SmCo Magnets Research Articles

Experimental Study on the Separation of Selected Metal Elements (Sm, Co, Fe, and Cu) from Nitric Acid Leachate Using Specific Precipitants

As more countries emphasize the importance of the circular economy, recycling resources from waste has become increasingly crucial. This study proposes a novel separation process for SmCo magnets, which can separate and recover metals by precipitation, thus reducing the amount of solvent used. The precipitation process involved the use of Na2SO4, NH4OH, and H2C2O4 to separate Sm, Fe, Cu, and Co, resulting in high precipitation efficiencies of 96.11%, 99.97%, 93.81%, and 98.15%, respectively. Moreover, the recovered metals can be directly used to create magnets after calcination, making this process a step towards achieving a circular economy.

Recovery of samarium and cobalt/iron oxide from SmCo magnets through acid baking and water leaching

AbstractRare earth elements (REEs) and cobalt (Co) are listed as critical raw materials because of their importance in global industrial production growth, high supply risk, and economic significance. The recovery of Co and REEs from secondary resources is therefore proposed as a key countermeasure to address this concern. In this study, a straightforward process that integrates acid baking and water leaching is proposed for the recovery of samarium (Sm) and Co from scrap SmCo magnets. Firstly, the chemical composition of SmCo magnets is revealed by ICP-OES and XRF. The Taguchi experimental design technique is employed to optimize nitric acid baking and water leaching. Based on the thermal decomposition behavior of Co, Fe, and Sm, the acid baking temperature is studied for the conversion of metal nitrates, excluding REEs nitrates, into metal oxides. The optimal conditions for acid baking and water leaching are identified, and a reactor for the pilot-scale acid baking process is proposed. The optimum parameters are tested with the proposed reactor.

Lamellar Zr-rich phase and its influence on coercivity for Sm(CoFeCuZr)z magnets

The precipitation-hardened Sm-Co permanent magnets relied on the pinning of nanocellular structures to achieve high coercivity, and have an irreplaceable position in high-temperature applications. In this article, by employing micromagnetic simulations and magnetic domain observations, the pinning behavior of lamellar phases (Z-phase) were investigated, which has not been well understood before. The results showed that the Z-phase can serve as a strong pinning position, but due to the parallel lamellar distribution, the magnetic domain walls can move around. Additionally, the effect of Z-phase on coercivity was achieved by changing the morphology of magnetic domain walls during magnetization reversal. For attractive pinning, the coercivity was reduced by the Z-phase, while for repulsive pinning, the Z-phase increased the coercivity when γZ＜0.54γH. Our findings can provide a novel understanding of the coercivity mechanism of precipitation-hardened Sm-Co permanent magnets.

Atomic-scale revelation of Cu diffusion mechanism in high-performance Pr-doped 2:17-type SmCo magnets

The coercivity of 2:17-type SmCo magnets is mainly determined by the gradient distribution of Cu within the cell boundary phase. However, the fundamental migratory behavior and driving force causing such Cu distribution remains unclear. In this work, the phenomenon of Cu enrichment at the lamellar/intracellular interface is reported at the atomic scale, and a new Cu diffusion mechanism of 2:17-type SmCo magnets is proposed via combining microstructure characterization with first-principles calculation. Our study indicates that Cu will migrate from the intracellular phase to the lamellar/intracellular phase interface following the migration of twin boundary, and then diffuses further along the lamellar phase interface to the cell boundary, achieving the expected Cu-rich cell boundary structure. Doping Pr results in a reduction of Cu substitution energy in the lamellar phase, leading to a decreased driving force during the subsequent Cu diffusion. As a result, the Cu does not completely diffuse into the cell boundary phase there is Cu enrichment at the interface between lamellar and intracellular phases. The Cu concentration of the cell boundaries could be increased in 2:17-type SmCo magnets by reasonable designing the substitution energy difference of intracellular phase, lamellar phase and cell boundary phase that promote Cu diffusion to cell boundary. Our study sheds light on the control of Cu segregation in magnets and a new strategy for enhancing the magnetic performance of 2:17-type SmCo magnets.

