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 (H2O), hydrochloric acid (HCl) and ammonia (NH4OH) 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 (∼0.2gcm−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.
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