Article
Chemistry, Physical
Ruipeng Qian, Hechang Han, Fugang Chen, Hui Sun, Yong Zhao, Peilei Zhang, Wenqiang Zhao
Summary: Grain boundary diffusion process was performed on sintered Nd-Ce-Fe-B magnets with different Ce concentrations. The coercivity increment and remanence improvement were observed in the magnets with higher Ce concentrations. The (Pr, Tb)-rich shells were formed, contributing to the enhancement of coercivity and remanence.
Article
Chemistry, Physical
Min Huang, Zhiqiang Qiu, Fang Wang, Hubin Luo, Changping Yang, Jian Zhang
Summary: The decomposition process of the Nd-Ce-Fe-B phase on the formation of the CeFe2 phase was observed to have a negative impact on its magnetic properties in this study. However, exploring the use of a Ce-Cu boundary phase instead of CeFe2 has been shown to efficiently improve the coercivity of Ce-rich Nd-Ce-Fe-B magnets, if the Ce-Cu boundary phase has an appropriate Ce to Cu ratio. These findings contribute to understanding the mechanism and design of high-performance Nd-Ce-Fe-B permanent magnetic materials.
Article
Materials Science, Multidisciplinary
Yuye Wu, Konstantin P. Skokov, Lukas Schafer, Fernando Maccari, Alex Aubert, Hao Xu, Haichen Wu, Chengbao Jiang, Oliver Gutfleisch
Summary: We report on the microstructure, hard magnetic properties, and thermal stability of hot-compacted nanocrystalline (Nd0.85Ce0.15)15(Fe1-xCox)7(8)B(7) permanent magnets. The substitution of Fe by Co influences the grain boundary phase composition and degrades the coercivity at lower Co concentrations (x < 0.3). At higher Co concentrations (x >= 0.6), the absence of a grain boundary phase leads to strong magnetic coupling. Additional RE(Fe,Co)2, RE(Fe,Co)4B, and RECo5 phases gradually form with increasing Co concentration (x > 0.6). A new type of microstructure with nanograins and good thermal stability is observed at x = 0.4 and 0.6. In (Nd0.85Ce0.15)(15)(Fe0.4Co0.6)78B-7 magnets, the temperature coefficient of coercivity exceeds 0.3%/K within the temperature range of 300 K-500 K and 0.23%/K for the temperature range of 300 K-650 K, demonstrating the potential for designing highly thermal-stable permanent magnets.
Article
Nanoscience & Nanotechnology
Y. M. Tao, J. Y. Jin, L. Z. Zhao, X. L. Liu, Z. H. Zhang, G. H. Bai, C. Wu, J. M. Greneche, K. Lv, B. Xin, M. Yan
Summary: Grain boundary (GB) engineering is used to control the composition and magnetism of the 1:2 phase in Nd-Ce-Fe-B nanostructured magnets. A Cu-mediated GB engineering strategy is proposed, which enables the formation of a continuous 1:2 GB phase and the generation of a novel Nd-dominated 1:2 phase with a ferro-paramagnetic transformation. At the optimal Cu doping, the magnet exhibits the highest coercivity and coexistence of paramagnetic and ferromagnetic 1:2 phases.
MATERIALS TODAY NANO
(2022)
Article
Materials Science, Multidisciplinary
Hao Chen, Yuqing Li, Hongguo Zhang, Weiqiang Liu, Zhanjia Wang, Ming Yue
Summary: This work presents a novel strategy to manipulate the chemical heterogeneity and grain boundary structures of MMP Nd-La-Ce-Fe-B sintered magnets, resulting in ultrahigh coercivity values. The addition of Al-Cu-Ga elements in LaCe-free alloys enhances chemical heterogeneity and optimizes grain boundary structures. This study provides an effective and feasible strategy for preparing high coercivity MMP-sintered magnets, crucial for promoting the comprehensive utilization of rare earth resources.
