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学者姓名：刘卫强
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Abstract ：
采用密度泛函理论方法系统研究分析了四方结构MnGa合金体在a轴1GPa应力下的结构、形成、电子性质和磁性质.结果表明，应力下MnGa合金a, b轴晶格参数增大，c轴晶格参数减小，三轴夹角有偏离90°的趋势，晶胞体积增大. Mn-Ga不成键，Mn-Mn之间的强键作用进一步增强，Ga-Ga之间的强键作用消失. Mn-Mn结合键长和Ga-Ga结合键长均减小，而Mn-Ga间距增大，排斥作用减弱.应力下MnGa合金形成焓由-4.85 eV减小到-5.4 eV,其更容易生成.应力下其能带整体向下移动，导带和浅能级价带分布较宽，有效质量较小；深能级价带分布较窄，有效质量较大.自旋向下的电子能带没有带隙，自旋...
Keyword ：
电子性质 电子性质 MnGa合金 MnGa合金 磁性质 磁性质 应力 应力
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| GB/T 7714 | 路清梅 , 张飞鹏 , 房慧 et al. 应力下MnGa合金体电子性质及磁性质的研究 [J]. | 原子与分子物理学报 , 2023 , 40 (01) : 134-142 . |
| MLA | 路清梅 et al. "应力下MnGa合金体电子性质及磁性质的研究" . | 原子与分子物理学报 40 . 01 (2023) : 134-142 . |
| APA | 路清梅 , 张飞鹏 , 房慧 , 李虹霏 , 刘卫强 , 张东涛 et al. 应力下MnGa合金体电子性质及磁性质的研究 . | 原子与分子物理学报 , 2023 , 40 (01) , 134-142 . |
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Abstract ：
高性能Nd-Fe-B磁粉是制备粘结磁体和增材制造磁体等的重要原料,直接影响着最终磁体的性能。但Nd-Fe-B磁粉由于含有稀土,表面活性较高,在使用过程中极容易受到氧气和化学介质的侵蚀。因此,在磁粉加工的过程中,防氧化工艺尤为重要。常用的方法是对磁粉进行表面包覆处理,在磁粉表面形成有机化合物或金属涂层,使粉末与外界的氧气和化学介质隔离。有机物涂层抗氧化效果显著,但耐湿热性差、抗老化性弱,且在包覆有机物涂层时容易引入杂质原子。金属涂层具有良好的热稳定性和抗氧化性,但包覆金属镀层的方法较为复杂,且难以控制金属镀层的沉积率。旋转包覆工艺是包覆介质在旋转的容器内高温下与物体短暂摩擦而沉积在物体表面的过程。该工艺包覆效果均匀、适应性强、包覆介质可重复使用、且成本低廉,容易实现量产。我们基于此开发了一种新型滚镀金属涂层包覆Nd-Fe-B磁粉的工艺。以锌包覆层为例,只需要将磁粉与锌粒混合均匀后放入可旋转的管式炉内进行加热处理,并通过调整加热温度、加热时间和炉内真空度等来获得所需厚度的均匀镀层,有效提高了磁粉的抗高温氧化能力。未经处理的磁粉质量在30～450℃的氧化增重实验中增加了2.82%,而镀锌磁粉的质量仅增加了0.40%,且后者的磁性能与未处理的磁粉相比变化不大。利用该工艺还可以包覆锌以外的其它低熔点金属或者合金,为研究开发高性能抗氧化腐蚀的Nd-Fe-B磁粉创造了有利条件。
Keyword ：
稀土永磁 稀土永磁 Nd-Fe-B Nd-Fe-B 抗氧化腐蚀 抗氧化腐蚀 旋转包覆 旋转包覆
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| GB/T 7714 | 张红国 , 刘卫强 , 高京园 et al. Nd-Fe-B磁粉的抗氧化改性研究 [C] //中国稀土学会第四届青年学术会议摘要集 . 2023 . |
| MLA | 张红国 et al. "Nd-Fe-B磁粉的抗氧化改性研究" 中国稀土学会第四届青年学术会议摘要集 . (2023) . |
| APA | 张红国 , 刘卫强 , 高京园 , 许福有 , 奚望 , 岳明 . Nd-Fe-B磁粉的抗氧化改性研究 中国稀土学会第四届青年学术会议摘要集 . (2023) . |
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Abstract ：
采用常规的陶瓷工艺制备了La_(0.572)Ca_xSr_((0.658-x))Co_(0.356)Fe_(12.4)O_(19)(x=0.1,0.2,0.3,0.4,0.5,0.6,0.658)磁粉,研究了预烧温度和Ca元素含量对磁粉晶体结构、显微组织和磁性能的研究。研究表明,在1 190～1 230℃的温度下预烧,磁粉均可形成具有典型M型六角晶系SrM铁氧体晶体结构的单一相结构。其中,在1 220℃预烧的磁粉具有最佳磁性能。Ca~(2+)取代Sr~(2+)导致M相的晶胞体积缩小,但是相结构稳定不变,随着Ca含量的升高,磁粉的饱和磁化强度出现了先升高后降低的变化规律,当x=0.5时M_s=5...
