High Effective Permeability Research Articles

Microstructure evolution and soft magnetic property optimization of core-shell FeSiBCCr@SiO2&ZrO2 amorphous magnetic powder cores

In this study, core-shell structured FeSiBCCr@SiO2&ZrO2 amorphous magnetic powder cores (AMPCs) were successfully prepared by the sol-gel method using tetraethyl orthosilicate (TEOS) and zirconium oxychloride hydrate (ZrOCl2·8H2O) as raw materials. The growth mechanism and potential chemical reactions of the SiO2&ZrO2 mixed insulation layer were analyzed by XRD, XPS and SEM‒EDS. In addition, the effect of the insulation layer content on the soft magnetic properties of FeSiBCCr@SiO2&ZrO2 AMPCs was systematically investigated. The SiO2&ZrO2 insulation layer can significantly increase the resistivity, effectively improve the DC bias performance and reduce the core loss of AMPCs. S2* (1.2 mL TEOS and 1.4 g ZrOCl2·8H2O) had a minimum core loss of 2290 mW/cm3 at high frequency (50 mT, 1 MHz). It had a high effective permeability of 48.2 and a superior direct current (DC) bias performance of 77.9% at 8 kA/m. This study provides a valid method to practically produce SMPCs with high resistivity, low core loss at high frequency and excellent DC bias performance through a novel insulation coating process.

Investigation of glass forming ability, crystallization behavior, and soft magnetic properties of Fe–B–P–C–Cu alloy ribbons

The effect of Cu content on GFA, crystallization behavior, and soft magnetic properties in high P Fe84+xB6P6C3Cu1−x (x = 0, 0.2, 0.4, 0.6, and 1.0 at. %) alloy ribbons were systematically investigated to balance the relationship between glass forming ability (GFA), heat treatment window, and soft magnetic properties of high saturation magnetic flux density (Bs) Fe-based nanocrystalline alloys. It was discovered that lowering Cu promotes the formation of an amorphous structure. The GFA of alloys rises from 23 μm for Fe84B6P6C3Cu1 to 29 μm for Fe84.4B6P6C3Cu0.6. Analysis of thermal physical properties shows that when Cu content is between 1.0 at. % and 0.6 at. %, reducing Cu in the alloys does not affect the onset temperature of the first crystallization peak (Tx1), the second one (Tx2), and ΔT (ΔT = Tx2 − Tx1), whereas when Cu content is less than 0.6 at. %, reducing Cu leads to an increase in Tx1 and a decrease in Tx2 and ΔT, which is not conducive to obtaining a wide temperature range of precipitation of a single α-Fe phase. The alloys have a wide range of crystallization annealing temperature (693–753 K) and annealing time (60–6 min) to obtain a low coercivity (Hc) of about 8.0 A/m, high Bs of about 1.80 T, and high effective magnetic permeability (μe) of about 10000 when Cu is between 1.0 at. % and 0.6 at. %. The Bs, Hc, and μe of Fe84.4B6P6C3Cu0.6 alloy annealed at 723 K for 30 min are 1.82 T, 8.1 A/m, and 10820, respectively.

Excellent magnetic softness-magnetization synergy and suppressed defect activation in soft magnetic amorphous alloys by magnetic field annealing

Fe-based amorphous alloys with high saturation magnetic flux density (Bs) are increasingly attractive from both scientific and technological points of view, however, they usually suffer from the trade-off between magnetization and softness. In this work, we explore the soft magnetic properties (SMPs), magnetic and atomic structures, and defect activation during creep deformation of as-quenched and annealed Fe82.65-xCoxSi2B14Cu1.35 (x = 0–20) amorphous alloys (AAs). Improved magnetic softness-magnetization synergy has been realized in all these alloys by field annealing. Particularly, superb SMPs with super-high Bs of 1.86 T, low coercivity of 1.2 A/m and high effective permeability of 16300 are obtained in the Fe66.65Co16Si2B14Cu1.35 AA. The locally regularized arrangement of domains, homogenized structure with less structural/magnetic defects and suppressed crystal-like ordering by field annealing contribute synergistically to the superb SMPs. Besides, the relaxation time spectra obtained from creep deformation indicate less liquid-like and solid-like defects activated in the field-annealed AA, which is correlated with the structural homogenization and superb SMPs. This work provides new and comprehensive insight into the interplay among external field, heterogeneous structure, SMPs and defect activation of Fe-based AAs, and offers a promising pathway for softening amorphous alloys with high Bs.

