Preparation And Characterization Of Porous Oxide Spherical Particles

The development of mesoporous silica materials by researchers of Mobil Corporation in 1992 stimulated explosive research on the preparation of porous materials through templates approaches. In this thesis, we focused on the preparation of monodispersed SiO₂ microspheres with high specific surface area, and then oxide particles deposited on the surface of the as-prepared SiO₂ microspheres by two main chemical methods to obtain monodispersed oxide composite microspheres with core/shell structures. The effects of experimental conditions and methods on particle size, morphology and microstructure of composite microspheres were investigated and discussed as main tasks in this paper.This thesis was divided into five major parts. The first part reported the synthesis of monodispersed microporous silica microspheres by hydrolysis and condensation of tetraethoxysilane (TEOS) using alkylamine as template. The results showed that the alkyl chain length of 1-alkylamine obviously influenced the morphologies and sizes of SiO₂ particles. With increasing the alkyl chain length of 1-alkylamine, the pore volume and average pore size increased, however, surface area decreased. The quality of the silica microspheres synthesized using hexadecylamine and octadecylamine as templates were inferior to that of the silica microspheres synthesized using dodecylamine as a template. The optimal synthesis conditions were as follows: [TEOS] = 0.11-0.18 mol L^-1, [DDA] = 0.016-0.24 mol L^-1 and hydrolysis temperature = 15°C. The small angle XRD and HRTEM results confirmed that the prepared SiO₂ microspheres had disordered pore structuresIn part 2, monodispersed porous SiO₂/TiO₂ composite microspheres with high specific surface areas were prepared by depositing titania colloid particles on the surface of monodispersed microporous silica microspheres using a simple electrostatic attraction strategy. Uniform titania coatings could be deposited on the surface of silica microspheres by adjusting the pH value of the reaction solution to a optimal pH value ranges of about 3-5. The specific surface area and pore volume of the SiO₂/TiO₂ composite microspheres calcined at 600°C were 960 m²g^-1 and 0.48 mLg^-1, respectively.In part 3, SiO₂/TiO₂ composite microspheres with microporous core/mesoporous...