Saturation Magnetic Flux Research Articles

Electrodeposition of bulk nanocrystalline Ni–Fe–P alloys and their mechanical and soft magnetic properties

Electrodeposited Ni–Fe alloys are expected to have an improved mechanical strength because of their nanocrystalline structure. However, unsatisfactory grain refinement yields a higher coercivity compared with conventional permalloys, which is undesirable in soft magnetic materials. We report electrodeposited Ni–Fe–P alloys that combine the mechanical properties of nanocrystalline materials with soft magnetism that is achievable in coarse-grained permalloys. In Ni–Fe–P alloy electrodeposition, the connections between the bath composition and Fe and P contents of the samples were demonstrated. For Ni–Fe alloys, the introduction of a few percent of P led to a preferable microstructure that was composed of ~10-nm-diameter grains. Up to 2.0 at% P, the resultant Ni–Fe–P alloys achieved a tensile strength of 2.1 GPa, along with a plastic deformability. The electrodeposited alloys exhibited a saturation magnetic flux density of 1.1 T and a coercivity of 8.4 A/m. Our approach indicates that grain refinement by the P alloying can result in a lower coercivity, according to the law of grain size and coercivity.

Ar ion irradiation effect on the soft magnetic performance of Fe-based amorphous alloys

We investigate the effect of Ar ion irradiation on the microstructure and soft magnetic behaviors of Fe80CoxB14-xSi2P3Cu1 (x = 0, 2, 4) amorphous alloys by using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and soft magnetic performance analysis. With increasing Co content, the alloy shows decreasing radiation resistance, i.e., more degree of nanocrystallization induced by irradiation. It is found that after irradiation with fluence of ~9.0 × 1014, the coercivity is reduced from 7.6 A/m to 7.0 A/m, but increases again with further increase of irradiation fluence due to the formation of larger nanosized α-Fe(Co) grains. And with increasing irradiation fluence, the saturation magnetic flux density first decreases slightly from 1.65 T to 1.64 T, and then increases gradually to 1.68 T. Further, the core loss and effective magnetic conductivity were tuned obviously by irradiation, which has been discussed in term of stress relaxation and nanocrystallization.

Preparation and Magnetic Properties of Fe@SiO<sub>2 </sub>Soft Magnetic Composites

In this work, the insulating SiO2 was coated successfully on the surface of reduced iron particles by a sol-gel method to decrease the core loss at low frequency. The scanning electron microscope images and elements analysis confirm that the surface of iron powders particles were covered by a thin insulating layer in the form of uniform core-shell structure. The samples were annealed at 400 °C in N2 atmosphere to obtain better magnetic properties. The annealed SMCs with 10 mL/h dropping rate of TEOS have optimum magnetic properties with low core loss Ps of 280.89 W/kg and high saturation magnetic flux density Bs of 1.038 T at 1000 Hz.

Electrodeposition of Bulk Nanocrystalline Ni-Fe-P Alloys and Their Mechanical and Soft Magnetic Properties

Electrodeposited Ni-Fe alloys are expected to have an improved mechanical strength because of their nanocrystalline structure. However, unsatisfactory grain refinement yields a higher coercivity compared with conventional permalloys, which is undesirable in soft magnetic materials. We report electrodeposited Ni-Fe-P alloys that combine the mechanical properties of nanocrystalline materials with soft magnetism that is achievable in coarse-grained permalloys. Up to 2.0 at% P, the resultant Ni-Fe-P alloys achieved a tensile strength of 2.1 GPa, along with a plastic deformability. The electrodeposited alloys exhibited a saturation magnetic flux density of 1.1 T and a coercivity of 8.4 A/m. Our approach indicates that graine refinement by the P alloying can result in a lower coercivity, according to the law of the grain size and coercivity.

Development of a rapid cooling atomizing method and production of high-Bs nanocrystalline powders containing large-sized particles

We attempted to produce nanocrystalline soft magnetic powders with a high saturation magnetic flux density (Bs) and containing large-sized particles using a modified water atomization system named “HPWA/YK.” Almost fully amorphous powders containing particles with median diameters of 15 μm and composed of Fe83.3Si4B8P4Cu0.7 were obtained. These results indicate that HPWA/YK reached a higher quenching rate than conventional water atomization systems. The powder circularity reached a value of 0.78 by changing the ratio of the gas to water pressure; moreover, after annealing at 713 K, the powders presented good magnetic properties (Bs = 1.66 T; Hc = 155 A/m).

