Preparation of super hydrophobic silica aerogel and study on its fractal structure

Abstract The experimental results on silica aerogels with super hydrophobic property are reported. Silica alcogels were prepared via a two-step acid/base process by keeping the molar ratio of tetraethyoxysiliane (TEOS), ethanol (EtOH), water (H 2 O), hydrochloric acid (HCl) and ammonia (NH 4 OH) constant at 1:6:8:1.0 × 10 −3 :1.1 × 10 −2 , respectively, and varying the molar ratio of N , N -dimethylformamide (DMF)/TEOS ( G ) from 0 to 1.2. After two aging treatment steps, they were modified by isopropyl alcohol (IPA)/trimethylchlorosilane (TMCS)/ n -hexane solution at 60 °C. It was found that G value at 0.8 resulted in low density (∼0.2 g cm −3 ) and the minimum volume shrinkage (∼6%), with the total water adsorption ratio ∼5.1% when exposed to water for 3 months and the contact angle θ ≈ 178°. Besides, the aerogels ( G = 0.8) had higher volume fractal dimension (∼1.8), which indicted that it possessed better connectivity and more uniform particle sizes.