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学者姓名：岳明
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Abstract ：
The synthesis of size-controlled Sm2Fe17 magnetic particles is a prerequisite for the fabrication of highperformance Sm2Fe17N3 permanent magnetic materials. Here, Sm2Fe17 was synthesized using a costeffective reduction-diffusion method. The calcium chloride molten salt was introduced to control the particle size and achieve a single phase of Sm2Fe17. The effects of reduction-diffusion reaction temperature and the amount of added calcium chloride on the phase constitution and microstructure of the final product of reduction-diffusion were systematically investigated. Adding an appropriate amount of calcium chloride can effectively inhibit the overgrowth and sintering of the reduced particles. By employing the strategy of adding 20 wt% of calcium chlorides into the green compacts, we were able to successfully synthesize uniform Sm2Fe17 particles that are well-dispersed, with an average size of 2.2 mm. Furthermore, by combining the optimal reduction-diffusion conditions and the nitriding process, the hard magnetic Sm2Fe17N3 material was successfully obtained. This study could be useful for the development of high-performance Sm2Fe17N3 magnetic materials utilizing reduction-diffusion technology. (c) 2023 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Keyword ：
Molten salt Molten salt Permanent magnets Permanent magnets Rare earths Rare earths Reduction-diffusion Reduction-diffusion
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| GB/T 7714 | Xi, Junhua , Yang, Zhi , Haseeb, Muhammad et al. Synthesis of size-controlled and dispersible Sm2Fe17N3 magnetic particles by reduction diffusion process using molten salt* [J]. | JOURNAL OF RARE EARTHS , 2024 , 42 (11) : 2105-2111 . |
| MLA | Xi, Junhua et al. "Synthesis of size-controlled and dispersible Sm2Fe17N3 magnetic particles by reduction diffusion process using molten salt*" . | JOURNAL OF RARE EARTHS 42 . 11 (2024) : 2105-2111 . |
| APA | Xi, Junhua , Yang, Zhi , Haseeb, Muhammad , Chen, Yuanyuan , Nie, Xiaofeng , Cong, Liying et al. Synthesis of size-controlled and dispersible Sm2Fe17N3 magnetic particles by reduction diffusion process using molten salt* . | JOURNAL OF RARE EARTHS , 2024 , 42 (11) , 2105-2111 . |
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Abstract ：
M-type ferrite exhibits good magnetic characteristics and resistance to oxidation, enabling the production of stable nanoparticles for applications such as medical delivery, hyperthermia therapy, and magnetic recording. Additionally, it serves as a valuable tool for studying the theory of coercivity. Here, the impact of surface and size on coercivity and associated mechanisms in M-type hexagonal ferrites has been thoroughly analyzed by a combination of micromagnetic models and experimental investigations. Based on a cubic model and without considering surface defects, the coercivity still cannot reach the theoretical value. It decreases with an increase in particle size, and the quasi-coherent and quasi-flower reversal modes appear continuously. Besides, surface defects do not affect the reversal mode, but they do decrease the coercivity and magnetic hardening effect, hence further amplifying the difference between coercivity and its theoretical value. The simulation results are strongly supported by experimental data. This study extensively examines the coercivity of M-type ferrite particles produced by various preparation methods, taking into account experimental observations and simulation results. Our findings can serve as guidance for the development of preparation technology for permanent magnet nanoparticles and contribute to a deeper understanding of the contradictions in coercivity and the mechanisms of magnetization reversal.
