[16a-315-1~10] 8.5 Plasma nanotechnology

△ [16a-315-8] Optical study on feedstock feeding timing during high-rate production of Si nanopowder using pulse-modulated thermal plasmas

〇(M1)Yosuke Ishisaka¹, Kotaro Shimizu¹, Naoto Kodama¹, Yasunori Tanaka¹, Yoshihiko Uesugi¹, Tatsuo Ishijima¹, Shiori Sueyasu², Shu Watanabe², Keitaro Nakamura² (1.Kanazawa Univ., 2.Nisshin Seifun Group Inc.)

Keywords:Si nanopowder, Induction thermal plasmas, 2-dimensional optical emission spectroscopy

Silicon (Si) nanopowder is anticipated as a high-capacity anode material for lithium ion battery. We have carried on developing a production method of Si nanopowder using induction thermal plasmas. Among the developed methods, our original ‘Pulse-modulated induction thermal plasmas with intermittent feeding of feedstock’ (PMITP-TCFF) method can provide high-rate synthesis of Si nanopowder. This high production rate of nanopowder originates from mainly two terms. The one is synchronized feeding of large amounts of feedstock powder to the modulated thermal plasmas under a higher coil-current input that can cause complete evaporation of feedstock. The latter is quenching of the thermal plasmas by rapid decrement of coil-currents that can reinforce nucleation of the evaporated materials. In the present work, firstly a spatiotemporal distribution of injected feedstock in the plasma torch was observed by high-speed video camera without a thermal plasma. In addition to this, that of the evaporated vapor in a modulated thermal plasma was estimated by a 2-dimensional optical emission spectroscopy (2D-OES).
As results, the injection of the feedstock was confirmed to be successfully synchronized with the thermal plasma modulation, demonstrated by both the high-speed video camera observation and 2D-OES. A large amount of the feedstock was injected to the plasma torch in the higher coil-current phase and it was restrained in the lower current-phase.