成果報告書詳細
管理番号20110000001389
タイトル*平成22年度中間年報 希少金属代替材料開発プロジェクト 希土類磁石向けディスプロシウム使用量低減技術開発(4)
公開日2011/12/13
報告書年度2010 - 2010
委託先名国立大学法人東北大学
プロジェクト番号P08023
部署名電子・材料・ナノテクノロジー部
和文要約和文要約等以下本編抜粋:研究開発項目(1)「結晶粒の微細化・原料粉末最適化による保磁力向上技術の開発」 (1)~3 高保磁力磁石の焼結組織最適化に関する研究【東北大学(杉本 諭)】【緒言】本研究開発項目では、(1)~1原料合金開発と(1)~2超微細結晶粒焼結磁石作製プロセス開発と連携して、Nd-rich相の組織形態などと保磁力の関係を明確化し、磁石作製工程における最適条件の確立に寄与する。今年度は(1)微細結晶粒焼結磁石の組織、(2)Nd2Fe14B/Nd-Oモデル界面を利用して保磁力に及ぼすNd-rich相に含まれる酸素の影響、を調べた。
英文要約Nd-Fe-B magnets are useful permanent magnets utilized in many applications such as hybrid electric vehicles (HEV). As high heat resistance and high coercivity are strongly required in HEVs, some amounts of Dy are added to Nd-Fe-B magnets. However, the natural abundance of Dy is quite low and producing countries are limited. Therefore, the development of Dy-free or Dy-less Nd-Fe-B sintered magnets with high coercivity is strongly demanded. In order to enhance the coercivity, grain refinement in sintered magnets and the microstructural control at the interface between Nd2Fe14B and Nd-rich phases are important. Therefore, the following researches were carried out in this research. 1.Optimization of the Microstructure in Nd-Fe-B Sintered Magnets; In this year, we evaluated microstructure of sintered magnets prepared from small jet-milled powders and investigated the influence of Nd2Fe14B/Nd-rich interface microstructure on coercivity by using a model interface. It is found that the distribution of Nd-rich phase in the sintered magnets from small jet-milled powders was evaluated to be close to ideal. From the investigation using a model interface, a Nd2O3 phase was observed at the interface, which induced defects into a Nd2Fe14B phase and caused the decrease of coercivity. 2.Coercivity Enhancement by Interface Structure Control using High-Magnetic-Field Processing; This year, we newly designed and constructed a high-magnetic-field processing apparatus for each manufacturing step of sintered Nd-Fe-B magnets. We observed surface migration phenomena of the Nd-rich phase induced by annealing under strong magnetic-force field. This suggests a wide feasibility of the high-field processing in manipulating the Nd-rich phase. We also succeeded in sintering Nd-Fe-B magnets under high magnetic fields of up to 10 T. This will lead to new sintered Nd-Fe-B magnets with a highly anisotropic internal structure. 3.Theoretical study on the origin of coercive force of rare-earth parmanent magnets; We study the crystal field parameter of Nd or Dy ions in crystalline Dy-doped Nd2Fe14B, based on the first principles calculations. We find that (a) the crystal field parameters for the Dy ions located around the (001) surface are also negative as well as Nd ion. We also carry out a micromagnetic simulations for the Nd (001) surface systems and find that (b) the coercivity of the (001) model is reduced by half from the bulk value and is recovered by substitution of Nd ions by Dy ions. 4.Magnetic reversal mechanism in the group of crystal grains in Nd-Fe-B magnets, and the controlling method of the reversal mechanism; The decrease in coercivity in the samples (1000-10000grains) depends on the polished plane, i.e. the c-plane polishing more deteriorates the coercivity than that in the c (⊥) plane. About the oxygen partial pressure in sample treated atmosphere, 0.1ppb is better than the 0.1ppm for keeping coercivity. The Dy coating treatment now can be done in our system.
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