Keyword ：
Magnetization reversal mechanism Magnetization reversal mechanism Coercivity Coercivity Surface defects Surface defects Micromagnetic simulations Micromagnetic simulations Hexagonal ferrites Hexagonal ferrites
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| GB/T 7714 | Haseeb, M. , Li, Y. Q. , Zhang, H. G. et al. Influence and mechanism of surface defects on coercivity of M-type ferrite particles [J]. | SURFACES AND INTERFACES , 2024 , 46 . |
| MLA | Haseeb, M. et al. "Influence and mechanism of surface defects on coercivity of M-type ferrite particles" . | SURFACES AND INTERFACES 46 (2024) . |
| APA | Haseeb, M. , Li, Y. Q. , Zhang, H. G. , Liu, W. Q. , Zhang, P. J. , Yue, M. . Influence and mechanism of surface defects on coercivity of M-type ferrite particles . | SURFACES AND INTERFACES , 2024 , 46 . |
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Abstract ：
The grain boundary diffusion (GBD) technology effectively utilizes heavy rare earth (HRE) elements to improve the coercivity of sintered Nd-Fe-B magnet. Significantly, clarifying its coercivity improvement mechanism is essential for further optimizing the process and performance. Through comparative analysis with commercial conventional magnets (CSH) processing equivalent coercivity, this study investigated the specific mechanism by which the GBD method enhances the coercivity of HRE elements in an efficient manner. To achieve the same coercivity (similar to 21.4 kOe), GBD magnets contained only 0.25 wt% Tb, whereas CSH magnets had 1.17 wt% Dy and 1.18 wt% Tb. The microstructure analysis revealed that the Tb element in the GBD magnet was concentrated in the outer layer of the grain, constituting 17.37 wt% of the total rare earth content. While, in CSH magnets, the HRE element in the main phase grains accounted for only 9.58 wt% of the total rare earth elements, including Dy (3.83 wt%) and Tb (5.75 wt%). The characteristic core-shell structural grains in GBD magnet also endowed it with an uneven magnetic domain structure and a more concentrated "abrupt" magnetization reversal. Based on the characterization results the nucleation positions of the two types of magnets were analyzed by fitting H-ci/M-s and H-a/M-s. The results can serve as a guide for enhancing coercivity in grain boundary diffusion sintered Nd-Fe-B magnets, aiding in process and property optimization, and advancing the understanding of nucleation type mechanisms.
Keyword ：
Sintered Nd-Fe-B magnets Sintered Nd-Fe-B magnets Grain boundary diffusion Grain boundary diffusion Microstructure Microstructure Coercivity Coercivity Domain structure Domain structure
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| GB/T 7714 | Wu, Haihui , Li, Yuqing , Liu, Weiqiang et al. Understanding the coercivity enhancement mechanism of grain boundary diffused Nd-Fe-B magnets by comparing with commercial equivalent coercivity magnets [J]. | MATERIALS CHARACTERIZATION , 2024 , 210 . |
| MLA | Wu, Haihui et al. "Understanding the coercivity enhancement mechanism of grain boundary diffused Nd-Fe-B magnets by comparing with commercial equivalent coercivity magnets" . | MATERIALS CHARACTERIZATION 210 (2024) . |
| APA | Wu, Haihui , Li, Yuqing , Liu, Weiqiang , Wang, Zhanjia , Qin, Yuan , Ji, Ming et al. Understanding the coercivity enhancement mechanism of grain boundary diffused Nd-Fe-B magnets by comparing with commercial equivalent coercivity magnets . | MATERIALS CHARACTERIZATION , 2024 , 210 . |
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Abstract ：
Iron-rich intermetallic compound Sm2Fe17N3 is considered to be a highly promising candidate for newgeneration permanent magnetic materials. Here, the Ti-substituted Sm-2(Fe, Ti)(17)N-3 alloys were synthesized using reduction-diffusion and nitridation. The microstructure and magnetic properties of Sm-2(Fe, Ti)(17) and its nitrides, in relation to the effect of Ti substitution, were systematically investigated through a comprehensive experimental approach combined with first-principles calculations. It was revealed that the Ti substitution is very effective in particle refinement of Sm-2(Fe, Ti)(17). The Rietveld analysis of X-ray data demonstrated an expansion in the unit cell volume of Sm-2(Fe, Ti)(17) phase with increasing Ti content. Subsequent nitridation experiments highlighted the beneficial impact of an appropriate Ti addition on the enhancement of both coercivity and remanence in Sm-2(Fe, Ti)(17)N-3 magnetic powder. The highest coercivity of 8.9 kOe was achieved in the sample with a Ti/Fe mole ratio of 0.04. Furthermore, the possible crystallographic occupancy of Ti and its effect on the phase stability are investigated using first-principles calculations. Our results indicated that the phase stability is influenced by the synergistic effect of Ti substitution atoms and interstitial N atoms. The significance of this study lies in its implications for the development of advanced permanent magnetic materials through reductiondiffusion technology.
