Permanent Magnet Powders Research Articles

Investigation of the Impact of SmFeN Doping on the Anisotropic NdFeB/SmFeN Composite Magnets

By incorporating various types of permanent magnetic powders, composite magnets with cost-effectiveness and a wide range of magnetic properties can be achieved. In this study, the anisotropic composite magnets were fabricated using the hot press forming method, which involved blending neodymium iron boron (NdFeB) powder and samarium iron nitrogen (SmFeN) powder. The experiment demonstrated that the magnet density reaches its maximum point when the doping level of SmFeN reaches 20 wt.%, aligning remarkably well with the corresponding theoretical value of 19.22 wt.% achieved through a cubic stacking arrangement. In the absence of an applied magnetic field or under a sufficiently high oriented magnetic field (3 T), the remanence variation pattern in composite magnets doped with different amounts of SmFeN aligns consistently with the density pattern, yielding a maximum value of 20%. However, in the actual solidification process, the orientation field is insufficient (e.g., 1.5 T), necessitating a doping amount that exceeds the value corresponding to peak density by 28% to achieve optimal remanence. This observation suggests that the incorporation of a higher proportion of small-sized and relatively low coercivity SmFeN magnetic powder can effectively facilitate the rotational alignment of neighboring large-sized NdFeB magnetic powder under weak magnetic fields, thereby inducing a synergistic effect.

The distribution coefficients of Nd3+ and Y3+ between 0.1 and 2.1 M HNO3 and HDEHP at 298.15 K

Rare earth metals are considered to be some of the most critical raw materials on the planet due to their use in many products and technologies, the difficulty in isolating the individual elements from ores and each other, and the market restrictions that threaten their supply. However, despite this, the recycling rates for rare earth metals remain low. Hydrometallurgy has been proposed to hold the greatest potential for the recovery of rare earth metals from waste materials. However, the design of hydrometallurgical processes for the recovery of rare earth elements from waste requires a good understanding of the behaviour of the rare earth metals between different phases.In this study, the distribution coefficients of two rare earth metals, yttrium, and neodymium, between an organic solvent; bis(2-ethylhexyl) phosphate, diluted in n-dodecane at between 0.25 M and 1 M; and an aqueous nitric acid solution at concentrations of between 0.1 M and 2.8 M were measured. Distribution measurements were performed using a series of liquid–liquid extraction cells at a constant temperature of 298.2 K. The concentration of the rare earth metals was measured using ICP-OES analysis. The distribution coefficients and the acid concentration were found to be inversely related to each other. Conversely, the distribution coefficients were directly proportional to the concentration of the solvent in the organic phase.The data reported in this paper will be used to design a counter-current liquid–liquid extraction column for the recovery of neodymium from waste permanent magnet powder.

Preparation and Deposition of Pr–Fe–B Permanent-Magnet Powder Using Pulsed Laser

We have already prepared a thin permanent magnet with the thickness of sub-millimeter by obtaining magnet powders using a pulsed laser deposition (PLD) method. In the article, the PLD followed by a flash annealing enabled us to deposit isotropic Pr–Fe–B magnet powders with coercivity $(H_{\mathrm {cj}})> 1000$ kA/m on a stainless thin shaft applicable to a miniaturized motor. Observation on the surface of Pr–Fe–B magnets and evaluation on the mechanical behavior were carried out. Since the surface of a Pr–Fe–B magnet was coated by a Pr oxide through an annealing process, their magnetic properties did not degrade after one year. We also confirmed that the Pr–Fe–B magnet has the possibility to be applied to a micro-magnetization process. It was clarified that the powder technology using the PLD is useful to propose a thin magnet applicable to a next-generation small motor.