Keyword ：
Ca含量 Ca含量 SrM铁氧体 SrM铁氧体 晶体结构 晶体结构 磁性能 磁性能 预烧温度 预烧温度
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| GB/T 7714 | 孙伟强 , Muhammad Haseeb , 耿赵文 et al. 预烧温度及Ca含量对La-Ca-Co系铁氧体磁粉结构及磁性能的影响 [J]. | 金属功能材料 , 2022 , 29 (01) : 45-49 . |
| MLA | 孙伟强 et al. "预烧温度及Ca含量对La-Ca-Co系铁氧体磁粉结构及磁性能的影响" . | 金属功能材料 29 . 01 (2022) : 45-49 . |
| APA | 孙伟强 , Muhammad Haseeb , 耿赵文 , 刘荣明 , 刘卫强 , 岳明 . 预烧温度及Ca含量对La-Ca-Co系铁氧体磁粉结构及磁性能的影响 . | 金属功能材料 , 2022 , 29 (01) , 45-49 . |
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Abstract ：
基于密度泛函理论方法系统研究了四方结构MnGa合金体的结构、形成、电子结构和磁性质。结果表明,四方MnGa合金晶胞的生成焓为-4.85 eV,高于一些不含d电子的体系。其呈现导体的能带结构,其中d电子主要形成深能级价带,定域性最强。四方MnGa合金存在着明显的自旋极化,靠近费米能级两侧的s电子和靠近费米能级下方的p电子具有较弱的自旋极化。形成浅能级价带和导带的d电子产生高强度的自旋极化,对磁性质贡献较大。Mn的s电子和Mn的p电子自旋极化作用较弱,Mn的d电子形成浅能级价带和导带,自旋极化作用最强。形成深能级价带的Ga的d电子自旋极化作用较弱,不同位置的Ga原子的自旋极化不同。四方MnGa合金...
Keyword ：
MnGa合金 MnGa合金 磁性质 磁性质 磁性材料 磁性材料 密度泛函理论 密度泛函理论 电子结构 电子结构
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| GB/T 7714 | 张飞鹏 , 路清梅 , 李虹霏 et al. MnGa合金体的电子结构与磁性质的研究 [J]. | 人工晶体学报 , 2022 , 51 (01) : 65-71 . |
| MLA | 张飞鹏 et al. "MnGa合金体的电子结构与磁性质的研究" . | 人工晶体学报 51 . 01 (2022) : 65-71 . |
| APA | 张飞鹏 , 路清梅 , 李虹霏 , 房慧 , 刘卫强 , 张东涛 et al. MnGa合金体的电子结构与磁性质的研究 . | 人工晶体学报 , 2022 , 51 (01) , 65-71 . |
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Abstract ：
We achieved ultra-high coercivity of 5.65 kOe in L1(0)-Mn1.33Ga alloy via the hot deformation (HD) method and revealed the hardening mechanism. Hot deformation led to recrystallization and grain refinement, where the average grain size was reduced to about 1.5 mu m for HD-88% magnet. The coercivity mechanism indicated a weak pinning model by magnetic mini-loop analysis. It was found that small grains were formed, accompanied by a certain number of {111} < 11-2 > twins for HD magnets. The magnetic domain observation showed that both the sub-micro grain boundary and the twin boundary were acted as the pinning center of the domain wall, but the latter had weaker pinning effect. The ultra-high coercivity of the HD-88% Mn1.33Ga magnet originated mainly from the pinning of the grain boundary enhanced by grain refinement. Further grain refinement and twin structure inhibition will be promising approaches in order to obtain higher magnetic properties for L1(0)-MnxGa bulk magnets. Published under an exclusive license by AIP Publishing.
