Preparation And Characterization Of Nanocomposites With Core-shell Structure

Nanocomposites with core-shell structure not only can behave small size effect, surface effect and quantum-dimension effect with nanomaterials, but also combine the advantages of all ingredients, so their properties are better than any ingredient. And the control of their properties is easy because of the core-shell structure. So they have widely applications in many fields and have become a vital part in nanomaterial research fields. The core of the core-shell nanocomposites is normally composed of metal or metal oxide, especially the material with especial performances, such as magnetic materials, photoelectron materials and electrochemical active materials. Either inorganic materials or organic materials can be used as the shell of the composites. Among the organic materials as the shell, polyanline(PANI) is easily accepted due to its unique electrochemical properties, environmental stability, low cost, facile synthetic process and readily controlled doping level. Silicon dioxide exhibits adsorption for various organic materials because of its typical porous structure. In this thesis, we have synthesized three kinds of nanocomposites with core-shell structure by selecting NiFe₂O₄ with excellent magnetic property and CeO₂ with good catalysis as the core materials, and investigated their structures and performances in many ways.The thesis consists of three sections as follows:NiFe₂O₄ nanoparticles were firstly synthesized by improved hydrothermal method, and then NiFe₂O₄/PANI nanocomposites were prepared via emulsion polymerization. Their component, morphology and crystalline phase were characterized by FTIR, TEM and XRD, respectively, and the magnetic property and thermal stability were measured by VSM and TGA techniques. The results of TGA indicated that the thermal stability of products was better than PANI. In addition, the electrical property was also studied, and the relations between conductivity and the amount of NiFe₂O₄ were discussed.NiFe₂O₄-SiO₂ nanocomposites with core-shell structure were fabricated by microemulsion technology. The components, morphology and crystalline phase of the resultants were characterized by FTIR, TEM and XRD, respectively. The magnetic parameters were measured by VSM technique. And the adsorption of products for cetylpyridinium bromide (CPB) in solution was also studied. These core-shell nanocomposites with appropriate magnetic property, high loading capacity, excellent compatibility and low poison effect are expected to be used as magnetic carriers in magnetic drug targeting.CeO₂ nanoparticles with uniform size were synthesized by sol-gel method, and then CeO₂/PANI nanocomposites were obtained by coating it with PANI. The structural components, crystalline phase, shape and size distuibution and thermal stability of the samples were characterized by FTIR, XRD, TEM and TGA. The results indicated that the resultants exhibited high thermal stability because of core-shell structure. They are candidate for preparing the catalyst of electrochemical reaction.