Nanocrystalline Magnetic Materials Research Articles

Structure and magnetic properties of nanocrystalline SmCo5 and SmCo3Cu2 prepared by using high-pressure torsion method

Nanocrystalline SmCo5 and SmCo3Cu2 alloys were prepared by using high pressure torsion (HPT) method. The effect of severe plastic deformation of HPT on the structure and magnetic properties of the samples were investigated systematically. The grain size of SmCo5 and SmCo3Cu2 alloys was refined to the nanocrystalline regime or even amorphous state by HPT, depending on the number of the HPT rotation. Lamellar microstructures of the grains were observed in the samples after HPT for 2 turns of rotation. With increasing number of HPT rotation, a further structural refinement and an increasing coercivity were observed. The coercivity of the as-cast SmCo5 and SmCo3Cu2 alloys after HPT reached up to 0.5 and 1.64 T, respectively. This work demonstrates that HPT is a high efficiency method in producing bulk nanocrystalline magnetic materials.

Structural, morphological, XPS, dielectric and spectral properties of sol-gel synthesized Ba–Zn–Cr U-type nanocrystalline magnetic oxide materials

Polycrystalline Cr3+ substituted Ba4Zn2Fe36-xCrxO60 (Zn2U) U-type hexaferrite compositions Ba4Zn2Fe36-xCrxO60 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) were fabricated using the sol-gel self-ignition technique. U-type hexaferrite structure was achieved by sintering the powdered samples for 6 h at 1200 °C in a muffle furnace. The phase identification and structural parameters of Zn2U hexaferrites were evaluated by X-ray diffraction peaks of the powdered samples. Lattice parameters (a,c) and unit cell volume decreased upon Cr3+ substitution. The crystallite size was measured between 61 and 57 nm. FTIR spectra revealed the existence of specific absorption (Fe–O) bands at wavenumbers 419 and 539 cm−1. These bands further verify the formation of U-type hexaferrite. SEM micrographs showed the platelet-like morphology of the grains with proper hexagonal structure. X-ray photoelectron spectroscopy (XPS) results confirmed the existence of all metal ions with their corresponding electronic states. The dielectric response of the fabricated Zn2U U-type hexaferrite pellets was investigated at room temperature through a vector network analyzer with a wide frequency band from 1 MHz to 6 GHz. Dielectric constant (εʹ) was increased for the compositions x = 1.0 and 1.5 while dielectric loss (εʺ), tangent loss (tanδ), and ac conductivity (Ϭac) were reduced upon Cr3+ substitution. Single semicircles in the impedance Cole-Cole plots revealed that grain boundaries play a vital role in the conduction process of prepared U-type hexaferrites. Microwave absorption (MW) was improved with Cr3+ substitution. The minimum reflection loss (RL) of −53dB (99.99% MW absorption) at frequency 1.3 GHz was obtained for composition x = 0.5. The dielectric analysis (low losses and high Q-values) of the prepared hexaferrites predicts their appropriate use in high-frequency device applications.

Developing High-Power-Density Electromagnetic Devices with Nanocrystalline and Amorphous Magnetic Materials

With the increasing demand for smaller, lighter, and more affordable electromagnetic devices, there is a growing trend toward developing high-power-density transformers and electrical machines. While increasing the operating frequency is a straightforward approach to achieving high power density, it can lead to significant power loss within a limited volume, resulting in excessive temperature rise and device degradation. Therefore, it is crucial to design high-power-density electromagnetic devices that exhibit low power loss and efficient thermal dissipation to address these challenges. Advanced techniques, such as the utilization of novel and advanced electromagnetic materials, hold great promise for overcoming these issues. Specifically, nanocrystalline and amorphous magnetic materials have emerged as highly effective solutions for reducing power loss and increasing efficiency in electromagnetic devices. This paper aims to provide an overview of the application of nanocrystalline and amorphous magnetic materials in transformers and electrical machines, along with key technologies and the major challenges involved.

