Transparent silica aerogel slabs synthesized from nanoparticle colloidal suspensions at near ambient conditions on omniphobic liquid substrates

Michal Marszewski; Sophia C King; Tiphaine Galy; Glareh N Kashanchi; Ali Dashti; Yan Yan; Man Li; Danielle M Butts; Patricia E McNeil; Esther Lan; Bruce Dunn; Yongjie Hu; Sarah H Tolbert; Laurent Pilon

doi:10.1016/j.jcis.2021.07.159

Transparent silica aerogel slabs synthesized from nanoparticle colloidal suspensions at near ambient conditions on omniphobic liquid substrates

J Colloid Interface Sci. 2022 Jan 15;606(Pt 1):884-897. doi: 10.1016/j.jcis.2021.07.159. Epub 2021 Aug 6.

Authors

Affiliations

¹ Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095, USA.
² Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA.
³ Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA.
⁴ Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
⁵ Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
⁶ Mechanical and Aerospace Engineering Department, 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. Electronic address: pilon@seas.ucla.edu.

PMID: 34454313
DOI: 10.1016/j.jcis.2021.07.159

Abstract

This paper presents a novel sol-gel method to synthesize large and thick silica aerogel monoliths at near ambient conditions using a commercial aqueous solution of colloidal silica nanoparticles as building blocks. To achieve slabs with high visible transmittance and low thermal conductivity, the method combines the strategies of (i) synthesizing gels on an omniphobic perfluorocarbon liquid substrate, (ii) aging at temperatures above room temperature, and (iii) performing solvent exchange with a low-surface-tension organic solvent prior to ambient drying. The omniphobic liquid substrates were used to prevent cracking and ensure an optically-smooth surface, while nanoparticle building blocks were small (<10 nm) to limit volumetric light scattering. Gels were aged at temperatures between 25 and 80 °C for up to 21 days to make them stronger and stiffer and to reduce shrinkage and cracking during ambient drying. Ambient drying was achieved by first exchanging water in the gel pores for octane, followed by drying in an octane-rich atmosphere to decrease capillary forces. The synthesized nanoparticle-based silica aerogel monoliths had thicknesses up to 5 mm, diameters up to 10 cm, porosities exceeding 80%, and thermal conductivities as low as 0.08 W m^-1 K^-1. Notably, the slabs featured visible transmittance exceeding 75% even for slabs as thick as 5 mm. The as-synthesized aerogel monoliths were exposed to TMCS vapor to induce hydrophobic properties resulting in a water contact angle of 140° that prevented water infiltration into the pores and protected the aerogels from water damage. This simple synthesis route conducted at near ambient conditions produces hydrophobic aerogel monoliths with promising optically transparent and thermally insulating properties that can be adhered to glass panes for window insulation and solar-thermal energy conversion applications.

Keywords: Aerogel; Ambigel; Liquid substrate; Mesoporous silica; Optically transparent thermal insulation; Silica nanoparticles.

MeSH terms

Gels
Nanoparticles*
Silicon Dioxide*
Suspensions
Thermal Conductivity

Substances

Gels
Suspensions
Silicon Dioxide