In silico evaluation of pharmacokinetics and acute toxicity of withanolides in Ashawagandha

• 75 withanolides and structures were identified in literature and databases. • QSAR models predicted physicochemical, pharmacokinetic and toxicity properties. • In silico prediction correlated well with published data. Ashwagandha is a medicinal plant used in traditional Asian medicines as an adaptogen to promote both physical and mental health. Withanolides are the major bioactive phytochemicals in Ashwagandha; they are a group of naturally occurring C 28 -steroidal lactones with an ergostane-based skeleton. Despite the broad use of Ashwagandha, data on the pharmacokinetic and toxicological properties of withanolides remain scarce. Here, 75 withanolides in Ashwagandha were identified in journal publications, databases, and monographs. In silico quantitative structure-activity relationship (QSAR) models were used to evaluate the physicochemical and pharmacokinetic properties as well as the acute toxicity of withanolides. Withanolides had high molecular weight and pKa, low aqueous solubility, and high lipophilicity. QSAR models also predicted high effective human jejunal permeability and plasma protein binding, tissue partitioning, extensive metabolism, hepatic uptake, and renal excretion for certain withanolides. In addition, two thirds of the withanolides evaluated had predicted median lethal dose (LD 50 ) under 100 mg/kg after oral administration in rats. These in silico results could be used to guide further testing and confirmed by in vitro and in vivo studies.

Preparation of FeNiMo/SiO<sub>2</sub> composite core and regulation of soft magnetic properties

Nowadays, metal soft magnetic materials are mainly used in electronic components such as high-frequency inductors. Since all the elements in the soft magnetic alloys are transition metals, dense oxide layer is easily formed on their surfaces, which can affect the regulation of soft magnetic properties. In order to solve the problems, in this work, an innovative high-temperature pretreatment process in H<sub>2</sub>/Ar mixture is adopted to pretreat FeNiMo raw powders. We confirm that the high temperature treatment in reducing atmosphere can effectively remove metal oxides from the FeNiMo material surface and increase the content of elemental states, thereby further significantly improving the effective permeability of FeNiMo raw powders. The pretreated FeNiMo powder is evenly coated with SiO<sub>2</sub> layers, forming the FeNiMo/SiO<sub>2</sub> soft magnetic composites. Compared with the untreated FeNiMo powder coated with SiO<sub>2</sub>, the FeNiMo/SiO<sub>2</sub> pretreated with H<sub>2</sub>/Ar mixture gas at high temperatures has high effective permeability and low loss. Our FeNiMo/SiO<sub>2</sub> cores prepared by the synergistic effect of high-temperature pretreatment process in H<sub>2</sub>/Ar mixture and insulation coating process have more excellent soft magnetic properties than other iron-based soft magnetic composites. Therefore, the insulation coating after being pretreated at high temperature in reducing atmosphere can greatly improve the permeability and reduce the core loss of soft magnetic composites. This will provide a new strategy for enhancing the soft magnetic properties of the composite cores.

Replacement effect with Ni on high-frequency permeability and core loss characteristics for FeNiPBSiC glassy alloys

The paper aims to develop an excellent soft magnetic glassy alloy with a series of (Fe1−xNix)79P5B12Si3C1 (x = 0, 0.2, 0.4, 0.5, 0.6). The annealing at (Tg-20) K for the 0.4Ni-0.5Ni alloys causes an extremely low coercivity below 1 A/m with very high effective permeability above 5·104 at 1 kHz in the maintenance of high saturation magnetic flux density of ⋍ 1.2 T. Good effective permeability characteristics were recognized as is evidenced from high μe values above 6000 at 1 MHz. The core losses at induction of 100 mT are as low as 43 W/kg for 100 kHz and 1150 W/kg at 1 MHz for the annealed 0.6Ni alloy. Excellent soft magnetic properties are presumably due to the achievement of the fully relaxed glassy state which can be obtained only for the glass-type alloys with SCL region. This complex of magnetic properties is promising for future use as high-frequency type soft magnetic materials.

