Preparation of titania microballoons by sol-gel process in reverse dispersion

Titania microballoons were prepared by sol-gel process of titanium tetra-2-propoxide in reverse dispersion. Hexane was used as continuous phase, in which sorbitan monooleate was dissolved as dispersion stabilizer. A buffer solution was used as dispersed phase, of which pH was adjusted from 5.0 to 7.0. These phases were mixed and stirred to prepare reverse dispersion. Titanium tetra-2-propoxide was added to the dispersion to start reaction, and stirring was kept for 24 h at 30 °C. The crystalline phase of specimens calcined at 500 °C was identified as anatase. Scanning electron microscopy showed that the products were hollow microspheres or microballoons. The effects of preparation duration, dispersion stabilizer concentration, and pH on the yield and the mean diameter were investigated.