Soft magnetic Co-based Co–Fe–B–Si–P bulk metallic glasses with high saturation magnetic flux density of over 1.2 T

Co-based (Co, Fe)75B15Si7P3 bulk metallic glasses (BMGs) without any early transition metal or rare-earth elements have been successfully developed, which possess outstanding soft magnetic properties with high saturation magnetic flux density (Bs) and good mechanical properties. Addition of an appropriate amount of P into a Co75B15Si10 alloy promotes the occurrence of glass transition and increases the stability of the supercooled liquid, and a Co75B15Si7P3 metallic glass exhibits a large supercooled liquid region of 33 K. Subsequent replacement of Co by 15–35 at.% Fe enhances the glass-forming ability (GFA) of the Co75B15Si7P3 alloy, and the BMG rods with diameters up to 2.0 mm are obtained. The improved GFA might be originated from the high thermal stability of the alloy melts as indicated from the large undercoolings. The Co-based (Co, Fe)75B15Si7P3 BMGs possess low coercivity of 0.8–4.6 A/m, high Bs of 1.02–1.24 T, effective permeability of 12700–18500 at 1 kHz, and Curie temperature of 739–789 K, indicating superior soft magnetic properties compared to other reported Co-based BMGs. The BMGs also exhibit high compressive yield strength of 3343–3590 MPa with distinct plastic strain up to 2.7% and high Vickers hardness of 1150–1175. The combination of high GFA and excellent soft magnetic and mechanical properties makes the Co-based BMGs a good prospect of functional materials.

Structural and magnetic characterization of Al microalloying nanocrystalline FeSiBNbCu alloys

The magnetic properties of nanocrystalline Fe77Si10B9Cu1Nb3-xAlx (x = 0 and 1) alloys have been investigated and their structural and electromagnetic parameters have been quantitatively studied by X-ray diffraction, transmission electron microscopy and Mössbauer spectra under one-step and two-step annealing processes. The nanocrystalline structure consists of single α-Fe(Si) phase embedded in a residual amorphous phase. Both saturation magnetic flux density (Bs) and permeability (μ) of the nanocrystalline alloys are increased by substituting 1 at% Al for Nb and one-step annealing, from Bs = 1.41 T to 1.47 T and from μ = 18,000 to 23,000 at 1 kHz, respectively. The two-step annealing has little effect on the Bs, coercivity (Hc) and grain size of the nanocrystalline alloys, but greatly improves the μ of the Al-doped alloy, reaching up to 28,000 at 1 kHz. The improved μ can be attributed to the increased magnetic moment and exchange stiffness constant, homogeneous chemical structure and reduced magnetostriction. The Al-doped nanocrystalline alloy with high Bs, high μ, low Hc and good frequency stability are good candidates for magnetic shielding pieces of wireless charging.

Effect of the stoichiometric ratio on phase evolution and magnetic properties of SrFe12O19 produced with mechanochemical process using mill scale

In this study, we have produced strontium hexaferrite (SrFe12O19) magnets by mechanochemically synthesizing the mill scale which is the waste material from the hot rolling process of steel slabs and strontium carbonate (SrCO3) powders. The mechanochemical synthesis process was conducted via high energy ball milling process. The stoichiometric ratio (SrCO3/Fe2O3) was changed from 1:5.5 to 1:6.6 by 0.1 increments, and the influence of stoichiometric ratio was investigated with regards to phase structure and magnetic properties. The relationship between the magnetic performances and structures was well established through Vibrating Sample Magnetometry (VSM) measurements and Rietveld refinement analysis of powder X-ray diffraction data. The primary phase formed in powder structures for all the stoichiometric ratios was SrFe12O19 and the other phases of α-Fe2O3, SrO, and SrFe2O4 with varying amount, depending on the stoichiometric ratios, were also obtained. The maximum magnetic properties were obtained with 1:6.0 SrCO3/Fe2O3 stoichiometric ratio. The coercivity (Hc), the saturated magnetic flux density (Bs), the residual magnetic flux density (Br), and maximum energy product (BH)max values for 1:6.0 stoichiometric ratio were obtained as 3682 Oe, 506 mT, 311 mT, and 3.11 MGOe, respectively.

