herein,the Fe-P-C-B nanocrystalline alloy system was selected for investigation.We produced as-spun ribbons with pre-existing nanocrystals through melt-quenching and then obtained a well-distributed a-Fe nanocrystalline structure through annealing below the first crystallization onset temperature(633 K)resulting in excellent magnetic properties(saturation magnetization of 1.65 T and coercivity of 1.6 A·m^(-1))ultra-wide annealing temperature window(from 613 to 733 K),and extremely high annealing stability(up to 480 min at 633 K).Furthermore,we propose a new in situ two-step mechanism for the uniformization of a-Fe nanocrystals,which is separately induced by the decomposition of the Au-P clusters and the pre-existing a-Fe nanocrystals during annealing.This work underscores the crucial significance of micro-alloying via metastable clusters primarily influenced by metal-phosphide interactions in the process of refining a-Fe nanocrystals.Furthermore,i introduces a new principle for optimizing the comprehensive properties of Fe-based amorphous/nanocrystalline alloys.

Fe-based multi-phase nanocrystalline ribbons with hierarchically flowerlike structured metal oxides after modified by Orange II for Cr^VI absorption

Three-dimensional flowerlike nanostructured metal oxides attached on the surfaces of Fe-based multi-phase nanocrys- talline ribbons （Fe-MNRs） were prepared by a simple way （through immersing the Fe-MNRs in Orange II solution）. It has been found that the as-prepared Fe-MNRs with 3D flowerlike nanostructures （Fe-MNRs ＋ FNs） exhibit good absorption property for a typical heavy metal ion （Cr^VI） in wastewater, while Fe-MNRs do not possess such properties. The Fe-MNRs ＋ FNs could remove 99% CrvI ions from the solution in 40 min, and this adsorption property can be attributed to the ion exchange between Cr^VI and surface hydroxyl groups （O-H） of 3D flowerlike nanostructures. The present result suggests that the Fe-MNRs ＋ FNs, prepared by facile way, possess great potentials in removing heavy metallic ions in wastewater.

Reduction of High-Frequency Core Loss of a Fe_(77.2)Si_(11)B_(8.5)Cu_(0.8)Nb_(2.5)Soft Magnetic Nanocrystalline Alloy by Minor Alloying

Enhancing saturation magnetic flux density(Bs)while reducing high-frequency core loss in Finemet-type nanocrystalline alloys is of great significance in achieving the miniaturization,high-frequency,and energy-saving of modern power electronic devices.In this work,we first designed a high-Bs Fe_(77.2)Si_(11)B_(8.5)Cu_(0.8)Nb_(2.5)alloy by appropriately reducing the non-magnetic elements in typical Finemet nanocrystalline alloys,and subsequently alloyed 2 at%Co,Al,and Mo,respectively.The effects of alloying elements on structure and static and high-frequency magnetic properties were studied.The results reveal that,alloying Al or Mo reduces the averageα-Fe grain size(Dα-Fe)in the nanocrystalline alloys,while Co exhibits a slight influence.The added Al or Mo results in decreases in both the Bs and coercivity(Hc)of the nanocrystalline alloys,whereas Co increases the Bs without changing Hc,and meanwhile,all alloying elements show minimal effects on effective permeability(μe).Furthermore,the addition of Co,Al,or Mo lowers the core loss(Pcv)at 0.2 T/100 kHz of the based nanocrystalline alloy with reductions of 10.9%,29.6%,and 26.8%,respectively.A Fe_(75.2)Si_(11)B_(8.5)Cu_(0.8)Nb_(2.5)Al_(2)nanocrystalline alloy exhibits outstanding soft magnetic properties with Bs,Hc,μe at 10 kHz and 100 kHz,and Pcv at 0.2 T/100 kHz of 1.34 T,0.8 A/m,27,400,18,000,and 350 kW/m3,respectively.The reduction in Pcv is primarily attributed to the decreased eddy current losses,originating from the increased electrical resistivity by elements alloying.

反相胶团软模板法制备氯化银晶体纳米线研究

The nanosystem has received considerable attention because of its peculiar pheno mena,which is different from macroscopy and microscopy. At present,the upsurge o f researching nanomaterials has shifted from nano particles to one dimensional na nosystem,such as nanowires,nanotubes,and so on.Seen from literatures, the repor ts on carbon nanotubes wer e more,on nanowires were less,and on transition metallic salt nanowires were noth ing .In this paper,AgCl nanocrystalline wires were successfully synthesized by Rever s e Micelle soft Templates, which will open a new way for the synthesis and applic ation of one dimensional nanomaterials.

