SPHERICAL SILICA-GELS PRECIPITATED FROM ACID-CATALYZED TEOS SOLUTIONS

Silica gel particles were obtained from the immiscible mixtures of TEOS and H2O with nitric acid, in which the H2O/TEOS molar ratio was less than 2. In the emulsion in which water was dispersed as the droplets in TEOS by stirring, TEOS dissolved into the droplets in proportion to time and was hydrolyzed by an excess of nitric acid water. The hydrolysis and polycondensation reactions of TEOS were restricted inside the droplets, and when the ratio of water to the dissolved TEOS for the droplets reached about 4.5 dense spherical particles were formed in TEOS. © 1990.