High-speed synthesis of fullerences by using low-frequency induction thermal plasma with pulse-modulated mode.

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(1) Synthesis of fullerenes using high-power induction thermal plasma and dependence of various parameters on the products. Fullerene synthesis were made using high-power induction thermal plasma and dependence of various parameters on the products was investigated. The parameters are as follows: (a) gas kind, (b) pressure, c input power, (d) power materials, (e) location for collection of the products. Through the investigation, the following conditions were found to be preferable for fullerene synthesis: (a) He as main ambient gas rather than Ar, (b) Lower pressure of 20kPa than 50 or 67 kPa, c Lower input power of 30kW than 50 or 70kW, (d) C+Si material power compared with C+Fe, C+Ni-Co and pure C, (e) long-distance location of 900mm from plasma torch rather than close location. Further investigation was made by numerical simulation of flow and temperature fields in a reaction chamber. This result indicates that use of He increases temperature gradient on the torch axis, which means the high cooling efficiency of gas. Also, it was found that low pressure increases axial flow velocity, which causes high cooling efficiency of gas.(2) Development of pulse-modulated induction thermal plasma torch and investigation of dynamic response of thermal plasma. A novel system was developed to sustain pulse-modulated induction thermal plasma with amplitude-modulated coil-current. This system has a MOSFET inverter power supply rated at a power of 50kW and a operating frequency of 450kHz. Dynamic response characteristics were investigated for Ar based induction thermal plasma with additional gases. This result indicates that C02 inclusion markedly lowers both operating region and dynamic response of pulse-modulated induction thermal plasma. This pulse-modulated induction thermal plasma is available for fullerene synthesis by high-speed cooling and heating.