成果報告書詳細
管理番号20110000001379
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(1)
公開日2011/12/13
報告書年度2010 - 2010
委託先名独立行政法人物質・材料研究機構
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:1. 研究開発の内容及び成果等 (1)目的 Nd-Fe-B系焼結磁石の界面ナノ構造や磁化過程の詳細な解析をすることによって、現状の保磁力が異方性磁場(90 kOe)の10%程度の値に留まっていること、従来の研究から結晶粒を小さくしても保磁力がある結晶粒径で急激に低減すること、などの理由を解明し、保磁力向上の指導原理を獲得する。得られた情報は微細化グループ及び界面グループの製造プロセスへ還元する。
(2)平成22年度研究実績 これまで、既存の商用焼結磁石のHRSEM, TEM, 3DAPによるマルチスケール解析により、最適化熱処理の有無、Cu, Al添加の有無、DyのNd置換による保磁力変化のメカニズムの解明を行い、焼結磁石で保磁力を高めるために必要な界面ナノ構造の設計指針の検討を行ってきた。
英文要約Microstructure of ultra fine grained high coercivity Nd-Fe-B sintered magnet
We report the mechanism of coercivity enhancement in the as sintered and post sinter annealed ultra fine grain sized Nd-Fe-B sintered magnets based on detailed microstructure characterizations. The coercivity values of the as-sintered and the optimally post-sinter annealed samples were 1361.5 kA/m and 1516.6 kA/m; respectively, with the same remanence magnetization of 1.42 T. The microstructure of these magnets is compared to that of conventional sintered magnets with 5μm and 3μm grain size. From SEM BSE images and EDS elemental mapping, it was understood that the volume fraction of NdOx is much smaller than that of conventional 3μm grain size sintered magnets. 3D tomographies of Nd-rich phases for the as sintered sample showed feature of interconnection for Nd-rich grains which was pronounced for the post sinter annealed sample. Also, volume fraction of different phases, such as NdOx, metallic Nd, and Cu-rich phase was calculated for the as sintered sample. Nd-rich grains are smaller and more uniformly distributed compared to that of conventional sintered magnets with larger grain size. TEM observations from grain boundaries showed the surface of powders are uniformly covered by thin Nd-rich grain boundary phase. Also, smooth interface was found between metallic Nd-rich phase and Nd2Fe14B grains. Atom probe tomography indicates control of oxygen can change the chemistry of some grain boundaries. It was found that in the grain boundaries containing thick grain boundary phase, amount of rare earth elements increased to around 48 at.%. Enrichment of Fe in the grain boundary phase is around 43 at.%. Despite to the depletion of Fe from the grain boundary phase, there is Co enrichment in the grain boundary phase with amount of 2.6 at.%. There is an enrichment of Cu in both sides of the thick grain boundary phase with amount of 9 at.% and 3.2 at.%. The fine grain size, the interconnected feature of the Nd-rich phase, chemistry of thick grain boundary phase, and the small volume fraction of Nd-oxide are the microstructural features for achieving high coercivity in the ultrafine grain sized sintered magnets.
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