Study On Synthesis Of Redispersible Oxide Nanoparticles And Their Application

In recent years, nanoparticles with redispersibility have aroused extensive attention of researchers due to their excellent performance in various applications. This paper aims to develop the solubility of nanoparticles through in-situ modification of surface of particles, using by-product produced during the hydrolysis reaction, which was covalently bonded on the particle surface, leading to the formation of aggregation-free powder. In this work, soluble oxide nanopowder including TiO2, γ-FeO2and Mn3O4were synthesized under mild conditions by a sol-gel strategy. And the performance of nanoparticles in composite silica monoliths and the electrochemical properties of TiO2/Polyaniline and Mn3O4were investigated. The main works of this thesis are summarized as followed:(1) In this work, water soluble TiO2nanopowder was synthesized through a surfactant-free sol-gel route based on the hydrolysis and condensation of titanium butoxide. Highly transparent Silica monolith embedded with high concentration TiO2nanoparticles was also prepared due to the high solubility of TiO2nanoparticles. The effects of concentration of HNO3, alkoxide and amount of added water on nanoparticle crystallinity were discussed as well as the reaction mechanism.(2) PANI/TiO2composite nanoparticles were prepared through in situ oxidative polymerization of aniline on the surface of water soluble TiO2nanoparticles using ammonium persulfate as an initiator. The composite was characterized by XRD, FTIR, UV-vis spectrascopy and transmission electron microscope (TEM). The FTIR and UV-vis spectra reveal that the chemical bonds were formed between TiO2and PANI. The electrochemical properties of TiO2/Polyaniline also were investigated.(3) Soluble γ-Fe2O3nanoparticles were synthesisized through an epoxide sol-gel reaction at150℃. Then, it was re-dissolved in silicon alkoxide-containing solution to reform a stable colloidal solution. The hydrolysis and condensation reaction of tetramethoxysilane was catalyzed by an organic base morpholine. Due to the large molecule size of morpholine, the electric double layer on colloidal particles was not compressed by the ionized morpholine and thus the colloidal solution remained stable during the gelation process. Through this procedure, preformed oxide nanoparticles were immobilized homogeneously in the pore of silica matrix, forming highly transparent and crack-free monoliths.(4) Mn3O4nanoparticles with cubic shape were prepared through the simple epoxide sol-gel route by hydrolysis and condensation reaction of [Mn(H2O)6]2+. Extending reaction time, increasing Mn2+concentration or elevating reaction temperature electrochemical properties of Mn3O4nanoparticles also were investigated.