Article
Chemistry, Physical
Sangen Luo, Munan Yang, Zaiping Xu, Tongyun Zhao, Sajjad Ur Rehman, Xi Yu, Shuwei Zhong, Haitao Wang, Chaoxiang Jin, Qiang Ma, Bin Yang
Summary: This paper investigates the effect of grain size in the diffusion matrix on the grain boundary diffusion mechanism of Tb element. The results show that with only 0.75 wt. % TbF3 diffusion, the intrinsic coercivity increases significantly for the magnet with finer average grain size compared to the coarse-grain magnet. The increase in intrinsic coercivity is attributed to the increase in defect density and the higher grain orientation caused by grain refinement, which leads to improved diffusion efficiency and magnetic properties.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Chemistry, Physical
Guangzong Xing, Takahiro Ishikawa, Yoshio Miura, Takashi Miyake, Terumasa Tadano
Summary: This study investigates the thermodynamic stability of binary R1-xFex compounds using first-principles calculations based on density functional theory at finite temperature. The findings show that entropy contributions, including electronic and vibrational free energies, are essential for accurately predicting the stability of these alloys. The results indicate that vibrational entropy plays a key role in stabilizing various R1-xFex compounds with increasing temperature, suggesting the possibility of synthesizing these compounds at high temperatures.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Materials Science, Multidisciplinary
Weisen Huang, Xuefeng Liao, Jiayi He, Hongya Yu, Zhongwu Liu
Summary: This study investigates and compares the microstructure, magnetic properties, thermal stability, corrosion resistance, and mechanical properties of bonded (La,Ce,Y)-Fe-B magnet with Nd-Fe-B and (Nd,La,Ce)-Fe-B magnets. The results show that bonded (La,Ce,Y)-Fe-B magnet exhibits a combination of magnetic properties with lower coercivity but higher performance-to-cost ratio compared to other magnets. It also demonstrates better thermal stability and corrosion resistance. The study suggests that bonded (La,Ce,Y)-Fe-B magnet has great potential for industrial applications.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
H. Sepehri-Amin, Xin Tang, T. Ohkubo, K. Hono
Summary: Understanding the magnetization reversal processes of permanent magnets is essential for developing magnets with high coercivity. Recent studies have used magneto-optical Kerr effect microscopy to observe the dynamic magnetic domains under an external magnetic field. Different microstructural features, such as grain boundaries and interfaces, influence the magnetization reversal processes of Nd-Fe-B-based permanent magnets. By manipulating these factors, it is possible to achieve magnets with higher coercivity.
Article
Materials Science, Multidisciplinary
Xuefeng Liao, Lizhong Zhao, Jiasheng Zhang, Ke Xu, Bang Zhou, Hongya Yu, Xuefeng Zhang, Jean-Marc Greneche, Alex Aubert, Konstantin Skokov, Oliver Gutfleisch, Zhongwu Liu
Summary: Nanocrystalline 2:14:1-type Ce-Fe-B alloy powders have shown potential for low-cost hard magnets. This study successfully fabricated bulk anisotropic Ce-based 2:14:1-type permanent magnets through hot-deformation and investigated the effects of La and Y substitutions. La substitution resulted in a clear preferred orientation, while the addition of Y improved thermal stability. The obtained magnet exhibited good hard magnetic properties.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Chemistry, Physical
Fugang Chen, Hechang Han, Tieqiao Zhang, Yong Zhao, Xiaoli Wang, Wenqiang Zhao
Summary: Grain boundary diffusion process (GBDP) can improve the coercivity and remanence of sintered Nd-Ce-Fe-B magnets. Ce substitution promotes the diffusion process, but excessive Ce content leads to the formation of abnormally large grains on the magnet surface.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Physical
Gabriel Gomez Eslava, Masaaki Ito, Claire Colin, Masao Yano, Tetsuya Shoji, Akira Kato, Emmanuelle Suard, Nora M. Dempsey, Dominique Givord
Summary: The study revealed that atom substitution in Nd-2(Fe1-xCox)(14)B, Y-2(Fe1-xCox)(14)B and Ce-2(Fe1-xCox)(14)B compounds shows some regularity, depending on the ratio of Co to Fe content. Steric hindrance primarily determines atom substitution, and enthalpy of mixing must also be considered for a more accurate description of Co preferential occupancies.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Physical
Wenbing Fan, Jiasheng Zhang, Xuefeng Liao, Jiayi He, Ke Xu, Bang Zhou, Hongya Yu, Jiangxiong Wei, Zhongwu Liu
Summary: Hot pressed and hot deformed nanocrystalline Nd-Ce-Fe-B magnets were prepared using dual-alloy method. Addition of Ce-Fe-B reduced the magnetic properties, but also led to an abnormal increase of coercivity at 10 wt.%. Grain boundary diffusion treatment improved the coercivity by modifying the grain boundary phase and forming a more significant core-shell structure.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Multidisciplinary
Christian Schneider, Serhiy Demeshko, Franc Meyer, C. Gunnar Werncke
