High-energy Permanent Magnets Research Articles

Hard Magnetic Properties and the Features of Nanostructure of High-Temperature Sm-Co-Fe-Cu-Zr Magnet with Abnormal Temperature Dependence of Coercivity

This paper presents methods and approaches that can be used for production of Sm-Co-Fe-Cu-Zr permanent magnets with working temperatures of up to 550 °C. It is shown that the content of Sm, Cu, and Fe significantly affects the coercivity (Hc) value at high operating temperatures. A decrease in the content of Fe, which replaces Co, and an increase in the content of Sm in Sm-Co-Fe-Cu-Zr alloys lead to a decrease in Hc value at room temperature, but significantly increase Hc at temperatures of about 500 °C. Increasing the Cu concentration enhances the Hc values at all operating temperatures. From analysis of the dependence of temperature coefficients of the coercivity on the concentrations of various constituent elements in this alloy, the optimum chemical composition that qualifies for high-temperature permanent magnet (HTPM) application were determined. 3D atom probe tomography analysis shows that the nanostructure of the HTPM is characterized by the formation of Sm2(Co,Fe)17 (2:17) cells relatively smaller in size along with the slightly thickened Sm(Co,Cu)5 (1:5) boundary phase compared to those of the high-energy permanent magnet compositions. An inhomogeneous distribution of Cu was also noticed in the 1:5 phase. At the boundary between 1:5 and 2:17 phases, an interface with lowered anisotropy constants has developed, which could be the reason for the observed high coercivity values.

Micromagnetic Simulation of Increased Coercivity of (Sm, Zr)(Co, Fe, Cu)z Permanent Magnets

The finite element micromagnetic simulation is used to study the role of complex composition of 2:17R-cell boundaries in the realization of magnetization reversal processes of (Sm, Zr)(Co, Cu, Fe)z alloys intended for high-energy permanent magnets. A modified sandwich model is considered for the combinations of 2:7R/1:5H phase and 5:19R/1:5H phase layers as the 2:17R-cell boundaries in the alloy structure. The results of the simulation represented in the form of coercive force vs. total width of cell boundary showed the possibility of reaching the increased coercivity at the expense of 180°-domain wall pinning at the additional barriers within cell boundaries. The phase and structural states of the as-cast Sm1-xZrx(Co0.702Cu0.088Fe0.210)z alloy sample with x = 0.13 and z = 6.4 are studied, and the presence of the above phases in the vicinity of the 1:5H phase was demonstrated.

The Microstructure and Magnetic Properties of the Strip-Cast (Sm,Zr)(Fe,Co)10.3Ti0.7 Alloy

Sm(Fe,Co,Ti)12-based alloys with low contents of rare-earth elements are promising materials for manufactoring high-energy permanent magnets. The (Sm,Zr)(Fe,Co)10.3Ti0.7 alloy has been produced by strip casting with low quenching rates. The structure and magnetic properties of the alloy were studied by scanning electron microscopy, as well as X-ray and thermomagnetic analysis. The initial inhomogeneous alloy was subjected to solid-solution treatment at 1150°С. The alloy retained a high-anisotropy state typical of the Sm(Fe,Co,Ti)12 phase.

Design considerations for a cycloidal mass analyzer using a focal plane array detector.

With the advent of technologies such as ion array detectors and high energy permanent magnet materials, there is renewed interest in the unique focusing properties of the cycloidal mass analyzer and its ability to enable small, high-resolution, and high-sensitivity instruments. However, most literature dealing with the design of cycloidal mass analyzers assumes a single channel detector because at the time of those publications, compatible multichannel detectors were not available. This manuscript introduces and discusses considerations and a procedure for designing cycloidal mass analyzers coupled with focal plane ion array detectors. To arrive at a set of relevant design considerations, we first review the unique focusing properties of the cycloidal mass analyzer and then present calculations detailing how the dimensions and position of the focal plane array detector relative to the ion source determine the possible mass ranges and resolutions of a cycloidal mass analyzer. We present derivations and calculations used to determine the volume of homogeneous electric and magnetic fields needed to contain the ion trajectories and explore the relationship between electric and magnetic field homogeneity on resolving power using finite element analysis (FEA) simulations. A set of equations relating the electric field homogeneity to the geometry of the electric sector electrodes was developed by fitting homogeneity values from 78 different FEA models. Finally, a sequence of steps is suggested for designing a cycloidal mass analyzer employing an array detector.

