- 學位論文
以定量RF3 (R=Dy 及Tb) 塗佈層進行NdFeB 燒結永磁體擴散及磁性強化之研究
Magnetic Properties Enhancement of Sintered NdFeB Magnets by Diffusing Controlled RF3 (R=Dy and Tb) Layer
摘要
本實驗以定量塗佈粉體進行晶界擴散，來達到提升磁石本質矯頑磁力為主要目的。第二部分探討粉體狀態（結晶度、粒徑）對磁石本質矯頑磁力提升之研究。 實驗中指出粉體結晶度不佳會影響重稀土的擴散效率。透過熱處理提升粉體結晶度後，可使重稀土的擴散效率得到改善。而當熱處理溫度過高則會使粉體粒徑粗化，導致稀土較不易進入磁石及晶界中，降低重稀土的擴散效益。對3.2 mm厚之燒結NdFeB磁石而言，非晶粉體B最佳熱處理條件為X2、X3 oC，而經沾覆及擴散處理後磁石之∆iHc=5.9 kOe；又非晶粉體C最佳熱處理條件為X1 oC， 而∆iHc可高達8.7 kOe。 第二部分探討為定量塗佈之研究。由薄膜胚體結果可發現2 mm厚磁石最佳磁特性出現在薄膜A厚度X1時，磁石之ΔiHc=6.0 kOe。對3.2 mm磁石而言，當薄膜A厚度X3時，磁石之ΔiHc=5.9 kOe，；而5 mm磁石最佳磁特性出現在薄膜A厚度X1時，其ΔiHc=4.4 kOe。但是若使用薄膜C在 3.2 mm磁石上時，其ΔiHc可達8.8 kOe。顯示其具有作為晶界擴散量產化的技術與成本優勢。
並列摘要
In this study, we adopted the grain boundary diffusion (GBD) process to improve the iHc of sintered NdFeB magnet. Powder were used as the diffusion source in this process. In order to study the effect of R content on the increment of iHc of sintered NdFeB magnet, film was prepared by screen printing. At first, the effect of crystallinity and particle size of powders on the magnetic properties of the GBD NdFeB magnets was also studied. It can be found that the powders with semicrystalline structure have to absorb thermal energy for crystallization prior to GBD process, which might degrade the GBD performance. As a result, low temperature, X oC, crystallization of powders before making screen printing film should be necessary. Nevertheless, too high temperature, i.e., Y oC, may cause particle coarsening to degrade the GBD efficiency. The optimum crystallization temperature for B powders is X2,X3 oC and results in the coercivity increment (∆iHc) of 5.9 kOe. In contrast, the best crystallization temperature for C powders is X1 oC and the ∆iHc reaches 8.7 kOe. At last, the films were adopted to study the controlled R content GBD effect on the sintered NdFeB magnets. It is found that, for 2-mm thickness magnet,A film is sufficient for giving the GBD magnet 6.0 kOe in ΔiHc. For 3.2-mm thickness magnet, the optimal magnetic properties of ΔiHc=6.0 kOe with A film. For 5-mm thickness magnet, the optimal magnetic properties of ΔiHc=4.4 kOe. More attractive results were found in the case of using C film, for 3.2-mm thickness magnet, the optimal magnetic properties of ΔiHc=8.8 kOe by using C µm film. From the above results, it reflects that the C film for GBD process is cost effective in enhancing the coercivity of sintered NdFeB magnets, which might be a suitable solution for mass production of GBD NdFeB magnets.