In situ SAXS analysis of silica gel formation with an additive
Gommes, C × Blacher, S Goderis, Bart Pirard, R Heinrichs, B Alie, C Pirard, JP #
Amer chemical soc
Journal of physical chemistry b vol:108 issue:26 pages:8983-8991
Time-resolved small-angle X-ray scattering (SAXS) measurements performed during the formation of tetraethyl orthosilicate (TEOS) based silica gels in alcohol with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS) as an additive are reported. The measurements reveal no discontinuity of the nanostructure at the gel point. A chemically induced spinodal phase separation is found to give a coherent picture of the collected data. Increasing the amount of EDAS induces the phase separation on a smaller length scale, which finally leads to a modified gel morphology. The SAXS measurements and the electron micrographs associated with the dry gels could be interpreted in terms of the suggested wet gel formation mechanism.