Keyword ：
Rare-earth permanent magnets Rare-earth permanent magnets Coercivity Coercivity Reduction-diffusion Reduction-diffusion First-principles calculation First-principles calculation Sm2Fe17N3 Sm2Fe17N3
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| GB/T 7714 | Xi, Junhua , Yang, Zhi , Wang, Xiangming et al. Magnetic properties and microstructure of Ti-doped Sm-Fe-N synthesized by reduction diffusion process [J]. | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS , 2024 , 603 . |
| MLA | Xi, Junhua et al. "Magnetic properties and microstructure of Ti-doped Sm-Fe-N synthesized by reduction diffusion process" . | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 603 (2024) . |
| APA | Xi, Junhua , Yang, Zhi , Wang, Xiangming , Zhang, Hongguo , Haseeb, Muhammad , Chen, Yuanyuan et al. Magnetic properties and microstructure of Ti-doped Sm-Fe-N synthesized by reduction diffusion process . | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS , 2024 , 603 . |
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Abstract ：
As a new technology for the short-process recovery of Nd-Fe-B sintered magnet sludge, the calcium thermal reduction diffusion method has attracted significant attention due to its low energy consumption, environmental friendliness, and high recovery rate. However, traditional calcium thermal reduction diffusion technology still has issues such as an insufficient reaction between the sludge and reducing agent after increasing the amount of reactants, the use of a large amount of reducing agent, and low recovery efficiency. Therefore, a novel dynamic calcium thermal reduction diffusion technology was proposed, with the calcium reduction diffusion of sludge and calcium undergoing a continuous mixing and diffusion state throughout the entire process, greatly improving the efficiency of the reaction. Compared with the traditional process, the amount of reactants was increased from a few grams to hundreds of grams, and the amount of reducing agent calcium was reduced by 25%. Subsequently, regenerated magnetic powder with a uniform particle size, good dispersion, and excellent magnetic properties was obtained. The saturation magnetization under a 3 T magnetic field was increased by 27.9% compared with the initial sludge. The maximum magnetic energy product of the magnet prepared by doping 50 wt% regenerated magnetic powder was 45 MGOe, which reached the highest level of the regenerated magnets prepared by recycling sludge. What is encouraging that this new technology had the advantage of achieving large-scale production and reducing production costs, providing a potential industrialization solution for the green and efficient recovery of Nd-Fe-B sintered magnet sludge.
