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Aerogel Synthesis Using Extractive Drying
Published online by Cambridge University Press: 10 February 2011
Abstract
The advent of ambient pressure aerogel technology may offer process advantages compared to supercritical drying. Since low density is required for most applications of interest, precursor gels must be very dilute (e.g. 6–8% SiO2). The remaining 92–94% is solvent which must be carried along for the entire process, then evaporated, condensed, separated, and recycled to be reused. These steps and associated unit operations represent a major cost (capital and operating). The drying step is problematic because of the large mass of solvent and the inherently low thermal conductivity of the gel. A new approach for drying aerogels is described whereby a wet gel containing a solvent is submerged in hot water or similar fluid which results in removal of the solvent without the drying fluid penetrating the gel. This results in a dried gel with aerogel properties but with the advantages of having a high heat transfer rate without using large temperature gradients as well as providing inherent separation of the dried material. We explore the effects of different solvents and drying temperature gradients on resulting gel microstructure.
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- Copyright © Materials Research Society 1996
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