Rolls-Royce@NTU Corporate Lab, Nanyang Technological University, 639798, Singapore.
Nanoscale. 2017 Sep 28;9(37):13956-13966. doi: 10.1039/c7nr02348k.
The excellent hard magnetic properties of NdFeB based magnets have an enormous range of technological applications. Exchange-coupled NdFeB/α-Fe magnets were chemically synthesized by a microwave assisted combustion process to produce mixed oxides, followed by a reduction diffusion process to form magnetic nano-composite powder. This synthesis technique offers an inexpensive and facile platform to produce exchange coupled hard magnets. The size dependent magnetic properties were investigated. The formation mechanisms of the oxide powders and the reduction diffusion mechanism were identified. The microwave power was found to play a crucial role in determining the crystallite size. The coercivity of the powder increased with increasing particle size. Room temperature coercivity (H) values greater than 9 kOe and magnetization of 110 emu g was obtained in particles with a mean size of ∼62 nm. An energy product of 5.2 MGOe was obtained, which is the highest reported value for chemically synthesized hard magnetic NdFeB/α-Fe powders.
基于 NdFeB 的磁铁具有优异的硬磁性能，在众多技术领域都有广泛的应用。通过微波辅助燃烧过程，化学合成了交换耦合 NdFeB/α-Fe 磁铁，生成混合氧化物，随后通过还原扩散过程形成磁性纳米复合粉末。这种合成技术为制备交换耦合硬磁体提供了一个经济、简便的平台。本文研究了尺寸依赖性磁性能。确定了氧化物粉末的形成机制和还原扩散机制。研究发现，微波功率在确定晶粒尺寸方面起着至关重要的作用。随着颗粒尺寸的增加，粉末的矫顽力增加。在平均粒径约为 62nm 的颗粒中，获得了大于 9kOe 的室温矫顽力（H）值和 110emu/g 的磁化强度。获得了 5.2MGOe 的能量积，这是化学合成硬磁 NdFeB/α-Fe 粉末的最高报道值。
