【作者】 王秀宇；

【导师】 杨桂琴；

【作者基本信息】 天津大学 ， 应用化学， 2003， 硕士

【摘要】 本文是围绕着磁流体的制备来进行研究的，并根据磁流体的组成将其制备流程分为以下三大环节：纳米级磁性粉体颗粒（粒径在10nm左右）的制备；磁性粉体颗粒的表面处理；磁流体的制备。首先，是小粒径的磁性粉体颗粒的制备。根据大量试验探索，本文找到制备小粒径 （~10nm）磁性粉体材料的较好方法——低温相转化法。并通过对反应中升温顺序的控制，发现用先升温法在制备10nm左右的小粒径磁性颗粒材料方面较具有优越性，并用这种方法相继制得了一系列纳米尖晶石型磁性粉体材料。另外还通过在制备样品的过程中掺杂Zn2+，使Zn2+进入所制备的尖晶石型样品的四面体间隙内，并通过尖晶石结构中离子间的超交换作用，可以使所制样品的磁性能得到很大的提高，从而优选出可以用来制备磁流体的纳米磁性粉体样品。其次，是用油酸对适合用来制备磁流体的磁性粉体颗粒进行表面处理，以降低粒子的表面能，从而可防止因两个磁性粒子互相接近而引起颗粒在载液中聚凝和沉降。并用紫外光谱仪对磁性粉体颗粒表面改性效果进行定量评估，探讨了pH值、温度、时间以及复合表面活性剂对颗粒表面包覆效果的影响，从而确定了磁性粉体颗粒表面改性效果的最佳条件。最后，是把表面改性效果最佳的磁性粉体颗粒通过过渡液均匀分散于载液中而制得磁流体。试验中采用DOP作载液，这是因为DOP的凝固点为-50℃，沸点为384℃，用其作载液不仅能耐一定的低温，而且也能耐高温，具有很宽的温度适用范围。文中探讨了过渡液、温度对制备磁流体稳定性的影响以及固液比与粘度的关系。试验表明，在制备磁流体时，温度不宜太高，否则会影响制备的磁流体的稳定性；并且磁流体的粘度随其所包含磁性颗粒量的增加而增大。本文对磁流体制备过程中的各个环节进行了较为详尽的研究，并进行了相应的表征、分析，取得了一些极为有价值的数据，尤其是在纳米磁性粉体颗粒的制备及其表面处理效果的评估方面作了很有意义的探索。更多还原

【Abstract】 In this article, the preparation of magnetic fluids was the center of investigation. According to the makeup of the magnetic fluids, for which the process of preparation was done as follow, first, the fabrication of magnetic powders with nanosize about 10nm; second, the disposal for the surface of magnetic powders; finally, the preparation of magnetic fluids.Firstly, magnetic powders with small nanosize were fabricated. According to abundant research in experiment, a better method, phase transformation at low temperature, was found using for the synthesis of magnetic powders with small nanosize about 10nm. By means of the control for the order of temperature-raising in the process of synthesis, pre-temperature-raising method was of more superiority in the preparation of magnetic powders with small nanosize about 10nm. And a series of magnetic powders with nanocrystalline structure was synthesized. In addition, in the process of the samples fabricated, a little of matter with Zn2+ ion was added in order to make Zn2+ ions enter the interspace of tetrahedron for the samples with spinel structure. Through the super-exchange reciprocity among the different ions in the spinel, the magnetization of the samples prepared could be raised in large degree. So samples of magnetic powders with nanosize about 10nm were chosen suitable for the preparation of magnetic fluid. Secondly, the disposal for the surface of magnetic powders, which met the requirements of the preparation of the magnetic fluids, was done so as to reduce the surface energy of the magnetic particles, and thus to prevent two magnetic particles from approaching which might lead to congregation and sedimentation of particles in carried liquids. The effects of the disposal for the surface of magnetic powders were evaluated by UV spectra apparatus，researching the impacts about vales of pH, temperature, time and compound surfactants on the effects of the disposal for the particle surface. So the best conditions on the effects of coating for particle surface were achieved. Finally, magnetic particles, which were coated best, were dispersed uniformly in <WP=5>the carried liquids by means of transition liquids, and thus magnetic liquids were formed. In the experiment, DOP was used for carried liquids. Because its freezing point and boiling point were at -50℃ and 384℃ respectively, so it can endure both a certain lower temperature and higher temperature, with a wide range of temperature application. In the paper, investigation was done in the impacts about transition liquids and temperature on the stability of magnetic fluids as well as the relation between liquid-solid ratios and viscosity of magnetic fluids. The results of experiment indicated that temperature had better be controlled properly in the preparation of magnetic fluids, of which, otherwise, the stability may be influenced if the temperature is much higher. And the viscosity of magnetic fluids increases with the increase of quantity of particles in the carried liquids.Each step in the preparation of magnetic fluids was investigated in more detail, with characterization and analysis done accordingly, and some more valuable data were obtained. Especially, meaningful quest was done in the aspects of preparation for magnetic particles with nanosize and evaluation for their surface coating effects.更多还原