粘结NdFeB 磁体的设计、制备与特殊应用

【作者】 吕丽；

【导师】 白书欣；

【作者基本信息】 中国人民解放军国防科学技术大学 ， 材料物理与化学， 2002， 硕士

【摘要】 本文从理论、实验和应用三方面对NdFeB粘结磁体进行了较系统的研究，包括磁体组分设计、工艺方案的选择、工艺参数对磁体性能的影响、磁体的防腐处理、超大磁体的设计、制备和检测等。 通过理论研究，得到了粘结磁体原料配比与组分参数间的关系、磁性能与组分组成间的定量关系表述、磁体在空间所产生磁场的理论公式；通过分析现有各种防腐方法的特点，确定了有效的防腐方案。这些结果为磁体制备和磁体使用前设计提供了理论依据，避免了工作的盲目性。 通过实验考察了各种工艺因素对磁体性能的影响，包括原料的种类和用量、成型工艺选择、防腐方法等方面，发现： 粘结剂在成型过程中所处的状态对磁体的致密化程度有较大影响，因此相同压力条件下，用液态或半固态粘结剂制备的磁体比使用固态粘结剂得到的磁体密度高；液态粘结剂中，以具有适当粘度和良好流动性的粘结剂使用效果最好；与磁性相体积分数变化趋势相同，磁体性能随粘结剂含量增加呈现先提高后降低的规律，当粘结剂与磁粉质量比为3％～4％时磁性能最佳。 偶联剂在磁粉和粘结剂之间起到了“分子桥”的作用，用经偶联剂预处理过的磁粉制备的磁体性能明显高于未经处理的磁体。偶联剂中，钛酸酯系列比硅烷系列的使用效果好。不同的偶联剂使用方法得到的表面预处理效果也不同，其中，以二甲苯为溶剂的湿混法最好。 与普通压制工艺相比，温压工艺更有利于在低压力下得到高密度的磁体。温度对温压效果影响明显，应当选择在粘结剂软化点以上、固化反应前的某一点，保证粘结剂具有适当的粘度和良好的流动性；与普通压制工艺相同，温压工艺制备的粘结磁体密度和磁性能均随压制压力的增大而提高，磁体性能和磁粉体积分数随粘结剂含量变化的规律一致。 用阴极电沉积法在粘结磁体表面涂覆环氧漆后，磁体的耐盐雾时间达250hr以上，是一种有效的表面防腐方法。 利用得到的理论分析结论和小样实验结果，并根据特殊的应用要求，可以在制备前对磁体进行设计。实际上，使用制备前设计得到的各项参数，采用温压工艺在低压力下得到的超大磁体性能与设想值偏差很小，磁场不均匀度可以控制在5％以内。另外，通过对磁体国防科学技术大学研究生院学位论文表面场的测量，并结合理论公式可以判断未知磁体类型。更多还原

【Abstract】 Bonded NdFeB magnet is studied systematically in the aspect of theoretic analysis, experiments and special application in the article. Several factors are discussed, including the amount of magnet constitutes, the choice of technical parameters, the method of anti-erosion, the pre-design , the preparation and the test of enormous NdFeB magnet.Several formulations are given in the article. They show many relationships, such as the relationship between component ratio and geometrical size of institutes, the relationship between magnet power and the volume percentage of magnet powder. Two expressions about magnetic field value are calculated, which make things convenient for the pre-design of magnetic circuit and the choice of magnet. A effective method of anti-erosion is concluded by comparing all kinds of post-treatment technics.By experiments, many factors that affect magnet performance are discussed in the article, including category and quantum of constitutes, technological conditions, and the way of anti-erosion. Results are as following,Firstly, the physical state of bond has an important effect on magnet densitification. Liquid or half-solid bond is helpful to improve the density of bonded magnet than solid bond does. The magnet performance will not rise linearly as the ratio of bond rises, but gets the maximum when its weight percentage is 3%?%. And the changing of magnet product is similar with the change of the volumepercentage of magnetic powder. In addition, the larger the pressure is, the higher the density and the magnet performance are.Secondly, coupling agent helps to improve the magnetic power and its anti-erosion capacity, which promote the combination of magnet powder and bond. Different coupling agent and different treatment conditions have different impacts on magnet performance. It is the best using titanate coupling agents as pretreatment reagent and dimethylbenzene as solvent.Thirdly, Magnet can get high density under lower pressure easily, usingheating-pressing process. Remarkably, the temperature must be limited between softening point and solidification value, at which the bond can get perfect fluidity and stickiness. Effects of bond content and pressure on magnet product during heating-pressing process are the same with effects during common-pressing process.Fourthly, it is more than 250 hours before magnet is eroded when it is coated with lacquer by way of cathode electrophoresis.Fifthly, it is successful to pre-design special magnet and magnetic circuit before magnet preparation and application, making the best use of theoretical formulations, experimental results and practical demands. All kinds of technical parameters of enormous magnets are gotten by pre-design method before they are produced by heating-pressing process. The uneven degree of magnetic field in circuit is within 5%. It should be said that heating-pressing process is a good way to get even magnet with high density.Lastly, calculating the magnet performance using theoretical formulation, which expresses the relationship of the external magnetic field and remanence of the magnet, can tell the type of unknown magnet. Similarly, incapable magnet can be abandoned in this way. Detailed approaches are given in the article.更多还原