Size Control of TiO_2 Nanoparticles Prepared by Oxidative Pyrolysis of Liquid-mist Precursors in RF Thermal Plasma

摘要

TiO_2 nanoparticles have been synthesized via Ar/O_2 RF thermal plasma oxidation of atomized liquid precursors containing titanium tetrabutoxide and diethanolamine. Quench gases (Ar, O_2 or He), either injected from the shoulder of the reactor (transverse injection) or injected counter to the plasma plume from the bottom of the reactor (counter-flow injection) are used to affect the quench rate and therefore particle size of the resultant powders. The experimental results show that counter-flow injection is more effective in reducing the particle size, while He is the most effective among three kinds of gasses. The average particle size of well-dispersed TiO_2 nano-size powders decreased down to 20 nm. The experimental results are well supported by numerical analysis on the effects of the quench gas on flow pattern and temperature field of the thermal plasma as well as trajectory and temperature history of the particles.