| Summary: | A spherical silica aerogel powder with hydrophobic surfaces displaying a water contact angle of 147° was synthesized from a water glass-in-hexane emulsion through ambient pressure drying. Water glass droplets containing acetic acid and ethyl alcohol were stabilized in <i>n</i>-hexane with a surfactant. Gelation was performed by heating the droplets, followed by solvent exchange and surface modification using a hexamethyldisilazane (HMDS)/<i>n</i>-hexane solution. The pH of the silicic acid solution was crucial in obtaining a highly porous silica aerogel powder with a spherical morphology. The thermal conductivity, tapped density, pore volume, and BET surface area of the silica aerogel powder were 22.4 mW·m<sup>−1</sup>K<sup>−1</sup>, 0.07 g·cm<sup>−3</sup>, 4.64 cm<sup>3</sup>·g<sup>−1</sup>, and 989 m<sup>2</sup>·g<sup>−1</sup>, respectively. Fourier transform infrared (FT–IR) spectroscopy analysis showed that the silica granule surface was modified by Si-CH<sub>3</sub> groups, producing a hydrophobic aerogel.
|
|---|