A large amount synthesis method for titanium dioxide (TiO2) nanopowder is proposed by direct evaporation of titanium powders using Ar-O 2 pulse-modulated induction thermal plasma (PMITP). To realize a large amount synthesis of nanopowder, the PMITP method was combined with the intermittent and heavy load feeding of raw material powder, as well as the quenching gas injection. The intermittent powder feeding was synchronized with the modulation of the coil current sustaining the PMITP for complete evaporation of the injected powder. Synthesized particles by the developed method were analyzed by FE-SEM and XRD. Results indicated that the synthesized particles by the 20-kW PMITP with a heavy loading rate of 12.3 g min −1 had a similar particle size distribution with the mean diameter about 40 nm to those with light loading of 4.2 g min −1 .

This paper describes the relation between the size of synthesized nanoparticles and the temperature variation of the surrounding plasma in TiO 2 nanoparticle synthesis using pulse-modulated induction thermal plasmas (PMITP). The Ar-O 2 PMITP at 20 kW was used to obtain repetitional temperature fields at pressure of 200 Torr. The TiO 2 nanoparticles were synthesized by direct injection of Ti powder with mean diameter of 45 µm. Dependence of the nanoparticle size on modulation parameters such as the duty factor and the shimmer current level of the PMITP were investigated experimentally. Instantaneous temperature evolution was evaluated through spectroscopic observation. Experimental results show that the temperature decay rate in the PMITP reached 10 5 -10 6 K/s, and that the mean diameter of synthesized particles decreased with the temperature decay rate.