Batch-fabrication and characterization of miniaturized axisymmetric electropermanent magnets

This work describes the simulation, batch fabrication, functional demonstration, and magnetic field/force characterization of highly miniaturized ∼3.8 mm3 axisymmetric electropermanent magnets (EPMs). Two different bonded high-coercivity, rare-earth permanent magnet powders (∼15 µm Sm2Co17 particles and 6 µm NdFeB particles) were evaluated for the fabrication of the fixed magnets in the EPM, reaching latching force on/off ratios of 191:1 and 303:1 respectively. Compared to conventional side-by-side architecture, the axisymmetric design provides: 1) symmetric magnetic field along the magnetization axis, as opposed to the asymmetric fields in the typical transverse configuration, 2) higher and controllable latching force in a smaller volume, and 3) a path for further batch-microfabrication and system integration.

The Role of Wheel Surface Quality on Structural and Hard Magnetic Properties of Nd–Fe–B Permanent Magnet Powders

Rapidly solidified Nd15Fe77B8 magnetic alloy powders have been produced by using melt-spinning method. Different wheel surface structures such as smooth and textured were tested to investigate the effect of wheel surface morphology on powder shape, microstructure, Curie temperature, and magnetic properties. Produced powders were subjected to surfactant-active ball-milling process for powder size reduction and to enhance magnetic and thermal properties. Generally, flaky-shaped powders were obtained with smooth surface wheels and spherical-shaped powders were produced with textured surface wheel. Microstructure of flaky-shaped powders consisted of polygonal fine equiaxed grains with an average grain size of 0.45 µm. Spherical-shaped powders had dendritic microstructure regardless of their sizes. Both flaky and spherical powders involved hard magnetic Nd2Fe14B phase located in the grain interior and a fine network of Nd-rich phase at the grain boundaries. Surfactant-active ball-milling process significantly contributed to magnetic and thermal properties of powders. The coercivity values of flaky-shaped powders milled for 90, 150, 210, 270, 330, and 390 min milling times were substantially higher than that of spherical-shaped powders milled for the same period of times. The Curie temperatures of Nd15Fe77B8 ingot alloy and spherical- and flaky-shaped powders were found as 279, 305, and 321 ∘C, respectively. On the other hand, the Curie temperatures of flaky- and spherical-shaped powders milled for 390 min were measured as 331 and 311 ∘C, respectively.

Soapnut extract mediated synthesis of nanoscale cobalt substituted NdFeB ferromagnetic materials and their characterization

Neodymium iron boron (NdFeB) permanent magnets have high energy product with suitable magnetic and physical properties for an array of applications including power generation and motors. However, synthetic routes of NdFeB permanent magnets involve critical procedures with high energy and needs scientific skills. Herein, we report on soapnut extract mediated synthesis of nanoscale cobalt substituted NdFeB (Co-NdFeB) permanent magnetic powders (Nd: 15%, Fe: 77.5%, B: 7.5% and Co with molar ratios: 0.5, 1, 1.5 and 2). A 10 ml of 10% soapnut extract was added to 90 ml of respective chemical composition and heated to 60 °C for 30 min and aged for 24 h. The dried powder was sintered at 500 °C for 1 h. The characterization of the prepared nanoscale Co-NdFeB magnetic powders was done using the techniques such as Dynamic Light Scattering (DLS for size and zeta potential measurements), X-ray diffraction (XRD) for structural determination, Scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS) for surface morphological and elemental analysis, Fourier transform infrared spectroscopy (FT-IR) for the identification of functional groups associated and hysteresis loop studies to quantify the magnetization. The results revealed that particles were in irregular and tubular shaped and highly stable (Zeta potential: −44.4 mV) with measured size <100 nm. XRD micrographs revealed a tetragonal crystal structure and FTIR showed predominant N–H and O–H stretching indicates the involvement of these functional groups in the reduction and stabilization process of Co-NdFeB magnetic powders. Hysteresis studies signify the effect of an increase in Co concentration.