Modelling PM dipoles with longitudinal field gradient for SILA facility

Computational models are described which were built for parametric simulations of permanent magnet (PM) dipoles with a longitudinal field gradient. The dipoles will be used as bending magnets in the synchrotron facility SILA, a new project of the National Research Center “Kurchatov Institute”. The dipoles employ a Sm-Co permanent magnet material and pure iron. The need for high magnetic performance and anticipated interference between neighbouring components is a challenge for design and construction of the magnet system. For this reason the magnet designs must rely on precision 3D simulations. The dipoles are described in detail with parameterized models. Parametric simulations are to be applied at all stages of the project till the commissioning to provide realistic prediction of the magnet behaviour.

Effect of solution temperature on the microstructure of 2:17 type SmCo magnets

The exceptional magnetic properties of 2:17 type SmCo magnet material is the results of its unique cellular structure. We conducted a systematic analysis of the evolution of the solid solution temperature on the microstructure of both the solid solution precursor and the final magnet, and revealed the distribution of elements affect by the magnet's properties. The findings show that a considerable number of short-range low-order microregions are observed with discontinuous alignment orientations, and overlapping zones are produced in the solid solution precursor by low-temperature solid solutions. The aging process makes these regions challenging to organize, and a lot of 2:17 R phases form close to 1:5 H cell boundary phase and grain boundary, which impedes the enhancement of magnetic characteristics. Increasing the solution temperature promotes the diffusion of Cu and Fe elements, accelerating the ordering of the 2:17 R phase and aiding in the creation of a cellular structure. The phase evolution of the 2:17 type SmCo magnet can be better understand by referring to the previously conducted research on the impact of solid solution temperature on the microstructure of the solid solution precursor and final magnet.

Simultaneous enhancement of magnetic properties and flexural strength in 2:17 type SmCo magnets induced by spherical WO3 particles doping

The influence of spherical WO3 particles doping on the flexural strength and magnetic properties of Sm(CobalFe0.23Cu0.07Zr0.02)7.8 magnets was investigated. As the doping amount increased from 0 wt% to 2.0 wt%, the magnetic properties initially exhibited an increase followed by a decrease, with coercivity increasing from 32.77 kOe to 36.01 kOe and remanence increasing from 11.16 kGs to 11.28 kGs at a doping amount of 0.5 wt%. Moreover, the flexural strength consistently rose from approximately 80 MPa to 127 MPa, representing a significant increase of about 59 %. The presence of WO3 particles optimizes the magnet’s orientation and Cu distribution in the cell boundary phase, thereby enhancing both remanence and coercivity. Additionally, a significant decrease in grain size from 72.04 μm to 33.41 μm was observed, accompanied by a noticeable increase in the content of Sm2O3 phase, which positively contributes to the enhancement of flexural strength. Our research presents a novel technical approach for simultaneously enhancing the magnetic and mechanical properties of 2:17 type SmCo magnets.

An Integrated Hydrometallurgical Treatment and Combustion Process for Sustainable Production of Sm2O3 Nanoparticles from Waste SmCo Magnets

Samarium (Sm), as one of the rare earth elements (REEs), has gained significant attention in the production of SmCo magnets due to their high corrosion and oxidation resistance, as well as their high-temperature stability. SmCo magnets find applications in various industries, including but not limited to national defense, aerospace, military, and medical equipment. Sm and Co have been classified as a critical metal due to its economic importance and supply risk. Recovering Sm from SmCo magnets is an effective method to ensure a stable supply. The present study investigates an integrated hydrometallurgical treatment and combustion process for the preparation of rare earth oxide (Sm2O3) powders from SmCo. Initially, SmCo powders is exposed to nitric acid, and the resulting slurry is selectively oxidized at 250 °C to obtain Sm(NO3)3, Co2O3, and Fe2O3. Subsequently, the selectively oxidized powders are leached with water to extract Sm. Sm2O3 powders are produced from the obtained leaching solution using an energy- and time-efficient solution combustion process. In this process, once the ignition point of the leaching solution-citric acid complex is reached, combustion occurs and concludes within a short time. The combusted powders are then calcined at different temperatures to produce crystalline Sm2O3 powders. Finally, the optimal conditions for the production of Sm2O3 are identified, and the produced powder is characterized through XRD and FESEM analysis.

