Structural Formation Studies of UV-Catalyzed Gels and Aerogels byLight Scattering
The skeletal structure of aerogel is determined before, during, and after the gel is formed. Supercritical drying of aerogel largely preserves the pore structure that is determined near the time of gelation. To better understand these gel formation mechanisms we carried out measurements of the time evolution of light scattering in a series of gels prepared without conventional acid or base catalysis. Instead, ultraviolet light was used to catalyze the formation of silica gels made from the hydrolysis of tetraethylorthosilicate and partly prehydrolyzed tetraethylorthosilicate in ethanol. Time evolution of light scattering provides information regarding the rate and geometrical nature of the assembly of the primary silica particles formed in the sol. UV-catalyzed gels show volumetric growth typical of acid-catalyzed gels, except when UV exposure is discontinued at the gel point, where gels then show linear chain formation typical of base-catalyzed gels. Long term UV exposure leads to coarsening of the pore network, a decrease in the clarity of the aerogel, and an increase in the surface area of the aerogel. Additionally, UV exposure up to the gel point leads to increased crystallinity in the final aerogel.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE. Office of the Chief Financial Officer. Other Costsand Credits
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 920145
- Report Number(s):
- LBNL-43804; JNCSBJ; R&D Project: 0; BnR: YN0100000; TRN: US200818%%1071
- Journal Information:
- Journal of Non-Crystalline Solids, Vol. 225; Related Information: Journal Publication Date: 1998; ISSN 0022-3093
- Country of Publication:
- United States
- Language:
- English
Similar Records
A Sol-Gel Route to Very High Porosity Silica Aerogels
Mechanical and microstructural properties of two-step acid-base catalyzed silica gels