Preparation and properties of hydrophobic and highly transparent SiO₂ aerogels

SiO₂ aerogels have an inherent optical transparency, but there is a hydrophilic defect and high transparency and hydrophobicity seem impossible to achieve at the same time. In order to realize the practical application value of highly transparent aerogel, our study used hexamethyldisilazane (HMDS) as the hydrophobic agent to improve the hydrophobicity of the prepared highly transparent SiO₂ aerogels. We investigated the effects of HMDS concentration and modification duration on SiO₂ aerogels through the chemical liquid method. Results showed that the concentration and modification time of HMDS have no significant effect on the microstructure and properties of highly transparent SiO₂ aerogels, which maintained uniform microstructure, low thermal conductivity, good thermal stability and contact angles were all above 136°. Hydrophobic and highly transparent SiO₂ aerogels hold great potential for use as observation windows in the aerospace applications, building thermal management, and transparent coating.