First report on soapnut extract-mediated synthesis of sulphur-substituted nanoscale NdFeB permanent magnets and their characterization

Biosynthesis of nanoscale materials has its own advantages over other physical and chemical methods. Using soapnut extract as reducing and stabilizing agent for the synthesis of inorganic nanoscale materials is novel and has not been exploited to its potential so far. Herein, we report for the first time on the effects of sulphur substitution on soapnut extract-mediated synthesis of nanoscale NdFeB (S-NdFeB) permanent magnetic powders (Nd 15%, Fe 77.5%, B 7.5% and S with molar ratios: 0.1, 0.2, 0.3, 0.4, and 0.5). To synthesize, a 10 ml of 10% soapnut extract was added to 90 ml of respective chemical composition and heated to 60 °C for 30 min and aged for 24 h. The dried powder was sintered at 500 °C for 1 h. The characterization of the as-prepared nanoscale S-NdFeB magnetic materials was done using the techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS for size and zeta potential measurements) and vibrating sample magnetometer (VSM)–hysteresis loop studies. The results revealed that particles were highly stable (with a negative zeta potential of 25.7 mV) with irregular and spherical shape (with measured hydrodynamic diameter 6.7 and 63.5 nm). The tetragonal structures of the formed powders were revealed by XRD micrographs. Hysteresis loop studies clearly indicate the effect of S concentration on the enhanced magnetization of the materials.

Application of a novel flash-milling procedure for coercivity development in nanocrystalline MnAl permanent magnet powders

This study shows the possibility of dramatically tuning microstructure and magnetic properties of gas-atomized Mn54Al46 particles by milling for an unprecedented duration of 30 s. This flash-milling procedure avoids the high temperatures typically achieved in lengthy conventional ball milling experiments, and is efficient to reduce the crystallite size to the nanometer scale, induce microstructural strain and ease phase transformations. This leads to the creation of the τ-MnAl phase providing magnetization, and the β-Mn phase operating in the mechanism for coercivity development. Post-annealing at 355 °C for 10 min results in a coercivity about three times larger than that of the annealed starting material, and thus reduces the optimum processing temperature in 75 °C by comparison with that needed for the latter to achieve the best combination of magnetic properties. A maximum obtained coercivity exceeding 5 kOe compares to the highest values reported to date for isotropic MnAl powders attained after milling for times above 20 h. This high coercivity is of additional relevance for further consideration of this material as a hard magnetic phase in the preparation of nanocomposite permanent magnets. The combination of the cost-efficient synthesis technique (gas-atomization) and novel processing route (flash-milling) for the production of low-cost isotropic nanocrystalline MnAl powders, opens new paths to the possible mass production of these materials as an alternative to permanent magnets containing critical raw materials.

Synthesis of AlNiCo core/shell nanopowders

Magnetic core/shell nanostructures have been recently received much interest owing to their utmost potential in permanent magnetic applications. In the present work, AlNiCo permanent magnet powders were synthesized by ball milling and a core/shell nanostructure was obtained using RF induced plasma. The effects of particle size and nanoshell structure on the magnetic properties were investigated in details. The coercivity of AlNiCo powders was found to increase with decreasing particle size, exclusively nanopowders encapsulated with Fe3O4 shell showed the highest coercivity values. The shell structure produced during plasma reaction was found to form a resistant layer against oxidation of metallic nanoparticles.

Application of Mechanochemical Synthesis to Manufacturing of Permanent Magnets

Synthesis of permanent magnet powders through mechanically and thermally activated reduction of metal oxides with calcium, which allows for the production of fine single crystal particles, may contribute to the ongoing search for alternatives to the Nd-Fe-B magnets. The reviewed efforts demonstrate the possibilities to prepare (1) high-coercivity SmCo5 nanoparticles for anisotropic exchange-coupled nanocomposites, (2) YCo5/LaCo5 powders with the magnetic properties superior to those obtained through other manufacturing methods and (3) submicron Mn-Bi powders with large concentration of the MnBi phase. Also discussed are less successful attempts to prepare Mn-Al, Zr-Co and Hf-Co hard magnetic alloys in which the principal phases are known or likely to be metastable.