Reluctance Synchronous and Flux-Modulation Machines Designs: Recent Progress

Electric machines provide the conversion of mechanical energy to electrical energy (in the generating mode) and vice versa (in the motoring mode), via magnetic energy storage in their airgap (mainly) and in their permanent magnets (PMs) (if any). They are crucial in electric energy conversion and processing and for motion (torque, speed, and position) control in all industries, for better productivity, energy savings, and less harm to environment. Traveling field electric machines are still standard as synchronous and induction machines. The former (synchronous) need dc rotor excitation, or PMs or magnetically salient rotor to create a-fixed-to-rotor traveling field while the latter (induction) implies a cage (or wound) rotor winding. The average torque is nonzero as stator and rotor traveling fields are at standstill with each other. In an effort to take advantage of the variable reluctance concept in producing nonzero magnetic co-energy (and torque) in the machine versus variation of rotor position, better reluctance synchronous machines (RSMs) (line-start or inverter-fed) in terms of efficiency <inline-formula> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> power factor, torque density, and costs without and with assisting PMs have been introduced lately. High magnetic saliency is implicit and requires a high ratio of pole pitch to airgap and a distributed ac stator winding, in the hope to meet the IEC 4, 5 standards of efficiency. On the other hand, better magnetic materials (with lower core losses) and higher fundamental frequency provided by pulsewidth modulation (PWM) static power converter (including silicon carbide (SiC) arrival) up to 1 kHz, in general, and the high price (and scarcity) of high energy PMs have triggered formidable Research and Development worldwide efforts to investigate many machine topologies without and with PMs (mainly ferrites or bonded NdFeB of lower cost), with mainly concentrated ac windings based on the principle of &#x201C;flux-modulation (F-M)&#x201D; provided by variable reluctance (magnetic anisotropy) concept. This article aims to summarize recent progress in reluctance electric machines, without and with PM assistance of synchronous and &#x201C;F-M&#x201D; types in terms of topologies, modeling, design, control, and merits and demerits based on comprehensive-technical and economic performance indexes.

The Structure and Magnetic Properties of (Sm,Er)-Fe-N Powders Prepared by Ball Milling

Nitrides of ‘2:17’ - type based on rare earth metals and iron are of interest as promising magnetic materials for the development of high-energy permanent magnets. The magnetic properties and phase composition of the starting compound Sm1.8Er0.2Fe17, nitride Sm1.8Er0.2Fe17N2.1 and its crushed powders have been investigated. The magnetic measurements of the samples were studied in magnetic fields up to 70 kOe at room temperature. It was found that the introduction of nitrogen atoms into the crystal lattice of the substituted composition (Sm,Er)2Fe17 in combination with the effect of high-energy milling of nitride leads to an increase in the saturation magnetization (σS) and coercive force (HC).

Spin Hydrodynamic Power Generation and Its Influence on Magnetohydrodynamic Effects

This paper reports on generation of electric power using Spin Hydrodynamics (SHD) and its impact on magneto hydrodynamics (MHD). The targeted system uses saltwater as conducting fluid in a channel that is equipped with high energy permanent magnets in that the direction of magnetic field is perpendicular to that of the working fluid. By measuring the induced voltage caused by turbulent motion of conducting fluid (with and without magnetic field) the relationship between the SHD and MHD has been investigated. This system has been further simulated and experimentally verified to validate the claims.

Sm-Co ALLOYS COERCIVITY PREDICTION USING STACKING HETEROGENEOUS ENSEMBLE MODEL

The use of machine learning tools in modern materials science can significantly reduce the duration and cost of developing new materials and improving the properties of existing ones. This is especially true in studying expensive and strategic importance materials like alloys of rare earth metals, which are used to manufacture high-energy permanent magnets. At the same time, single machine learning algorithms do not always provide the accuracy required to solve a particular applied task. Therefore, the current paper aimed to develop an ensemble model for predicting the magnetic properties of Sm-Co system alloys with high accuracy. Based on literature data, we have collected the dataset of the relationship between phase composition, sample state, crystallographic orientation, microstructure, and magnetic properties. We have compared different machine learning algorithms. A stacking ensemble model was designed based on high-precision machine learning algorithms: Neural Networks, AdaBoost, Gradient Boosting, and Random Forest algorithm. The proposed ensemble scheme showed a significant increase in the accuracy for predicting the magnetic properties of Sm-Co alloys on the example of coercivity.

