ELECTRICALLY CONTROLLED FLAME SYNTHESIS OF NANOPHASE TIO2, SIO2, AND SNO2 POWDERS

Nanophase particles with precisely controlled characteristics are made by oxidation of their halide vapors in electrically assisted hydrocar bon flames using needle-shaped or plate electrodes. The particle size and crystallinity decrease with increasing field strength across the f lame. The field generated by the electrodes across the flame decreases the particle residence time in the high temperature region of the fla me. Furthermore, it charges the newly formed particles, resulting in e lectrostatic repulsion and dispersion that decreases particle growth b y coagulation. Electric fields reduced the primary particle size of Ti O2, the agglomerate size of SnO2, and both the agglomerate and primary size of SiO2.