Vapor-phase synthesis of uniform silica spheres through two-stage hydrolysis of SiCl4

We report, for the first time, a vapor-phase synthesis of nearly monodispersed silica spheres 250–300 nm in size through a two-stage hydrolysis of SiCl4. In the first stage, SiCl4 vapor was partially hydrolyzed with water vapor in a batch reactor at 150 °C to form silicon oxychloride particles, nearly monodispersed and spherical. In the second stage, these oxychloride particles were converted into silica particles through further hydrolysis at 1000 °C in a tubular reactor, while the morphology and size after the first-stage reaction remained virtually unchanged.