Recovery of valuable metals from SmCo magnets through sulfation, selective oxidation, and water leaching

ABSTRACT Samarium-cobalt (SmCo) magnets, comprised of rare earth elements (REE), and cobalt (Co) are widely employed in diverse sectors such as aerospace, medical, defense, automotive, and more due to their unique properties such as outstanding high-temperature resistance, superior corrosion resistance, a higher Curie temperature, and high energy density. REE and Co are on the critical metals list for many years, along with increased production costs and challenges. With the increasing amount of waste SmCo, the recycling of these magnets has gained importance. This study investigates the recycling of SmCo magnet scraps through sulfation, selective oxidation, and water leaching. The effect of experimental parameters, such as powder/acid concentration, selective oxidation temperature, selective oxidation time, solid/liquid ratio and leaching time for water leaching are studied in detail. The optimal parameters are determined: 800°C selective oxidation temperature, 1-h selective oxidation time, 1/3 g/ml magnet: acid ratio, 2-h water leaching time and 1/20 water leaching s/l ratio. Under the optimum conditions the extraction efficiency of Sm reached approximately 65%, The solubility of Fe, Co, and Cu metals in the solution is negligible.

Structure and magnetic properties of SmCo4.5Cu0.3Sn0.16Ga0.04 ribbons melt-spun at 10–40 m/s

The anisotropic Nd-Fe-B magnets prepared by as-spun ribbons using hot-pressing and hot-deformation methods have been commercialized. However, the Sm-Co magnets face challenges in obtaining strong c-axis deformation textures due to the absence of a low-melting intergranular phase to facilitate grain deformation. After simultaneously adding gradient low-melting metals of Cu, Sn, and Ga to SmCo5 alloy, SmCo4.5Cu0.3Sn0.16Ga0.04 ribbons were prepared by melt-spinning at 10–40 m/s. These ribbons comprise the Sm(Co, M)5 main phase, Sn-rich Sm2(Co, M)7 grain boundary phase, and Sm117Co55.58Sn115.94-type particulate phase. Notably, the ribbons melt-spun at 30 m/s contain the highest Cu, Sn, and Ga content in the grain boundary phase, making them most suitable for producing hot-pressed and hot-deformed magnets. Additionally, the ribbons melt-spun at 20 m/s have a maximum coercivity of 26.4 kOe, while those melt-spun at 40 m/s have the highest magnetization of 61.6 emu/g.

Large Coercivity and High Remanence in Iron‐Rich 2:17‐Type SmCo Magnets:Effect of Dislocation on Solid‐Solution Precursors

Large Coercivity and High Remanence in Iron‐Rich 2:17‐Type SmCo Magnets:Effect of Dislocation on Solid‐Solution Precursors

Selective recovery of Sm from Sm-Co magnet scrap by vacuum distillation

Sm-Co rare earth permanent magnet materials are widely used in special fields such as new energy and electronic information. Sm-Co permanent magnet scraps are generated during the preparation and the use of end-of-life permanent magnets, which need to be recycled for the sustainable development. It is proposed to selectively recover Sm from the Sm-Co permanent magnet scraps by vacuum distillation. The experimental investigations were carried out in a vacuum furnace with double temperature zones for the efficient condensation of Sm vapor based on the thermodynamic and kinetic calculations. The recycling feasibility of the recovery of rare earth and the evaporation mechanism of Sm were also demonstrated in this work. The results show that Sm with the purity over 99% was obtained by the molybdenum condenser used as a condensing collectors at given conditions, providing a reference for the pyrometallurgical recovery of rare earth secondary resources.

Recycling of SmCo Magnets by Removal of Iron via Oxidative Leaching

In the production of SmCo permanent magnets with excellent temperature stability, corrosion resistance, and oxidation resistance, samarium (Sm), one of the rare earth elements (REEs), and cobalt (Co) are employed. Cobalt (Co) is a crucial component in tool materials, nickel-based alloys, tablet and smartphone batteries, and electric car batteries. REEs and Co have been listed as critical raw materials by the European Union Commission for many years. Due to the ever-growing demand for Co and REEs in technological applications, the recovery of these elements from secondary sources has garnered significant interest. There are two types of SmCo magnets, one of which contains a high amount of iron, approximately 15.2%. This paper focuses on the recycling of Fe-bearing SmCo. In this study, an oxidative leaching process with nitric acid was developed to eliminate iron through in situ hydrolysis and to dissolve REEs and Co. The influence of experimental conditions on the formation of an amorphous iron compound through the hydrolysis of Fe3+ in a nitric acid environment was thoroughly examined based on a Taguchi orthogonal array. The optimal parameters for oxidative leaching were determined to be an acid concentration of 3 mol/L, a solid-to-liquid ratio of 1/10, and a process temperature of 60 °C.

