Silica nanowires reinforced self-hydrophobic silica aerogel derived from crosslinking of propyltriethoxysilane and tetraethoxysilane

Silica aerogels are utilized in the industry and scientific investigations. However, most silica aerogels are brittle, which hinders their development and application. In this paper, we reported the design and synthesis of a silica aerogel composite reinforced with silica nanowires by using two silicon sources: propyltriethoxysilane and tetraethoxysilane. The effects of varying silica nanowires contents on the properties of the silica aerogel composites were studied and compared with those of neat silica aerogel under identical conditions. The composites were obtained by mixing silica nanowires with hybrid silica sol without surface modification and dried in ambient atmosphere. The samples showed low density (0.172 g cm−3), high porosity (over 90%), and super hydrophobicity (the water contact angle reached 153°). The cross-linked silica aerogel composites showed excellent mechanical behavior and can be compressed by as high as 70% of their initial length before they were broken. The maximum completely recoverable compressive strain reached 50%. The elastic modulus of the optimal silica nanowires/silica aerogel composite increased by 67% (from 0.21 to 0.35 MPa) compared with that of the neat silica aerogel. The cross-linked propyltriethoxysilane and tetraethoxysilane can be used to synthesize new types of elastic silica aerogels, and the excellent performance of the silica nanowires/silica aerogels composite will enable its application in various fields.