Synthesis of silica aerogel films in liquid molds

Galit Bar; Linoy Amar; Michal Marszewski; Assaf Bolker; Ali Dashti; Raphy Dror; Laurent Pilon

doi:10.1016/j.jcis.2023.06.004

Synthesis of silica aerogel films in liquid molds

J Colloid Interface Sci. 2023 Oct 15:648:418-426. doi: 10.1016/j.jcis.2023.06.004. Epub 2023 Jun 7.

Authors

Galit Bar¹, Linoy Amar², Michal Marszewski³, Assaf Bolker⁴, Ali Dashti⁵, Raphy Dror², Laurent Pilon⁶

Affiliations

¹ Applied Physics Department, Soreq Nuclear Research Center, Yavne 81800, Israel; Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Sciences, University of California Los Angeles, Los Angeles, CA 90095, USA. Electronic address: gali@soreq.gov.il.
² Applied Physics Department, Soreq Nuclear Research Center, Yavne 81800, Israel.
³ Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Sciences, University of California Los Angeles, Los Angeles, CA 90095, USA; Department of Chemistry and Biochemistry, University of Toledo, Toledo, OH 43606, USA.
⁴ Space Environment Department, Soreq Nuclear Research Center, Yavne 81800, Israel.
⁵ Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Sciences, University of California Los Angeles, Los Angeles, CA 90095, USA.
⁶ Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Sciences, University of California Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA 90095, USA; Institute of the Environment and Sustainability, University of California Los Angeles, Los Angeles, CA 90095, USA.

PMID: 37302225
DOI: 10.1016/j.jcis.2023.06.004

Abstract

By virtue of their low density and thermal conductivity, aerogels constitute attractive thermal insulators. Of those, aerogel films are best suited for thermal insulation in microsystems. Processes for the synthesis of aerogel films with thicknesses smaller than 2 µm or thicker than 1 mm are well established. However, for microsystems films in the range of a few microns and up to several hundred microns would be beneficial. To circumvent the present limitations, we describe a liquid mold made of two immiscible liquids, used here to produce aerogel films thicker than 2 µm in a single molding step. Following gelation and aging, the gels were removed from the liquids and dried using supercritical carbon dioxide. In contrast to spin/dip coating, liquid molding avoids solvent evaporation from the gel's outer surface during gelation and aging, films are free-standing and have smooth surfaces. The choice of liquids determines the aerogel film thickness. As a proof of concept, 130 µm thick homogeneous and high porosity (>90%) silica aerogel films were synthesized in a liquid mold with fluorine oil and octanol. The resemblance of the liquid mold approach to the float glass technique offers the prospect of mass production of large sheets of aerogel films.

Keywords: Aerogel film; Controlled evaporation; Floating aerogel; Free-standing film; Liquid encapsulation; Liquid mold; Silica aerogel; Sol-gel.