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.

Effect of Phosphating and Heat Treatment on Magnetic Properties of Fe-3.3Si-6.5Cr Soft Magnetic Composites

Fe-3.3Si-6.5Cr powders were first treated by phosphoric acid solution and then mixed with epoxy-modified silicone resin uniformly, forming insulation coating. The Fe-3.3Si-6.5Cr soft magnetic composites were prepared by compaction and annealing treatment of the coated Fe-3.3Si-6.5Cr powders. The microstructure and composition of Fe-3.3Si-6.5Cr powders were analyzed by scanning electron microscope coupled with energy-dispersive spectrometer, Fourier-transform infrared spectra, and X-ray photoelectron spectroscopy, respectively. The magnetic properties were determined by the LCR bridge tester and an auto testing system for magnetic materials (MATS-2010SA). Results show that both proper phosphating treatment and annealing at higher temperature can improve the permeability and reduce the core loss of the Fe-3.3Si-6.5Cr SMCs. When the concentration of phosphoric acid was 0.5 wt% and the heat treatment temperature reached 500 °C, the Fe-3.3Si-6.5Cr SMCs showed the optimized magnetic properties, including the permeability (μe) of 44.7 H/cm, the core loss (P) of 521.8 mW/cm3 at the saturated magnetic flux density of 50 mT, and the frequency of 100 kHz. The Fe-3.3Si-6.5Cr SMCs with distinguished magnetic properties provide great application prospect in various fields such as filter inductors, transformers, and sensors.

High saturation magnetic flux density of Novel nanocrystalline core annealed under magnetic field

In the present study, the magnetic and microstructural properties were investigated of Fe-based nanocrystalline soft magnetic alloy with the composition of Fe80Si7B9Nb3Cu1 fabricated by the melt-spinning method. The annealing under varying transverse magnetic field was applied to induce the uniform distribution of α-Fe nanocrystals. The lowest core loss (Pcv) was 124.0 mW/cm3 achieved with the specimen annealed at 560 °C. Furthermore, the core annealed at 560 °C showed the Bs as high as 1.57 T which is significantly higher than that of conventional FINEMET core (Bs = 1.23 T). The combination of high Bs with excellent magnetic properties makes this nanocrystalline alloy a promising candidate for the application in high frequency (f) region.

Thermal, structural and soft magnetic properties of FeSiBPCCu alloys

Lower Si and C-content Fe83.3Si2B13-xPxC1Cu0.7 alloys were prepared in order to investigate the influence of P substitution on thermal, structural and soft magnetic properties. Thermodynamic investigation reveals that proper P addition not only favors the amorphous formation but also expands the crystallization window and inactivates the annealing sensitivity of alloys. Microstructure and X-ray photoelectron spectroscopy analysis indicate P addition facilitates homogeneous precipitation of α-Fe nanocrystals but results in the formation of loose packing structure, favors the p-d hybridization and promotes the annihilation of effective magnetic moments of Fe atoms, leading to the decrease in saturation magnetic flux density (Bs) of amorphous phase. By proper isothermally annealing, the Fe83.3Si2B9P4C1Cu0.7 nanocrystalline alloy was developed combined with high Bs of 1.78 T, low coercivity of 4.6 A/m, and high permeability of 15100.

