快速凝固纳米晶镧铈替代钕铁硼合金永磁性能研究

发布时间：2018-05-26 23:43

  本文选题：钕铁硼永磁 + La\Ce取代　； 参考：《华南理工大学》2016年博士论文

【摘要】：永磁材料作为一些装置中必不可少的组成部分,已经在扬声器、硬盘和风力发电等领域得到了广泛的应用。迄今为止,NdFe B永磁仍然是性能最好的室温永磁材料。但是,NdFeB永磁高温性能较低,昂贵的稀土元素Nd、Pr、Dy等导致磁体的成本增加。因此,本论文瞄准于开发高性能低成本的钕铁硼永磁材料,主要研究了廉价的La和Ce元素单独和复合取代稀土元素Nd熔体快淬单相和纳米复合(Nd_(1-x)Mx)yFe94-yB6(M=La,Ce,LaCe;x=0-0.7;y=10,12)磁体以及[Dy_(1-x)(La_0.5Ce_0.5)_x]10Fe84B6磁体的磁性能、微观组织、特征温度、矫顽力机制和交换耦合效应的影响。同时研究了Co替代Fe对[(NdDy)(La/Ce)]FeB合金室温磁性能和热稳定性的影响。论文还探讨了磁性能变化的物理机制。首先分析了不同La部分替代Nd的NdFeB合金室温磁性能。研究发现,10%La取代Nd和5%La取代Nd有利于提高纳米复合磁体和单相磁体的磁性能。其中前者的磁性能可达到:剩磁106 emu/g、最大磁能积138 kJ/m~3、矫顽力465 kA/m,后者可达到:剩磁104 emu/g、最大磁能积(BH)max=151 kJ/m~3和矫顽力721 kA/m。并且发现La取代也降低了磁体的居里温度和自旋重取向温度。对于部分Ce取代的NdFeB合金,研究表明,随着Ce替代Nd量的增加,纳米晶单相和纳米复合合金的剩磁、磁能积和矫顽力下降。但是,20%Ce取代纳米复合磁体的矫顽力发生了反常的增加,导致磁性能有一定程度的改善,磁性能达到:剩磁99 emu/g、最大磁能积103 kJ/m~3和矫顽力392 kA/m。对于单相合金,Ce取代磁体的磁性能随着取代量增加逐渐降低的主要原因是Ce2Fe14B相的各向异性场低于Nd2Fe14B相在La_0.5Ce_0.5复合取代Nd的纳米复合磁体中,也可以获得较好的磁性能。x=0.1磁体的磁性能为剩磁114 emu/g、最大磁能积147 kJ/m~3和矫顽力471 kA/m。其中10%La或者La_0.5Ce_0.5取代Nd磁体的矫顽力表现出反常的增加。对比La_0.75Ce0.25和La0.25Ce_0.75替代的NdFe B合金,Ce替代导致更严重的磁性能下降,La更有益于合金的磁性能。作为对比,也研究了La_0.5Ce_0.5取代Dy元素的快淬[Dy_(1-x)(La_0.5Ce_0.5)_x]10Fe84B6合金。结果表明,30%La_0.5Ce_0.5取代Dy的磁体获得了最佳的磁性能:Hcj=714 kA/m,(BH)max=43kJ/m~3。此外,研究还发现,La_0.5Ce_0.5取代Nd和Dy磁体的高温性能和矫顽力机制都有所不同。其中La_0.5Ce_0.5取代Nd的磁体的矫顽力机制更偏向于钉扎机制,而La_0.5Ce_0.5取代Dy的磁体更偏向于形核机制。通过对不同取代(La、Ce或者LaCe)磁体磁性能随温度的变化研究发现,磁体的居里温度TC和自旋重取向温度TSR都有所降低。纳米晶合金的TSR低于常规的微米晶合金。TEM结果显示了La_0.5Ce_0.5混合取代磁体的晶粒细小,分布均匀,这也是它剩磁增强的原因。研究了磁体的Henkel曲线,回复曲线和磁导率以分析磁体的交换耦合作用。结果显示,10%La取代Nd的纳米复合磁体和5%La取代Nd的单相磁体的纳米晶间的交换耦合作用也有所增加。最后,研究了Co取代Fe元素对富Nd和单相的磁体中磁体磁性能的影响。研究发现,磁体的剩磁、矫顽力和饱和磁能积都随着Co含量的上升而降低;但Co替代导致居里温度增加,从而改善La、Ce替代合金的热稳定性。采用La_0.5Ce_0.5取代Nd和Dy的磁体在300-400 K范围内具有较低的矫顽力温度系数和剩磁温度系数。本论文研究表明,在快淬钕铁硼磁体中,采用低成本的La或Ce元素部分取代Nd元素,通过成分优化,可以在降低纳米晶钕铁硼永磁成本的基础上,可以保持较好的磁性能。Co替代Fe可以进一步改善这类磁体的高温性能。
[Abstract]:As an essential component of some devices, permanent magnetic materials have been widely used in the fields of loudspeaker, hard disk and wind power generation. So far, NdFe B permanent magnet is still the best room temperature permanent magnetic material. However, the high temperature performance of NdFeB permanent magnet is low, and the cost of the precious rare earth elements Nd, Pr, Dy and so on leads to the increase of the cost of the magnets. Therefore, this paper is aimed at developing high performance and low cost Nd-Fe-B permanent magnetic materials, mainly studying the magnetic properties of the cheap La and Ce elements Nd melt fast quenching single phase and nanocomposite (Nd_ (1-x) Mx) yFe94-yB6 (M=La, Ce, LaCe; x=0-0.7, y=10,12) magnets and the magnetic properties of the magnets. The influence of microstructure, characteristic temperature, coercive force mechanism and exchange coupling effect on the magnetic properties and thermal stability of the Fe (NdDy) (La/Ce)]FeB alloy at room temperature was studied. The physical mechanism of the change of magnetic energy was also discussed. The magnetic properties of the NdFeB alloy at room temperature of the different La part of the substitute Nd were analyzed. Replacing Nd with Nd and 5%La helps to improve the magnetic properties of nanocomposite magnets and monophasic magnets. The magnetic properties of the former can be achieved: the magnetic energy of the former is 106 emu/g, the maximum magnetic energy product is 138 kJ/m~3, the coercive force is 465 kA/m, the latter can be reached: the remnant magnetic 104 emu/g, the maximum magnetic energy product (BH) max=151 kJ/m~ 3, and the coercive force 721 kA/m. and found La substitution