Regulation of magnetic and electrical performances in core-shell-structured FeSiCr@BaTiO3 soft magnetic composites

Soft magnetic composites (SMCs) are extensively used for designing and manufacturing high-performance electronic devices, such as inductors, filters, mutual inductors and chokes, owing to their high effective permeability (μe) and stable magnetic properties. However, the production of SMCs that meet the demands of high resistivity, high effective permeability (μe), and low core losses (Pcv), which are required for high-frequency miniaturized electronic systems, is challenging. In this study, we improve the electromagnetic performance of SMCs by coating FeSiCr metal particles with BaTiO3 dielectric ceramic powder at various concentrations (0.00–3.75 wt%). The micro-morphological, static magnetic, resistivity (ρ), and core loss (Pcv) properties of FeSiCr@BaTiO3 SMCs are comprehensively investigated. Energy dispersive spectroscopy elemental distribution mapping is used to confirm the formation of core-shell structures with excellent coating quality. With an increase in the BaTiO3 dielectric powder content, the core losses, Pcv (at 800 kHz, 10 mT and 25 °C), initially decrease and subsequently increase, and comprise hysteresis losses (Ph) and eddy current losses (Pe). Moreover, owing to the introduction of the non-magnetic-phase BaTiO3 powder, hysteresis losses increase monotonically, whereas eddy current losses exhibit the opposite trend. The FeSiCr@BaTiO3 SMCs with 2.25 wt% BaTiO3 dielectric ceramic powder exhibit outstanding comprehensive electromagnetic properties with an effective permeability of μe = 48, saturated magnetization of Ms = 115 emu/g, core losses of Pcv = 42 mW/cm3 (at 800 kHz, 10 mT and 25 °C), and resistivity of ρ = 2.74 × 105 Ω∙m. These state-of-the-art FeSiCr@BaTiO3 SMCs present considerable potential for application in high-performance power devices and components.

Gas-generative potential for the post-Messinian megasequence of Nile Delta Basin: a case study of Tao Field, North Sinai Concession, Egypt

The main aim of the article is to evaluate the gas potentiality for the post-Messinian megasequence in TAO Field, North Sinai Concession, offshore Nile Delta Basin. The detailed petrophysical analysis for three deviated wells in the study area (Tao-3 ST1 Well, Tao-5 STA Well and Tao-7 Well) revealed that the Pliocene Kafr El-Sheikh Formation includes eleven gas-bearing zones. These zones were named: A, B, C in Tao-3 ST1 Well and D, E, F in Tao-5 STA Well. In Tao-7 Well, the interesting zones are named G, H, I, J and K. All of these sandy intervals are relatively shallow in depth and differ in thickness between 4 and 56 m. These zones are characterized by shale volume (10%), total porosity (30–40%), effective porosity (30–35%), gas saturation (50–90%), high effective permeability to gas and low permeability to water. The seismic data displayed that listric faults and the associated rollover folds have an important role in forming structural traps for the examined gas-bearing zones in Tao Field and its surroundings. This work revealed that the success rate in discovering new gas prospects within the Pliocene–Pleistocene succession at North Sinai Concession is very high.

High permeability and low core loss Fe-based soft magnetic composites with Co-Ba composite ferrite insulation layer obtained by sol-gel method

To balance the core loss and permeability of soft magnetic composites (SMCs), a Co-Ba composite ferrite insulation layer was employed to clad the surface of reduced iron powder by sol-gel method. The successful preparation of the honeycomb-like Co-Ba composite ferrite coating layer was verified by scanning electron microscopy (SEM), the composition of the coating was determined by X-ray diffraction (XRD), and the magnetic properties were tested with a B-H curve analyzer. BSEM images of the polished cross-section and core loss separation results confirmed that an excessively high annealing temperature causes the composite ferrite insulation layer to fail. A high effective permeability of up to 121 at 300 kHz and low core loss (Pcv) of 129 kW/m3 at 100 kHz and 0.02 T were obtained in prepared samples at the optimized annealing temperature of 500 °C. Subsequently, simulation analysis based on the Clausius-Maxwell formula model was used to confirm the feasibility of the enhancement on effective permeability in Fe@Co-Ba composite ferrite theoretically. The agreement between simulation and experimental results further indicated that a good balance between the core loss and permeability of Fe-based SMCs was achieved by Co-Ba composite ferrite cladding.