Optimizing laser additive manufacturing process for Fe-based nano-crystalline magnetic materials

Fe-based amorphous magnetic alloys offer new opportunities for magnetic sensors, actuators and magnetostrictive transducers due to their high saturation magnetostriction (λs = 20–40 ppm) compared with that of amorphous Co-based alloys (λs = −3 to −5 ppm). Due to the conventional production limitations of Fe-based glassy alloys, including dimensional limitations and poor mechanical properties, this has led to a search for novel fabrication techniques. Recently, the laser powder bed fusion (LPBF) technique has attracted attention for the production of Fe-based magnetic bulk metallic glasses (BMGs) as it provides high densification, which brings about excellent mechanical properties, and high cooling rate during the process. Optimization of process parameters in the LPBF technique have been studied using the volumetric energy input (E), which includes the major build parameters; laser power (P), scan speed (v), layer thickness (t) and hatch spacing (h). This study investigates how the major process parameters influence the physical and magnetic properties of LPBF-processed Fe-based amorphous/nanocrystalline composites ((Fe87.38Si6.85B2.54Cr2.46C0.77 (mass %)). Various process parameter combinations with P (90, 100, 120 and 150 W) and v (700, 1000 and 1300 mm/s) were applied with t of 30, 50 and 70 µm and h of 20, 30, 40, 50 and 60 µm. It was found that bulk density improves as P and t increases, v and h decreases, i.e., high E is necessary, however, 99.45% of bulk density was achieved with E of 61.22 J/mm3 (P = 150 W, v=700 mm/s, h=50 µm and t = 70 µm), which indicates the importance of understanding how parameters affect the specific materials. In addition, the magnetic properties differ significantly due to the nanocrystalline phases present in the microstructure, with their size depending on the process parameters considerably. Owing to the laser scanning nature, the microstructure evolves as molten pools (MP) and heat affected zones (HAZ) due to the high thermal gradient that occurred between laser tracks. MP form around the scans, containing α-Fe(Si) nanograins mainly, whereas HAZ generally contains Fe2B and Fe3Si nanocrystalline clusters. The size and quantities of those nanocrystallites determine the magnetic properties. With the same E (60 J/mm3), v (1000 mm/s) and t (50 µm), only changing P and h caused samples to have different saturation magnetization; 206 emu/gr (P: 90 W and h: 30 µm) and 150 emu/gr (P: 150 W and h: 50 µm). In general, the saturation magnetisation, Ms of LPBF-processed samples changes between 130 and 206 emu/gr, which is much higher than that of feedstock powder (102 emu/gr) due to their nanocrystalline structures. The coercivity (Hc) is in the range of 14.55 and 34.68 Oe, which is considered high for soft-magnetic behaviour (Hc ≤ 12.5 Oe), resulting from the larger crystallite size and the presence of defects (pores and cracks) in the microstructure.

Structure and Magnetic Properties of Fe-B-La-Al Alloy

Nanocrystalline magnetic materials are of great interest in order to meet the needs of electronics and electrical engineering. There are many possibilities to modify the synthesis parameters and chemical composition in order to obtain the most desirable magnetic properties and microstructure. The paper discusses an iron-based alloy with the addition of boron lanthanum and aluminium. The alloy was obtained by induction melting and casting with a melt-spinner. The main purpose of the work was to analyze the structure and properties of both the starting alloys in the form of ingots and the obtained tapes. X-ray diffraction (XRD), scanning electron microscopy (SEM), vibration magnetometry (VSM) and microhardness measurements using the Vickers method were carried out.

Iron Loss and Hysteresis Properties of Nanocrystalline Magnetic Materials Under High Frequency Inverter Excitation

Iron Loss and Hysteresis Properties of Nanocrystalline Magnetic Materials Under High Frequency Inverter Excitation

Modeling and Control of SiC-Based High-Frequency Magnetic Linked Converter for Next Generation Solid State Transformers