Summary: This study reports a dinuclear monosulfido bridged diiron(II) complex with a similar [Fe-S-Fe] core geometry that can be stepwise oxidized to different oxidation states while retaining the core structure. The cleavage of the [Fe-S-Fe] unit by CS2 is also demonstrated in this research. The complexes have been characterized crystallographically and electron structures have been studied using various techniques such as Fe-57 Mossbauer spectroscopy and SQUID magnetometry.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Article
Physics, Condensed Matter
Shu Wang, Ji-Bing Sun, Zhi-Xia Xiao, Ming-Xu Yang, Wei-Dong Shi
Summary: Doping 1 wt% Al89.5Cu9.7Fe0.8 alloy promotes the phase separation and microstructure evolution of Nd13.53Fe74.89Co5.54B6.04 alloy. Low-temperature annealing improves the disorder degree, reduces composition difference between phases, and results in the formation of small particles or nanoparticles.
PHYSICA B-CONDENSED MATTER
(2022)
Article
Materials Science, Multidisciplinary
Hao Li, Lu Wei, Yuan Hong, Yuanwei Zhang, Zhaoguo Qiu, Gang Wang, Lizhong Zhao, Xiaolian Liu, Xuefeng Zhang, Deyang Chen, Z. G. Zheng, Weixing Xia, Dechang Zeng, J. Ping Liu
Summary: This paper presents the preparation of SmCo-based thin films using magnetic field assisted magnetron sputtering and rapid thermal annealing. By decreasing in-plane magnetic anisotropy and increasing out-of-plane coercivity, the magnetic properties of the films are improved. Micromagnetic simulations confirm the significance of the proportion of magnetic moment direction in controlling magnetic anisotropy and coercivity.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Wei Hao Zhu, Lei Ma, Mu Fen He, Zhi Kun Li, Huan Zhi Zhang, Qing Rong Yao, Guang Hui Rao, Kun Peng Su, Xi Chun Zhong, Zhong Wu Liu, Xin Qiang Gao
Summary: The complex magnetic transition, magnetocaloric effect, refrigerant capacity, and magnetic-phase diagram of single-phase TbDyHoEr high-entropy alloy were investigated. Results showed that the melt-spun treatment significantly improved the refrigerant capacity of TbDyHoEr from 883.19 to 1049.22 J kg(-1) due to complex magnetic transition and ideal table-like magnetocaloric effect. The improved application potential of TbDyHoEr as a high-efficient magnetic refrigeration material and the ideal table-like magnetocaloric effect in a large temperature range enable this material to meet the requirements of cryogenic and mesothermal refrigeration for an Ericsson cycle.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Zhen Shi, Hang Zeng, Yusheng Yuan, Nan Shi, Lin Wen, Huawei Rong, Dapeng Zhu, Liang Hu, Lianze Ji, Lizhong Zhao, Xuefeng Zhang
Summary: A controllable and effective strategy for constructing robust superhydrophobicity using hydrophobic interaction driving self-assembly (HIDS) is demonstrated. Polydopamine (PDA) is used as the binder and SiO2 particles as the nano-sized structures to achieve low-adhesive property. The coatings have excellent stability and can be assembled on various substrates, regardless of their size, roughness, chemistry, and rigidity.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Zhenhua Zhang, Xiaodi Zhao, Jian Zhang, Guohua Bai, Hua Guo, Weiwei Liu, Bin Zhang, Jin Wang, Lianze Ji, Fu-rong Chen, Lizhong Zhao, Xuefeng Zhang
Summary: This article introduces a new type of micro-pillar structure that allows remote control of micro-pillars through the metal-insulator transition (MIT) of vanadium dioxide (VO2) in response to an electromagnetic field. By adding layers of amorphous silicon oxide, accurate control of the bending of the micro-pillars is achieved.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Zhen Shi, Hang Zeng, Zejun Zhang, Xiaowei Zhang, Lidija Curkovic, Vilko Mandic, Song Fu, Wei Wang, Jun Liu, Lizhong Zhao, Xuefeng Zhang
Summary: This article investigates the influence of surface coating treatment on the corrosion resistance of Nd-Fe-B permanent magnets, and proposes the optimum anti-corrosion performance of bilayer thin Al/Cr films. The film effectively prevents the penetration of corrosive ions and has no significant impact on the magnetic and mechanical properties.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Computer Science, Artificial Intelligence
Amirhossein Zaji, Zheng Liu, Takashi Bando, Lihua Zhao
Summary: This article introduces a novel approach to design traffic lights in a city using evolutionary-based optimization algorithms combined with an ontology-based driving behavior simulation framework. A machine-understandable knowledge of roads, intersections, traffic rules, and driving behaviors is provided through an ontology-based knowledge base, and car behavior is inspected in real time through a simulation environment. Traffic lights are optimized by defining sine-based equations for each traffic light and considering the total travel time of vehicles as the cost function in the optimization algorithm. The results show that optimized traffic lights can significantly reduce total travel time compared to uncontrolled intersections without traffic lights.