Single-well production history matching and geostatistical modeling as proxy to multi-well reservoir simulation for evaluating dynamic reservoir properties of coal seams

Reservoir properties of coal seams such as gas and water effective permeabilities and gas content, as well as spatial distributions thereof, affect the success of gas production and CO2-enhanced gas recovery (EGR) with simultaneous CO2 sequestration. These properties change during production and injection operations due to variations in reservoir pressure, matrix shrinkage/swelling, and water saturation and are therefore referred to as dynamic properties. Predicting distribution of such important reservoir properties and how they evolve during production, or injection, at unsampled locations can be particularly important for field development and project economics.In this work, dynamic properties of Black Creek coal seam of Black Warrior Basin, Alabama were mapped using pointwise results from single-well production history matching of 45 wells and classical geostatistics. It is explored if this approach can be a proxy, with its limitations, to multi-well reservoir simulation. For this purpose, a reservoir model was built using available reservoir, well and production data to compare its results with those of the geostatistical maps for the same properties. Despite the expected local discrepancies due to differences between the two approaches, the results showed similar patterns and global distributions. Specific results showed that despite long-time operation of the wells in this area, there were still areas with high gas content and low gas effective permeability within the modeled time interval that might have benefited from further development using additional wells.

Novel Fe-C-B-P-Cu nanocrystalline alloys with superb magnetic properties and processability

In this article, we present a new kind of Fe-C-B-P-Cu nanocrystalline alloys containing high P content with excellent comprehensive magnetic properties and processability. This kind of nanocrystalline alloys exhibits the high saturation magnetic flux density (Bs), low coercivity (Hc) and high effective permeability (μe) in the range of 1.73–1.84 T, 3.2–8.4 A/m and 6000–13000, respectively. It was found that increase of P content remarkably decreases the sensitivity of Hc to annealing temperature (Ta) and widen the optimum annealing temperature range to obtain a low Hc. With the increase of P content, the growth of α-Fe grains is retarded, but the nucleation of α-Fe grains is increased, resulting in reduced grain size and the intergranular amorphous layer, and precipitated high density of α-Fe nanocrystals. Based on the crystallization and structural features, the relationship between soft magnetic properties and microstructure for this kind nanocrystalline alloy was discussed in detail.

Influence of P content on SMPs in Fe–Si–B–P–C–Cu–Nb amorphous alloys under longitudinal field annealing

The influence of P content on Curie temperature, magnetic properties and microstructures of Fe81.5Si3B10+xP3.5−xC0.2Cu0.8Nb1 (x = 0, 1, 2, and 3 at.%) alloys subjected to magnetic field annealing has been studied. Here, the decrease in P content can improve Curie temperature of alloys from about 575 to 584 K, which increases the operating temperature of magnetic device. Via optimal field annealing technique, the amorphous alloy with x = 3 exhibits good soft magnetic properties, including saturation magnetic flux density of 1.53 T, high effective permeability above 12,000, low coercivity below 3 A/m, and low core loss around 0.18 W/kg. The hysteresis loops show that tuning down the content of P relative to B can increase the saturation magnetic flux density of alloy system. Besides, the investigation about the microstructures of alloys annealed at optimal conditions indicates that longitudinal magnetic field annealing can improve the stability of amorphous phase, thereby ensuring the amorphous structure annealed at a higher annealing temperature compared with the general annealing for alloys.

Tunable and attractive magnetic properties of FeBPSiCu alloys

Novel Fe76-xB10P5Si9Cux (x = 0, 0.5, 1 and 1.5 at.%) amorphous alloys with low Fe content were successfully synthesized with aim of investigating the crystallization behaviors and magnetic properties. Thermodynamic behavior revealed that Cu substitution triggered the transition of primary precipitation phase from Fe23B6 to α-Fe, which favored the high saturation magnetic flux density (Bs) of alloys after annealing. Through adjustment of Fe/Cu ratio, the Fe75B10P5Si9Cu1 alloy exhibited the attractive and tunable magnetic properties, i.e. the high effective permeability (μe) of 25000 and low coercivity (Hc) of 1.3 A/m in amorphous state as well as the high Bs of 1.62 T and μe of 18000 in crystallization state. The high Bs could be attributed to the uniform refined composite microstructure, whereas the excellent magnetic softness characterized by magnetic domain patterns was determined by magnetic anisotropy induced via different atomic structures. Such tunable performance can promise alloy a potential soft-magnetic material to meet the requirement of most electric devices.

