Fe-based Nanocrystalline Ribbons Research Articles

Effect of ultralow Dy and Gd contents on surface crystallization and domain wall motion of FeCuSiBNbMo alloys

Surface crystallization of Fe-based melt-spun ribbons with high saturation induction leads to the formation of coarse grains after nanocrystallization, which results in a deterioration of the soft magnetic properties. Herein, doping with an ultralow concentration (0.1 at.%) of RE (RE = Dy and Gd) inhibits the surface crystallization of melt-spun FeCuSiBNbMo samples using industrial-grade Nb–Fe raw materials. This inhibition of surface crystallization promotes the formation of uniform and ultrafine nanograins after optimal annealing. Furthermore, the movement of domain wall is significantly affected by the presence of large grains (∼600 nm) in the free surface, which exerts a strong pinning effect on the domain wall motion. This pinning effect can be attributed to the higher magnetic anisotropy energy of the free surface compared to that of the nanocrystal region. The low coercivity observed in the samples with 0.1 at.% Dy and Gd addition is ascribed to the presence of dense and ultrafine nanocrystals, low effective magnetic anisotropy, and a weak pinning effect. This work provides insights into the relationship between surface crystallization, coercivity, domain wall motion, and magnetic anisotropy energy in Fe-based nanocrystalline ribbons.

Magnetic properties and giant magneto-impedance effect of FINEMET/IGZO composite ribbons

In order to study the magnetic properties and giant magnetoimpedance (GMI) effect of FINEMET/IGZO composite ribbons. A series of ZnGaInO4 film (IGZO) with different thickness (t) were deposited by RF magnetron sputtering from targets of nominally identical compositions onto Fe-based nanocrystalline ribbon. The results of hysteresis loops show that the FINEMET/IGZO composite ribbons has good soft magnetic properties, and the GMI ratio of the composite ribbons are enhanced. The GMI ratio of FINEMET/IGZO composite ribbons increases at first and then decreases with the increase of IGZO layer thickness (0 ∼ 200 nm). This result was attributed to the relative contribution of electromagnetic interaction and stress interaction between IGZO coating layer and FINEMET ribbon. These results provide a method for improving the GMI effect in composite ribbons, optimizing the GMI effect of semiconductor materials and exploring new GMI magnetic sensors compatible with semiconductor electronics.

Impact of surfaces on the magnetic properties of Fe-based nanocrystalline ribbons

The properties of Fe-Co-Sn / P-B ribbons prepared by planar flow casting of the melt were investigated by various methods in as-cast and nanocrystallized state. To examine the influence of surfaces on ribbon’s magnetic properties was the major aim. As the surfaces and the ribbon interior possess slightly different properties, mutual macroscopic force is generated and it can affect the magnetic properties. The ribbon with P 2 at % and P-free one was annealed at two different temperatures to achieve partially nanocrystalline structure. P-free ribbon shows tilted hysteresis loop after annealing, what indicates a possible surface squeeze effect. The increase of coercivity after higher temperature annealing at 380 °C is due to the formation of a bcc-Fe phase with a larger grain size and higher crystallinity contents. Oxides, mainly Fe2O3 have been confirmed on surfaces of both the lower temperature (350 °C) annealed ribbons. P substitution appears to reduce the mutual force by impeding the formation of crystalline phase during 350 °C annealing.

Significant improvement of soft magnetic properties for Fe-based nanocrystalline alloys by inhibiting surface crystallization via a magnetic field assisted melt-spinning process

Abstract Fe-based soft-magnetic amorphous and nanocrystalline ribbons made with a single-side fast-cooling process always suffer from the surface crystallization which deteriorates the magnetic properties and inhibits the wide applications. In this study, a static magnetic field assisted melt-spinning process was employed to prepare the typical Fe84.75Si2B9P3C0.5Cu0.75 alloy ribbon with an attractive application prospect. According to the comparative investigations of the crystallization behavior, structural evolution process and magnetic properties, it is found that the applied magnetic field can effectively inhibit the formation of compound phases and decrease the size of textured α-Fe grains in the surface layer of the as-spun ribbon. The Fe84.75Si2B9P3C0.5Cu0.75 samples made with low purity raw materials and under an optimal field exhibit superior magnetic properties, including a high saturation magnetization (Bs) over 1.82 T, low coercivity (Hc) of 8.5 A/m, high permeability (μ) of 2.76 × 104 at 1 kHz and much lower losses, after nanocrystallization by annealing. The apparent effect of the applied magnetic field was discussed from the disturbance of a Lorentz force of the fast-moving molten alloy and a magnetic force of preformed grains in a magnetic field during the melt-spinning process. These results provide a novel solution of surface crystallization and an effective route for improving magnetic properties of Fe-based amorphous and nanocrystalline alloy ribbons.

