Synthetic of Uniform Spindle-Type Titania Particles by the Gel-Sol Method
Uniform spindle-type titania (TiO2) particles were prepared by a novel gel-sol method. A mixed solution of titanium(IV) isopropoxide and triethanolamine at molar ratio 1:2 prepared in a drybox was mixed with doubly distilled water to make the final concentration of titanium(IV) 0.50 mol dm-3. The mixture was further mixed with an equal volume of 2.0 mol dm-3 ammonia solution, and the resulting solution was aged for 24 h at 100°C. By this aging a highly viscous gel was formed, but there was no sign of nucleation of titania at this stage. The gel was then aged at 140°C for 3 days to nucleate and grow the titania particles. The gel network formed in the first aging played a decisive role in the second aging to produce the uniform particles of titania, as a reservoir of the metal ions to lower the supersaturation for preventing extensive nucleation and as an anticoagulant fixing the growing particles in the matrix. The product was identified by XRD as anatase particles elongated in the direction of the c-axis. The aspect ratio, as well as the size of the resulting particles, was reduced as the concentration of ammonia was decreased. Copyright 1997Academic Press