The high-frequency magnetic linked solid-state transformer (SST) has the tremendous potential to solve the issues related to interfacing the grid with renewable energy sources and the non-linear loads as well as to provide the additional control functionalities. Several H-bridges are usually connected in series for the medium voltage grid integration of the SST. The number of the dual active bridge modules and the number of high-frequency magnetic links (HFMLs) usually increase with the increase of the number of series connected H-bridges. This increases the possibility of parameter mismatches and system instability. Therefore, the multiple-active bridge (MAB) dc-dc converter concept has been proposed for next generation SST, where multiple H-bridges share the same HFML. This configuration reduces the number of HFML and increases the cross-coupling power transfer capability. However, the design process of the MAB converter involves a multi-physics research in the field of power electronics, magnetics, switching, control, and energy management. In this paper, the detailed analytical modelling and the control technique of the silicon carbide (SiC)-based MAB converter are investigated. The small and large signal average models of the converter are developed and a voltage balance controller is designed for the better understanding of the controller characteristics. The effect of connecting several H-bridges to a single HFML is investigated in detail. Moreover, to reduce the switching loss, the converter topology adopts the SiC-based switching devices instead of the traditional silicon (Si)-based devices and the nanocrystalline magnetic material is used for the HFML design due to its low specific core loss. A scaled down laboratory prototype of the MAB converter is implemented in the laboratory and can be utilized as a basic building block for the next generation SST.

Design of Novel High-Frequency 2-D Magnetic Properties Tester for Nanocrystalline Alloy

To broaden the applications of promising nanocrystalline magnetic materials in electrical engineering at high frequency, the materials must be characterized well at a wide range of frequencies and fields. This paper proposes a novel two-dimensional (2-D) magnetic properties tester up to 20 kHz. The finite element method is used to optimize the tester design by calculating the magnetic field distributions in the specimen and yokes. Considering the dimension and physical properties of the specimen, a particular B - H sensing structure is designed to measure the flux density and field intensity in the specimen. Furthermore, a frequency-domain feedback control system is integrated into the measurement system in order to control the waveform of flux density. Moreover, the paper discusses the factors which impact on the experimental results. This paper demonstrates that the novel tester is reliable to study the magnetic properties of materials. At last, the 2-D rotational magnetic properties of nanocrystalline alloy are preliminary measured.

Manipulation of dipolar magnetism in low-dimensional iron oxide nanoparticle assemblies.

The manipulation of magnetic states in nanoparticle supercrystals promises new pathways to design nanocrystalline magnetic materials and devices. Trench-patterned silicon substrates were used as templates to guide the self-assembly of iron oxide nanoparticles. Grazing incidence small angle X-ray scattering shows that the nanoparticles form a long-range ordered structure along the trench direction while in the direction perpendicular to the trenches, no coherent structure is observable. Electron holography provides evidence of an ordered magnetic state of nanoparticle moments in the remanent state after the application of a saturation magnetic field parallel to the trenches. However, a disordered magnetic state was observed in a perpendicular geometry. Hysteresis loops indicate that the nanoparticle moments form a superferromagnetic state for the geometry parallel to the trenches. Memory effect investigations reveal that the disordered magnetic state corresponds to a collective superspin glass state in the perpendicular geometry, while the superferromagnetic state in the parallel geometry suppresses the superspin glass state.

Core Loss Properties of a Motor With Nanocrystalline Rotor and Stator Cores Under Inverter Excitation

In this paper, we develop and examine permanent magnet synchronous motors (PMSMs) by use of both stator and rotor cores made of nanocrystalline magnetic materials (NMMs). We report core loss properties of the PMSM with the NMM under inverter excitation. In addition, we compare core losses of the PMSM with conventional non-oriented (NO) steel sheets under inverter excitation to discuss the core loss characteristics of the NMM motor. In average, under inverter excitation, the reduction ratio in core loss of the PMSM made of NMM is about 60% as compared with the core loss of the PMSM with NO sheets. In particular, the average decrease obtained by using NMM rotor core instead of NO rotor core is about 30%.

Industrial Approach to Design a 2-kVa Inverter for Google Little Box Challenge

Uninterruptible power system, photovoltaics inverters, home appliances, motor drives, and automotive systems require highly efficient, reliable, and compact single-phase inverters. This paper presents different industrial design approach and experimental performance of high power density (100 W/in3) single-phase inverter with power output of 2 kVA that was presented for Google Little Box challenge. Multiple technical challenges were addressed, different methodologies described to achieve high power density and high efficiency reliable design. High power density was achieved by using the combination of optimized forced air cooled heatsinks, fully digital control, optimized component packaging, and by the introduction of a series active filter that enabled to reduce the size of dc bus capacitors. Low-loss high flux density magnetic materials such as Amoflux powder iron for power inductors and nanocrystalline magnetic materials for electromagnetic interference filter were also used. To minimize inverter switching losses, SiC devices operating at low switching frequency were adopted. Also, an innovative ground current control strategy is devised to minimize the ground leakage currents.

