激光可控烧蚀制备新型交换弹性磁体探索

Both theoretical and experimental work proved that an enhanced magnetic energy product would be achieved in magnetic hard/soft exchange spring magnets with optimized structures. However, it is usually difficult to prepare magnets with ideal micro-structures with the traditional methods. The aim of the proposal is to prepare high performance exchange spring magnets by ablating the targets of Sm-Fe, Mn-Bi, Nd-Fe-B as well as the transition metals, etc., with a novel self-made laser ablation device. The laser beam is capable of evaporating the targets to form different nano-clusters, which would deposit in the space, forming well-mixed nano-crystalline structures with strong interfaces after magnetic and heat treatment. The laser beams in the device can move from one target to another in a fast speed and scan any spot within a large area in a controlled way. The nano-clusters ablated by laser from different targets deposited in the wall of the chamber almost simultaneously. We are proposing to study the relationship between the microstructure and the laser power, the time parameters, the targets composition, and the post treatment parameters. The effect of the microstructure on the magnetic performance of the exchange spring magnet would also be investigated. Several novel systems with high magnetic energy product would be expected. In summary, the laser ablation method can largely expand our choice of the exchange spring counterparts and enhance the controllability. The project is expected to obtain a novel laser ablation device and with which a novel preparation method for nano materials is developed. We are going to searching novel exchange spring magnet with high magnetic energy product. This proposal is important from both fundamental and experimental points of view.

理论和实践都表明经结构优化的硬磁/软磁交换弹性磁体可具高磁能积，而传统工艺较难得到理想的微观结构导致性能不佳。本项目以钐铁、锰铋、钕铁硼及过渡金属等磁性材料为靶材，采用自主研制的程控激光烧蚀设备，使不同靶材几乎同时被剥离出来的纳米团簇在空间交织沉积，经磁场热场处理得到三维强界面纳米复合体，制备多组分、微观结构可控的交换弹性磁体。研究激光功率、时间参数、靶材组成以及成型磁场和热处理条件等对交换弹性磁体微结构的影响，研究微结构对硬磁/软磁交换耦合作用和磁能积的影响规律，以期得到高磁能积三维强界面纳米复合体系。激光烧蚀工艺扩大了交换弹性体系材质成分选择范围，增强了产物微结构可控性，突破了传统工艺局限。项目可形成自主知识产权激光烧蚀热处理技术及装备，开辟一个纳米晶复合材料合成新方法，并期望得到新型高磁性能交换弹性磁体。研究开展有重要基础意义和应用前景。

项目利用激光烧蚀方法获得纳米晶材料，辅助其它后处理技术实现材料的结构和性能调控。我们设计完成了激光烧蚀装置，实现激光束在靶面空间和持续时间可调控，实现真空制备室气氛可调控。利用激光烧蚀法制备了矫顽力高达1.05 T的Mn3O4纳米颗粒、制备了含亚铁磁Mn4C相和反铁磁MnO相的磁性交换偏置粉末、制备了MnBi纳米颗粒并研究了其磁性。我们首次成功制备了高纯度Mn4C并研究了其磁性、给出了其第一张XRD数据卡片，发现了其饱和磁化强度在50K-590K范围内随温度升高而升高的反常现象，Mn4C也是目前已知的唯一在室温以上饱和磁化强度随温度升高而升高的物质，其在调控材料热磁行为方面有应用价值。我们采用40MPa高压氧气，以三氧化铬为原料，在加热条件下，通过始终使二氧化铬处于热力学稳定状态获得了史上最高纯度的二氧化铬。我们发展了一种测试锰铝基磁性材料相变的方法，该法可精确确定不同成分锰铝基合金的不同相变模式的相变开始温度和结束温度，为制备纯相锰铝铁磁相奠定了基础。我们用透射电镜原位观察了锰铝基磁性材料的相变过程，使人们对锰铝基磁性材料相变过程物理机制的认识更加清晰。我们用锰纳米颗粒与镓直接反应制备了L10Mn1+xGa和bcc-Mn23Ga77纳米颗粒并研究了其磁性。利用高磁场辅助合成MnBi各向同性纳米颗粒及各向异性块体，研究了镓掺杂对MnBi合金结构和磁性的影响。多年来MnAl合金的低矫顽力已成为发展高性能MnAl基磁体的障碍。我们通过对MnAl施加强塑性变形获得了室温矫顽力达到创纪录的0.59特斯拉的块状磁体。利用高压和快冷甩带技术合成了高矫顽力MnAl-C并研究了其磁性。利用高压和原子化技术合成了高矫顽力MnAl-C并研究了其磁性。