抄録
Titania microballoons were prepared by sol-gel process of titanium tetra-2-propoxide in reverse dispersion. Continuous phase was hexane, in which sorbitan monooleate was dissolved as dispersion stabilizer. Dispersed phase was a buffer solution, 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 hexane solution was added to the dispersion to start reaction, and stirring was kept for 24 h at 30°C. The titania wet gel particles produced were dried in argon at 30°C and calcined at 500°C to obtain titania. The crystalline phase was identified as anatase. It was confirmed that the products were microballoons by scanning electron microscopy. The mean diameter and the wall thickness were measured as 76 and 4µm, respectively. The wall has two-layered structure, suggesting that it was formed by different two mechanisms, film formation and particle deposition. The yield exceeded 80% for 4 h, and the reaction was almost completed for 24 h. The diameter of the wet gel particles decreased as duration increased. This change may be due to escape of by-product 2-propanol from the dispersed phase to the continuous phase. pH of the dispersed phase did not have any significant effect on diameter. From these results and information of DTA/TGA analysis, the gel formation process was interpreted.
