Dense silica microspheres from organic and inorganic acid hydrolysis of TEOS

Citation
B. Karmakar et al., Dense silica microspheres from organic and inorganic acid hydrolysis of TEOS, J NON-CRYST, 272(2-3), 2000, pp. 119-126
Citations number
27
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF NON-CRYSTALLINE SOLIDS
ISSN journal
00223093 → ACNP
Volume
272
Issue
2-3
Year of publication
2000
Pages
119 - 126
Database
ISI
SICI code
0022-3093(200008)272:2-3<119:DSMFOA>2.0.ZU;2-P
Abstract
It has been observed that any acid-water mixture (irrespective of the type of acid organic and inorganic) in the pH range 1.35-2.25 can produce silica microspheres from tetraethyl orthosilicate (TEOS) with only a restriction of the water/TEOS molar ratio which varies in the ranges 1.0-1.5 for strong acids and 1.5-4.0 for weak acids. Microspheres have been found to form in situ from an intermediate heavier liquid phase of polysilicic acid which ha s been segregated and separated from the sol during the progress of the rea ction. FTIR spectral analysis reveals that this intermediate liquid predomi nantly consists of four-membered siloxane rings (Si4O12) as identified by t heir absorption frequencies in the ranges 550-600 and 670-710 cm(-1). The s egregated liquid phase has been transformed into glass-like non-porous dens e microspheres during stirring. FTIR analyses of these silica spheres are s imilar to that of fused silica. Density, surface area and size of the dried (150 degrees C) microspheres vary in the ranges 2.10-2.16 g cm(-3), 0.5-0. 9 m(2)/g and 10-60 mu m, respectively. Their high densities and FTIR spectr al data indicate a similar structure to that of silica glass. (C) 2000 Else vier Science B.V. All rights reserved.