Water glass-based aerogel monolith prepared with formamide catalyst and SiO2 nanofiber reinforcement: Nanoarchitectonics and enhanced mechanical property

Abstract

Water glass-based aerogels (WAGs) are poor in mechanical properties, which seriously limits their application. At the same time, the strong acid used for the gelation of water glass is corrosive to equipment. In this work, water glass-based aerogel monolith with significantly improved mechanical property were prepared with flexible electrospun SiO₂ nanofibers (SNF) as reinforcing agents and formamide (FA) as the hydrolysis catalyst (SNF/WAG). The introduced SNF can reduce the density and shrinkage of the aerogel, which are decreased to 8.9 % and 0.107 g cm⁻³ for the SNF/WAG-2, respectively. Most importantly, the introduction of SNF can transform the brittle structure of WAG into the plastic structure of SNF/WAG, improving its mechanical properties. The high adsorption capacity for CH₂Cl₂ (11.33 g g⁻¹) enables SNF/WAG to serve as an efficient oil absorbent material. Owing to the low density, hydrophobicity and good insulation, the evaporator assembled with SNF/WAG as insulator exhibits evaporation rates of 1.932, 2.622, and 3.082 kg m⁻² h⁻¹ at 1, 2, and 3 sun illumination, and the evaporation rate can still be maintained at 1.728 kg m⁻² h⁻¹ after 5 cycles at 1 sun intensity. This study offers a feasible approach to overcome the key limitations of conventional water glass-based aerogels. It significantly enhances the overall material performance while maintaining low-cost preparation, thus paving the way for broader application of aerogels in areas such as high-strength thermal insulation.