New synthesis method produces nanoparticles in high quantities

TiO2 nanoparticles are in increasingly high demand for a range of applications, including photocatalysts, photonic crystals, photovoltaic cells, gas sensors, fuel cells, pigments and cosmetics. Now researchers in Japan have demonstrated a new method for synthesis of TiO2 nanoparticles in large amounts.

Researchers have already used inductively coupled thermal plasmas (ICTPs) as a useful source of heat and chemicals in synthesis. These plasmas are forms of the chemical that have been ionised by energy produced by electric currents produced by fluctuating magnetic fields, so-called electromagnetic induction. However application of ICTPs in nanoparticle synthesis has met with difficulties in controlling the particle size.

Yasunori Tanaka and colleagues at Kanazawa University and Nisshin Seifun Group in Japan had previously modified the ICTP approach using a modulated current coil to give voltage pulses and other arbitrary waveforms. The modulated current provides a means of controlling the temperature and density of the chemical species during synthesis. Applying these pulse-modulated inductive thermal plasmas (PMITP) to TiO2 nanoparticle synthesis allowed control over the particle size and mineral phase. However, due to the latent heat of evaporation of the powders, there was a limit to how much the feed rate could be increased before the ICTP failed to evaporate all the powder.

Now the researchers have demonstrated that carefully timed intermittent feeding combined with gas quenching to synchronise with the pulse modulation of the induction thermal plasmas allowed oxidation of all the titanium into TiO2 nanoparticle even when synthesised in large amounts. They conclude, “The results indicated that the synthesized particles by the 20-kW PMITP with a heavy loading rate of 12.3 g/min had a similar particle size distribution with the mean diameter about 40 nm to those with light loading of 4.2 g/min.”

Publication and Affiliation
Yasunori Tanaka*¹, Tatsuya Tsuke¹, Weixuan Guo¹, Yoshihiko Uesugi¹, Tatsuo Ishijima¹, Shu Watanabe², Keitaro Nakamura². 　A large amount synthesis of nanopowder using modulated induction thermal plasmas synchronized with intermittent feeding of raw materials. Journal of Physics: Conference Series 406 (2012) 012001. Link

^1. Faculty of Electrical and Computer Engineering, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan
^2. Research Center for Production & Technology, Nisshin Seifun Group Inc.,5-3-1 Tsurugaoka, Fujimino 356-8511, Japan

*corresponding author, e-mail address: tanaka@ec.t.kanazawa-u.ac.jp

ID: 201302H018