细晶增强多主相(Nd,Ce)-Fe-B磁体矫顽力及其微观机制研究

Multi-main phase (Nd,Ce)-Fe-B magnet was thought to be the most potential candidate with strategic and economic values among the permanent magnets family. However, high-Ce-content magnet exhibits decreased magnetic properties, especially the coercivity, which can not even satisfy the basic applications (≥12 kOe). Based on the rules of remaining the long-ranged magnetostatic interactions and suppressing the short-ranged exchange coupling interactions among the grains of multi-main-phase (MMP) magnets, present research is proposed to fabricate high-Ce-content (Nd,Ce)-Fe-B magnet with improved coercivity by refining the grain size. The submicron particles will be prepared by high energy ball-milling with Pr/Nd-containing organic solvent, and further wet-compress molding will be applied to prevent the oxidation of ultra-fine particles. Fine-grain-sized (less than 3 μm ) (Nd,Ce)-Fe-B MMP magnet will be obtained by subsequent sintering and annealing process. The local chemistry changes as well as structure fluctuates of fine-grained magnets on magnetic reversal process will be characterized and studied. Based on the results, the mechanism of grain growth, rare earth interdiffusions and multi-scaled magnetic coupling effects within the fine-grained MMP magnets will be characterized and discussed. The correlations between the local structure changes and coercivity will be established. This work is promising to obtain high-Ce-content and high-coercivity (Nd,Ce)-Fe-B magnets, which is of great significance from both the scientific and economic point of view.

多主相(Nd,Ce)-Fe-B磁体较同成分单主相磁体具有更高的磁性能，有望推动高丰度稀土Ce在永磁材料中的大量应用。然而，高Ce含量磁体的矫顽力离实际应用要求(≥12 kOe)仍有较大差距。本项目在保持多主相磁体晶粒间静磁耦合和消除交换耦合理论基础上，提出进一步细化晶粒减少反磁化畴形核中心，提高(Nd,Ce)-Fe-B矫顽力。拟通过Pr/Nd配合物有机溶剂包覆球磨制备亚微米超细磁粉，湿压成型控氧，实现晶粒尺寸小于3 μm的多主相磁体制备。系统研究烧结过程中不同成分主相的晶粒长大、元素互扩散及晶界结构的演变规律，阐明其理化反应过程和调控机理。并在此基础上，深入研究细化晶粒对多主相磁体磁畴结构和反磁化动态过程的影响，揭示细晶磁体中主相间的多尺度磁耦合规律，深化对细晶多主相磁体矫顽力机制的认识，为发展高性能低成本永磁材料奠定理论基础。

发展高性能、资源节约型钕铁硼永磁材料是我国当前稀土应用领域的一个重要基础研究方向。本项针对我国稀土资源高效利用，通过细化晶粒及多主相等技术手段，来实现高性能、低成本多主相(Nd,Ce)-Fe-B富Ce磁体的制备并研究其组织结构、性能调控方法。包括，以材料局域成分、结构和多尺度磁耦合机制为切入点，设计了不同成分和Ce取代量合金及烧结磁体，完成了(Nd,Ce)-Fe-B磁体的微观结构和磁性的关联性研究。系统的表征了多主相磁体的显微组织结构演变规律及化学非均质性特征，验证了多主相富Ce磁体析出相的形成规律及对磁体性能，尤其是矫顽力的贡献。通过反复的制备工艺探索和总结，掌握了不同稀土元素互扩散和晶粒长大过程的精细调控方法。通过对动态磁畴的观测，建立了成分、结构及磁性的一致性规律模型，为理解多尺度磁相互作用以及矫顽力的影响机制奠定了基础。项目完成了预期的研究目标。