Metal Oxide Nanopowder Production by Evaporation–Condensation Using a Focused Microwave Radiation at a Frequency of 24 GHz

Abstract

The new method for metal oxide nanopowder production is proposed. It is the evaporation–condensation using a focused microwave radiation. The source of microwaves is technological gyrotron with frequency of 24 GHz and power up to 7 kW with the energy density flux of 13 kW/cm2. Radiation was focused on the layer of powder of the treated material to ensure its evaporation, subsequent condensation of vapor in the gas stream, and deposition of particles on the water-cooled surface. Deposited powders consist of particles whose sizes are in the range of 20 nm to 1 μm. The powder consists of particles having different shapes—close to spherical shape as well as octahedral, which indicates that the mechanism of particles formation is “vapor–liquid–crystal” as well as “vapor–crystal.” The maximum evaporation rate was 100 g/hr. The proposed approach is original and extends the possible methods of producing nanoparticles.