Structure and topology of silica aerogels during densification
Abstract
A combination of scattering techniques, neutron powder diffraction, small-angle X-ray scattering (SAXS), neutron spin echo (NSE) and neutron time-of-flight (TOF), is used to follow the structure and topology of silica aerogels during densification. NSE and TOF show that short-scale branching increases at the expense of large-scale connectivity leading to micron-size fluctuations, the existence of which is confirmed by SAXS. On shorter length scales, heat treatment leads to a transition from a spaghetti-like polymeric network to a colloidal microstructure. With increasing exposure to temperatures of the order of 1000°C, the chord length of the colloidal solid phase increases exponentially with bulk density, even though the microscopic skeletal density remains at half that of amorphous silica.
- Publication:
-
Journal of Non Crystalline Solids
- Pub Date:
- September 1994
- DOI:
- 10.1016/0022-3093(94)90503-7
- Bibcode:
- 1994JNCS..172..647S