THE CONTROL OF SIZE AND SURFACE MORPHOLOGY OF SILICA MICROSPHERES BY SOL-GEL EMULSION APPROACH

The influence of mixing speed and amountof solvent on the size and surface morphology of hollow silica microspheres was studied. Hollowsilica microspheres were prepared via a sol-gel emulsion method. An aqueous phase of water, ammonium hydroxide and Tween 20 was emulsified in an oil phase of 1-octanol and Span 80, and stabilized by hydroxypropyl cellulose (HPC). Tetraethyl orthosilicate (TEOS) was added to the emulsion and mixed at a speed of either 400, 800, or 1200 rpm. The resulting silica particles were air-dried and calcinated at 773 K for 3 h. The characteristic bonds of silica were detected by Fourier Transform Infrared Spectroscopy and the surface morphology and size of silica microspheres were characterized by scanning electron microscopy. The particle size distribution was measured with laser diffraction and the specific surface areas and pore sizes distributions by Coultier Omnisorp 100 CX. The results indicate that the size of silica decreases from 3.1 to 2.3 μm as mixing speed increases from 400 to 1200 rpm. At constant mixing speed, the silica particles prepared from 160 ml 1-octanol exhibited the greatest specific surface area and total pore volume compared with those of 80 and 240 1-octanol.