Evolution of structural and magnetic properties due to nanocrystallization of mechanically milled amorphous Pr-Co-B powders

Pr2Co14B permanent magnet powders were prepared by mechanical milling of an arc-melted ingot. X-ray diffraction analysis revealed the presence of the 2:14:1 phase after 1 h of milling which transformed into an amorphous phase with additional milling time. Increasing the milling time also lowered the intrinsic coercivity while the saturation magnetization increased up to 105 emu/g. Differential scanning calorimetry measurements revealed a crystallization temperature of around 560 °C. Upon annealing 30 h of as-milled amorphous powders between 500 and 900 °C, we observed the precipitation of the 2:14:1 phase. The optimum post-milling annealing temperature was 600 °C with an intrinsic coercivity of 7 kOe and maximum energy product of 6 MGOe.

Magnetic properties and scale-up of nanostructured cobalt carbide permanent magnetic powders

CoxC magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co2C and Co3C phases possessing magnetization values exceeding 45 emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of surfactants, reaction temperature, and reaction duration on the crystallographic structure and magnetic properties of CoxC, while tetraethylene glycol was employed as a reducing agent. The role of the ratios of Co2C and Co3C phases in the admixture magnetic properties is discussed. The crystallographic structure and particle size of the CoxC nanoparticles were characterized by X-ray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 g per batch was demonstrated with no significant degradation of magnetic properties.

Leaching kinetics of neodymium in sulfuric acid from E-scrap of NdFeB permanent magnet

The leaching kinetics of neodymium in NdFeB permanent magnet powder was analyzed for the purpose of recovery of neodymium in sulfuric acid (H2SO4) from E-scrap (electric scrap) of NdFeB permanent magnet powder treated by oxidation roasting to form a reactant. The reaction was conducted with H2SO4 concentrations ranging from 2.5 to 3.5M, a pulp density of 110.8 g/L, an agitation speed of 750 rpm, and a temperature range of 30 to 70 °C. After 4 h of leaching, the neodymium content in the E-scrap powders was completely converted into a neodymium sulfate (Nd2(SO4)3) solution phase in H2SO4 in the condition of 70 °C and 3.0M H2SO4. Based on a shrinking core model with sphere shape, the leaching mechanism of neodymium was determined by the rate-determining step of the ash layer diffusion. Generally, the solubility of pure rare earth elements in H2SO4 is decreased with an increase in leaching temperatures. However, the leaching rate of the neodymium in E-scrap powders increased with the leaching temperatures in this study because the ash layer included in the E-scrap powder provided resistance against the leaching. Using the Arrhenius expression, the apparent activation energy values were determined to be 2.26 kJmol−1 in 2.5M H2SO4 and 2.77 kJmol−1 in 3.0 M H2SO4.

A study of hybrid bonded magnets of Sm-Co and Sr-ferrite using a mixture design

The present paper deals with the study of hybrid polymer bonded magnets of strontium ferrite and samarium cobalt. A three-component constrained mixture design, employing ten runs for the experiment, was used. The magnetic properties such as remanence (Br), coercivity (Hc), and energy product (B.H)max were used as the response. The results are modeled in the form of mathematical equations to predict the response as a function of the samarium cobalt and strontium ferrite permanent magnet powders percentage and polymer content. The predicted results from the obtained mathematical equation are compared with the experimentally measured values.

Coercivity Enhancement in Nd2Fe14B Permanent Magnetic Powders through Rotating Diffusion Process with DyHxPowders

Nd 2 Fe 14 B permanent magnetic powders ( i H c = 9.2 kOe, B r = 12.2 kG) were produced by HDDR process. Their coercivity was enhanced to 12.6 kOe through the grain boundary diffusion process with dysprosium hydride (DyH X ). DyH X diffusion process was optimized through rotating diffusion process, resulting in distinct phases rich in Nd and Dy observable by field emission scanning microscopy and transmission electron microscopy. The mechanism of coercivity enhancement that resulted in restrain the coupling effect between Nd 2 Fe 14 B grains is also discussed.