Synthesis of V2O5-Doped and low-sintered NiCuZn ferrite with uniform grains and enhanced magnetic properties

NiCuZn ferrites with high permeability and low magnetic loss have great application potential in high-frequency electronics. In this study, the excellent magnetic properties of (Ni0.2Cu0.2Zn0.6O)1.03(Fe2O3)0.97 ferrites are explored by doping low-melting point V2O5. The results demonstrate that the introduction of V2O5 can promote grain growth, reduce pores between grains, and obtain a denser microstructure of NiCuZn ferrites. NiCuZn ferrites with high permeability (μ’≈693.2), high saturation magnetic flux density (Bs = 325.1 mT), high remanence (Br = 174.3 mT), high Q value (~47.60), and low coercivity (Hc = 69.06 A/m) are obtained when the samples are sintered at 900 °C. However, when excessive V2O5 is added, the presence of the non-magnetic V2O5 liquid phase weakens the magnetic properties and deteriorates the grain uniformity. A dense and uniform NiCuZn ferrite sample with excellent magnetic properties can be obtained by doping 0.50 wt% V2O5. The results indicate that V2O5 can be a good candidate for low-temperature sintering.

High-Performance Metallic Amorphous Magnetic Flake-Based Magnetodielectric Inductors

Flake-shaped FeSi-based metallic amorphous alloy particles, having an aspect ratio as high as 175 to 1, were prepared by ball milling gas atomized amorphous powders of an effective diameter of 20 micrometers. The starting powder had a saturation magnetic flux density, Bs, of 1.5 T and a coercivity, Hc, of 94 A/m. The aspect ratio of the flakes, as well as their magnetic properties, were controlled by milling process parameters, such as duration, speed, and the type, mass and diameter of the milling balls. To minimize the oxidation of the charge, the powders were handled in an argon gas-purged glove box, milled in toluene, and subsequently dried in vacuo. Subsequently, soft magnetodielectric composites were prepared by suspending and aligning the FeSi-based powders in paraffin wax or epoxy resin. The composites were then pressed into toroids for measurements of their high frequency complex permeability by a vector network analyzer. The influence of the flake aspect ratio and volume loading fraction on the permeability of the composites were investigated. Results indicate that the composite permeability increases with the flake aspect ratio. For example, for a given loading factor of 30 vol.%, the composite permeability at 0.1 GHz nearly tripled and approached the value of 10 by increasing the aspect ratio of the FeSi-based inclusions from 1 (spheres) to greater than 175 to 1 (flakes).

FeBNbP nanocrystalline alloy powder with high amorphous forming ability and high B s for magnetic core

The influence of P content on amorphous forming ability and the magnetic characteristics were investigated in the FeBNbP nanocrystalline alloys using metallic ribbons. The Fe84-xB9Nb7Px(x=0-3) and Fe80B10Nb7P3 nanocrystalline alloy metallic ribbons prepared by a single-roller melt-spinning method. The Fe84-xB9Nb7Px (x=0-3) and Fe80B10Nb7P3 nanocrystalline alloys annealed at 873-923 K consist of stable α-Fe grain formed in a residual amorphous phase, and the nanocrystal α-Fe grain showed the average diameter from 6.3 to 7.7 nm. The critical thickness of ribbons indicating amorphous forming ability was increased from 20 μm to 68.7 μm with Fe81B9Nb7P3 by increasing P content. The Fe81B9Nb7P3 alloy also exhibited a high saturation magnetic flux density, Bs, of 1.51 T. In addition, Fe81B9Nb7P3 alloy indicated a good magnetic softness with a low coercivity, Hc, of 4.8 A/m. The Fe80B10Nb7P3 alloy increasing B content succeeded to obtain the powder with precursor of a stable amorphous phase by rapid quenching gas atomization method.

Effect of Calcination Temperature on Magnetic Properties of MnZn Ferrites for High Frequency Applications

With the development of switching power supplies, miniaturization and high efficiency become hot research issues, and decreasing high-frequency losses is an effective method to achieve it. In this article, the effect of different calcination temperature on the power losses of MnZn ferrites at high frequency (500 kHz) over a broad temperature range is reported. The MnZn ferrites samples were prepared by ceramic process and the effect of calcination temperature was analyzed. The raw materials were calcined at 775 ℃, 800 ℃, 825 ℃, 850 ℃, 875℃, 900 ℃, 925 ℃ and 950 ℃, and the regular fluctuations of particle size (as-calcined), density (as-sintered) and magnetic properties are presented in this work. It is shown that the samples calcined at 850 ℃ exhibit optimal microstructure and magnetic properties. The newly developed MnZn ferrites are characterized by sintered density of 4.61 g/cm³, initial permeability of 1223 (10 kHz/0.1 mT/25 ℃), saturation magnetic flux density of 488 mT (10 kHz/1200 A/m/25 ℃) and power losses of 68 mW/cm³ (500 kHz/50 mT/100 ℃).

