Fluoroalkane modified silica aerogels with excellent strength and self-cleaning property

Abstract

Silica aerogel, regarded as one of the lightest solid materials with porous structures, shows properties such as low thermal conductivity, high porosity, and extensive surface area, making it highly suitable for application in pipeline thermal insulation, aerospace engineering, oil-water separation, and various other fields. However, due to the neck effect in the pearl-like network formed by the direct and random interconnection between silica nanoparticles, the mechanical property is poor. Although the mechanical property is enhanced by modifying silica aerogels with inorganic and organic compounds, the thermal insulation is usually sacrificed with enhancing of mechanical property. In this study, low surface energy fluoroalkane modified silica aerogels (SAF) are prepared to enhance the compressive mechanical and superhydrophobic properties. In order to balance the mechanical property and the thermal insulation property, SAF with different contents of fluoroalkanes are studied in detail. The compressive strength of SAF with 10 % molar ratio of fluoroalkanes is greatly enhanced while the thermal conductivity keeps the same as unmodified silica aerogel to balance the mechanical and thermal insulation properties. Study on the structure and property of SAF aerogels shows that the mechanical property is enhanced at proper molar content of fluoroalkanes, which probably thickens the necks between silica particles and lower the crosslinking density. The SAF aerogels shows excellent insulation against thermal and cold conditions. Furthermore, the surfaces of SAF aerogels are superhydrophobic by introducing low surface energy fluoroalkanes, and show self-cleaning property, facilitating the application of silica aerogels.