界面调配提高纳米晶复合永磁材料矫顽力的研究

纳米晶复合永磁材料的矫顽力低是制约高性能永磁材料发展的主要原因之一，同步提高磁化强度和矫顽力是进一步提高纳米晶复合永磁材料磁性能的关键。本申请采用热压结合低温退火技术在α-Fe/Nd2Fe14B纳米晶的界面处引入低熔点合金NdCu，利用热变形结合退火技术将重稀土元素Dy扩散至α-Fe/Nd2Fe14B纳米晶的界面处。利用正电子湮灭等研究α-Fe/Nd2Fe14B纳米晶界面结构和成分特征及其控制，研究不同热压/热变形工艺及退火条件下NdFeCoB 合金所制备的α-Fe/Nd2Fe14B纳米晶磁体界面结构和成分的变化规律及其对合金矫顽力和磁能积的影响。测定磁体初始磁化曲线和小磁滞环的矫顽力Hci，根据其磁化强度M和矫顽力Hci随磁化场强度的变化规律来研究纳米晶复合永磁体的矫顽力机制。 本项研究通过α-Fe/Nd2Fe14B纳米晶界面结构和成分的调配来提高纳米晶复合永磁材料矫顽力从而改善其磁能积

In general, there is a trade-off between magnetization and coercivity in nanocomposite magnets, that is, high magnetization usually accompanied by small coercivity is a major barrier for achieving high-energy products in the magnets . Thus, the simultaneous enhancement of both the magnetization and coercivity is a fundamental challenge in the quest for high performance α-Fe/Nd2Fe14B nanocomposite magnets. The NdCu eutectic alloy or a heavy rare-earth element such as Dy is introduced to the grain boundary in α-Fe/Nd2Fe14B nanocomposite magnets prepared via a hot pressure or hot deformation process compared with thermally annealing. The interfacial structure and composition of the nanocomposite magnets are studied by employing positron lifetime measurements combined with a coincident Doppler broadening (CDB) measurement of the positron-electron annihilation photons. The influence of interfacial structure and composition on the coercivity and energy product is analyzed. The hysteresis loop of the magnets is measured at room temperature using a vibrating sample magnetometer, and their magnetization reversal mechanism was studied by analyzing initial magnetization curves and minor hysteresis loop. In conclusion, the coercivity and energy product of α-Fe/Nd2Fe14B nanocomposite magnets are enhanced by interfical modification such as interfacial structure and composition.