School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
Nanoscale. 2017 Dec 7;9(47):18651-18660. doi: 10.1039/c7nr04703g.
With increasing demand for magnets in energy conversion systems, the quest for the development and understanding of novel processing routes to produce permanent magnets has become urgent. We report a novel mechanochemical process for the synthesis of Nd(Fe,Co)B magnetic particles with a high coercivity of 12.4 kOe. This process involves the reduction of neodymium oxide, iron oxide, cobalt oxide and boron anhydride in the presence of a calcium reducing agent and a CaO diluent. The formation mechanism of Nd(Fe,Co)B changed with increasing CaO content, and the average crystal size of the Nd(Fe,Co)B particles also increased, resulting in an increase in the coercivity values. The reaction mechanism during milling was revealed through a study of the phase transformations as a function of milling time. It was found that unlike self-propagating reactions, this reduction reaction during milling requires continuous input of mechanical energy to reach a steady state.
随着能源转换系统对磁铁需求的增加，开发和理解生产永磁体的新加工方法变得尤为紧迫。我们报告了一种用于合成具有 12.4kOe 高矫顽力的 Nd(Fe,Co)B 磁性颗粒的新型机械化学工艺。该工艺涉及在钙还原剂和 CaO 稀释剂的存在下还原氧化钕、氧化铁、氧化钴和无水硼。Nd(Fe,Co)B 的形成机制随着 CaO 含量的增加而变化，Nd(Fe,Co)B 颗粒的平均晶粒尺寸也增加，导致矫顽力值增加。通过研究随着球磨时间的变化的相转变，揭示了球磨过程中的反应机制。结果发现，与自蔓延反应不同，球磨过程中的这种还原反应需要连续输入机械能才能达到稳定状态。
