基于核-壳-壳结构的耐高温各向异性Sm-Fe-N磁性材料及其机制研究

各向异性钐铁氮是一种内禀性能优异的新型稀土永磁材料。然而受限于其矫顽力的高温损失，难以满足军工等领域对耐高温永磁材料的严苛需求。如何构建新的磁粉模型，优化元素组成，获得高Br、高Hcj、高(BH)max，并揭示其内在机制是亟待解决的重要科学问题。为此，本项目拟充分发挥Sm2Fe17N3相的高Bs特性，以其单晶颗粒为主相，并通过“还原-扩散-掺杂”的手段使其均匀包裹Mn、Co等元素的扩散层，以抑制表层“反磁化形核”，增加磁畴壁移动与翻转所需能量，维持矫顽力；此外，包覆SiO2使磁性相隔绝空气。从而构筑Sm2Fe17N3@Sm2Fe17-xMxN3@SiO2三层结构。系统研究核-壳-壳磁粉的构筑及结构调控方法，探究表层元素组成、扩散层厚度、包覆条件等因素对矫顽力的作用规律，深入探究成分结构与矫顽力之间的内在关联机制，为各向异性钐铁氮磁粉的高矫顽力化及其在高温领域的应用提供理论基础与实验依据。

Anisotropic Sm-Fe-N is a new type of rare earth permanent magnet material with excellent intrinsic properties. However, due to the high-temperature loss of its coercivity, it is difficult to meet the strict requirements of high temperature for permanent magnet materials in the military industry and other fields. In this field, how to construct a new magnetic particle model, optimize the element composition, obtain high Br, high Hcj, and high (BH)max, and reveal its internal mechanism have become important scientific issues that need to be addressed urgently. To solve these problems, this project proposed to give full play to the high Bs characteristics of the Sm2Fe17N3 phase, with its single-crystal particles as the main phase, and through the "reduction-diffusion-doping" method to make it uniformly wrap the diffusion layer of Mn, Co, and other elements to inhibit the "reversal magnetization nucleation" of the surface layer, increase the energy required for the movement and turnover of the magnetic domain wall, and maintain the coercive force. Furthermore, the coating of SiO2 makes the magnetic phase isolated from the air. Accordingly, a three-layer structure of Sm2Fe17N3@Sm2Fe17-xMxN3@SiO2 is constructed. The construction and structure control methods of core-shell-shell magnetic powder will be systematically studied, and the effect of surface element composition, diffusion layer thickness, coating conditions, and other factors on the coercive force will be carefully characterized. Additionally, the internal relationship between the compositional structure and the coercive force will be deeply explored. This project would provide an experimental and theoretical basis for the high coercivity of anisotropic Sm-Fe-N magnetic powder and its better application in the high-temperature field.