| Electrorheological (ER) fluids are materials that undergo fast, reversible and obvious changes in their rheological properties upon the application of electric field. Such kind of materials can be used in auto and machine building industries. There are many things can be used as electrorheological (ER) materials, such as polymer semiconductor ER materials, inorganic nonmetal materials et al. The advantage of polymer semiconductor ER materials attributes to theirs high mechanical mass, lower density and fine hydrophobic properties, at the same time, theirs conductivity can be adjusted by doping and after-treatment, but theirs poor thermo-stability confines theirs extensive use. The main characteristic of inorganic compound such as BaTiO3, TiO2 lies in theirs high permittivity, the main disadvantages for inorganic compound used as electrorheological materials are theirs high density and low shear stress et al.Organic-inorganic nanocomposite, which are the complex of inorganic nanopraticles with organic compound, is a popular study subject in nanoscale composite. The nanocomposite can not only take advantage of several advantage, but also produce new properties. In this thesis, taking account of the problems in electrorheological fluids such as high leakage current, low yield stress and stability, the PAn-BaTiO3 nanocomposite with different structure are prepared by in-situ complex technology and modified sol-gel method. The structure, properties and their application in ER fluids are studied by the numbers.In this thesis, several subjects have been studied in detail. First, PAn-BaTiO3 nanocomposite have been prepared by in situ complex technology and modified sol-gel method. Second, the size and shape of the nanoparicles complex and the complex mechanism of PAn with BaTiO3 nanoparticles and have been studied, at the same time, the structure model of PAn-BaTi03 nanocomposite have been studied and put forward. Third, several properties of PAn-BaTiO3 nanocomposite such as dielectric properties, conduct electric properties ,heatstability, and long period stability have been studied. Fourth, the electrorheoldgical fluids composed of PAn/BaTiO3 nanocomposite and chlorated paraffin oil are prepared and the relationship between dielectric performance and electrorheological effect are discussed. Fifth, The advantage and disadvantage of electrorheological fluids composed of different structure PAn-BaTiO3 nanocomposite are compared, which put a favorable basis for farther design and prepare electrorheological fluid with high performance.In order to prepare insitu-composite PAn-BaTiO3, the BaTiO3 nanoparticles with the different size has been prepared by sol-gel processing primarily, the shape, structure and the relationship between dielectric properties and conducting properties with temperature and frequency are studied. The result shows: 900℃ is the optimum heat-treated temperature for the preparing BaTiO3 nanoparticles. With the heat-treated temperature increasing, the size of BaTiO3 increase and the dielectric constant decrease. At the same condition, the maximal dielectric constant value appears at 120℃. At the existence of BaTiO3, the PAn/BaTiO3 nanocomposite are prepared by in situ complex technology. The shape of complex is not regular and their mean size is in the range of 1~2 u m There are chemical bond between PAn and BaTiO3 in PAn/BaTiO3 nanocomposites, For the complex mechanism of PAn with BaTiO3 nanoparticles, first, there are complex between PAn and BaTiO3 nanoparticles. PAn have the function of cohering BaTiO3 nanoparticles. A considerable number of PAn combine with BaTiO3 nanoparticles on the surface of the BaTiO3 to form PAn-BaTiO3 nanocomposite . All the processes above take place spontaneously. BaTiO3 nanoparticles scatter inside the PAn-BaTiO3 nanocomposite without order, on the surface of complex has only the existence of PAn. Such kind structure can be described with the model "cake-peanut", the cake refers to polymer and the peanut refers to BaTiO3 nanoparticles. As far as the dielect...
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