In-situ synthesis of nanocrystalline soft magnetic Fe-Ni-Si-B alloy

Fe-based nanocrystalline ribbons (e.g. FINEMET) has been applied widely in electric industry due to its excellent soft magnetic properties. However, their preparation involves annealing at high temperature for the formation of α-Fe nanograins, which not only consumes additional energy but results in the embrittlement of the ribbon. In this work, the ductile nanocrystalline ribbons of Fe-Ni-Si-B with good soft magnetic properties have been in-situ prepared just using the melt-spinning method. The nanocrystals have a size less than 45 nm. After the stress relief annealing, the ductility is still available and the magnetic performance is improved. It's worth noting that the industrial grade rather than analytically pure raw materials are used in this work. Therefore, the results have profound implications for academic study and engineering application.

Formation mechanism of stress-induced anisotropy in stress-annealed Fe-based nanocrystalline ribbon alloys

The formation mechanism of stress-induced anisotropy in Fe73.5Cu1Nb3Si13.5B9 alloys is studied in-situ using synchrotron radiation XRD. The evolution of the diffraction spectra during the nanocrystallization and relaxation annealing of the ribbon samples is shown. The results reveal that the stress-annealed sample possess a positive and larger structural anisotropy Δq compared to the insignificantly negative Δq in the sample annealed without stress. Macroscopic strain (ε) and microscopic strain (e) measurements reveal that the structural anisotropy of the stress-annealed sample is released after the annealing process as residual strain, which confirms the stress-induced anisotropy to be magnetoelastic in origin. Relaxation annealing of the stress-annealed sample reveals that the structural anisotropy (Δq), induced transverse magnetic anisotropy (Hk), and anisotropy energy (Ku) are significantly affected while the macroscopic strain is insignificantly affected. We have then suggested the origin of stress-induced anisotropy can be attributed to magnetoelastic effects due to residual strains.

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

Three-dimensional flowerlike nanostructured metal oxides attached on the surfaces of Fe-based multi-phase nanocrystalline 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 (CrVI) 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 CrVI 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.

Multi-phase nanocrystallization induced fast degradation of methyl orange by annealing Fe-based amorphous ribbons

Different from the common understanding that crystallization deteriorates the degradation capability of amorphous alloys, we show here that the Fe-based multi-phase nanocrystalline ribbons (Fe-MNRs) exhibit 3 and 17 times higher degradation rate than its amorphous counterpart and the conventional zero valent iron powders, respectively. The formation of multi-phase nanocrystals and nanoporous structure resulted from selective corrosion during degradation is responsible for the high degradation capability of Fe-MNRs. The present results suggest that suitable nano-crystallization annealing treatment could be a novel approach to enhance the degradation capability of Fe-based amorphous alloys.

Study of stress annealing effect on giant magneto-impedance of Fe-based ribbons

Fe-based nanocrystalline ribbons were successfully prepared. The giant magneto-impedance (GMI) effect that was found in these studies could be effectively increased by temperature annealing together with stress annealing. After applying a certain stress, the same GMI effect can be obtained with a much lower annealing temperature. In the present paper, it was found that the crystallization of Fe-based sample can reach its best GMI effect with a ratio of ΔZ to Z at 1141% at 500°C annealing and 53 MPa, showing that the stress and temperature annealing is an effective way of annealing which can improve the material soft magnetic properties and the GMI effect and also reduce the annealing temperature (GMI = ΔZ/Z = {[Z(H) − Z(H max)]/Z(H max)}*100%, Z(H) and Z(H max), respectively the impedance value under any additional magnetic field and the maximum magnetic field). The preferential agglomeration along the transverse direction in the ribbon is formed during stress annealing, leading to the transverse magnetic anisotropy of the iron-based nanocrystalline ribbon, which influences the GMI effect of the iron-based nanocrystalline.