Development of high-coercivity state in high-energy and high-temperature Sm-Co-Fe-Cu-Zr magnets upon step cooling

The work compares the peculiarities of the high-coercivity state formation in the Sm-Co-Fe-Cu-Zr high-temperature and high-energy permanent magnets (HTPM and HEPM) in the course of the heat treatment with the stepwise decreasing temperature from 830 to 400 °C. Two types of magnets with varying Fe concentration, i.e., Sm(Co0.88-xFexCu0.09Zr0.03)7 with x = 0–0.12 (the HTPMs) and Sm(Co0.91-xFexCu0.06 Zr0.03)7.5 with x = 0.24–0.33 (the HEPMs) were studied at different temperatures of heat treatment for phase formation by x-ray diffraction followed by magnetic property measurements. Microstructure characterization was performed using transmission electron microscopy, whereas the three-dimensional elemental distribution at near-atomic scale was obtained using atom probe tomography. In HEPMs, the main increase in coercivity and relaxation of stresses accompanied by intensive enrichment of the 1:5 phase in Cu are observed at high temperatures (Т ≈ 700 °C). In HTPMs, the coercivity monotonously increases in the entire temperature range of the slow cooling from 700 to 400 °C at a rate of 0.5 °C/s. At the temperature close to the Curie temperature (∼550 °C) of the Sm(Co,Cu)5-type phase, the anomaly of the coercivity increment has been observed. The interphase stresses grow and the elemental redistribution appears to be accelerated simultaneously. The non-uniform Cu distribution in the 1:5 phase can be described by the formation of Cu-rich interlayers at the interface of the Sm(Co,Cu)5 and Sm2(Co,Fe)17-type phases.

Structure and magnetic properties of (Sm0.9Zr0.1)Fe11Ti alloys with ThMn12-type structure

Abstract Rapidly increasing demand for high-energy permanent magnets and volatility of the rear-earth market encourage a search of hard magnetic materials that can compete with those based on the Nd2Fe14B phase. Sm-Fe compounds with the ThMn12-type crystal structure are considered as promising candidates for it. However, their synthesis and achievement of theoretically predicted magnetic properties are still challenging tasks that have not been solved yet. This paper addresses this problem. Its aim was to synthesize and to study magnetic properties of the (Sm0.9Zr0.1)Fe11Ti compound with ThMn12-type structure. Initially amorphous alloy was obtained by melt spinning and its subsequent heat treatments were performed. Structural and phase transformations of the (Sm0.9Zr0.1)Fe11Ti alloy with annealing temperatures were studied along with magnetic properties. For the optimally annealed alloy features of magnetization reversal were discussed and temperature dependences of coercivity and maximum energy product were obtained.

Magnetic and Magnetothermal Properties of Hydrogenated Materials Based on Rare Earths and Iron

Iron-rich rare-earth compounds are the basis for high-energy permanent magnets. These include the R(Fe,T)12, R2Fe17, and R2Fe14B intermetallics (R = rare earth; T = Ti, V, Mo, Si) that readily absorb hydrogen, which changes their fundamental and functional characteristics. In this letter, we investigate the stability of the magnetic properties of some hydrides with maximum hydrogen content (namely, TmFe11TiH1 and Tm2Fe17H5.5) in a wide temperature range using high magnetic fields. The magnetic phase transition from the ferrimagnetic to the ferromagnetic state was studied immediately after hydrides were obtained, as well as after one year of storage of the samples at ambient temperature. Only the TmFe11TiH hydride is stable over time. The effect of hydrogen on the magnetothermal properties of the Nd2Fe14B and Nd1Pr1Fe14B compounds and a range of magnetic phase transitions were also investigated. Hydrogenation leads to a decrease in the magnetocaloric effect in all investigated compounds as a result of an increase in the distance between magnetically active ions due to the lattice expansion. A magnetic phase diagram is constructed.