Effects of Si content on structure and soft magnetic properties of Fe81.3SixB17-xCu1.7 nanocrystalline alloys with pre-existing α-Fe nanocrystals

The as-spun structure, thermal stability, crystallization structure and soft magnetic properties of Fe81.3SixB17-xCu1.7 (x = 0–8) alloys were investigated. The Fe–Si–B–Cu amorphous alloys contain α-Fe nanocrystals with a high number density (Nd) in as-spun state and show uniform nanocrystalline structure and typical soft magnetic characteristics after annealing. The rise of Si content from 0 to 4 at% increases the Nd, while the further rise to 8 at% shows an adverse effect. The increased Nd enhances competitive growth between the crystals during crystallization process, then refines structure and improves soft magnetic properties of the nanocrystalline alloys. Contrarily, the decreased Nd results in coarsened nanostructure and deteriorated magnetic softness. The alloy with Si content of 4 at% contains α-Fe crystals with a high Nd of 2.2 × 1023 m−3 in as-spun state and possesses fine α-Fe grains with an average size (D) of 14 nm, low coercivity (Hc) of 7.1 A/m, high effective permeability (at 1 kHz) of 16,500 and saturation magnetic flux density of 1.77 T after annealing at 668 K for 60 min. In addition, the Hc of present Fe–Si–B–Cu nanocrystalline alloys is almost proportional to D3 due to the high ratio of uniaxial anisotropy to average random anisotropy.

Terahertz metamaterial with broadband and low-dispersion high refractive index.

A broadband and low-dispersion high refractive index (HRI) metamaterial formed by symmetrically etching two identical metasurfaces on both sides of a dielectric slab has been numerically and experimentally demonstrated in the terahertz region. The unit cell of the metasurface is a Jerusalem cross surrounded by a square metal ring, in which there are two magnetic resonances and one electric resonance. The proposed metamaterial simultaneously possesses high effective permittivity and permeability in broadband frequencies, since the multiple resonances result in a significant bandwidth expansion of a HRI. The simulation results reveal that the refractive index of the proposed metamaterial reaches up to 27 in the frequency range of 0.39-0.65 THz, and the relative bandwidth is about 44%. Furthermore, the fluctuation of the refractive index in this frequency band is less than 6%, showing a good low-dispersion characteristic. We also fabricated a sample to verify this HRI property. Experimental results are in good agreement with numerical simulations. This broadband HRI metamaterial is desirable in many fields, such as in high-resolution imaging and optical communications.

Correlation among the amorphous forming ability, viscosity, free-energy difference and interfacial tension in Fe–Si–B–P soft magnetic alloys

To clarify the underlying mechanism of effects of P on amorphous forming ability (AFA) for Fe–Si–B–P alloy system, the AFA and melting viscosity of (Fe76Si9B10)(100-x)/95Px (x = 0–3) amorphous alloys measured in the temperature range of 1200–1450 °C by oscillating cup method were investigated. A viscosity hysteresis occurs at about 1350 °C between the heating and cooling processes for all alloys, and the values of viscosity almost increase as P content increases at each measured temperature under cooling process. However, only considering viscosity cannot provide a satisfactory explanation for the trend of AFA for this alloy system. Afterwards, the mechanism was well revealed by calculating the Gibbs free-energy difference and speculating the interfacial tension. In addition, a positive correlation between magnetic properties (coercivity and effective permeability) and the AFA of this alloy system was also founded, which can provide an auxiliary in understanding the mechanism of AFA to some extent. Meanwhile, when x = 3, the alloy shows excellent soft magnetic properties including low coercivity of 0.9 A/m and high effective permeability of 17,000, which is promising for future electromagnetic device application.

Composition dependence of amorphous forming, crystallization behavior, magnetic and electronic properties of silicon-rich FeSiBCuNb alloys

