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Microstructure Control and Improvement in Magnetic Properties of Rare-Earth Magnet Powders by Absorption Treatment

吸收处理稀土磁粉微观结构控制及磁性能改善

基本信息

批准号：
14350342
负责人：
KUWANO Noriyuki
金额：
$ 9.47万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

NdFeB magnet is a typical rare-earth magnet made of Nd_2Fe_<14>B phase that has a high coersive power. However, it has some problems that it has a low corrosion resistance and a tendency of decreasing in magnetics with time (seasoning effect). We have proposed a new method. (Zn-absorption) to give a high corrosion resistance. It has been found that the Zn-absorption treatment also give an improvement in time-dependence in magnetic properties. In this research project, the microstructures in HDDR-NdFeB magnet powder and bond magnets, made from the powders were characterized by means of transmission electron microscopy (TEM), scanning electron microscopy with a field emission gun (FE-SEM) and x-ray diffraction experiments (XRD). From the experimental results, we drew the conclusions as follows :1.After the Zn-absorption treatment, phases of Fe_<11>Zn_<40> and NdZn_5 are formed on the surface of the powders and on the grain boundaries of Nd_2Fe_<14>B.2.In HDDR-NdFeB without the Zn absorption treatment, α-Fe domains are formed in addition to h-Nd_2O_3 on the surface of the powders and on the grain boundaries of Nd_2Fe_<14>B after corrosion treatment.3.The seasoning effect in magnetic properties of NdFeB without Zn absorption treatment is attributable to the presence of α-Fe domains.4.In HDDR-NdFeB with the Zn-absorption treatment, α-Fe domains are NOT formed.5.Since there are not domains of a-Fe in HDDR-FeNdB with the Zn absorption treatment, it can have the value for coersive power as high as the original one by re-magnetization.6.The Zn absorption treatment can improves the corrosion resistance and the seasoning in magnetic properties. The present study has clarified the mechanism of the improvement.

NdFeB磁体是一种典型的稀土磁体，由Nd_2Fe_<14>B相制成，具有高矫顽力。然而，它也存在一些问题，即耐腐蚀性较低，并且磁性会随着时间的推移而下降（老化效应）。我们提出了一种新方法。（吸锌）赋予高耐腐蚀性。已经发现，Zn吸收处理还改善了磁性能的时间依赖性。在该研究项目中，通过透射电子显微镜（TEM）、场发射扫描电子显微镜（FE-SEM）和X射线衍射实验（XRD）对HDDR-NdFeB磁体粉末和由该粉末制成的粘结磁体的微观结构进行了表征。根据实验结果，我们得出以下结论：1.吸Zn处理后，粉末表面和Nd_2Fe_<14>B晶界上形成了Fe_<11>Zn_<40>和NdZn_5相。2.未经吸Zn处理的HDDR-NdFeB中，除h-Nd_2O_3外，还形成了α-Fe相域。 3. 未经吸锌处理的 NdFeB 磁性能的老化效应归因于 α-Fe 磁畴的存在。 4. 在经过吸锌处理的 HDDR-NdFeB 中，没有形成 α-Fe 磁畴。 5. 由于吸锌处理后的 HDDR-NdFeB 中不存在 a-Fe 磁畴。 HDDR-FeNdB经吸锌处理后，再充磁后，矫顽力值可达到原来的水平。 6、吸锌处理可提高耐腐蚀性和磁性能。本研究阐明了改善的机制。