Transparent ultralow-density silica aerogels prepared by a two-step sol-gel process

• Published in: Journal of non-crystalline solids 1992, Vol.145 (1-3), p.44-50
• Main Authors: Tillotson, T.M., Hrubesh, L.W.
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/S0022-3093(05)80427-2

Interest in lowering aerogel densities for applications involving high energy charged particle detection via the Cherenkov effect has led to the development of a two-step sol-gel method for preparing ultralow-density aerogels. This method has been used in the authors' laboratories to produce uncracked, transparent aerogel tiles with densities from 3 to 80 kg/m 3. Comparative characterization of conventional single-step base-catalyzed aerogels to aerogels prepared by this two-step approach is presented. Results indicate that the aerogel microstructure for the two-step approach differs from the bead-like structure proposed for single-step base-catalyzed TMOS aerogels. TEM micrographs of aerogels prepared by the two-step method show an interlinked polymer-chain-like structure with an average chain diameter of 2–3 nm and an average chain length of approximately 15 nm. UV-VIS spectrophotometry shows the transmittance over the visible spectrum (400–800 nm) to be improved for the two-step aerogels by as much as 30%. Other measurements of the ultralow-density aerogels include BET surface area, and compressive modulus.