【作者】 吴叶军；

【导师】 诸跃进； 王军；

【作者基本信息】 宁波大学 ， 理论物理， 2008， 硕士

【摘要】 由于高密度磁存储介质、磁流体以及生物医学等领域中的巨大应用前景,磁性纳米材料的合成研究受到了越来越广泛的关注。尤其是磁性的有序纳米结构由于单元的空间取向和排列而具有许多崭新的性质,也是制备小型化纳米器件的基础,因此将磁性纳米粒子组装成各种有序结构具有显著的科学意义和应价值。本论文旨在探索用水热法合成新颖结构的磁性纳米材料,研究其物理性能,特别是磁性能,与纳米材料结构之间的内存关联。详细内容归纳如下:1.以FeCl3·6H2O、Ba(OH)2·8H2O、BaCl2·2H2O为原料,采用温和的水热反应体系合成了BaFe12O19纳米棒,在空气和氩气气氛下烧结处理后,其直径约为40nm,长度约为150nm,尺寸分布比较均匀。振动样品磁强计测量结果显示,BaFe12O19纳米棒具有较高的饱和磁化强度(67.3emug-1)和矫顽力(4511Oe)。空气中烧结处理,提高了BaFe12O19纳米棒的结晶性,降低了BaFe12O19中的氧空位数量,从而戏剧性地影响了Fe-O-Fe的超交换作用,提高了BaFe12O19的磁性能。2.以Fe(C5H5)2、C3H6O、N2H4·H2O为原料,在磁场诱导的水热体系中合成了Fe3O4纳米棒的组装结构。用XRD、MS、SEM等表征了Fe3O4纳米棒的形貌及磁性能。每个Fe3O4纳米棒组装结构由2-5个纳米棒组成,呈3D结构。磁场在Fe3O4纳米棒的组装过程中起了关键的作用。基于这些实验结果我们提出了Fe3O4纳米棒组装结构可能的生长过程。振动样品磁强计测量结果显示,Fe3O4纳米棒的饱和磁化强度(Ms)约为82.6emug-1,讨论了纳米粒子定向生长对磁性能的影响。更多还原

【Abstract】 For the promising applications in high-density magnetic data storage media, ferrofluids and biomedicine, an important research effort has been directed towards the study on the synthesis of nanoscale magnetic materials. Moreover, ordered functional structures of magnetic nanometerials have some brand-new properties resulted from the spatial orientation and arrangement of the building blocks and can be viewed as the foundation for the formation of novel miniaturized nanodevices. So research on the assembly of nanoscale magnetic materials is very important from the point of view of science and application.The objective of this dissertation is to explore new structure of nanoscale magnetic materials, based on solvothermal synthesis, investigate the relationship between their magnetic parameters and their structure (size and/or shape). The main parts of the results are summarized below:1. Rod-shaped BaFe12O19 nanoparticles were synthesized via a mild hydrothermal process, combined annealing process in air, using iron chloride, barium hydroxide, and barium chloride as starting materials. The magnetic nanorods with diameters ~40nm and lengths ~150nm were visible in TEM and SEM images. Magnetic measurements showed that the rod-like BaFe12O19 nanoparticles exhibited a great coercive field and high saturation magnetization of up to 4511 Oe and 67.3 emu/g, respectively. It is found that heat treatment in air can create less oxygen vacancies, which dramatically affects the Fe-O-Fe superexchange coupling. The results of this paper suggest that oxygen vacancies should be responsible for the decrease of saturation magnetization in nanosized magnetic materials.2. The complex nanorods of Fe3O4 have been synthesized by an induced magnetic-field-assisted solvothermal process. X-ray diffraction (XRD), M?ssbauer spectroscopy (MS) and scanning electron microscopy (SEM) have been used to investigate the complex nanorods. Each complex of the Fe3O4 is composed of two to five nanorods. The solvothermal process under induced magnetic field makes possible to assemble the Fe3O4 nanorods. In addition, magnetic properties of Fe3O4 nanorods have been detected by a vibrating sample magnetometer, showing relatively high saturation magnetization (Ms) of ~82.6 emug-1. The mechanism for the improved magnetic properties of the magnetite nanorods is discussed based on the oriented growth of nanoparticles.更多还原