Potentials of locally manufactured wound-field flux switching wind generator in South Africa

The China-based monopoly of high-energy permanent magnet materials used in modern wind generators impact the economic viability and local content value of most wind turbines installed in South Africa, especially large installations. It is possible to design with less expensive excitation technologies using locally-sourced wound-field electromagnets, which might promote local content. This study involves the optimum design performance comparison of the wound-field flux switching machine (WF-FSM) technology based on two variants – Design I and II (D-I and D-II) – the difference being in the arrangement of their DC wound-field coils. The machines are evaluated using finite element analyses (FEA) with optimum performance emphasised on design parameters such as torque density, efficiency and power factor. The selected design targets are meant to improve the performance to cost fidelity of the proposed wind generator variants. In 2D FEA, D-II can produce up to 18.8% higher torque density (kNm/m3) and 17.1% lesser loss per active volume (kW/m3) than D-I. In 3D FEA, the torque density of D-II remains higher at 10.6%, but its loss per active volume increases by 15% compared to D-I. The discrepancy observed in 2D and 3D FEA is due to an underestimation of the end-winding effects in D-II. The power factor of D-II is higher than D-I, both in 2D and 3D FEA, which may translate to lower kVA ratings and inverter costs. A higher total active mass ensues for the studied WF-FSMs than a conventional direct-drive PMSG, but avoiding rare earth PMs translate to significantly lower costs.

Авиационные генераторы с постоянными магнитами

The capacity of aircraft generators reaches several hundred kV×A. For decreasing their specific mass, the generators are designed for limiting rotation frequencies in terms of strength considerations. With increasing the capacity of aircraft generators, their excitation system on the basis of high-energy permanent magnets can be regarded as an alternative to the electromagnetic excitation system. This is because the volume of magnets is several times smaller than that of ferromagnetic poles with windings. Therefore, permanent-magnet generators can be made with a rotor having a smaller mass and a shaft diameter several times larger than in a generator with electromagnetic excitation, due to which it becomes possible to increase their critical frequency and limit power capacity. In addition a rotor with permanent magnets has a higher strength and can be designed for higher rotation frequencies and for a larger number of poles than in case of using electromagnetic excitation. Permanent-magnet generators have higher efficiency values and higher overloading ratios. Rotors fitted with tangential magnets produce higher magnetic induction values in the air gap than the rotors fitted with radial magnets, due to which it becomes possible to make a high-frequency generator with a shorter length while keeping its mass almost unchanged. On the other hand, generators fitted with radial magnets have a stronger rotor and can be designed for higher capacities and rotation frequencies than generators with tangential magnets. Among many design arrangements of rotors, those with nonmagnetic yokes are the simplest ones, whereas arrangements with yokes made of gradient material are the most efficient ones. The most rational application of multipole permanent-magnet generators is in DC systems involving electronic converters.

Mathematical simulations of the electromagnetic system of a subminiature magnetoelectric engine

This paper is devoted to simulations of a valve electric engine with excitation from high-energy permanent rare-earth magnets. A feature of the design of the engine under consideration is that a stator is manufactured using the polycapillary glass-fiber technique. The conductors of the distributed stator winding are placed in holes pm the tube wall. The cylindrical bipolar rotor is made of iron–neodymium–boron. The assumption accepted in the work during the solving the Laplace equation has made it possible to obtain analytical solutions for the magnetic flux, emf, current, electromagnetic torque, and electromagnetic power.

Compare the Direct Torque Control of Permanent Magnet Synchronous Motor withAsynchronous Motor by Increasing Levels of Inverter

Industrial automation have been developed mostly the around of motion control systems in which the controlled electric motor have vital role as heart of system. So, motor control systems with a very good performance to a large extent result in optimum performance of the automation of production that this work is associated with increased production and quality of products. In fact, the performance of modern automation systems, which in terms of speed, accuracy, flexibility and performance are defined, mainly related to control strategies. Recent developments in the power electronics industry has led to a significant increase of power that can exchanged by semiconductor equipment. Despite this, most voltage supported by this equipment is a major obstacle in the applications of medium & high Voltage. Multilevel converters have been introduced for such applications. These inverters have less harmonic distortion compared with standard two-level inverters when they are working a switching frequency. Permanent magnet synchronous motors (PMSM) newly developed with high energy permanent magnet materials if properly controlled can provide fast dynamic and performance with high efficiency and compatibility are very good in various applications. In spite of all these, motor control including PMSM control is a challenge due to dynamic of very fast motor and very linear models of machines. So, much of motor control development includes extraction of appropriate mathematical models. Modelling & simulation is performed on MATLAB\SIMULINK software.

Magnetic and electronic properties of hard|soft magnetic interface in (YCo5|Co)[0001] and (YFe5|Co)[0001] superlattices

The physics of interface between the hard- and soft-magnetic phases play an important role in determining the performance of exchange-coupled multilayers towards development of high-energy permanent magnets. Herein, we employed first principles calculations to understand the magnetic and electronic properties of exchange-coupled hard and soft magnetic superlattices of (YCo5|Co)[0001] and (YFe5|Co)[0001]. The calculated spin moment and exchange-coupling parameter for the (YFe5|Co)[0001] superlattice are found to be higher than that of the (YCo5|Co)[0001]. The results of present study suggest that the (YFe5|Co)[0001] superlattice can be used as exchange-coupled magnet with enhanced magnetic performance.