Injection molded asymmetric spur gear — development and preliminary performance evaluation

Innovative gear designs are essential to meet the increasing demands of high load carrying capacity, high endurance, low cost, long life, and high speeds in automobile, aerospace, and wind turbine industries. Conventional gears are having symmetric teeth; however most of the applications necessitate power/motion transmission in one direction. This unidirectional transmission leads to the design of asymmetric teeth in a gear. Extensive research work on design and optimization and asymmetric gear tooth profile for improved bending and contact strength has been attempted. However, very little experimental investigation has been attempted and no work has been attempted in the experimental investigation of asymmetric polymeric gears. In this work, unreinforced polypropylene material is injection molded for the asymmetric spur gears. Gears are molded to the size of 3 mm module, 18 number of teeth and having pressure angle of 34° and 20° at drive and coast side respectively. To examine surface durability and the kinematic characteristics of asymmetric gear, a gear test rig is developed in the laboratory with permanent magnet direct current motor and powder clutch dynamometer as driving and power absorption unit with necessary inline torque sensors and non contact temperature sensor. Preliminary transmission efficiency and surface temperature of test gears promises wide scope for asymmetric composite gears in motion transmission application. Due to the increase in pressure angle at drive side of gear tooth, relative sliding velocity found to decrease and hence asymmetric gear exhibit superior gear pair efficiency and less surface temperature.

&lt;I&gt;γ&lt;/I&gt;-Ray Irradiation on Microsized Nd-Fe-B and Sr-Ferrite Magnets at Low Temperature

The gamma-ray irradiation on microsized Nd-Fe-B and Sr-Fe permanent magnet at low temperature and room temperature was investigated. The change of shape and magnetic properties of two kinds of magnet powder before and after irradiation at low temperature was measured. The crystal structure of each permanent magnet powders was analyzed using X-ray powder diffraction (XRD) and the size and shape were characterized by scanning electron microscope (SEM). The changed magnetic properties of magnet such as saturation magnetization (M(s)) and coercivity (H(c)) were measured by VSM.

Effect of different production methods on the properties of permanent magnet powders

The paper examines how the properties of permanent powder magnets depend on their chemical and phase composition and production methods. It is shown that magnetic materials produced by powder metallurgy methods can compete with YUNDK-15.18 industrial cast alloys.

A novel elastomer-based magnetoresistive accelerometer

In this paper, we present a novel type of biaxial accelerometer based on a polydimethylsiloxane (PDMS) structure as the mass–spring system and using magnetoresistive (MR) sensors as the detection method. The proof mass of the sensor is a mushroom-shaped polymer magnet made of PDMS filled with permanent magnet powder, whose minute movement under lateral acceleration is precisely sensed by a set of MR sensors. The device aims at consumer electronics applications of low g range and low frequency, such as inclination measurements and motion sensing. An experimental device has been successfully fabricated which showed a linear transfer curve without significant hysteresis. A sensitivity of 0.32mV/(Vg) was obtained.

The influence of concentration of Nd-Fe-B powder in composite coating of optical fiber to the sensibility to external magnetic field

Multi-mode optical fiber with magnetic composite coating was investigated as an optical fiber sensor element (OFMSE) for magnetic field sensing The composite coating was formed with dispersions of permanent magnet powder of Nd-Fe-B in poly (ethylene-co-vinyl acetate)-EVA solutions in toluene. The influence of the applied external magnetic field on the change of intensity of the light signal propagate trough developed optical fibers sensor element was investigated. In this paper the influence of the content of magnetic powder in the composite coating on the optical propagation characteristics of optical fiber were particularly investigated.