Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Patent
1985-09-04
1986-09-09
Doll, John
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
423336, 502 10, C01B 3312
Patent
active
046108637
ABSTRACT:
An improved supercritical drying process for forming transparent silica aerogel arrays is described. The process is of the type utilizing the steps of hydrolyzing and condensing aloxides to form alcogels. A subsequent step removes the alcohol to form aerogels. The improvement includes the additional step, after alcogels are formed, of substituting a solvent, such as CO.sub.2, for the alcohol in the alcogels, the solvent having a critical temperature less than the critical temperature of the alcohol. The resulting gels are dried at a supercritical temperature for the selected solvent, such as CO.sub.2, to thereby provide a transparent aerogel array within a substantially reduced (days-to-hours) time period. The supercritical drying occurs at about 40.degree. C. instead of at about 270.degree. C. The improved process provides increased yields of large scale, structurally sound arrays. The transparent aerogel array, formed in sheets or slabs, as made in accordance with the improved process, can replace the air gap within a double glazed window, for example, to provide a substantial reduction in heat transfer. The thus formed transparent aerogel arrays may also be utilized, for example, in windows of refrigerators and ovens, or in the walls and doors thereof or as the active material in detectors for analyzing high energy elementry particles or cosmic rays.
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Hunt Arlon J.
Tewari Param H.
Carnahan L. E.
Doll John
Freeman Lori S.
Gaither Roger S.
Hightower Judson R.
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