Abstract
Spherical silica particles were prepared by the hydrolysis of orthoethyl silicate in a alcoholic solution in the presence of ammonia catalysis. The thermal behaviors of the obtained spherical particles were examined by TEM, TG-DTA, IR and XRD. Results obtained were as follows.
(1) The hydrolysis product of orthoethyl silicate was homogeneous and truly spherical. Their diameters were changed by the mol ratio H2O/Si(OC2H5)4, NH3/Si(OC2H5)4 of the solution and the reaction temperature.
(2) By heat treatment, the combustion of organic matters in silica occurred at about 400°C, and the dehydration from silanol group at nearly 450°C. The autoclave treatment removed the organic matters from silica particles and decreased silanol group. The Si-O bond became strong.
(3) By heat treatment, the density approached to that of silica glass and the specific surface area decreased. But the autoclave treatment, its density and specific surface area remained unchanged, but the autoclaved powder was highly dispersive in alcohol.
