Metal oxide aerogels
Preparation of monolithic silica aerogels, the aerogels thus obtained and their use for the preparation of silica glass articles and of heat-insulating materials Patent #: 4432956
ApplicationNo. 06/772528 filed on 09/04/1985
US Classes:423/338, By gelling423/336, By hydrolyzing vapor phase silicon compound502/10Treating preformed sphere only
ExaminersPrimary: Doll, John
Assistant: Freeman, Lori S.
Attorney, Agent or Firm
International ClassesC01B 33/158 (20060101)
C04B 38/00 (20060101)
B01J 13/00 (20060101)
C01B 33/00 (20060101)
AbstractAn 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 CO2, 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 CO2, to thereby provide a transparent aerogel array within a substantially reduced (days-to-hours) time period. The supercritical drying occurs at about 40° C. instead of at about 270° 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.