藉由RF3(R=Dy、Tb)定量塗層探討晶界擴散強化NdFeB磁石之量產可行性研究

Feasibility study of mass production of GBD strengthened NdFeB magnets by controlling RF3 (R=Dy、Tb) quantity

林明忠(Ming-Chung Lin)

指導教授 ： 張文成

國立中正大學/理學院/物理學系/碩士(2015年)

摘要

本實驗以定量塗佈RF3 (R=Dy、Tb)粉體進行晶界擴散強化燒結NdFeB磁石特性，並探討量產之可行性。第一部分探討3.5 mm厚磁石經定量轉印A薄膜後之放大實驗。當工作壓力為X1及X2時，磁石載具四角與中心處之本質矯頑磁力不均；而當工作壓力為X3時，所擴散之整體磁石之磁特性較平均，且本質矯頑磁力也較前兩者高。第二部分探討轉印與未轉印薄膜之NdFeB磁石其他方面表現之差異。結果顯示轉印A薄膜超過Y4時，磁石碳含量明顯提升，顯示在擴散過程前需要更長時間來將黏結劑排除乾淨。而所有經擴散Dy之磁石經PCT測試後，其表面並無任何凸點、起泡及生鏽。在高溫磁特性中，M等級之磁石經轉印A薄膜並熱處理後，其iHc達到SH之等級。不過，商用SH等級之磁石在角型性方面，優於經晶界擴散後之M等級磁石。不過，商用SH等級之磁石在角型性方面，優於經晶界擴散後之M等級磁石。第三部份探討將晶界擴散法應用到更厚的NdFeB磁石(=5 mm)上。結果顯示採用B與A作為黏結劑後在經GBD處理之磁石之ΔiHc皆接近4.5 kOe。但當轉印厚度超過Y5時，A會有趕除不乾淨之問題，而B薄膜則不會。另外，於3.2 mm磁石上轉印C薄膜，僅需0.35 wt % Tb即可提升∆iHc =8.1 kOe，而A薄膜需0.62 wt % 且僅提升∆iHc =5.9 kOe ，可知當RF3在可定量塗佈為前提下，Tb提升磁石之本質矯頑磁力有更好之效率。對於更厚 (≧ 5 mm)之NdFeB磁石，應可選擇較容易揮發之黏結劑B，及以C取代A來進行晶界擴散處理。
關鍵字: 晶界擴散、NdFeB磁石

關鍵字

晶界擴散

並列摘要

In order to meet the demand of mass production of grain boundary diffusion (GBD) treated NdFeB magnets, detail studies on the quality of magnets and their properties in comparison with commercial magnets are needed. In this study, A films were adopted in controlling the amount of Dy usage. At first, a mold with 4 x 4 pieces magnets was adopted for the experiments. The result showed that Ar back ground partial pressure plays an important role on the variation of magnetic properties of GBD treated magnets. The coercivity (iHc) of the magnets at edge side is slightly lower than those at the center part for X1 and X2. Meanwhile, all magnets exhibit better and homogeneous iHc enhancement for X3 Ar atmosphere. Secondly, the effect of binder system on residue carbon, oxgen content, PCT test and high temperature magnetic properties of GBD treated magnets were investigated. The results showed that the carbon concentration increases with increasing the thickness of A film up to Y4, yet the coated nickel layer of the magnets all showed comparable corrosion behavior to the conventional sintered NdFeB magnets after PCT test. For high temperature magnetic properties, the GBD treated magnets showed almost identical coercivity coefficienct, β, to commercial SH sintered magnets. Thirdly, for Y4-A tape, it was found that B binder system has an identical effect to A in enhancing iHc of about 4.5 kOe. However, with increasing tape thickness up to Y5, A binder is hard to remove thoroughly. B binder system seems to be much suitable for making thicker A tape. Meanwhile, C powders have superior effect on iHc enhancement than that of A powders for GBD treated NdFeB magnets. It can be concluded that using B binder system together with C powders should be the optimum combination for mass production of GBD treated NdFeB magnets thicker than 5 mm.
關鍵字: GBD、NdFeB magnet

並列關鍵字

GBD

參考文獻

[4] Nesbitt, E. A., Wernick, J. H. & Corenzwit, E. Magnetic Moments of Alloys and Compounds of Iron and Cobalt with Rare Earth Metal Additions. Journal of Applied Physics30, 365-367, (1959).

[5] Hubbard, W. M., Adams, E. & Gilfrich, J. V. Magnetic Moments of Alloys of Gadolinium with Some of the Transition Elements. Journal of Applied Physics31, S368-S369, (1960).

[6] G. Hoffer, and K. Strant, IEEE Trans. Magn., 2, 487, (1966).

[11] D. Das, "Twenty million energy product samarium-cobalt magnet," Magnetics, IEEE Transactions on, vol. 5, pp. 214-216, (1969).

[15] Tawara, Y. & Senno, H. Bulk Hardened Magnet of Nonstoichiometric Rare-Earth Cobalt. Japanese Journal of Applied Physics12, 761, (1973).