Iron-Based Amorphous Magnetic Properties by Ni Content Tuning and Isothermal Treatment

In this work, we have developed a series of amorphous alloy ribbons of Fe75Co4B13Y4Nb4-xNix(x=0, 0.5, 1, 2, 3 and 4) which were prepared by industrial purity alloy. Besides, the effects of Ni substitution and isothermal annealing on the saturation magnetization (Ms) and intrinsic coercive force (jHc) were systematically investigated. The SQUID-VSM data pointed out the Mshas been increased by Ni content addition with largest enhanced by 57 % from 114 emu/g to 180 emu/g. After quickly annealing at the optimal temperature, the Msreached 199 emu/g and jHcdecreased from 50 Oe to 33 Oe. DSC measurements displayed that this system has a multi-step crystallization in the heating process. Under the premise of maintaining the excellent amorphous forming ability (AFA), the gap between the two crystallization peaks was broadened with Ni addition, which is good to the forming of α-Fe phase at the annealing treatment. And this was also consistent with the X-ray diffractometer (XRD) results. The Scherrer formula calculated results suggested that isothermal annealing has significant effect on size of α-Fe nanocrystals in annealing process, which obvious affect the Msand jHc. The annealing temperature and time can not only affect the precipitation of nano-crystalline, but also control the grain size. Hence, an appropriate annealing process is very important to improve the properties of these iron-based nanocrystalline magnetic materials. In conclusion, the results will help us to understand the influence of Ni elements and isothermal annealing on the microstructure and magnetic of Fe75Co4B13Y4Nb4-xNixamorphous alloys.

Iron-rich (Fe1-x-yNixCoy)88Zr7B4Cu1 nanocrystalline magnetic materials for high temperature applications with minimal magnetostriction

As inductor technology advances, greater efficiency and smaller components demand new core materials. With recent developments of nanocrystalline magnetic materials, soft magnetic properties of these cores can be greatly improved. FeCo-based nanocrystalline magnetic alloys have resulted in good soft magnetic properties and high Curie temperatures; however, magnetoelastic anisotropies persist as a main source of losses. This investigation focuses on the design of a new Fe-based (Fe,Ni,Co)88Zr7B4Cu1 alloy with reduced magnetostriction and potential for operation at elevated temperatures. The alloys have been processed by arc melting, melt spinning, and annealing in a protective atmosphere to produce nanocrystalline ribbons. These ribbons have been analyzed for structure, hysteresis, and magnetostriction using X-Ray diffraction, vibrating sample magnetometry (VSM), and a home-built magnetostriction system, respectively. In addition, Curie temperatures of the amorphous phase were analyzed to determine the best performing, high-temperature material. Our best result was found for a Fe77Ni8.25Co2.75Zr7B4Cu1 alloy with a 12 nm average crystallite size (determined from Scherrer broadening) and a 2.873 Å lattice parameter determined from the Nelson-Riley function. This nanocrystalline alloy possesses a coercivity of 10 A/m, magnetostrictive coefficient of 4.8 ppm, and amorphous phase Curie temperature of 218°C.

나노결정 연 자성 물질로 제조한 코어를 이용한 유도결합기 특성

나노결정 연 자성 물질로 제조한 코어를 이용한 유도결합기 특성

Development of New Amorphous and Nanocrystalline Magnetic Materials for Use in Energy-Efficient Devices

ABSTRACTFe-based amorphous and nanocrystalline soft magnetic alloys have been intensively researched for many applications, including high efficiency electrical distribution and power conditioning applications. New amorphous foils with a saturation magnetization of 1.63T and new nanocrystalline foils with saturation up to 1.9T have been developed. Often these new materials are not drop-in replacements for the conventional competing alloys and require significant changes in processing to be able to fabricate commercial devices.

Iron Loss Reduction in Permanent Magnet Synchronous Motor by Using Stator Core Made of Nanocrystalline Magnetic Material

This paper presents the results of experimental trials carried out on a permanent magnet synchronous motor (PMSM) that uses a stator core made of a nanocrystalline magnetic material (FINEMET). It is demonstrated that the manufactured stator can reduce the PMSM total iron loss by 64% to 75% compared with an equivalent motor using a stator made of conventional non-oriented silicon steel. The experimental results are confirmed by 2-D finite-element analysis.