Design of Magnetometer Based on GMI Effect in Fe-based Nano-crystalline Ribbon

基于巨磁阻抗效应(GMI)的磁强计是近年来磁强计研究领域的热点. 相比其他类型磁强计, GMI磁强计具有微型化、高灵敏度、快速响应、高温度 稳定性和低功耗的优点. 本文以铁基纳米晶带材为敏感材料, 设计并实现了GMI 磁强计传感器与后续信号处理电路, 组成一台GMI磁强计. 实验结果表明, 该磁 强计在-25000~25000nT量程内灵敏度为0.176mV·nT^-1, 满足实际弱磁场测量要求, 并且具有体积小及功耗低的特点, 有望应用于空间 探测等磁测量领域.

Suppression effect of transformer oil on plasma ion ablation and expansion stress in large air gap between fe-based nanocrystalline ribbon and coating falls off

Fe-based nanocrystalline ribbon (FBNR) has important applications in pulse transformers. During the breakdown course, large areas of air gaps appear between FBNR and its insulated coating that falls off. In this paper, the suppression effect of transformer oil on the plasma channel expansion stress and ion ablation in the air gaps aforementioned is explored. It revealed that the “fall off” effect of coating and the physical smashing effect on the insulated coating caused by the discharge plasma expansion stress were suppressed by oil. The coating ablation and gasification caused by the discharge ion bombardment in the coating cracks mainly attributed to the coating breakdown in oil, and the coating breakdown voltage was enhanced.

Analysis of the low-frequency magnetoelectric performance in three-phase laminate composites with Fe-based nanocrystalline ribbon

The theoretical analysis of magnetoelectric (ME) performance in three-phase Terfenol-D/PZT/FeCuNbSiB (MPF) laminate composite is presented in this paper. The ME couplings at low frequency for ideal and less than ideal interface couplings are studied, respectively, and our analysis predicts that (i) the ME voltage coefficient for ideal interface coupling increases with the increasing layers (n) of Fe-based nanocrystalline ribbon FeCuNbSiB (Fe73.5Cu1Nb3Si13.5B9) while the sizes of PZT (Pb(Zr1−xTix)O3) and Terfenol-D (Tb1−xDyxFe2−y) are kept constant, and then it tends to be a constant when the layers of FeCuNbSiB are >100; (ii) by introducing the interface coupling factor k and considering the degradation of d33m,f with n, the ME voltage coefficient for a less than ideal interface condition is predicted. As the FeCuNbSiB layer increases, it first increases and reaches to a maximum value, and then slowly decreases. Various MPF laminates are fabricated and tested. It is found that the theoretical predictions for the consideration of actual boundary conditions at the interface are in agreement with the experimental observations. This study plays a guiding role for the design of MPF composite in real applications.

Accumulated destructive effect of nanosecond repetitive voltage pulses on the insulated coatings of Fe-based nanocrystalline ribbon

Fe-based nanocrystalline ribbon is widely employed in pulsed power devices and accelerators. A temperature accumulation model is put forward to explain the accumulated destructive effect of discharge plasma bombardment on the TiO2 coatings of nanocrystalline ribbon under 50 Hz/100 ns voltage pulses. Experimental results revealed that the plasma channel expansion caused by air breakdown in the coating crack heated the coating repetitively, and the coating temperature was increased and accumulated around the crack. The fact that repetitive voltage pulses were more destructive than a single pulse with the same amplitude was caused by the intensified coating ablation under the temperature accumulation effect.

High Temperature Ageing of Fe-based Nanocrystalline Ribbons

The impact of long-term high-temperature stress on nanocrystalline Finemet materials is measured by keeping samples at 200 °C for 1300 hours. The standard industrialized, high permeability Finemet materials as well as the recently available low permeability Finemet materials are investigated. Characterizations are performed at different frequencies, temperatures and magnetic field excitations on both aged and non-aged samples. Their complex permeability is also measured during the ageing test. Irreversible changes are pointed out on permeability, coercive field and magnetic flux density at saturation. Regarding the design considerations for high temperature power electronics, the suitability of these materials is demonstrated but an ageing effect has to be considered nonetheless. The presented data can be extrapolated to several thousand hours at 200 °C using the presented empiric ageing law.

