A flexible silica aerogel with good thermal and acoustic insulation prepared via water solvent system

Abstract

In this paper, transparent flexible hydrophobic silica aerogels were prepared by replacing the traditional alcohol solvent with water, using methyltriethoxysilane (MTES) and cetyltrimethylammonium bromide (CTAB), via acid-base two steps method and CO2 supercritical drying. The role of surfactant CTAB in the gel–sol process was revealed, and the effect of CTAB concentration on the gel structure was analyzed. With the concentration increasing, the skeleton structure of the gel gradually changed from coarse graininess to continuous fiber. The obtained aerogels showed good elastic properties. With the increasing of density, the elastic modulus of aerogels gradually increased, so that the length could be restored to 63% of the original length after 50% compression strain. Aerogels also had low thermal conductivity and good thermal stability. The thermal conductivity at room temperature was only 0.0215 W/(m·K) and the initial decomposition temperature was up to 511 °C. For the aerogel with thickness of 11.8 mm and density of 60 mg/cm3, it showed good sound absorption and sound insulation properties. When the sound frequency was 2000 Hz, the sound absorption coefficient was 0.91, and the sound transmission loss between 500 and 1600 Hz was 13–21 dB. This work provides a facile approach to fabricate lightweight and flexible silica aerogels for thermal and acoustic insulation applications.