Superhydrophobic sodium silicate based silica aerogel prepared by ambient pressure drying

• New and simple two-step MTES-TMCS modification method by ambient pressure drying.
• Excellent physical properties of sodium silicate based silica aerogel.
• Cost-effective for application in a large scale production.

The superhydrophobic silica aerogel was prepared by using less expensive sodium silicate as a main silica source through a cost-effective and simple route via ambient pressure drying. The sodium impurity was first eliminated by mixing sodium silicate with a co-precursor methyltriethoxysilane (MTES) followed by ion exchange process. The hydrogel was formed by gelation and the alcogel was further obtained by alcoholization of the hydrogel. The surface of alcogel was modified by reacting with trimethylchlorosilane (TMCS) diluted in n-hexane. It was suggested that MTES accelerated water expelling from the hydrogel, while TMCS modified the surface of silica network by replacing Si–OH with Si–C. As a result, the obtained silica aerogel exhibited excellent physical properties with less than 10% volume shrinkage. The density, surface area and cumulative pore volume were 0.12 g cm−3, 684.44 m2 g−1, and 3.55 cm3 g−1, respectively. The optical transmission reached 82.8% with the water contact angle of 146°.