【作者】 熊隆荣；

【导师】 文玉华；

【作者基本信息】 四川大学 ， 材料加工工程， 2007， 硕士

【摘要】 磁流体是由磁性粒子、表面活性剂以及载液三者混合而成的一种稳定的胶状溶液。由于这种胶状液体既有固体磁性材料的磁性，又有液体材料的流动性，且这种胶体溶液在重力场和磁场作用下是稳定而不沉淀的，具有许多其它固体磁性材料与液体材料所不具有的特殊性质，可以广泛地应用于密封、研磨、热疗、靶向给药等领域。但是磁流体稳定性差的问题一直没有得到很好的解决，这大大限制了磁流体的应用。为了解决这一问题，我们系统地研究了制备工艺参数、表面活性剂及其包覆结构对磁流体稳定性的影响，并初步研究了磁流体靶向载药微球的制备技术，得到了以下一些主要结论：1)获得了共沉淀法制备Fe₃O₄磁性粒子的最佳制备工艺：最佳的反应温度为75℃，反应浓度是0.5mol／L。反应温度主要影响Fe₃O₄的晶体结构，在低温时主要得到反铁磁性α-FeOOH相，降低了Fe₃O₄磁性；反应浓度主要影响Fe₃O₄的生成速度，进而影响Fe₃O₄的晶体结构。2)油酸钠包覆磁流体的反应最佳pH值是5.5，载液的pH值是10；油酸钠同磁性粒子间形成化学吸附，降低了磁性粒子的表面能，增加了粒子间的阻力，大大提高了磁流体的稳定性。由于表面活性剂在磁性粒子表面的钉扎包覆后的磁性粒子的饱和磁化强度小于未包覆的磁性粒子。3)油酸钠化学吸附在第一层，多余的油酸钠物理吸附在第二层。我们提出了形成良好稳定性磁流体的表面结构条件：一是必须有一定的驱动力使表面活性剂向磁性粒子靠拢；二是粒子同表面活性剂必须形成牢固的吸附；油酸钠包覆磁流体的过程：共沉淀法制备磁性粒子在表面吸附了大量的羟基，在酸性条件下，这些羟基吸附了大量的H+而使整个粒子带正电荷。加入的油酸钠电离出带负电的油酸根，油酸根和磁性粒子间由于库仑力的作用相互靠拢在一起，油酸根中的-C=O均裂成两个相等的-C-O-单键，同磁性粒子表面结合形成第一层吸附；这时溶液中还有过量的油酸钠，而油酸钠一端疏水，另一端亲水，这种疏水和驱水的形成的驱动力使得溶液中的油酸钠疏水端物理吸附在第一层，形成第二层，而亲水端则深入水中。但是物理吸附的第二层并不牢固，很容易被有机溶剂洗掉，而化学吸附的第一层则很牢固。油酸钠包覆后的磁流体这种两层特性可以使磁流体分散在极性和非极性溶液中。4)磁流体可以作为靶向载药给药的载体；更多还原

【Abstract】 Magnetic Fluid (MF) is a stability colloid which is composed of magnetic particles, surfactant and based liquid. MF has many special qualities which other solid materials and liquid materials don’t have, such as solid’s magnetism and liquid’s fluidity. MF is also a stable colloid under gravity and magnetic field. It can be extensive used in the filed of seal, polishing, target drug deliver, hyperthermia and so on. But the problem of MF with low stability has not been solved well, limiting the extensive application. To solve this problem, we systemic studied how the method of preparation, surfactant, and the surface structure of coated layer influenced the stability of MF. At last, we primary investigated the preparation of the magnetic nano-microspheres with target drug deliver. The paper drew some original results as follows.The results show that the optimal reaction temperature is 75°C and the optimal concentration is 0.5mol/L.The temperature mainly influenced the crystal and then the magnetism in the conventional coprecipitation method, while the concentration mainly influenced on growth speed of magnetic particles and then on the diameter of magnetic particles.The optimal pH value when coated by oleate sodium was 5.5. While the optimal pH value for oleate coated magnetic fluid dispersing into water was 10. There was a chemical adsorbed between the magnetic particles and oleate sodium which decreased the surface tension and increased the resistance, so the stability of MF improved obviously. The magnetization of coated magnetic particles was lower than the uncoated ones, and this reduction is likely due to the existence of disordered spins at the surface as discussed.We characterized the structure of oleate coated MF layer: the oleate sodium was chemical adsorbed on the surface of particle to form the primary layer while the excess oleate sodim was physical adsorbed on the first layer to form second layer. We concluded the key condition to prepare MF with the stable structure was a drive which can make the surfactant close to the surface of magnetic particles and the surfactant was firmly adsorbed on the surface of particles. We found that the magnetic nanoparticles prepared by co-precipitation had extensive hydroxyl groups on the surface. And the H+ would adsorb on these hydroxyl groups under acidic environment. When added oleate sodium into solution, the electrostatic interaction between their carboxylic acid head groups and the hydroxyl groups will make them combine tougher. Consequently, the iron oxide particles were coated by a well-organized primary oleic acid radical molecule. Then, the excess oleate sodim was weakly adsorbed on the primary layer of the oleate sodium-coated magnetic particles to form a hydrophobic shell through the hydrophobic interaction between the subsequent molecule and the hydrophobic tail of oleate of the primary layer. So the second layer will be easily washed by acetone or alcohol. The magnetic particles coated by oleate sodium can disperse into polar or unpolar solution.MF can be used as target drug deliver更多还原