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| GB/T 7714 | Lu, Q. M. , Gao, S. , Li, Y. Q. et al. Grain refinement leading to the ultra-high coercivity in L1(0)-Mn1.33Ga bulk magnet via hot deformation [J]. | APPLIED PHYSICS LETTERS , 2022 , 120 (15) . |
| MLA | Lu, Q. M. et al. "Grain refinement leading to the ultra-high coercivity in L1(0)-Mn1.33Ga bulk magnet via hot deformation" . | APPLIED PHYSICS LETTERS 120 . 15 (2022) . |
| APA | Lu, Q. M. , Gao, S. , Li, Y. Q. , Zhang, H. G. , Liu, W. Q. , Yue, M. . Grain refinement leading to the ultra-high coercivity in L1(0)-Mn1.33Ga bulk magnet via hot deformation . | APPLIED PHYSICS LETTERS , 2022 , 120 (15) . |
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Abstract ：
To further optimize the comprehensive magnetic properties of LaCe-based sintered magnets prepared by constructing a multi-main-phase (MMP) structure, Pr-Fe-B was used as a LaCe-free alloy to prepare MMP sintered magnets with 40 wt% LaCe substitution. Due to the high anisotropy field (H-A) of Pr2Fe14B grains, strong chemical heterogeneity could be provided in MMP magnets. In addition, the Pr-rich phase with a lower melting point enters the MMP magnet, optimizing the composition and structure of the grain boundary (GB) phase. It is beneficial to improve the wettability and promote the formation of continuous GB layers. As a result, the H-cj and (BH)(max) of the MMP magnets reached 9.64 kOe and 37.70 MGOe, leading to an excellent overall magnetic performance of (BH)(max) (MGOe) + H-cj (kOe) = 47.34. This will serve as a reference for the high performance of MMP LaCe-based magnets.
Keyword ：
Magnetic properties Magnetic properties Magnetic materials Magnetic materials Chemical heterogeneity Chemical heterogeneity Microstructure Microstructure Grain boundaries Grain boundaries
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| GB/T 7714 | Chen, Hao , Liu, Weiqiang , Guo, Zizhen et al. Construction of high-performance multi-main-phase LaCe-based sintered magnets by chemical heterogeneity enhancement [J]. | MATERIALS LETTERS , 2022 , 325 . |
| MLA | Chen, Hao et al. "Construction of high-performance multi-main-phase LaCe-based sintered magnets by chemical heterogeneity enhancement" . | MATERIALS LETTERS 325 (2022) . |
| APA | Chen, Hao , Liu, Weiqiang , Guo, Zizhen , Yang, Tianyuan , Qin, Yuan , Li, Yuqing et al. Construction of high-performance multi-main-phase LaCe-based sintered magnets by chemical heterogeneity enhancement . | MATERIALS LETTERS , 2022 , 325 . |
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Abstract ：
Nitrogenation is an indispensable process for the formation of Sm2Fe17N3 and has a major influence on its magnetic properties. In this work, the effect of nitrogenation on the magnetic properties of Sm2Fe17N3 was investigated by micromagnetic simulation. The normal coercivity, remanence, and the maximum energy product of incompletely nitrided Sm2Fe17N3 with a nonnitrided Sm2Fe17 core size less than 16 nm approach nearly 99% of their values in fully nitrided Sm2Fe17N3. Thus, a small nonnitrided Sm2Fe17 core does not affect the effective utilization of Sm2Fe17N3 permanent magnets. The magnetization reversal mode of incompletely nitrided Sm2Fe17N3 with different sizes of nonnitrided Sm2Fe17 cores was evaluated, providing an in-depth fundamental understanding of the demagnetization processes in Sm2Fe17N3 particles. This work could be useful for optimizing nitrogenation conditions to improve the magnetic properties of Sm2Fe17N3 permanent magnets.
