Preparation of hydrophobic silica aerogel using sodium silicate as raw material

Abstract This study successfully prepared high-performance hydrophobic silica aerogels using low-cost sodium silicate as the precursor. The preparation process involved the optimization of the sol-gel technique, integrating ion exchange, the sol-gel process, and a two-component hydrophobic modification technology using trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS). Improvements were also made to the gel aging, solvent exchange, and ambient pressure drying (APD) processes. Multiple sample sets were prepared by controlling reagent ratios, reaction time, and temperature, and their properties were systematically characterized. The results indicate that the optimally prepared SiO 2 aerogel possesses an amorphous structure (confirmed by XRD analysis), high hydrophobicity (contact angle > 128°), high porosity, low density, and strong water repellency. Compared to traditional methods relying on supercritical drying, the APD method adopted in this study not only maintained excellent thermal insulation performance (thermal conductivity as low as 0.0239 W·m −1 K −1 ) and hydrophobicity (contact angle up to 128.8°) but also significantly reduced production energy consumption and costs. The process optimization effectively lowers production costs, offering significant economic benefits and practical value for large-scale applications in building energy efficiency, industrial pipeline insulation, and other fields. This research provides a feasible technical pathway for the low-cost, large-scale production and commercial application of silica aerogels, promoting their use in broader applications.