电弧喷涂纳米结构涂层的组织与磨损性能

基于机器人自动化高速电弧喷涂技术在45#钢基体上制备了铁基纳米结构涂层.研究了纳米结构涂层在不同磨损速度、不同载荷下的磨损行为,并利用3Cr13涂层进行对比试验.采用扫描电镜、能谱分析仪,透射电镜和X射线衍射仪等设备对涂层的组织结构进行了表征,利用纳米压痕仪对涂层的力学性能进行了分析.结果表明:涂层的组织主要由非晶相和α(Fe,Cr)相纳米晶组成;平均尺寸为46nm的α(Fe,Cr)相纳米晶均匀分布于非晶基体内.涂层的组织均匀,结构致密,平均孔隙率含量为1.7%.纳米结构涂层具有较高的显微硬度;随着磨损速度升高,载荷增加,纳米结构涂层的磨损量也随之增加.纳米结构涂层具有良好的耐磨性,同一磨损条件下,其相对耐磨性为3Cr13涂层的2.6倍.纳米结构涂层主要磨损机制为脆性断裂机制.

钢线材硫酸盐体系电镀纳米晶锌镀层工艺研究

为了克服传统线材高速电镀锌工艺存在的镀层耐蚀性能差问题,研究了硫酸盐电镀纳米晶锌镀层的工艺.采用场发射扫描电子显微镜、透射电镜和X-射线衍射技术对镀锌层的表面形貌及晶粒尺寸进行了表征,利用极化曲线和线材缠绕试验对纳米晶锌镀层的耐蚀性能和延展性能进行了研究.结果表明:在基础硫酸盐镀液体系中,仅通过改变脉冲电镀参数并不能得到纳米晶锌镀层;而在含有唯一添加剂(晶粒细化剂1 g/L)的基础硫酸盐镀液体系中,通过对双脉冲电镀参数的优化,得到了平均晶粒尺寸为31 nm,结晶细密、平整、光亮的纳米晶锌镀层;该纳米晶锌镀层在低碳钢板材和线材表面重现性良好;纳米晶锌镀层的耐蚀性能优于传统粗晶锌镀层,且具有良好的延展性.

不同驱动方法下Fe基纳米晶丝的GMI研究

本文分析了Fe73.5Cu1Nb3Si13.5B9晶丝在内径为1.75mm、0.4mm、0.1mm线圈纵向驱动和环向驱动下的巨磁阻抗效应,发现在环向驱动下,当驱动频率为1.925×107Hz时,磁致阻抗变化最大值为:(Z(H)-Z(Hmax))/Z(Hmax)×100%=14.24135%。在纵向驱动下铁基纳米晶丝的巨磁阻抗效应与驱动线圈的内径有关,内径越小,阻抗效应越大,用内径为1.75mm线圈驱动时,(Z(H)-Z(Hmax))/Z(Hmax)×100%=18.54342%;用内径为0.4mm线圈驱动时,(Z(H)-Z(Hmax))/Z(Hmax)×100%=104.91793%;用内径为0.1mm线圈驱动时,(Z(H)-Z(Hmax))/Z(Hmax)×100%=140.56741%。实验结果表明,纵向驱动比环向驱动磁阻抗变化效果明显。

脉冲频率对铁基纳米非晶丝的GMI影响研究

Fe基纳米非晶丝通过脉冲电流获得Fe基纳米晶丝,可以改善其巨磁阻抗效应。通过在不同的脉冲频率下对非晶丝进行退火,并进行巨磁阻效应分析,得出当脉冲频率为25 Hz时,可获得最佳的巨磁阻抗效应,其退火效果(ΔZ1-ΔZ0)/Z00达到12.287%,巨磁阻抗效应(ZHex-Z0)/Z0达到21.988%。

Fe_(74)Cu_1Nb_3Si_(15.5)B_(6.5)纳米晶丝的巨磁阻抗效应

采用熔融抽拉法制备了Fe74Cu1Nb3Si15.5B6.5非晶丝材料.分别研究了不同温度和交流电流退火后该种丝的GMI效应,结果发现两种退火方式都能够使其GMI效应显著增强且电流退火更有利于GMI效应.当退火电流密度为1.3×107A/m2时,样品最大GMI比率达到338%,高于550℃退火后的最大GMI比率320%.分析表明两种退火方法都使材料中析出α2Fe(Si)纳米晶粒,大大改善了材料的软磁性能和GMI效应.

软磁纳米晶丝的巨应力阻抗和巨扭矩阻抗效应

在频率f=1MHz和纵向直流磁场H=0～±11.2kA/m下,分别测量了Fe73.5Cu1Nb3Si13.5B9纳米晶丝(由非晶退火而得)在外加应力(σ=0～157MPa)及扭矩(ξ=0～62.8rad/m)作用下的磁阻抗效应分别为-35%和-66%。基于感生磁弹性各向异性的概念,对应力阻抗效应和扭矩阻抗效应进行了理论分析。与实验结果的对比表明,阻抗随应力和扭矩的改变可由感生各向异性模型来解释。

Direct synthesis of Fe-Si-B-C-Cu nanocrystalline alloys with superior soft magnetic properties and ductile by melt-spinning

