Changes in porosity and amounts of adsorbed water in sol-gel derived porous silica films with heat treatment

Citation
A. Matsuda et al., Changes in porosity and amounts of adsorbed water in sol-gel derived porous silica films with heat treatment, J SOL-GEL S, 20(2), 2001, pp. 129-134
Citations number
17
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Material Science & Engineering
Journal title
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY
ISSN journal
0928-0707 → ACNP
Volume
20
Issue
2
Year of publication
2001
Pages
129 - 134
Database
ISI
SICI code
0928-0707(200102)20:2<129:CIPAAO>2.0.ZU;2-J
Abstract
Porous silica films were obtained by a heat treatment of poly(ethyleneglyco l)-containing gels for micro-patterning. Changes in porosity and the amount of adsorbed water with the heat treatment temperature in the silica films were evaluated from the refractive index of the films. The apparent refract ive index of the silica films in an ambient atmosphere was much higher than the intrinsic refractive index of the film due to the large amount of adso rbed water in the films. The amount of adsorbed water in the films decrease d with an increase in the heat treatment temperature and became almost zero after a heat treatment at 850 degreesC. The decrease in the amount of adso rbed water in the films was caused by the decrease in silanol groups, which acted as the sites for water adsorption in the films. The drastic decrease s in thickness and in porosity of the films at temperatures from 850 to 950 degreesC occurred after the disappearance of silanol groups in the films. The densification of the films due to collapse of the pores at high tempera tures should have resulted from the viscous flow of silica network.