Preparation of Hydrophobic SiO_2 Aerogels at Ambient Pre ssure

The alcogel prepared by sol-gel process of polyd ieth oxysiloxane (PDEOS) according to the mass ratio of C_2H_5OH∶ PDEOS∶HF∶H_2O =20 ∶10∶3∶0.5, was modified by methyltriethoxysilane(MTES) and washed with alcoho l a nd n-hexane. The obtained gel was then dried under ambient pressure to prepare hyd rophobic SiO_2 aerogel. It is shown that hydrophobic SiO_2 aerogels can be obt ained when the mass ratio of MTES/ PDEOS is higher than 1.2. The contact angle b etween hydrophobic SiO_2 aerogels and water is larger than 110°, the densities and specific surface areas of hydrophobic SiO_2 aerogels are in the range of 1 25～160kg/m~3 and 560～900m~2/g respectively.