Fe-Si-B-Cu-Nb nanocrystalline alloys have been commercially applied at higher frequencies. However, few research works are focused on improving high-frequency magnetic properties for these alloys. In this paper, we reported crystallization behavior, soft magnetic properties and permeability spectra for silicon-rich Fe72.5Si16B7 Cu1Nb3.5-xMx (where × = 1.5 and M = Nb, P, Mo, V) nanocrystalline alloys prepared by crystallization from amorphous precursors. Through the copper roller melting spinning technique, we can attain complete amorphous alloy ribbons when M is 1.5 at.% Nb, P or Mo. After annealing at appropriate temperatures, by comparison with the alloy of M = 1.5 at.% Nb, the alloy with addition of 1.5 at.% P shows a lower coercivity (Hc = 0.8 ~ 1.5 A/m), and a higher effective permeability (µe) at 1 kHz–20 kHz (µe = 116,600 at 1 kHz) while the µe gets much lower at 30 kHz–200 kHz; the alloy with addition of 1.5 at.% Mo exhibits a larger Hc (Hc = 2.9 ~ 3.4 A/m), and a lower µe at 1 kHz − 20 kHz but then the µe becomes higher at 30 kHz–200 kHz (µe = 31,000 at 100 kHz).

A novel FeNi-based bulk metallic glass with high notch toughness over 70 MPa m1/2 combined with excellent soft magnetic properties

A novel Fe39Ni39B12.82Si2.75Nb2.3P4.13 bulk metallic glass (BMG) with high notch toughness of 72.3 MPa m1/2, large plastic strain of 9.8%, high yield strength of 2930 MPa, and a large critical diameter of 2.5 mm was successfully developed. This BMG also exhibits excellent soft magnetic properties, i.e., higher saturation magnetic flux density of 0.86 T, extremely low coercivity of 0.65 A/m, and high effective permeability of 23,250 with high frequency stability. Its toughness value is the highest among Fe-based BMG family. The origin of high toughness was also investigated in detail by using synchrotron X-ray diffraction and aberration-corrected high-resolution transmission electron microscopy. It was found that the high toughness are attributed to atomic-scale structural heterogeneity that resulted from large free volume, high content of metal-metal bonds and high structural disorder degree, which can promote the multiple shear bands and hinder the subsequently propagation. This work provides useful guidelines for developing tough FeNi-based BMGs with high strength and excellent soft magnetic properties from an atomic structural perspective.

High Bs of FePBCCu nanocrystalline alloys with excellent soft-magnetic properties

High saturation magnetic flux density (Bs) nanocrystalline alloys are increasingly attractive due to their unique microstructure and outstanding magnetic performance. In this work, we report that the substitution of B for P essentially improves the Bs of FePBCCu amorphous alloys. Based on high Bs amorphous matrix, the Fe83.2P8B2C6Cu0.8 nanocrystalline alloy with high Bs of 1.77 T, low coercivity of 3.6 A/m and high effective permeability of 20,600 was developed. Such magnetic performance of Fe83.2P8B2C6Cu0.8 nanocrystalline alloy is closely associated with the uniform refined composite microstructure, where the α-Fe nanocrystals with high volume fraction, small size and high number density (~1.8 × 1023 m − 3) were formed. This finding makes the FePBCCu composite a kind of promising soft-magnetic material in electrical and electronic fields.

Optimization of the structure and soft magnetic properties of a Fe87B13 nanocrystalline alloy by additions of Cu and Nb

The effects of Cu and Nb additions on the structure and magnetic properties of a Fe87B13 alloy in melt-spun and annealed states were investigated. Increase in Cu content from 1.0 to 1.7 at.% changes the melt-spun Fe87-xB13Cux alloy ribbons from a single amorphous phase to a composite of high-number-density nano-order α-Fe phase with an average grain size (Dα-Fe) of 12.1 nm dispersing in the amorphous matrix. The crystallized structure after annealing gets refined with increasing the Cu content, and a small Dα-Fe of 18.1 nm is obtained for the Fe85.3B13Cu1.7 alloy, which possesses a low coercivity (Hc) of 32.6 A/m and high saturation magnetic flux density (Bs) of 1.87 T. Minor addition of Nb reduces the Dα-Fe in melt-spun Fe85.3-yB13Cu1.7Nby alloys but not obviously lowers the number density, while 3 at.% Nb makes the formation of fully amorphous phase. The Dα-Fe in the crystallized alloys is decreased to 15.3 nm by alloying 2 at.% Nb, but increased to 31.4 nm with 3 at.% Nb. The Fe83.3B13Cu1.7Nb2 nanocrystalline alloy exhibits a lower Hc of 9.5 A/m combined with high Bs and effective permeability at 1 kHz of 1.75 T and 15000, respectively. The combined effects of competitive growth of the pre-existing nano-order α-Fe particles and Nb-inhibited atoms diffusion contribute to the refinement of the nanocrystalline structure.