Keyword ：
Large-scale production Large-scale production Dynamic Dynamic Nd-Fe-B sintered magnet sludge Nd-Fe-B sintered magnet sludge Calcium thermal reduction diffusion Calcium thermal reduction diffusion Short -process recovery Short -process recovery
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| GB/T 7714 | Cong, Liying , Xu, Haibo , Lu, Qingmei et al. An efficient process for preparing regenerated magnets by dynamic recovery of Nd-Fe-B sintered magnet sludge [J]. | JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING , 2024 , 12 (2) . |
| MLA | Cong, Liying et al. "An efficient process for preparing regenerated magnets by dynamic recovery of Nd-Fe-B sintered magnet sludge" . | JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING 12 . 2 (2024) . |
| APA | Cong, Liying , Xu, Haibo , Lu, Qingmei , Yu, Lichao , Zhou, Quangui , Wu, Qiong et al. An efficient process for preparing regenerated magnets by dynamic recovery of Nd-Fe-B sintered magnet sludge . | JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING , 2024 , 12 (2) . |
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Abstract ：
In recent years, the research focus has shifted towards the preparation of non-heavy rare earth (RE) -Fe -B magnets with high coercivity ( H cj ) by reducing the content of B element. In this work, we achieved resource-saving sintered (Nd, Ce) -Fe -B magnets by adjusting the B element content, optimizing microstructure, and enhancement of Nd/Ce element distribution. We conducted an analysis on the magnetic characteristics, phase composition, microstructure, magnetization reversal mechanism, and economic viability of these sintered magnets. With a decrease in the B element content from 0.96 wt% to 0.90 wt%, there is a increase of approximately 1 kOe in H c j .At the same time, the temperature coefficient of H cj has been improved, resulting in a absolute value decrease from 0.67%/ degrees C to 0.63%/ degrees C. The findings suggested that reducing the mass fraction of B element could facilitate the formation of a thicker grain boundary phase between the grains. It could significantly weaken the ferromagnetic coupling effect, and enhance the magnetic isolation effect between grains, resulting in a higher H cj . From an economic perspective, compared to the cost of magnet with similar coercivity prepared by increasing the RE content, the cost of magnet with low B element content was reduced by 554.4 US$/t , approximately saving 3.08%. This study provides a new theoretical foundation and experimental basis for resource-saving sintered (Nd,Ce)-Fe-B magnet preparation.
Keyword ：
Resource-saving Resource-saving Sintered (Nd Ce)-Fe-B magnets Sintered (Nd Ce)-Fe-B magnets B element content B element content Temperature stability Temperature stability Coercivity Coercivity
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| GB/T 7714 | Qin, Yuan , Liu, Weiqiang , Li, Yuqing et al. Analyzing the mechanism of reducing B content on the coercivity of sintered (Nd, Ce)-Fe-B magnets [J]. | MATERIALS CHARACTERIZATION , 2024 , 211 . |
| MLA | Qin, Yuan et al. "Analyzing the mechanism of reducing B content on the coercivity of sintered (Nd, Ce)-Fe-B magnets" . | MATERIALS CHARACTERIZATION 211 (2024) . |
| APA | Qin, Yuan , Liu, Weiqiang , Li, Yuqing , Wang, Zhanjia , Chen, Hao , Wu, Haihui et al. Analyzing the mechanism of reducing B content on the coercivity of sintered (Nd, Ce)-Fe-B magnets . | MATERIALS CHARACTERIZATION , 2024 , 211 . |
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Abstract ：
The Electrophoretic deposition grain boundary diffusion (EPD-GBD) technology for sintered Nd-Fe-B magnets has garnered significant attention. In this study, TbF3 3 nano-powders were synthesized via sand milling (SM) process, and the optimal processes were subsequently explored. Notably, the SM powders exhibit two morphologies: blocky and flocculent. With prolonged SM time, the proportion of larger blocky powders decreases gradually, while the proportion of smaller flocculent powders increases. The morphology and proportion of the powders significantly impact the EPD rate and the effectiveness of GBD. Higher blocky powders proportion improved diffusion, reducing residual Tb layer and enhancing magnet coercivity. Higher flocculent powders proportion caused cracking, poor diffusion, thicker residual layer, and lower coercivity. However, a high EPD rate was achieved with a high proportion of flocculent powders. Considering both EPD rate and diffusion effect, the SM process at 1500 r/min for 30 minutes was identified as the optimal parameter. The TbF3 3 nano-powders prepared by these conditions exhibited superior advantage in the EPD process and the coercivity of GBD magnets compared to traditional micron-scale TbF3 3 powders, demonstrating the benefits of the SM process in the EPD and GBD processes of Nd-Fe-B magnets.