Understanding of magnetization reversal mechanism of precipitation-hardening samarium-cobalt magnets from micromagnetic simulation

The precipitation-hardening Sm-Co magnets not only have irreplaceable applications under extreme conditions such as high temperatures, but are also the most typical magnets with pinning-controlled magnetization reversal mechanism. However, there have always been two views on this type of pinning, attractive or repulsive. In this article, the modification of the parallel interface to the titled interface, led to occurrence of quasi-repulsive and quasi-attractive pinning modes, by employing micromagnetic simulation methods. The corresponding domain wall energy relationship between the pinning phase and main phase was analyzed for different pinning modes, according to the morphology of domain wall from the simulation results. The analysis results indicated that relatively small difference in domain wall energy between the two phases led to quasi-repetitive and quasi-attractive pinning modes. Our findings can provide a reference for further understanding of the magnetization reversal mechanism of precipitation-hardening Sm-Co magnets. The emphasis on the influence of 1:5/2:17 interface orientation on pinning also provided a perspective on the magnetization reversal mechanism of other nanostructured permanent magnet materials.

Multi-pole magnetization of NdFeB magnetic elastomers via a programmable magnetic stamp inspired by movable type printing

Multi-pole magnetization is crucial for enhancing the magnetic field strength of magnetic films. Programmable multi-pole magnetization with adjustable pole pitch and covering thicknesses from submillimeter to millimeter are challenging tasks. This paper introduces a programmable magnetic stamp method inspired by movable printing. Demagnetization curves at various temperatures illustrate that NdFeB has lower coercivity when heated, making it easier to magnetize. SmCo magnets as high temperature resistant magnetic stamps provide enough external magnetic field. Heating transfers the magnetic pole distribution of magnetic stamps to the NdFeB film. Using this method, we magnetize the NdFeB magnetic film with a checkerboard pattern (interlaced N and S poles). The minimum width of the pole pitch is 1.3 mm. Comparing the measured magnetic field results with the simulation values of ANSYS Maxwell, the trends are relatively close. Furthermore, we investigate the magnetic field component (Bz) related to height and compare the differences between direct and reverse magnetization. Additionally, five magnetic patterns are customized using arranged SmCo magnet arrays. Notably, this study accomplishes multi-pole magnetization with up to 100 poles, covering a magnetic film thickness ranging from 100 µm to 1 mm. The proposed approach provides submillimeter/millimeter-thick NdFeB magnetic films that work as powerful flux sources and exhibit promising applications in magnetic tactile sensors and soft robots.

Effect of interfacial stress on microchemistry and coercivity in 2:17-type SmCo sintered magnets

The coercivity of 2:17-type SmCo magnets is mainly determined by the gradient distribution of Cu element within the cell boundary phase, and the gradient of Cu distribution increases with aging time, together with coercivity. However, the fundamental origin of such Cu gradient distribution is not clear. In this work, the element redistribution and interfacial stress change during the aging process were simultaneously analyzed by employing typical Sm(CobalFe0.16Cu0.08Zr0.03)7.6 magnets with and without slow cooling. The increased atomic diffusion after slow cooling leads to a narrow width and large Cu distribution gradient of 1:5H phase, contributing to a high coercivity. Meanwhile, the lattice mismatch at the 1:5H/2:17R interface along 〈1¯010〉2:17R direction was enhanced in the magnet with slow cooling, giving rise to a large interfacial stress. Such interfacial stress was found, via physical chemistry analysis, to contribute to the gradient of Cu distribution in the 1:5H phase. The combined analysis of transmission electron microscopy, geometric phase analyses, and micromagnetic simulations reveal the presence of the interfacial stress together with a large concentration and gradient of Cu distribution in the 1:5H phase can improve the coercivity. These findings provide new considerations for the design of high-performance 2:17-type SmCo magnets.