ACM TRANSACTIONS ON INTELLIGENT SYSTEMS AND TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Zhigao Yu, Xiangyi Liu, Jiayi He, Jiali Cao, Wenbing Fan, Yaxiang Wu, Hongya Yu, Zhongwu Liu, Zhan Wang, E. Niu
Summary: This study compares the different element diffusion and demagnetization behaviors in Tb-Cu diffused single-main-phase (SMP) and multi-main-phase (MMP) Nd-Fe-B magnets. The results show that although the infiltration of Tb is deeper in MMP magnets, the coercivity enhancement is much less compared to SMP magnets. This is attributed to the composition homogenization caused by strong inter-diffusion between the main phases in MMP magnets during the grain boundary diffusion (GBD) treatment. The non-concurrent magnetic reversal and poor loop squareness in the MMP magnets are mainly due to the large difference in H-A between the surface and the center after composition homogenization.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Materials Science, Multidisciplinary
Xichun Zhong, Yucai Wu, Yuanxin Li, Xuan Huang, Jiaohong Huang, Cuilan Liu, Hongya Yu, Zhongwu Liu, Minglong Zhong, Zhenchen Zhong, R. V. Ramanujan
Summary: A series of LaFe11.8Si1.2/La65Co35 bulk composites were fabricated by spark plasma sintering (SPS) followed by diffusion annealing. The sintering temperature was found to have an effect on the mechanical and magnetocaloric properties of the composites. The annealed samples exhibited a 1:13 phase content of approximately 90 wt% and showed improved properties when the sintering temperature was adjusted.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Engineering, Electrical & Electronic
Jiaming Li, Hongya Yu, Pan Luo, Han Yuan, Zhongwu Liu, Yu Wang, Lu Yang, Wenjie Wu
Summary: Amorphous soft magnetic powder cores (AMPCs) were prepared through inorganic-organic multiple-layer coating. The influence of phosphating treatment on the performance of AMPCs was investigated. The results showed that phosphoric acid-ethanol coating at relatively high temperature resulted in uniform and dense phosphate coating, leading to significantly reduced eddy current loss of the AMPCs. Optimized magnetic properties, including good frequency stability and low core loss, were achieved by coating the AMPCs with a 0.6 wt.% phosphoric acid-ethanol solution at 55 degrees C.
JOURNAL OF ELECTRONIC MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Jiayi He, Wenyue Song, Xiangyi Liu, Wenbing Fan, Bang Zhou, Zhigao Yu, Jiali Cao, Hongya Yu, Xichun Zhong, Zhongwu Liu, Huayun Mao
Summary: Grain boundary diffusion (GBD) is an effective method to enhance the coercivity of Nd-Fe-B magnets with lower consumption of heavy rare earths (HREs). This study proposes a macroscopically heterogeneous GBD (MHGBD) process to further reduce the use of HRE resources. The MHGBD process strengthens the edge area using HRE-based diffusion source and the center area using light rare-earth-based diffusion source. The results show that the MHGBD process significantly increases the coercivity from 1182 to 1911 kA/m.
