Electrically Controlled Flame Synthesis of Nanophase TiO₂, SiO_2, and SnO₂ Powders

Nanophase particles with precisely controlled characteristics are made by oxidation of their halide vapors in electrically assisted hydrocarbon flames using needle-shaped or plate electrodes. The particle size and crystallinity decrease with increasing field strength across the flame. The field generated by the electrodes across the flame decreases the particle residence time in the high temperature region of the flame. Furthermore, it charges the newly formed particles, resulting in electrostatic repulsion and dispersion that decreases particle growth by coagulation. Electric fields reduced the primary particle size of TiO₂, the agglomerate size of SnO₂, and both the agglomerate and primary size of SiO₂.