Nanoparticle synthesis by tandem modulated induction thermal plasma

Abstract This report describes experimentally obtained results on nanoparticle synthesis using two-coil tandem-type modulated induction thermal plasma (tandem-MITP). The developed tandem-MITP is operated by two coils with independently modulated high-frequency coil current. Tandem-MITP can offer unique temporo-spatially controlled high-temperature fields in thermal plasmas, as well as high-rate quenching of thermal plasma around the downstream region of the plasma torch. This high-rate quenching of the thermal plasma can promote supersaturation of evaporated feedstock vapour, resulting in nanoparticle nucleation. First, as described herein, Fe3+-doped TiO2 nanoparticle synthesis was conducted using single-MITP and tandem-MITP. The single-MITP is a conventional type of induction thermal plasma that is operated by one coil with modulated high-frequency coil current. Results show that a smaller nanoparticle can be synthesized using tandem-MITP than by single-MITP because the tandem-MITP with larger modulation can offer a lower temperature field during off-time, which can engender suppression in particle growth. In addition, nanoparticles synthesized by tandem-MITP were found to have sufficient doping of Fe3+ on TiO2 for photocatalytic properties by visible light. This finding suggests tandem-MITP as suitable for high-rate production of metallic ion doped nanoparticles.