Comparison of the growth mechanism of TiO2-coated SiO2 particles prepared by sol-gel process and water-in-oil type microemulsion method

TiO2-coated SiO2 particles were synthesized by sol-gel process and microemulsion method, respectively, in order to compare the growth mechanism of TiO2 particles coated on SiO2 core particles. Firstly, monodispersed SiO2 core particles were prepared and then the SiO2 particles were allowed to coat and grown by further addition of TEOT as a precursor of TiO2 particles. In this work, Nielsen's chronomal analysis and Overbeek's theory were applied to elucidate the growth mechanism of TiO2 particles coated on the surface of SiO2 core particles. As a result, it was found that the growth mechanism of all of the TiO2-coated SiO2 particles obtained by sol-gel process and microemulsion method was presumed to be surface nucleation growth in which the rate-determining step was a first-order polynuclear layer growth mechanism. In the case of particle size distribution, however, sol-gel process was more advantageous than microemulsion method. In addition, the growth rate constant of TiO2-coated SiO2 particles prepared by sol-gel process (2.95 × 10−6 cm/s) was much faster than that by microemulsion method (6.06 × 10−8 cm/s). So, sol-gel process was suitable to increase the particle size of TiO2-coated SiO2 particles.