A sustainable separation strategy for recovering Sm/Co from SmCo magnets with fatty acid and primary amine

Acidic extractant is a kind of extractants commonly used in critical metal recovery industry, but the saponification wastewater generated during the saponification process inevitably causes environmental pollution. In order to develop a sustainable separation strategy for rare earth, the synergistic effect between lauric acid (LA) and primary amine N1923 (RNH2, with R = C19-C23) was investigated in this paper. The study revealed that the hydrogen bond between LA and RNH2 was helpful to realize the saponification of LA, thereby significantly improving the extraction and separation performance of LA. Unlike the quaternary ammonium or quaternary phosphonium in ionic liquid saponification studied in the previous study, RNH2 can independently combine hydrogen ions to achieve the deprotonation of LA without adding alkali or basic resin, which makes the extraction and separation process more environmentally friendly. Aiming at the recovery of samarium cobalt (SmCo) magnet, the separation of Sm and Co in chloride medium was systematically studied. When LA and RNH2 were combined in equal molar proportions to extract Sm, the extraction system demonstrated a high synergistic coefficient of 61.94, and separation coefficient of Sm and Co was remarkably high at 5326.2. It showed that the LA-RNH2 extraction system for recovering Sm and Co from actual SmCo magnets could achieve 93.19 % recovery of Co, 90.53 % recovery of Sm and 16,222 Sm/Co separation factor. The LA-RNH2 extraction system has shown potential applications in Sm/Co separation and waste SmCo magnet recovery processes. It also provides a novel strategy for the saponification of acidic extractant without alkali consumption and saponification wastewater discharge.

X-ray Fluorescence Analysis of Waste Sm-Co Magnets: A Rational Approach

Determination of the chemical composition of waste Sm-Co magnets is required for their efficient recycling. The non-stereotypical composition of said magnets makes an analysis extremely challenging. X-ray fluorescence spectrometry is a promising analytical tool for this task. It offers high accuracy and simplicity of sample preparation as it does not require sample dissolution. However, a serious limitation of X-ray fluorescence analysis is the spectral interference of matrix elements and impurities. In this work, a two-stage technique has been developed for the determination of the main components (Sm, Co) and impurities (Fe, Cu, Zr, Hf, Ti, Ni, Mn, Cr) in samples of spent samarium–cobalt magnets using wavelength dispersive X-ray fluorescence spectrometry. In order to overcome the main limitation of the chosen method and to maximize its capabilities of qualitative and quantitative analysis, we propose an approach to the selection of analytical lines and experimental conditions, as well as a preparation method for the calibration standards. The obtained results have been shown to have a good correlation with ICP-OES. The limits of detection are in the range of 0.001–0.02 wt%, and the limits of quantification are 0.003–0.08 wt%.

Coercivity mechanism of high-performance anisotropic heterostructure SmCo5 magnets

Due to its large magnetocrystalline anisotropy field and high Curie temperature, SmCo-based magnets are irreplaceable in high-temperature applications. The hot-deformed SmCo-based magnets are especially attractive for their excellent corrosion resistance, making them more suitable for harsh environments. However, it is still challenging for hot-deformed SmCo-based magnets to obtain high magnetization and high coercivity simultaneously. Therefore, it is necessary to analyze the relationship between its microstructure and magnetic properties and explore its magnetic hardening mechanism to guide the further improvement of magnetic properties. In this paper, the anisotropic heterostructure SmCo5 magnet was prepared by combining large height-reduction and introducing a nano-grained Sm-rich phase. Strong c-axis texture, (BH)m of 16.1 MGOe, and Hci of 9.6 kOe were obtained via the heterostructure with SmCo5 micron-grain and Sm-rich nano-scale precipitates. The magnetic domain observation and technical magnetization analysis demonstrate that the coercivity mechanism is dominated by nucleation. The results also show that the smooth and Sm-rich precipitated grain boundary provides weak pinning effects. It provides a reference for the development of high-performance nanocrystalline SmCo5 magnets.

Microtwin evolution and grain boundary phase formation in iron-rich 2:17-type Sm-Co magnets: The effect of iron content

Iron-rich 2:17-type Sm-Co magnets are expected to possess a high energy product due to their elevated saturation magnetization. However, achieving high energy in manufactured magnets poses a challenge, and the mechanism by which the microstructure is affected by the iron content remains unclear. Here, we investigate the microstructure of 2:17-type Sm-Co magnets with varying iron contents in both single solid-solution precursors and aged magnets. Our study indicates that a higher iron content results in microtwin structures with a lower dislocation density in the 1:7H precursor phase, leading to an increased energy barrier and decreased driving force during the subsequent phase transformation. As a result, the 1:7H phase does not completely decompose, causing an increase in the intermediate phases. Furthermore, the impact of iron content on the 1:7H phase causes the aged magnets to have insufficient cell boundaries and massive grain boundary phases. Our study provides an understanding on the iron-rich 2:17-type Sm-Co magnets through the manipulation of the free energies and the defects in the solid-solution precursors.