Keyword ：
Grain boundary diffusion Grain boundary diffusion TbF3 TbF3 Nd-Fe-B magnets Nd-Fe-B magnets Electrophoretic deposition Electrophoretic deposition Sand Milling Sand Milling
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| GB/T 7714 | Ji, Ming , Liu, Weiqiang , Wang, Zhanjia et al. Application of TbF3 3 Nano-powders by sand milling process in preparing high performance grain boundary diffusion Nd-Fe-B magnets [J]. | MATERIALS TODAY COMMUNICATIONS , 2024 , 41 . |
| MLA | Ji, Ming et al. "Application of TbF3 3 Nano-powders by sand milling process in preparing high performance grain boundary diffusion Nd-Fe-B magnets" . | MATERIALS TODAY COMMUNICATIONS 41 (2024) . |
| APA | Ji, Ming , Liu, Weiqiang , Wang, Zhanjia , Fan, Min , Wu, Haihui , Du, Ruihua et al. Application of TbF3 3 Nano-powders by sand milling process in preparing high performance grain boundary diffusion Nd-Fe-B magnets . | MATERIALS TODAY COMMUNICATIONS , 2024 , 41 . |
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Abstract ：
To balance the utilization of rare-earth resources and reduce the preparation cost, the La and Ce substituted Nd2Fe14C hard magnetic alloys were prepared by a facile mechanochemical method for the first time. A two-step process is typically employed: 1) Decomposition of hydrocarbon and disproportionation of (Nd1-xREx)(2.5)Fe14B0.08 (RE=La or Ce, x=0-0.3) alloys during high-energy ball milling, Nd+Nd2Fe17+n-hexane -> NdH2+delta+alpha-Fe+Fe7C3; 2) (Nd, RE)(2)Fe14C hard magnetic powders were obtained via the vacuum annealing at 800 degrees C for 2 min. The phase relation, magnetic properties and microstructural evolution of (Nd, RE)(2)Fe14B0.08C0.92 (named Nd-RE-Fe-C-based) alloys were systematically investigated. Substitution of La for x=0.1 Nd in the Nd-RE-Fe-C-based alloy increase the coercivity from 15.6 kOe to 18.6 kOe without reducing the remanence. First-principles calculation was performed to study the mechanism of magnetic properties La and Ce substituted samples. The results showed that La tends to be expelled from 2:14:1 phase to form more minor phases which act as the domain wall pinning center, increasing the coercivity. However, Ce prefers to enter the 2:14:1 phase, diminishing the permanent magnetic properties due to the poor intrinsic magnetic properties. This paper provides a novel viewpoint for the effective utilization of high abundant rare earth and the investigation of low cost Nd2Fe14C permanent magnet materials.
Keyword ：
Mechanochemistry Mechanochemistry Magnetic materials Magnetic materials High abundant rare earth High abundant rare earth First-principles calculation First-principles calculation
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| GB/T 7714 | Shang, Xiaoyun , Wang, Xiangming , Chen, Min et al. High-abundant rare earth La/Ce substituted Nd2Fe14C based permanent magnet materials prepared by mechanochemical method [J]. | MATERIALS TODAY COMMUNICATIONS , 2024 , 41 . |
| MLA | Shang, Xiaoyun et al. "High-abundant rare earth La/Ce substituted Nd2Fe14C based permanent magnet materials prepared by mechanochemical method" . | MATERIALS TODAY COMMUNICATIONS 41 (2024) . |
| APA | Shang, Xiaoyun , Wang, Xiangming , Chen, Min , Tu, Haoran , Zhang, Hongguo , Yue, Ming et al. High-abundant rare earth La/Ce substituted Nd2Fe14C based permanent magnet materials prepared by mechanochemical method . | MATERIALS TODAY COMMUNICATIONS , 2024 , 41 . |
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Abstract ：
The effectiveness of employing La-Ca-Co co-doping has been demonstrated as the optimal approach for enhancing the magnetic performance of strontium ferrite. However, limited studies have explored the evolution of the magnetoplumbite phase and its correlation with the sintering temperature. In our research, La-Ca-Co doped strontium ferrite permanent magnets were fabricated using a conventional ceramic process and a two-step sintering technique. After sintering at different temperatures, all the samples possess proper c-axis orientation. When the sintering temperature was raised from 1175degree celsius to 1205 degree celsius, there was an upward trend observed in the remanence Br, increasing from 430 mT to 439 mT. The coercivity Hcj exhibited an increase from 380 kA/m and reached its peak at 397 kA/m at 1185degree celsius. Although the Br value remained favorable, the coercivity experienced substantial deterioration, reaching its lowest point at 303 kA/m at 1205degree celsius. Under a sintering temperature of 1195 degree celsius, magnetic performance with optimal energy product was achieved, with Br of 439 mT, H-cj of 379 kA/m, H-cb of 318 kA/m, and (BH)(max) of 35.5 kJm(-3).
