【作者】 马小娟；

【导师】 李建；

【作者基本信息】 西南师范大学 ， 凝聚态物理， 2003， 硕士

【摘要】 本文首先回顾磁性液体的发展历史，将多种磁性液体从三个不同角度进行细致的分类，并简要介绍磁性液体的重要应用及应用原理。 在化学共沉淀法的基础上，利用共沉淀——酸蚀法制备出CoFe₂O₄离子型磁性液体。通过改变基液（聚乙二醇）的质量百分比浓度S和磁性微粒的体积分数φ_ν两个重要的参量，我们得到六种磁性液体。制备过程中，用分析天平准确称取所需物质的质量，实验操作的注意事项时刻牢记在心，使得磁性液体的质量得到保证。 用透射电子显微镜（TEM）观察到：微粒在磁性液体中均匀分散，有少数微粒形成聚集体。以DLVO理论为基础，利用扩散双电层结构分析得知，影响CoFe₂O₄离子型磁性液体稳定性的因素有：磁性微粒粒径D、磁性液体的Q值、磁性微粒的体积分数φ_ν，以及磁性微粒表面粘性层的存在。 用粘度计测量了不同磁性液体在有无外磁场时的粘滞性，并分别讨论其变化原因。在无外磁场的情况下，利用Smoluchowsky和Mooney的流变学理论分析了磁性液体的粘滞系数η随基液质量百分比浓度S和磁性微粒体积分数φ_ν的增加 中文摘要而增加的原因。在外磁场的作用下，综合Rosensweis公式及流体力学理论很好的解释了在外界温度一定时，基液质量百分比浓度S和磁性微粒体积分数人确定的磁性液体，其粘滞系数司随外磁场的增加而增加的原因。 用相消法设计了测试磁光效应一一透射光强的装置，测试了光线与外磁场方向一致（都垂直于磁性液体薄膜）的情况下，透过六种CoFe。0。离子型磁性液体的激光强度随时间的变化情况。整个测试过程共5005。未加外磁场时，光透射率下一；505施加外磁场的瞬间，T迅速上升，随着时间的推移逐渐下降，减小到某个值后又回升，慢漫趋于一个稳定值；3505撤掉外磁场，丁瞬时减小，接着缓慢回升，趋于一个稳定值。为了明确各因素对磁性液体光透射率的影响，分以下三种情况作了详细讨论八1)人和S相同，B不同；u)人和J相同，J不同；（3）S和B相同，人不同。 利用磁偶极子模型和磁链模型描述了磁性液体在各种条件下内部结构随时间的变化，并用有效场理论解释了磁性微粒成链，链的变化以及链间相互作用的机理，从而说明了由于磁性液体内部结构变化导致的光透射率的变化。更多还原

【Abstract】 This paper reviews the history on the progress of magnetic fluid, classifies all kinds of magnetic fluid from three different perspectives, and briefs the application of magnetic fluid and the principle.On the base of chemical coprecipitated method, we prepare CoFe2O4 ionic magnetic fluid by coprecipitated and acid erode method. We get six kinds of magnetic fluid through changing two important parameters, which are mass percent S of basicliquid and magnetic particulate volume ratiov. In order to get magnetic fluid of highquality, we carefully weigh the needed material by the analytical balance and keep in mind the points for attention of the experimental operation during the course of experiment.Utilizing the Transmitted Electronic Microscope (TEM), we can observe that particles disperse uniformly and some of them congregate. Using the structure of diffused electric doublet layer based on DLVO theory, we analyze the factors which influence the CoFe2O4 ionic magnetic fluid’s stability, and they include magneticparticles’ diameter D, magnetic fluid’s Q, magnetic particulate volume ratio v, and the viscous layer on the surface of particles.We respectively measure some different magnetic fluid’s viscosity by theviscometer in the magnetic field and not in the magnetic field, and discuss what result in it. Using Smoluchowsky and Mooney’s rheology theory we analyze that withoutmagnetic field 77 will increase as S andv increase; using the Rosensweig’s formula and hydromechanical theory, we can illustrate that in the magnetic field and the outside temperature being certain, 77 will increase as the magnetic field increase,when the magnetic fluid’s S and v are determined.We design a set of devices that can test magneto-optical effects-transmitted laser’s intensity using quits method. And we test how the laser’s intensity changes with time through six kinds of CoFe2O4 ionic magnetic fluid when laser has the same direction as the magnetic field (be perpendicular to the magnetic fluid film). The whole test course takes 500s. Without magnetic field, transmitivity T equals 1; At the moment of 50s, when the magnetic field is added, T increases rapidly, then decreases gradually, and increases again when it is minimum, later reaches a stable value slowly; At the time of 350s, when the magnetic field is got rid of, T decreases instantaneously and increases by inches until it is a stable value. In order to explain how the factors influence the magnetic fluid’s transmissivity, we use discuss the following three cases in detail: (1)v and S are same, while B is different; (2) v and B are same, while S isdifferent; (3) S and B are same, while v is different.We describe how magnetic fluid’s inner structure transforms with the time under all kinds of conditions using magnetic dipole model and magnetic chain model. And using effect field theory we analyze the mechanisms of the magnetic particles being chains, change of the chains and reciprocity in chains. So we can make out that the transmissivity varies with the magnetic fluid’s inner structure.更多还原