A study on the role of Ni content on structure and properties of Fe–Ni–Si–B–P–Cu nanocrystalline alloys

Amorphous-forming ability (AFA) and thermal stability of melt-spun Fe85-xNixSi2B8P4Cu1 (x = 0–20) alloys and their crystallized structure, magnetic and mechanical properties have been investigated. The increase of Ni content from 0 to 20 at.% gradually improves the AFA with enlarging the critical thickness for amorphous formation from 14 to 38 μm. Adding 5 at.% Ni increases the number density (Nd) of nucleation sites by properly delaying the Cu atoms clustering process during annealing and refines the α-(Fe, Ni) grains, which leads to a magnetic softness improvement of the nanocrystalline alloys. The excessive Ni (≥10 at.%) decreases the Nd due to the overinhibition of the Cu clustering, resulting in the grains coarsening and magnetic softness deterioration. The Fe80Ni5Si2B8P4Cu1 nanocrystalline alloy possesses finer α-(Fe, Ni) grains with an average size of 22 nm, a lower coercivity of 14.3 A/m and saturation magnetic flux density of 1.77 T as compared with those of 40 nm, 105.3 A/m and 1.84 T, respectively, for the Fe85Si2B8P4Cu1 alloy. In addition, the nanocrystalline alloys with 2.5–10 at.% Ni show reduced brittleness compared with the Ni-free alloy owing to the grain refinement, and the alloys with 15–20 at.% Ni possess further decreased brittleness as a consequence of the reduced α-(Fe, Ni) phase volume fraction.

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.

A general rule for transition metals doping on magnetic properties of Fe-based metallic glasses

The magnetic and electronic properties of Fe77X5Si4B10P4 (X = V, Cr, Mn, Fe, Co, and Ni) metallic glasses were investigated based on first-principle calculations. While the ability of losing electrons is increasingly weaker, that of acquiring charges is stronger with increasing the number of valence electrons from V to Ni atoms. For the addition of V, Cr, and Mn nonmagnetic atoms, while they all behave antiferromagnetic character, the magnetic moments of nearest neighboring (NN) Fe atoms around them are weaker compared to that of Fe82Si4B10P4, resulting from the strong hybridization between 3d states of impurity and Fe. For Co and Ni magnetic atoms, while the magnetic moments of NN Fe atoms are increasingly stronger than that in Fe82Si4B10P4, the local magnetic moments of additive atoms reduce. These result in that the addition of X atoms weakens the saturation magnetic flux density of Fe82Si4B10P4. Moreover, if Co with a minor proportion is incorporated, it will enhance the total magnetization compared to Fe82Si4B10P4 metallic glass, which is certified by experimental results.

Maintaining high saturation magnetic flux density and reducing coercivity of Fe-based amorphous alloys by addition of Sn

The effect of minor Sn on crystallization behavior, soft magnetic properties and corrosion resistance of Fe83B10-xC3Si3P1Snx (x = 0.25, 0.5 and 0.75) amorphous alloys was investigated. Sn added alloys exhibit excellent saturation magnetic flux density (Bs) of 1.63–1.72 T, low coercivity of 2.5–5.4 A/m and higher corrosion resistance. Furthermore, coercivity of as-spun alloys is lowered by Sn addition, and mechanisms behind the change of soft magnetic properties were discussed. The finding suggests that soft metal Sn may act as a stress reliever in as-spun alloys, leading to low coercivity while maintaining ductility. This theory was then confirmed in high Co content amorphous alloys with Bs of 1.75 T, in which case Sn addition causes significant reduction of coercivity but no decline of Bs. The present strategy of Sn addition may pave a new and universal way for Fe-based amorphous alloys to simultaneously obtain high Bs, lower Hc and high ductility.