Synthesis of Hydrophobic Silica Aerogels via Ambient Pressure Drying

Hydrophobic silica aerogels were prepared using vinyltriethoxysilane (VIES) as precursor and ethanol (EtOH) by two-stage acid-base catalyzed sol-gel process followed by ambient pressure drying. The structure of silica aerogels were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The hydrophobicity of aerogels was quantified by optical contact angle measurement. The results show that the contact angle of water was mainly in the range of 115 degrees similar to 150 degrees. The molar ratio of EtOH/VTES, oxalic acid and base catalyst concentrations were systemically changed to learn their influence on the volume shrinkage and bulk density. The result reveals that these preparing conditions have a great influence on the properties of the silica aerogels. The bulk density of the as-prepared aerogels is distributed from 0.13 to 0.43 g/cm(3) while the volume shrinkage is in the range of 20%-70 %.