Soft Magnetic Material Status and Trends in Electric Machines

This paper gives an overview on the history and trends of magnetic materials used in electrical machines and motors. The presented materials include silicon–iron, nickel–iron, and cobalt–iron lamination steels, as well as amorphous and nanocrystalline magnetic materials and soft magnetic composites. Development trends and current usage of these selected materials are presented, giving an outlook on the new magnetic material research with regard to electrical machine applications.

Preparation of nanocrystalline Ce1−xSmx(Fe,Co)11Ti by melt spinning and mechanical alloying

Permanent magnetic materials based on Ce(Fe, Co)12−xTix with the ThMn12 structure are promising candidates for replacing NdFeB magnets. Its intrinsic magnetic properties are not far below the values of Nd2Fe14B, and the high amount of Fe and the fact that Ce is much more abundant and less expensive than Nd encourages the reasonable interest in these compounds. Nanocrystalline magnetic material of the composition Ce1−xSmxFe11−yCoyTi (x=0−1 and y=0; 1.95) has been produced by both melt spinning and mechanical alloying. Alloys containing only Ce as rare earth element (x=0) show coercivities below 77kA/m, while for x=1 Hc,J values up to 392kA/m are reached. Coercivity shows rather an exponential than a linear dependence on the gradual substitution of Ce by Sm.

Preparation of bulk Fe75Nb3Si13B9 amorphous and nanocrystalline alloys by spark plasma sintering

ABSTRACTBulk Fe75Nb3Si13B9 amorphous and nanocrystalline alloy with 10 mm in diameter and 6 mm in height was fabricated by mechanical alloying and spark plasma sintering technology. The phase composition, glass transition temperature (Tg), onset crystallization temperature (Tx), peak temperature (Tp) and super-cooled liquid region (ΔTx) of Fe75Nb3Si13B9 amorphous alloy powders were analysed by X-ray diffraction and differential scanning calorimetry. The phase transition, microstructure, mechanical properties, resistivity and magnetic properties of the bulk alloys at different sintering temperatures were discussed by X-ray diffraction, scanning electron microscope, transmission electron microscope, Gleeble 3500, power conversion efficiency measuring instrument and vibration sample magnetometer, respectively. It is found that with the increase of the sintering temperature at the loading pressure of 500 MPa, the density, compressive strength, micro-hardness and saturation magnetization of the sintering samples were improved significantly, the amorphous phase gradually began to crystallization. Finally, the desirable amorphous and nanocrystalline magnetic materials under the loading pressure of 500 MPa at the sintering temperature of 883 K has a a density of 6.604 g/cm3, compressive strength of 1196.45 MPa and a saturation magnetization of 156.11 emu/g.

Softening and good ductility for nanocrystal-dispersed amorphous Fe–Co–B alloys with high saturation magnetization above 1.7 T

Abstract Fe 80−x Co 20 B x (x = 12–15 at%) alloy ribbons consisting of single bcc phase (12%B), amorphous plus bcc-Fe(Co) mixed phases (13%B) and amorphous single phase (14%B and 15%B) were synthesized by the melt-spinning technique. It is noticed that all the alloy ribbons containing amorphous phase exhibit good bending ductility in the as-spun state and even after annealing which leads to the precipitation of nanoscale bcc-Fe(Co) phase. The amorphous plus bcc-Fe(Co) phase alloys with lower hardness exhibited a number of microcracks in the region near the hardness indentation trace, in addition to distinct slip step markings. The decrease in hardness and the maintenance of ductility in the nanocrystalline state are interpreted to originate from microcrack-induced softening phenomenon. The nanocrystalline alloys also exhibit good soft magnetic properties with high saturation magnetization above 1.7 T in combination with low coercivity of about 20 A/m. The good bending ductility as well as the microcrack-induced softening for the amorphous alloys including nanoscale bcc-Fe(Co) phase is believed to be the first evidence in the long development history of Fe-based nanocrystalline soft magnetic alloys. The finding of the ductile Fe-based nanocrystalline alloys with high saturation magnetization is encouraging for further extension of nanocrystalline magnetic materials.