Keyword ：
Hard magnetic materials Hard magnetic materials Magnetic cores Magnetic cores Nitrogen Nitrogen micromagnetic models micromagnetic models Magnetic anisotropy Magnetic anisotropy Coercive force Coercive force Perpendicular magnetic anisotropy Perpendicular magnetic anisotropy magnetic alloys magnetic alloys Iron Iron Saturation magnetization Saturation magnetization
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| GB/T 7714 | Yang, Zhi , Chen, Yuanyuan , Li, Yuqing et al. Micromagnetic Simulation of Nitrogenation Effect on the Magnetic Properties of Sm2Fe17N3 Alloy [J]. | IEEE MAGNETICS LETTERS , 2022 , 13 . |
| MLA | Yang, Zhi et al. "Micromagnetic Simulation of Nitrogenation Effect on the Magnetic Properties of Sm2Fe17N3 Alloy" . | IEEE MAGNETICS LETTERS 13 (2022) . |
| APA | Yang, Zhi , Chen, Yuanyuan , Li, Yuqing , Zhang, Dongtao , Liu, Weiqiang , Lu, Qingmei et al. Micromagnetic Simulation of Nitrogenation Effect on the Magnetic Properties of Sm2Fe17N3 Alloy . | IEEE MAGNETICS LETTERS , 2022 , 13 . |
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Abstract ：
Retaining the chemical heterogeneity of 2:14:1 main phase grains and forming continuous grain boundary (GB) layers are considered two significant contributions to high coercivity in multi-main-phase (MMP) Nd-La-Ce-Fe-B sintered magnets. In this work, the trade-off between chemical heterogeneity and the GB layers in MMP Nd-La-Ce-Fe-B sintered magnets was tackled by designing the composition of LaCe-free alloys. The coercivity of the MMP LaCe-40 (LaCe/TRE = 40 wt.%, TRE: total rare earth) magnets prepared by replacing conventional Nd30.5FebalM1.8B0.96 (Nd-normal) with Nd42.1FebalB0.79 (Nd-rich) as a LaCefree alloy increased by 52.7%, reaching an ultra-high coercivity of 11.10 kOe. Analysis of the microstructure showed that chemical heterogeneity was retained in the MMP LaCe-40 sintered magnets prepared with Nd42.1FebalB0.79. In addition, thick Nd-rich hard magnetic shells and continuous GB layers were constructed. On the one hand, magnetization reversal of the LaCe-rich grains was hindered by the adjacent strongly magnetic LaCe-free grains. On the other hand, this enhanced the anisotropic field of the LaCerich grains and weakened the ferromagnetic coupling effect. These provided a guarantee for preventing the nucleation and propagation of reversed domains, thereby achieving high coercivity. This study offers a new solution for the contradiction between the retention of chemical heterogeneity and the regulation of the GB structure in the MMP Nd-La-Ce-Fe-B sintered magnets, creating the conditions for further improving the coercivity of magnets. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Keyword ：
Grain boundary Grain boundary Multi-main-phase Multi-main-phase Nd-La-Ce-Fe-B Nd-La-Ce-Fe-B Magnetic properties Magnetic properties Chemical heterogeneity Chemical heterogeneity
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| GB/T 7714 | Chen, Hao , Liu, Weiqiang , Guo, Zizhen et al. Coercivity enhancement of Nd-La-Ce-Fe-B sintered magnets: Synergistic effects of grain boundary regulation and chemical heterogeneity [J]. | ACTA MATERIALIA , 2022 , 235 . |
| MLA | Chen, Hao et al. "Coercivity enhancement of Nd-La-Ce-Fe-B sintered magnets: Synergistic effects of grain boundary regulation and chemical heterogeneity" . | ACTA MATERIALIA 235 (2022) . |
| APA | Chen, Hao , Liu, Weiqiang , Guo, Zizhen , Yang, Tianyuan , Wu, Haihui , Qin, Yuan et al. Coercivity enhancement of Nd-La-Ce-Fe-B sintered magnets: Synergistic effects of grain boundary regulation and chemical heterogeneity . | ACTA MATERIALIA , 2022 , 235 . |
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Abstract ：
In this paper, the microstructure and texture formation mechanism of nanocrystalline anisotropic Nd-Fe-B magnets prepared by a one-step heating forward-extrusion method were systematically studied. The hot extruded (HE) Nd-Fe-B magnet showed the same heterogeneous microstructure characteristics as the traditional die-upsetting magnet. With the decrease of extrusion width (w1), the c-axis texture gradually enhanced, accompanied by an increasing proportion of fine-grain region and the improvement of the ordered arrangement of platelet grains. In addition, strong c-axis texture was formed by the ordered arrangement of platelet grains benefiting from the difference of stress distribution caused by the difference of side length of the extrusion port. By adjusting the dimension of the rectangle extrusion port, the magnetic properties of HE Nd-Fe-B magnets were optimized. The optimized magnetic properties with (BH)(max) of 241.3 kJ/m(3), H-ci of 1025.3 kA/m, M(r )of 0.94 MA/m can be acquired for the hot extrution (HE) Nd-Fe-B magnet with extrusion width (w1) of 2.5 mm. In this method, the demoulding process can be avoided successfully by using cold pressing instead of hot pressing, which is of great significance for continuous and high-volume production.