Structure,magnetic properties and ductile of melt-spun Fe_(83-x)Si_(4)B_(13-y)C_(y)Cu_(x)(x=0-1.7;y=0-8)alloys were investigated.The addition of 1.7 at.%Cu in a Fe_(83)Si_(4)B_(13) amorphous alloy generates abundantα-Fe crystals by providing nucleation sites,and further C doping promotes the growth of the crystals by suitable turning amorphous-forming ability,hence they increase saturation magnetic flux density(B_(s))and slightly worse magnetic softness of the as-spun alloys.The as-spun Fe_(81.3)Si_(4)B_(7)C_(6)Cu_(1.7) alloy possesses a combined structure of a fully amorphous layer in wheel side surface and predominating nanocrystalline structure with gradually enlargedα-Fe crystal,whose average size and volume fraction are determined as about 12 nm and 32%,respectively,therefore superior soft magnetic properties and ductile with a high B_(s)of 1.74 T,coercivity(H_(c))of 32.7 A/m,effective permeability(μ_(e),at 1 kHz)of 3200 and high relatively strain at fracture(ε_(f))of 3.61%can be achieved directly in this alloy by only using melt-spinning.The annealing at 578 K releases internal stress,promotes the growth of theα-Fe crystals and remains the amorphous layer of the Fe_(81.3)Si_(4)B_(7)C_(6)Cu_(1.7) alloy,then improves the soft magnetic properties and maintains the superior ductile with increasing the B_(s)andμ_(e)to 1.80 T and 14,100,respectively,lowering the H_(c)to9.4 A/m and slightly reducing theε_(f)to 2.39%.The combination of superior soft magnetic properties and ductile and simplified synthesis process entitles the Fe-Si-B-C-Cu nanocrystalline alloys great potentials in high performance electromagnetic applications.

Microstructure and magnetic properties of Fe81.3Si4B13Cu1.7 nanocrystalline alloys with minor Nb addition

The amorphous matrix contAlning dispersive high number density （Na） α-Fe nuclei with average grAln sizes （D） of 4.3-6.2 nm was formed in the melt-spun Fe81.3-xSi4B13Cu1.7Nbx （x = 0-2） alloys, and the Nd and D values reduce with increase in the Nb content. The fine nanocrystalline structure with α-Fe grAlns of 14.0-21.6 nm in size was obtAlned for the annealed alloys, which showed high saturation magnetic flux density of 1.60-1.77 T and low coercivity （He） of 7.1-17.0 A/m. Addition of minor Nb significantly expands the optimum annealing temperature range for obtAlning good soft magnetic properties, while coarsens the α-Fe grAlns, leading to a slight increase in the Hc. The mechanism of the effect of Cu and Nb elements on the structure and magnetic properties was discussed in terms of the formation and growth of the α-Fe nuclei of the alloys.

Effects of Ribbon Thickness on Structure and Soft Magnetic Properties of a High-Cu-Content FeBCuNb Nanocrystalline Alloy

The effects of ribbon thickness(t)on the structure and magnetic properties of a Fe_(82.3)B_(13)Cu_(1.7)Nb_(3) alloy in melt-spun and annealed states have been investigated.Increasing the t from 15 to 23μm changes the structure of the melt-spun ribbons from a single amorphous phase to a composite with denseα-Fe nanograins embedded in the amorphous matrix.The grain size(D_(α-Fe))of theα-Fe near the free surface of the ribbon is about 6.7 nm,and it gradually decreases along the cross section toward the wheel-contacted surface.Further increasing the t to 32μm coarsens the D_(α-Fe) near the free surface to 15.2 nm and aggravates the D_(α-Fe) ramp along the cross section.After annealing,the ribbon with t=15μm has relatively largeα-Fe grains with D_(α-Fe)>30 nm,while the thicker ribbons possessing the pre-existing nanograins form a finer nanostructure with D_(α-Fe)<16 nm.The structural uniformity of the ribbon with t=23μm is better than that of the ribbon with t=32μm.The annealed ribbons with t=23 and 32μm possess superior soft magnetic properties to the ribbon with t=15μm.The ribbon with t=23μm exhibits a high saturation magnetic flux density of 1.68 T,low coercivity of 9.6 A/m,and high effective permeability at 1 kHz of 15,000.The ribbon with t=32μm has a slightly larger coercivity due to the lower structural uniformity.The formation mechanism of the fine nanostructure for the ribbons with suitable t has been discussed in terms of the competitive growth effect among the pre-existingα-Fe nanograins.

FePCCu nanocrystalline alloys with excellent soft magnetic properties

The effect of Cu addition on crystallization behavior and soft magnetic properties of Fe84-xP10C6Cux （x = 0-1.15） alloys was investigated. Low-cost FePCCu nanocrystalline alloys dispersed with ct-Fe phase with an average grain size of 15-35 nm were obtained by appropriately annealing the melt-spun ribbons at 683 K for 5 min. The Fe83.25P10C6Cu0.75 nanocrystalline alloy ex- hibits a high Bs of 1.65 T, low Hc of 3.3 A/m and high μc at 1 kHz of 21 100, which is superior to the traditional FePC soft magnetic alloys. The core loss is as low as 0.32 W/kg at 1.0 T and 50 Hz, which is 60% that of nonoriented Fe 6.5 mass% Si-steel. It is encouraging to synthesize this Fe-based nanocrystalline alloy with excellent soft-magnetic properties even using commercially industry-grade raw materials, which is promising for the future industrial applications.