元素添加对纳米晶Nd-Fe-B磁性能影响机理研究与服役特性评价

发布时间：2018-11-18 11:02

【摘要】：随着高端永磁电机在风力发电、节能家电、新能源汽车等领域的推广和应用,极大增加了Nd-Fe-B稀土永磁材料的需求。但Nd2Fe14B的居里温度(585 K)偏低,磁性能随温度升高衰减越来越严重,极大限制了其高温环境下的使用。改善磁体温度稳定性通常可通过元素添加,提升磁体的矫顽力和居里温度来实现。因此,本文通过熔体快淬制备Nd-Fe-B合金,结合同步辐射等表征技术,系统研究元素添加效用及其对Nd-Fe-B合金居里温度的影响机理,并对等离子烧结磁体的服役特性展开了评价。首先研究了一系列重稀土元素添加对Nd-Fe-B快淬带磁性能的影响,并分析了主相晶体结构和合金微观组织的变化规律。同时,针对高丰度轻稀土元素Ce添加对磁性能的影响展开全面系统研究。采用高分辨透射电镜、扫描电镜和能谱分析等表征方法对快淬带的纳米晶微观组织及其成分起伏进行了详细观测分析,并结合电子衍射花样与X射线衍射分析测定主相晶胞参数随Ce添加量的变化规律,通过同步辐射X射线吸收精细结构谱分析不同添加量时Ce的价态变化,探索Ce元素对磁性能的作用机理。在添加单一元素Ce的基础上,复合添加Co与Cu元素,通过高分辨透射电镜表征纳米晶晶界处富稀土相的微观形貌及其分布规律,揭示Co与Cu元素影响Nd-Fe-B稀土永磁材料磁性能的微观机制。此外,使用同步辐射技术,测定元素添加前后X射线吸收精细结构谱Fe-K边的变化,拟合Fe-Fe间原子间距,分析原子交换作用对居里温度变化趋势的影响,阐明稀土元素对居里温度的影响机理。同时通过测定不同稀土元素添加对剩磁温度系数及矫顽力温度系数的作用,综合分析Nd-Fe-B稀土永磁材料的高温稳定性。采用放电等离子烧结技术制备各向同性Nd-Fe-B烧结磁体,研究复合添加Ce、Co、Cu磁体磁性能及其温度稳定性,并通过高压加速腐蚀和循环冷热冲击评估磁体在模拟工况条件下的服役特性。本文从原子局域结构、晶格畸变、微观组织演化等角度,深入分析元素复合添加影响Nd-Fe-B稀土永磁材料磁性能及温度稳定性的微观机制,构建稀土永磁材料宏观性质与原子微观结构之间的关联,为建立Nd-Fe-B稀土永磁材料“成分—组织—性能—服役特能”数据库提供部分相关数据,并为设计制备新型高性价比Nd-Fe-B稀土永磁材料提供理论与实验指导。
[Abstract]:With the popularization and application of high-end permanent magnet motor in wind power generation, energy-saving household appliances, new energy vehicles and other fields, the demand of Nd-Fe-B rare earth permanent magnet materials has been greatly increased. However, the Curie temperature (585K) of Nd2Fe14B is relatively low, and its magnetic properties decay more and more seriously with the increase of temperature, which greatly limits its use at high temperature. Improving the temperature stability of magnets is usually achieved by adding elements to enhance the coercivity and Curie temperature of magnets. Therefore, in this paper, Nd-Fe-B alloy was prepared by melt rapid quenching, and combined with synchrotron radiation and other characterization techniques, the effect of element addition and its influence on Curie temperature of Nd-Fe-B alloy were systematically studied. The service characteristics of plasma sintered magnets are evaluated. The effect of addition of a series of heavy rare earth elements on the magnetic properties of the Nd-Fe-B quenched zone was studied, and the changes of the main phase crystal structure and the microstructure of the alloy were analyzed. At the same time, the effect of Ce addition on magnetic properties was studied systematically. High resolution transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the microstructure of nanocrystalline and its component fluctuation. Combined with electron diffraction pattern and X-ray diffraction analysis, the variation of the cell parameters with the addition of Ce was determined, and the valence changes of Ce were analyzed by synchrotron radiation X-ray absorption fine structure spectroscopy. The action mechanism of Ce element on magnetic properties was explored. On the basis of adding single element Ce and adding Co and Cu elements, the morphology and distribution of rare earth rich phase at the grain boundary of nanocrystalline were characterized by high resolution transmission electron microscopy (TEM). The microcosmic mechanism of the influence of Co and Cu elements on the magnetic properties of Nd-Fe-B rare earth permanent magnetic materials is revealed. In addition, synchrotron radiation technique was used to measure the changes of Fe-K edge of X-ray absorption fine structure spectrum before and after adding elements, to fit the atomic distance between Fe-Fe and to analyze the effect of atomic exchange on Curie temperature change trend. The mechanism of the effect of rare earth elements on Curie temperature is explained. At the same time, the high temperature stability of Nd-Fe-B rare earth permanent magnet was analyzed by measuring the effect of different rare earth elements on the temperature coefficient of remanence and coercivity. Isotropic Nd-Fe-B sintered magnets were prepared by spark plasma sintering (SPS) technique. The magnetic properties and temperature stability of composite Ce,Co,Cu magnets were studied. The service characteristics of magnets under simulated conditions were evaluated by high pressure accelerated corrosion and cyclic cold and heat shock. From the aspects of atomic local structure, lattice distortion, microstructure evolution and so on, this paper analyzes the microcosmic mechanism of the effect of the addition of elements on the magnetic properties and temperature stability of Nd-Fe-B rare earth permanent magnetic materials. The relationship between the macroscopic properties and the atomic microstructure of rare earth permanent magnetic materials was constructed to provide some relevant data for the establishment of the database of Nd-Fe-B rare earth permanent magnets "composition, microstructure, properties and special energy". It also provides theoretical and experimental guidance for the design and preparation of new Nd-Fe-B rare earth permanent magnetic materials with high performance and price ratio.
【学位授予单位】：江西理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG146.416

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