Research of Dysprosium, Terbium and Neodymium Oxides Fluoration

Production of high energy permanent magnets (HEPM) on the basis of rare-earth metals is one of leading knowledge intensive branches of world industry. Raw materials for production of magnets are magnetic alloys. In order to increase magnetic features scientists implement the additives of certain metals and their compounds, such as dysprosium and terbium additives in substantial amounts – up to 7-8 %.Within the framework of a ladle fluoride technology of HEPM manufacturing on the basis of a system Nd-Fe-B, developed by authors, scientists implement the additives of dysprosium and terbium fluoride, by virtue where of there was conducted a research on fluoration kinetics of corresponding oxides by elemental fluorine. The present article quotes results of such research and defines main kinetic parameters of examined processes – diffusion coefficient, kinetic constant and activation energy. Aiming to cost reduction of fluoride manufacture ammonium fluoride was used as a fluorinating agent by the example of fluoration of neodymium oxide.

Structural and Magnetic Properties of New Type Ca&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;Sr&lt;sub&gt;1-&lt;/sub&gt;&lt;i&gt;&lt;sub&gt;x-y&lt;/sub&gt;&lt;/i&gt;La&lt;i&gt;&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt;O•&lt;i&gt;n&lt;/i&gt;Fe&lt;sub&gt;(2n-z)/&lt;/sub&gt;&lt;i&gt;&lt;sub&gt;n&lt;/sub&gt;&lt;/i&gt;Co&lt;i&gt;&lt;sub&gt;z/n&lt;/sub&gt;&lt;/i&gt;O&lt;sub&gt;3&lt;/sub&gt; Magnets

Considering that Ca2+has the similar ion radius and the substituted ability as Sr2+and Ba2+but the same family, CaxSr1-x-yLayO•nFe(2n-z)/nCoz/nO3ferrites have been synthesized by the conventional ceramic process. Structure and magnetic properties of CaxSr1-x-yLayO•nFe(2n-z)/nCoz/nO3compounds have systematically been investigated by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM) andB-Hhysteresis curve measurements. Several compositions are selected to investigate the formation of M phase with the joint replacement of Ca-La-Co. It is found that the formation mechanism is based on the replacement of Sr2+by La3+plus Ca2+and the charge compensation by Co2+. In futher results, the unexpectedly intrinsic coercivity of 436 kA/m and residual flux density of 0.445 T were obtained. In terms of material preparation, we believe that CaxSr1-x-yLayO•nFe(2n-z)/nCoz/nO3is effective in the production of future high energy permanent magnets.

Efficiency estimation for permanent magnets of synchronous wind generators

Abstract Application of wind generators opens wide possibilities for raising the efficiency of low- and medium-power wind generators (WGs). The mass of generators in the proposed version is smaller, their reliability higher, while maintenance costs are lower. At the same time, the use of high-energy permanent magnets in generators of enhanced power comes up against some obstacles, which can be overcome through proper orientation of magnetization at creation of a magnetic field in the airgap of electrical machine. In this regard, it might be preferable to use magnets with indirect action on the airgap instead of those with direct action. A convincing example of the former variant is a generator with tangentially oriented magnetization of permanent magnets. In the work, an attempt is done to prove the advantages of such installation in modern low- and medium-power WGs

High-specific output bidirectional moving magnet actuator for use in active vibration control of rotorcraft

A high-specific output, moving magnet actuator topology suitable for active vibration control in a helicopter rotor blade is presented. Within the constraints imposed by the potential application the electromagnetic design is optimised for minimum weight using parametric 2D finite-element field analyses coupled to a particle swarm optimisation. A particular attribute is that the pole shape has been optimised to ensure that restoring magnetic forces act on the effector at zero current. A mathematical model is developed to study the dynamic performance of the device. A prototype was constructed from cobalt iron laminates and high-energy product permanent magnets and is used to validate the design. Tests undertaken on this prototype demonstrate a bidirectional-specific force and work capability of 320 N/kg and 0.26 J/kg, respectively, metrics which compare favourably with piezoelectric alternatives proposed for rotorcraft active vibration control.