also reduces the magnet. The Curie temperature and the spin reorientation temperature. For some Ce substituted NdFeB alloys, the study shows that the remanence, the magnetic energy product and the coercive force of the nanocrystalline and nanocomposite alloys decrease with the increase of the Ce substitution of Nd. However, the coercivity of the 20%Ce substituted nanocomposite magnets has been abnormal increasing, resulting in a certain degree of magnetic energy. The magnetic energy is improved: the magnetic properties of the remanence are 99 emu/g, the maximum magnetic energy product 103 kJ/m~3 and the coercive force 392 kA/m. for the single-phase alloy. The main reason for the gradual decrease of the magnetic properties of the Ce substituted magnets is that the anisotropy field of the Ce2Fe14B phase is lower than that of the Nd2Fe14B phase in the nanocomposite magnets of the La_0.5Ce_0.5 composite replacement Nd. The magnetic energy of the good magnetic energy.X=0.1 magnet is 114 emu/g, the maximum magnetic energy product 147 kJ/m~3 and the coercive force 471 kA/m. in which the coercive force of the 10%La or La_0.5Ce_0.5 substitution of the Nd magnet shows an abnormal increase. The magnetic properties of the alloy. As a contrast, the fast quenched [Dy_ (1-x) (La_0.5Ce_0.5) _x]10Fe84B6 alloy with La_0.5Ce_0.5 replacing the Dy element is also studied. The results show that the magnets with 30%La_0.5Ce_0.5 replace Dy have the best magnetic properties: Hcj=714 kA/m, (BH) max=43kJ/m~3.. The coercivity mechanism of the magnets with La_0.5Ce_0.5 instead of Nd is more biased towards the pinning mechanism, and the magnets with La_0.5Ce_0.5 instead of the Dy are more biased towards the nucleation mechanism. The magnetic properties of the magnets with different substitutions (La, Ce or LaCe) have been found by the change of the magnetic properties with the temperature, and the temperature TC of the magnets and the spin reorientation temperature TSR are found. The TSR of nanocrystalline alloy is lower than the conventional Microcrystalline Alloy.TEM results. The results show that the grain size and distribution of the La_0.5Ce_0.5 mixed magnets are fine and uniform. This is also the reason for its remanence enhancement. The Henkel curve, recovery curve and permeability of the magnets are studied to analyze the exchange coupling effect of the magnets. The results show that 10%La is a substitute for Nd. The interaction between nanocomposite magnets and the nanocrystals of single phase magnets with 5%La instead of Nd has also increased. Finally, the effect of Co substitutions on the magnetic properties of the magnets in Nd rich and single-phase magnets is studied. The study shows that the remanence of the magnets, coercive force and the saturated magnetic energy of the magnets are all decreased with the increase of the Co content; but the substitution of Co causes the substitution of the Co. Curie temperature increases, thus improving the thermal stability of La, Ce substitute alloy. The magnets with La_0.5Ce_0.5 to replace Nd and Dy have lower coercive force temperature coefficient and remanence temperature coefficient in the range of 300-400 K. On the basis of reducing the cost of nanocrystalline NdFeB permanent magnet, it is possible to maintain a better magnetic energy.Co instead of Fe to further improve the high temperature properties of these magnets.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM273
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本文编号：1939468