Fabrication and characterization of a new MEMS fluxgate sensor with nanocrystalline magnetic core

This paper presents a new MEMS fluxgate sensor with a Fe-based nanocrystalline ribbon magnetic core and 3D micro-solenoid coils. The excitation coils were placed vertically to the sensing coil on the chip plane. Second harmonic operation principle was adopted in this fluxgate sensor. The total size of the fluxgate sensor was 6.25mm×4.85mm×120μm. A simple testing system was established to characterize the fabricated devices. A band pass filter was used to pick up the second harmonic signals in the sensing coils. When excitation rms current of 120mA and the operational frequency of 200kHz were selected for the testing of the fabricated devices, the sensitivity of the developed fluxgate sensor was 1005 V/T in the linear range of −500μT to +500μT. Due to the combination of the 3D structure coils with the nanocrystalline core, relatively low sensor noise was achieved. The noise power density was 544pT/Hz0.5@1Hz and the noise rms level was 9.68nT in the frequency range of 25mHz–10Hz.

Mesostructural origin of stress-induced magnetic anisotropy in Fe-based nanocrystalline ribbons

The cross-sectional mesostructure of a stress-annealed Fe-based (Fe73.5Cu1Nb3Si13.5B9) ribbon (SAR) has been investigated by atomic force microscopy. The magnetic anisotropy field was measured via the curves of the giant magnetoimpedence effect in SAR. The stress-induced magnetic anisotropy field (ΔHk) showed a linear correlation with the transverse congregating vector Kv of the agglomerated grains. This indicated that the ΔHk originated from the directional congregation of the agglomerated grains formed in SAR. A model for this directional congregation has been established. The previous diverse viewpoints on the mechanism of stress-induced magnetic anisotropy have been unified in this model.

Soft-Magnetic Fe-Based Nano-Crystalline Thick Ribbons

Fe-based nano-crystalline thick ribbons (up to 150 mum) with excellent soft magnetic properties were developed in Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">71</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sub> Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6-x</sub> Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> alloys (x=1 ~ 5) alloys. The design of these Fe-based alloys was based on a ternary bulk metallic glass (BMG) Fe-B-Y system; Ta and Ag were added to achieve optimal nano-crystallization and to improve soft magnetic properties. An optimal composition Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">71</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sub> Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> was worked out showing good glass forming ability, and sound soft magnetic properties after nano-crystallization at 615 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> C for 5 min: saturation magnetization 1.44 T (152 emu/g), coercivity 35 A/m, and effective permeability at 1 kHz higher than 28000. The nanocrystalline Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">23</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> phase was found to be magnetically soft in these thick ribbons.

Mesostructure investigation of the transverse magnetic anisotropy field in stress-annealed Fe-based nanocrystalline ribbons

The mesostructure in Fe-based (Fe73.5Cu1Nb3Si13.5B9) nanocrystalline ribbons annealed under different stress (FNRAS) was investigated by observation of the cross section images of the ribbons with atomic force microscopy (AFM) and X-ray diffraction. The longitudinally driven giant magneto-impedance and transversal magnetic anisotropy field (Hk) were measured. The mechanism of the transversal magnetic anisotropy field can be explained by the mesostructure of the directional preference of crystalline grain (coated with amorphous shell) gathering, along the transverse direction, induced in the course of annealing of the Fe-based alloy ribbons under stress.

Fe-based Nanocrystalline Alloy Ribbon as Coaxial Cable Shielding Material

This paper describes the application of an Fe-based nanocrystalline ribbon as a shielding material for coaxial cable in the 10 MHz to 1GHz frequency range. A 0.01 mm thick Fe-based amorphous ribbon was converted into an Fe-based nanocrystalline ribbon by annealing it at 570 °C for 10 min. The ribbon exhibited high impedance characteristics when it was annealed in a transverse magnetic field. The noise attenuation value of cable covered with Fe-based nanocrystalline alloy ribbon annealed in a transverse magnetic field was 12.9 dB. This value exhibited 13 % higher than that of cable covered with Fe-based nanocrystalline alloy ribbon annealed without a magnetic field.

Giant Magnetoimpedance in as Quenched Fe Based Nanocrystalline Ribbons

FeCuNbSiB and FeZrBCu nanocrystalline ribbons can be obtained directly through the melt- spinning technique without additional annealing processes. The giant magnetoimpedance can be observed in FeCuNbSiB and FeZrBCu as quenched ribbons. The addition of Cu improves the nano-crystallization of a-Fe(Si) or a-Fe phase and reduces the grain size in FeCuNbSiB and FeZrBCu as quenched ribbons, which enhances the magnetoimpedance via increasing the variation of permeability under fields. The present experimental results reveal a novel route to fabricate the Fe based nanocrystalline soft magnetic materials with giant magnetoimpedance effect.