JOURNAL OF MATERIALS SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Xuefeng Liao, Weiwei Zeng, Lizhong Zhao, Qing Zhou, Jiayi He, Wei Li, Xiangyi Liu, Hongya Yu, Xiaolian Liu, Haoyang Jia, Jean-Marc Greneche, Xuefeng Zhang, Zhongwu Liu
Summary: This article introduces a new method to improve the magnetic properties of rare earth-iron-boron magnets. By using a two-step grain boundary diffusion process, a magnet with excellent magnetic properties was obtained. The formation of RE-rich grain boundary layer through doping and diffusion was found to contribute to the enhancement of coercivity, supported by differential scanning calorimetry and transmission electron microscopy.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2023)
Article
Chemistry, Physical
Xichun Zhong, Yucai Wu, Yuanxin Li, Xuan Huang, Cuilan Liu, Jiaohong Huang, Zhongwu Liu, Dongling Jiao, Wanqi Qiu, Minglong Zhong, Zhenchen Zhong, R. V. Ramanujan
Summary: A novel transient liquid phase bonding (TLPB) technique was used to prepare binder-free La-Fe-Si based bulk materials by spark plasma sintering (SPS). Compared to hot-pressing sintering (HPS) samples, the SPS samples exhibited significantly higher maximum compressive strength (sigma(bc))(max) of about 637.9 MPa at a strain of 4.7%, good thermal conductivity of about 7.6 W·m(-1)·K(-1) at 300 K, and a large (-Delta S-M)(max) value of about 11.7 J·kg(-1)·K(-1) at Tc=193 K under a magnetic field change of 0 - 5 T. Thus, binder-free La-Fe-Si based bulk magnetocaloric materials with excellent properties were successfully prepared by TLPB assisted SPS technology.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Physics, Applied
Bang Zhou, Wei Li, Lin Wen, Chengyuan Xu, Xuefeng Liao, Jinbo Wei, Yu Pan, Xiaolian Liu, Song Fu, Lizhong Zhao, Hongya Yu, Xichun Zhong, Xuefeng Zhang, Zhongwu Liu
Summary: This study introduces the non-rare earth element Ge into Ce, La, and Y-based RE-Fe-B nanocrystalline alloys, successfully enhancing their magnetic properties. The (BH)(max) of 65.6 kJ/m(3) and H-cj of 346 kA/m are achieved in the [(Ce0.8La0.2)(0.5)Y-0.5](16)Fe77.5B6Ge0.5 alloy. The improvement is attributed to the increased content of the hard magnetic RE2Fe14B phase with refined grain size, which is confirmed by micromagnetic simulation. Ge addition effectively suppresses the laves phase by forming the Ce5Ge3 phase with the lowest formation energy. This work clarifies the positive role of Ge in enhancing the H-ci and (BH)(max) of nanostructured (Ce,La,Y)-Fe-B alloys.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Ceramics
Weijie Zhong, Hanlin Peng, Dongling Jiao, Wanqi Qiu, Zhongwu Liu, Wenyong Xu, Zhou Li, Guoqing Zhang
Summary: This study investigates and compares the cooling rate, surface morphology, and microstructure of nickel-based super-alloy powders produced by atomization with argon and nitrogen. The results reveal that the FCC structured γ-phase and γ'-strengthening phase are the main phases in atomized powders of both gases, with no apparent nitride or oxide detected on the powder surface. The powders atomized by argon exhibit higher sphericity and smoother surfaces compared to those atomized by nitrogen, while nitrogen-atomized powders have more split particles. The cooling rate significantly affects the surface characteristics of the powder, with nitrogen-atomized powders showing higher cooling rates and lower secondary dendrite arm spacing compared to argon-atomized powders.
POWDER METALLURGY AND METAL CERAMICS
(2023)
Article
Chemistry, Physical
Xiangyi Liu, Bang Zhou, Bin Yuan, Zhongwu Liu
Summary: The magnetic properties of magnetic nanocomposites consisting of hard and soft magnetic phases depend on both intrinsic properties and the grain structure and volume ratio of the two phases. The grain size has a greater effect on the magnetic properties compared to the volume fraction of the hard magnetic phase. The effects of phase ratio and grain size on magnetic properties have been verified by experiments.
