【作者】 王志峰；

【导师】 张明；

【作者基本信息】 扬州大学 ， 物理化学， 2005， 硕士

【摘要】 磁性聚合物微粒兼具磁性粒子和聚合物粒子的特性,既可方便地从介质中分离,又可对其表面进行修饰从而赋予其表面多种功能团,被广泛应用于生物医学、细胞学和生物工程等诸多领域。为了充分显示磁性聚合物微粒迅速、简便的分离特点,微粒本身应具有较高的磁响应性和比表面积。本文就是将具有较高磁矩的稀土元素对铁氧体进行掺杂,在W/O反相微乳液体系中制得了稀土铁氧体/聚丙烯酰胺纳米复合微粒。利用FTIR、XRD、TG-DTA、TEM等手段对典型样品进行了表征,讨论了pH值、NaOH加料方式、熟化过程等对产物的影响,用古埃磁天平研究了其磁性能。同时还分别采用磁移动法、比浊法、磁天平法三种方法对稀土铁氧体/聚丙烯酰胺磁性复合微粒的磁响应性进行了测定,讨论了稀土元素种类和用量对复合微粒磁响应性的影响。最后我们还将复合微粒用于磁流变液的制备和粘度性质的研究。 在由聚乙二醇辛基苯基醚(OP)为表面活性剂、正己醇为助表面活性剂、环己烷为油相和水组成的W/O反相微乳液体系中,以丙烯酰胺为单体、AIBN为引发剂,一步法制得了平均粒径大约在25nm左右的稀土镝铁氧体/聚丙烯酰胺复合微粒。当一次性快速将NaOH溶液加入体系,控制体系pH值为11,产物在80℃下熟化1h后可得磁性较强的微粒。另外,此反应对除氧气防氧化的要求较高。 对磁性复合微粒磁性能的测试表明复合微粒在外磁场作用下会发生磁化现象,镝铁氧体/聚丙烯酰胺复合微粒属于亚铁磁性材料,其摩尔磁化率高于不掺稀土镝时复合微粒的摩尔磁化率,表明稀土镝的加入可以提高铁氧体的磁性能。水基镝铁氧体/聚丙烯酰胺磁流体在低磁场范围内属于顺磁性材料,磁场变强后磁化达到磁化饱和状态,测定了其饱和磁化强度M_s。 通过对复合微粒磁响应性的测定发现,由于磁移动法、比浊法自身的特点,这两种方法不适宜用于本文制得的磁性复合微粒磁响应性的测定。相比较而言,磁天平法对测定粒径较小、磁含量较低的复合粒子的磁响应性更有优势,更适宜更多还原

【Abstract】 Magnetic polymer microparticle combines the property of magnetic particle with that of macromolecule particle. It not only can be separated from the medium easily, but also can be surface-modified in order that the surface of magnetic microparticle was endued with functional groups. So it has broad application in the fields of biomedicine, cytology and biology engineering, etc. The microparticle must possess high magnetic responsibility and specific surface area, so that magnetic separation is quick and convenient. In this paper ferrite was doped with rare earth elements of great magnetic moment and rare earth ferrite/polyacrylamide magnetic composite microparticles were prepared by one-step method in a single inverse microemulsion. The typical composite microparticles were charactered by FTIR, XRD, TEM and TG-DTA. The influencing factors, such as pH value, the charging mode of sodium hydroxide, temperature, were discussed respectively. Magnetic properties of composite microparticles were studied by Gouy magnetic balance. At the same time magnetic motion method, turbidimetric method, magnetic balance method were used to determine and study the magnetic responsibility of rare earth ferrite/polyacrylamide composite microparticles. Then the effect of the species and consumption of rare earth on magnetic responsibility were discussed. At last, the composite microparticles were used for preparation of magnetorheological fluid and research of viscosity property.Dysprosium ferrite / PAM composite microparticles with an average particle size about 25nm were prepared by inverse microemulsion system of polyethylene glycol octylphenyl ether, n-hexyl alcohol, cyclohexane and water phase, using acrylamide as monomer and AIBN as initiator. In the process of the preparation of Dy_xFe₃-xO₄/PAM composite microparticles, we find that Dy_xFe₃-xO₄/PAM nano-composite microparticles could be obtained with the condition of adding NaOH solution quickly at once into reaction system, changing pH to 11 and aging for 1h at 80 °C. We also find that deoxidize and preventing oxidizing is important to this reaction.The results of testing magnetic property of composite particles indicate that composite particles can be magnetized under exterior magnetic field and composite particles are ferrimagnetism material. Bulk magnetic susceptibility of DyxFe3.xO4/PAM is higher than that of FeaO/j/PAM, which indicates that the addition of dysprosium can improve magnetic property of ferrite. At the same time, magnetic properties of water-based dysprosium ferrite/PAM magnetic fluid was investigated. In the downfield the magnetic fluid is paramagnetism material. The magnetic fluid reaches the state of magnetization saturation in the high magnetic field and saturation magnetization were measured.Research of magnetic responsibility of rare earth ferrite/polyacrylamide indicates that the magnetic motion method and turbidimetric method aren’t applicable to the determination of magnetic responsibility of composite particles prepared in this paper. Magnetic balance method is more suitable to the particles with smaller diameters and low magnetic content, which can be used to measure magnetic responsibility of composite microparticles prepared in this paper. Magnetic responsibility of composite microparticles doped Dy, Er, Tb or Gd rises up. The changing tendency of magnetic responsibility is similar to that of magnetic moment of rare earth ions. Magnetic responsibility of dysprosium ferrite/PAM composite microparticles increases at first and decreases later with growth of dysprosium content. The microparticles show the strongest magnetic responsibility when the molar ratio of Dy3+/iron is 0.20.DyxFe3.xO4/PAM magnetic composite microparticles were dispersed in silicon oil and magnetorheological fluid （MRF） was prepared. Viscosity behavior of magnetorheological fluid under exterior magnetic field was investigated and the influencing factors, such as rotate speed, magnetic field strength, content of magnetic particles and temperature, were also discussed respectively. T更多还原