高性能各向异性钕铁硼纳米永磁材料的结构、磁性能及矫顽力机理

The permanent magnetic nanoparticles, which possess numerous unique nanostructures and excellent magnetic properties, have been widely used in many fields of magnetic recording storage, targeted drugs, magnetic resonance imaging et al., and especially act as the essential base materials for two-phase composite permanent magnets — the next generation permanent magnets — with potential ultra-high energy product, need depth and systematic research as soon as possible in order to promote the process of development and practical use. .Therefore, this project select Nd-Fe-B compounds conducting as the focus and hotspots permanent magnetic materials as the main research objects, and utilize the current international advanced surfactant-assisted high-energy ball milling technique supplemented by ultrasonic vibration and centrifugal separation technology for nanoparticles classification, to product Nd-Fe-B permanent magnetic nanoparticles and nanoflakes in this "Top-down" approach with their particle-sizes controllable ranged from a few to a few hundred nanometers. .For the current status and problems that the coercivity values of Nd-Fe-B nanoparticles and nanoflakes are still too low, this project will analysis in-depth the effects of alloy composition, preparation process parameters on their particle-size distribution, phase structure, microstructure, magnetic properties and further investigate their formation mechanisms, coercivity mechanism and others, in order to achieve a breakthrough improvement of their coercivity values ultimately and to provide primitive permanent magnetic materials with structure controllable and excellent permanent magnetic properties for the high-temperature magnets, small and special electrical machines, two-phase composite permanent magnets and other permanent magnets with extremely promising application prospects.

永磁纳米颗粒具有独特的纳米结构和优异的磁性能，广泛应用在磁记录存储、靶向药物、磁共振成像等诸多领域，更是下一代双相纳米复合永磁体必备基元材料，亟需深入和系统研究以促进其开发并实用化。本项目选择Nd-Fe-B合金这一重点与热点永磁材料作为主要研究对象，选用当前国际先进的表面活性剂辅助高能球磨技术（SABM技术）和随后辅以的超声振荡加离心分离的纳米颗粒分级技术，以“自上而下” 的方式研制出颗粒尺寸在几个纳米到几百个纳米内可控的Nd-Fe-B永磁纳米颗粒和纳米片材料；针对当前Nd-Fe-B纳米颗粒矫顽力非常低的现状和难题，本项目通过深入分析合金成分、制备工艺参数等对其颗粒尺寸及其分布、相结构、显微组织、磁性能的影响规律，及进一步探讨其形成机理、矫顽力机理等机理问题，最终实现其矫顽力等指标的明显提高，为极具应用前景的高温磁体、微特电机、双相纳米复合永磁体等提供结构可控、磁性能优良的永磁基元材料。

永磁纳米颗粒因其独特的纳米结构和优异的磁性能而广泛应用在磁记录存储、靶向药物、磁共振成像、下一代双相纳米复合永磁体等方面。本项目选择Nd-Fe-B合金这一重点与热点永磁材料作为主要研究对象，选用当前国际先进的表面活性剂辅助高能球磨技术（SABM技术）和随后辅以的超声振荡加离心分离的纳米颗粒分级技术，以“自上而下”的方式研制出颗粒尺寸在几个纳米到几百个纳米内可控的Nd-Fe-B永磁纳米颗粒和纳米片材料。首先，利用SABM技术与HDDR技术相结合，制备高性能的各向异性纳米钕铁硼磁粉，其易轴和难轴的矫顽力分别达到7.8和6.2kOe的水平，着重解决了Nd-Fe-B纳米颗粒矫顽力难以突破3kOe的突出难题。其次，利用该技术研制了高性能的片状Sm2Co17纳米颗粒，其易磁化轴和难磁化轴方向的室温矫顽力分别达到7.7 kOe和3.5 kOe，研制了高性能的片状CeCo5纳米颗粒，其难轴和易轴的矫顽力分别达到3.4 和 5.4 kOe。然后，利用红外傅里叶测试技术，明确了油酸、油胺表面活性剂的具体影响机理和物理图景，直接证实了它们在SABM球磨过程中的细化晶粒、防止团聚、防止氧化、诱致各向异性、保持晶型的有效作用机制。不但如此，利用美国NIST开发的OOMMF软件对片状NdFeB纳米永磁材料与软磁相Co、软磁相FeCo、及Sr-M锶铁氧体组装成为软磁/硬磁纳米复合磁体和双硬磁主相纳米复合材料进行模拟计算研究，最大磁能积分别达到553.35kJ/m3和692.24kJ/m3，均超过单相NdFeB的理论最大磁能积，均表现除了显著的剩磁增强效应。在研究过程中，本项目还对钕铁硼永磁纳米颗粒尺寸及其分布、相结构、显微组织、磁性能的影响规律及其形成机理进行了深入探讨。钕铁硼永磁纳米颗粒的研制将有可能为极具应用前景的高温磁体、微特电机、双相纳米复合永磁体等提供结构可控、磁性能优良的永磁基元材料。