【作者】 何敏博；

【导师】 李曦； 张超灿；

【作者基本信息】 武汉理工大学 ， 应用化学， 2008， 硕士

【摘要】 纳米磁性材料是20世纪70年代后逐步发展、壮大而成为最富有生命力和广阔应用前景的新型磁性材料与常规磁性材料相比。纳米磁性材料在很多方面体现出了优越的性能,如超顺磁性和较高的矫顽力。四氧化三铁（Fe₃O₄）是一种重要的尖晶石类铁氧体,是应用最为广泛的软磁性材料之一。在实际应用中,纳米级的Fe₃O₄更以其显著的磁敏、气湿敏特性在高密度磁记录材料、磁流体材料、磁性高分子微球、气湿敏传感器件、核磁共振的造影成像以及药物控制释放等领域显现出了巨大的应用前景。其中,磁流体和磁性高分子微球是目前研究较多的两类磁性材料。目前的研究中,制备分散性好的、稳定性高的油基磁流体一直是磁流体制备过程的难点。本论文对油基磁流体的六种制备工艺进行了研究,制备出了在多种有机介质中纳米分散的四氧化三铁磁流体。红外光谱和X-射线衍射实验表明,油酸在Fe₃O₄粒子表面形成了包覆,且磁流体制备过程中表面活性剂油酸和有机介质的加入并不影响Fe₃O₄粒子的晶形。制备的Fe₃O₄粒子洗涤后,不经过干燥过程分散在有机介质中,得到的磁流体磁含量最高,达到12%;磁流体中Fe₃O₄粒子粒径分布窄,绝大多数粒子粒径在6-10nm范围。在Fe₃O₄粒子制备过程中加入有机介质制得的磁流体粒径分布均一,粒子集中分布在5-7nm,磁含量在10%左右。得到的磁流体均具有很好的磁响应性和稳定性。制备粒径均一、磁含量高、表面功能基含量高的功能高分子磁性微球一直是人们追求的目标。环氧基作为一种可以向多种功能基转化的“活性基团”,在实际应用中体现出了很强的适应性。本论文在制备的油基磁流体和水基磁流体存在下,以苯乙烯和甲基丙烯酸缩水甘油酯为共聚单体,采用分散聚合法制备出了粒径在3μm以下,分布均一、表面光滑、磁含量2.5%的磁性微球,该微球的单体转化率在75%以上,环氧基含量在0.02 mmol/g左右。考察了分散介质、稳定剂、油基/水基磁流体对微球粒径和磁含量的影响。更多还原

【Abstract】 Nano-magnetic materials originated in late 1970s. Now it became one of the most promising new magnetic materials. Compared with the traditional magnetic materials, nano-magnetic materials manifest many outstanding qualities, such as superparamagnetism and higher coercivity. Fe₃O₄ is an important spinel type ferrite, one of the widely-used soft magnetic materials. Because of its magnetic sensitivity and gas and humidity sensitivity, Fe₃O₄ nanoparticles display extensive application prospect in such fields as high density record materials, magnetic fluids materials, magnetic polymer microspheres, gas and humidity sensors, magnetic resonance imaging and drug controlled releasing. At present, the research about magnetic fluids and polymer microspheres is popular.However, how to get the oil-based magnetic fluids with good dispersibility and stability is a critical problem.In this paper, oleic acid-coated Fe₃O₄ magnetic fluids, which can be dispersed in different organic media, were successfully synthesized by studying six different preparing methods. The results of infrared spectrum and X-rays spectrum show the surface of Fe₃O₄ particles was coated by oleic acid. The crystal shape of Fe₃O₄ was not affected by the adding of surfactants or organic solvents during the preparation of oil-based magnetic fluids. The magnetic content was the highest（12%） when fresh Fe₃O₄ particles were directly dispersed into the organic solvents without dryness after washing. Moreover, this kind of Fe₃O₄ nanoparticles has narrow diameter distribution, most in the range of 6-10nm. When the organic solvent was added during the preparation of Fe₃O₄, the fluids had more narrow diameter distribution, most in the range of 5-7nm. The magnetic content is about 10% and this kind of fluids had good magnetic response and high stability.The research focus of polymer magnetic microspheres is how to acquire monodispersing polymer magnetic microspheres with high magnetic contens and abundant functional groups on the surface. Epoxy groups can be transformed into many "active" groups. In this paper, magnetic microspheres are obtained by dispersion polymerization of styrene and glycidyl methacrylate in the present of oil-based or water-based magnetic fluids. The average size of microspheres is smaller than 3μm and the microspheres are almost monodispersed. The magnetic content is 2.5%. The surface of microspheres is smooth and Epoxy groups content is about 0.02 mmol/g. The monomer conversion is larger than 75%. The effects of dispersing medium, stabilizing agents, water/oil-based magnetic fluids on the mircrospheres sizes and magnetic content are also studied.更多还原