2004 Fiscal Year Final Research Report Summary
Microstructure Control and Improvement in Magnetic Properties of Rare-Earth Magnet Powders by Absorption Treatment
| Project/Area Number |
14350342
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
KUWANO Noriyuki Kyushu University, Art Science and Technology Center for Cooperative Research, Professor, 産学連携センター, 教授 (50038022)
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| Co-Investigator(Kenkyū-buntansha) |
ITAKURA Masaru Kyushu University, Interdisciplinary Graduate School of Engineering Sciences, Associate Professor, 大学院・総合理工学研究院, 助教授 (20203078)
HATA Satoshi Kyushu University, Interdisciplinary Graduate School of Engineering Sciences, Research Associate, 大学院・総合理工学研究院, 助手 (60264107)
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| Project Period (FY) |
2002 – 2004
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| Keywords | rare-earth magnet / bond-magnet / transmission electron microscopy / microstructure / Zn- absorption / corrosion resistance / neodymium magnet |
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| Research Abstract |
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.
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Research Products
(5 results)