Keyword ：
Hot-extruded Nd-Fe-B magnet Hot-extruded Nd-Fe-B magnet Heterogeneous microstructure Heterogeneous microstructure Magnetic properties Magnetic properties C-axis texture C-axis texture
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| GB/T 7714 | Li, Y. Q. , Tang, Y. Y. , Liu, W. Q. et al. Microstructure and texture formation mechanism of nanocrystalline anisotropic Nd-Fe-B magnets by novel hot forward-extrusion [J]. | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS , 2022 , 555 . |
| MLA | Li, Y. Q. et al. "Microstructure and texture formation mechanism of nanocrystalline anisotropic Nd-Fe-B magnets by novel hot forward-extrusion" . | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 555 (2022) . |
| APA | Li, Y. Q. , Tang, Y. Y. , Liu, W. Q. , Yue, M. , Xu, X. C. , Zhang, H. G. et al. Microstructure and texture formation mechanism of nanocrystalline anisotropic Nd-Fe-B magnets by novel hot forward-extrusion . | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS , 2022 , 555 . |
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Abstract ：
The oil-based Nd-Fe-B sludge waste was directly recycled to single-phase Nd2Fe14B powders via the combination of purification and modified Ca-reduction reaction method. The impurities and organics in the purified Nd-Fe-B sludge waste were greatly reduced, reducing calcium consumption in the subsequent reduction and diffusion (RD) process, thereby reducing the cost. By further optimizing the Ca-reduction diffusion parameters, especially the mass ratio of CaCl2 and KCl, where the liquid CaCl2, along with the gaseous KCl provide conditions for sufficient and uniform Ca-reduction reaction, high-property Nd-Fe-B magnetic powders with good dispersion, uniform particle sizes, and excellent orientation, were successfully obtained. Using the mixed diffusion medium of CaCl2 and KCl with a mass ratio of 1:1, the room-temperature magnetization of the recycled Nd-Fe-B powders was increased to 157 emu/g at 3 T-magnetic field, which was about 28 % higher than that of the original sludge. The contents of carbon, hydrogen, and oxygen in the recycled magnetic powders were significantly reduced from 6.8, 1.8, and 5.9 wt% to 0.1, 0.19, and 0.56 wt%, respectively. In addition, the uniform grain size with X-50 = 3.6 mu m and good distribution greatly improved the orientation, which can be beneficial to the preparation of the bonded or sintered Nd-Fe-B based magnets. The reasons that CaCl2-KCl mixed diffusion medium can lead to well-dispersed, uniform recycled powder with high magnetization arise from a combination of factors for improving the liquid phase reaction environment and the gaseous KCl to prevent agglomeration and inhibit particles merging or growth.
Keyword ：
Recycling Recycling Purification Purification Nd-Fe-B sludge waste Nd-Fe-B sludge waste Ca-reduction reaction Ca-reduction reaction
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| GB/T 7714 | Xu, Haibo , Wang, Feng , Lu, Qingmei et al. Nd-Fe-B: From sludge waste to powders via purification and modified Ca-reduction reaction process [J]. | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS , 2022 , 543 . |
| MLA | Xu, Haibo et al. "Nd-Fe-B: From sludge waste to powders via purification and modified Ca-reduction reaction process" . | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 543 (2022) . |
| APA | Xu, Haibo , Wang, Feng , Lu, Qingmei , Qiu, Yubing , Liu, Weiqiang , Chen, Jingwu et al. Nd-Fe-B: From sludge waste to powders via purification and modified Ca-reduction reaction process . | JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS , 2022 , 543 . |
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