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Title: Structural Formation Studies of UV-Catalyzed Gels and Aerogels byLight Scattering

Abstract

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.

Authors:
;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE. Office of the Chief Financial Officer. Other Costsand Credits
OSTI Identifier:
920145
Report Number(s):
LBNL-43804
Journal ID: ISSN 0022-3093; JNCSBJ; R&D Project: 0; BnR: YN0100000; TRN: US200818%%1071
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Journal of Non-Crystalline Solids
Additional Journal Information:
Journal Volume: 225; Related Information: Journal Publication Date: 1998; Journal ID: ISSN 0022-3093
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; CATALYSIS; DRYING; ETHANOL; GELATION; HYDROLYSIS; LIGHT SCATTERING; PORE STRUCTURE; SILICA; SILICA GEL; SURFACE AREA

Citation Formats

Hunt, Arlon J, and Ayers, Michael R. Structural Formation Studies of UV-Catalyzed Gels and Aerogels byLight Scattering. United States: N. p., 1998. Web. doi:10.1016/S0022-3093(98)00132-X.
Hunt, Arlon J, & Ayers, Michael R. Structural Formation Studies of UV-Catalyzed Gels and Aerogels byLight Scattering. United States. https://doi.org/10.1016/S0022-3093(98)00132-X
Hunt, Arlon J, and Ayers, Michael R. Wed . "Structural Formation Studies of UV-Catalyzed Gels and Aerogels byLight Scattering". United States. https://doi.org/10.1016/S0022-3093(98)00132-X. https://www.osti.gov/servlets/purl/920145.
@article{osti_920145,
title = {Structural Formation Studies of UV-Catalyzed Gels and Aerogels byLight Scattering},
author = {Hunt, Arlon J and Ayers, Michael R},
abstractNote = {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.},
doi = {10.1016/S0022-3093(98)00132-X},
url = {https://www.osti.gov/biblio/920145}, journal = {Journal of Non-Crystalline Solids},
issn = {0022-3093},
number = ,
volume = 225,
place = {United States},
year = {1998},
month = {4}
}