Floating combustion synthesis of spherical vitreous silica nano-powder

Vitreous silica nano-powder, with spherical particles of 50-300 nm in size, was successfully produced via floating combustion synthesis. Mechano-chemically activated and spray-dried Si-powder was oxidized in fluidized bed between 900 °C and 1550 °C in air. After 10 min, rapid removal of powder from the furnace and quenching maintained silica's vitreous nature. The process comprises sequential cycles of the following stages until nano-sized particles of silica are obtained. Superficial melting of Si-particles initially occurs and the particles obtain a spherical shape. The surface of the particles is oxidized. The stress at silica/silicon interface causes collapse of particles to smaller ones.