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| GB/T 7714 | Haseeb, Muhammad , Zhang, Hongguo , Li, Yuqing et al. Sintering temperature optimization for enhanced magnetic performance in La-Ca-Co doped strontium ferrite [J]. | AIP ADVANCES , 2024 , 14 (2) . |
| MLA | Haseeb, Muhammad et al. "Sintering temperature optimization for enhanced magnetic performance in La-Ca-Co doped strontium ferrite" . | AIP ADVANCES 14 . 2 (2024) . |
| APA | Haseeb, Muhammad , Zhang, Hongguo , Li, Yuqing , Zhang, Pengjie , Geng, Zhaowen , Yue, Ming . Sintering temperature optimization for enhanced magnetic performance in La-Ca-Co doped strontium ferrite . | AIP ADVANCES , 2024 , 14 (2) . |
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Abstract ：
The advent of NdFeB bonded magnets with freedom of shape design is effective in achieving motor size and weight reductions. In this paper, the NdFeB bonded magnets were produced through calendaring molding, and the effect of powder shape on degree of alignment (DOA) of NdFeB bonded magnets was investigated. The magnetic measurement results demonstrate that platelet-shaped anisotropic Master Quality Authenticated (MQA) powders exhibit a significantly higher DOA compared to sphere-shaped anisotropic HDDR powders. Microstructural analysis reveals the presence of an oriented structure induced by mechanical stress in MQA bonded magnets, resulting in magnetic anisotropy. This observation is consistent with the difference in X-ray diffraction (XRD) patterns between the cross-section and surface of MQA bonded magnets. Conversely, spherical HDDR particles display minimal orientation and maintain a random distribution, resulting in magnetic isotropy. The XRD pattern of the cross-section of HDDR bonded magnets closely resembles that of its surface. In summary, our findings highlight the superior potential of platelet-shaped anisotropic MQA powders for achieving enhancing magnetic properties during the calendaring molding process, in contrast to sphere-shaped anisotropic HDDR powders. This study provides valuable insights into the determinants of mechanical particle orientation during the fabrication of anisotropic NdFeB bonded magnets, with implications for the development of high-performance bonded magnets.
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| GB/T 7714 | Qu, Zhongjie , Wu, Qiong , Zhang, Mengkang et al. The effect of powder shape on the magnetic anisotropy in NdFeB bonded magnets [J]. | AIP ADVANCES , 2024 , 14 (2) . |
| MLA | Qu, Zhongjie et al. "The effect of powder shape on the magnetic anisotropy in NdFeB bonded magnets" . | AIP ADVANCES 14 . 2 (2024) . |
| APA | Qu, Zhongjie , Wu, Qiong , Zhang, Mengkang , Wang, Zhanjia , Yue, Ming , Liu, Weiqiang . The effect of powder shape on the magnetic anisotropy in NdFeB bonded magnets . | AIP ADVANCES , 2024 , 14 (2) . |
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