芯壳结构复合磁性纳米丝的制备及其磁畴结构研究

The challenging problem is that the crystal structure and the nano-scale grain boundary how to affect the structure, the configuration and the wall structure of magnetic domains in the core-shell structured magnetic nanowire composite materials, which impact to the magnetic properties. The core-shell structured magnetic nanowires with core or shell materials of the hard magnetic material, soft magnetic material or the dilute magnetic semiconductor material would be prepared by coaxial double nozzle electrospinning method. The magnetic composite nanowires with one-dimensional core-shell structure have good orientation, smooth surface, clear interface, and the continuous uniform diameter less than the critical domain size. The nanowire magnetic anisotropy and cylindrical, cylinder single magnetic domain configuration and the inner relationship between crystal geometrical anisotrop could be revealed after studying its crystal structure, grain interface structure, the configuration and the wall structure of the magnetic domain. The difference of axial and radial magnetic properties of the alignment nanowires, moreover, the giant magnetoresistance effect and magnetoelectric effect of soft/hard magnetic nanofiber composites are investigated. The growth mechanism and crystal structure of magnetic nanofibers is studied on the base of crystal structures of magnetic composite nanowire and crystal growth dynamics. Experimental analysis and calculate the critical dimension of cylindrical magnetic domains based on the theory of spintronics with its crystal structure and band structure which may explore the effect of compound nanowire magnetic.

在芯壳结构磁性复合纳米丝中晶体结构、晶粒界面结构以及纳米晶粒尺度是如何影响磁畴结构、磁畴分布以及磁畴壁结构并进而影响磁性材料的磁性能是一些更具有挑战性的问题。本课题组拟采用改进的同轴双喷嘴静电纺丝工艺制备出分别以硬磁材料、软磁材料和稀磁半导体材料为芯层及壳层的芯壳结构磁性复合纳米丝。该丝是定向排列、表面光滑、界面清晰、均匀连续并具有芯壳结构的一维磁性复合纳米丝，直径小于临界磁畴尺寸。通过研究其晶体结构、晶粒界面结构、磁畴分布以及磁畴壁结构进而揭示出纳米丝的磁各向异性和圆柱状、圆筒状单磁畴分布与晶体几何各向异性之间的内在关联。研究定向排列的纳米丝在轴向和径向的磁性能和同轴芯壳结构软/硬磁复合材料的巨磁阻效应、磁电效应，分析磁性复合纳米丝的生长机理和晶体结构。基于自旋电子学理论，结合实验分析计算圆柱状磁畴的临界尺寸，并研究其晶体结构、界面结构及能带结构等对复合纳米丝磁性能的影响。

本课题利用静电纺丝法制备出了出定向排列、长度可达数毫米、结晶完整、的一维复合磁性纳米丝；确定出了静电纺丝最佳的溶液配比和纺丝工艺参数。利用改进的同轴双喷嘴静电纺丝法和热处理工艺制备出成功制备出多种具有芯壳结构的一维多功能复合纳米丝。探究了热处理过程中CoFe2O4磁性纳米丝圆柱状单晶体的生长机理；研究了CoFe2O4@NiO，CoFe2O4@ZnFe2O4，SrFe12O19@ZnFe2O4一维芯壳结构硬软磁复合材料的结构、磁性能和两相间作用，比较了定向排列的磁性纳米纤维和散乱排列的纳米纤维及纳米粒子的磁性能，发现纳米纤维具有比纳米颗粒更强的软、硬磁相变耦合作用这是因为晶粒交换耦合作用的强度与晶粒耦合程度、晶粒尺寸和各向异性有关，对晶体结构和磁性能进行表征，研究了晶体结构和电子结构对其磁畴结构的影响；研究了NiFe2O4@CoFe2O4芯壳复合纳米丝的电化学性能，表明由于多金属协同作用导致了电化学性能的提高；还探究了BiFeO3纳米管和BiFeO3/CeO2/Bi2Fe4O9复合材料的磁性能和光催化性能，其中由于Ce3+粒子的加入及软硬相协同作用使得复合材料的磁性能和光催化性能较好。受资助期间发表该研究的学术论文37篇，其中 SCI 和 EI 收录23篇，培养博士生3名和硕士生25名。完成了各项任务。