Development of Low-Fregnency Induction Thermal Plasma for Cluster Synthesis

在该项目的第三年，也就是1998年的最后一年，利用MOSFET逆变电源成功地产生了频率为450 kHz、功率为50 kW的广域感应等离子体，等离子体的反应区域宽至直径150 mm、长度150 mm，使我们能够进行材料的高速加工或合成。用Ar、He和CO2诱导热等离子体合成了C&lt；60&gt；富勒烯。结果表明：1)晶体管逆变电源可用于建立频率为450 kHz的电感耦合等离子体。在功率为30kW时，在Ar、He和CO2气体环境中可以产生多种等离子体。与Ar和He等离子体相比，CO2等离子体在10000 K附近具有相对较高的温度。2)这些感应热等离子体足够稳定，可以注入高达10g/min的冷碳粉，这足以产生高速率的C&lt；60&gt；团簇。3)在几种条件下进行的实验中，从等离子体的气体种类、压力和功率来看，Ar/He惰性气体等离子体显示出最高的C&lt；60&gt；合成速率，而解离的CO2气体等离子体没有合成C&lt；60&gt；结果表明，自由基C原子和C2分子的强烈猝灭效应对于合成这种高阶富勒烯材料是必不可少的。

In the third and final year of the project, 1998, a wide area induction plasma was successively generated by using MOSFET inverter power supply with a low frequency of 450 kHz and a power of 50 kW.The reaction area of the plasma is as wide as 150-mm diameter and 150-mm length, which enable us the high speed processing or synthesis of materials. C_<60> fullurene synthesis was carried out by using Ar, He and CO_2 induction thermal plasmas. Remarkable results are as follows.1) The transistor inverter supply was found to be useful to establish the inductively coupled plasma with a frequency of 450 kHz. At a power level of 30kW, several kinds of plasma can be generated in Ar, He and CO2 gas circumstance. The CO2 plasma was found to have relatively high temperature around 10,000 K compared to Ar and He plasma.2) These induction thermal plasmas were sufficiently stable for the injection of cold carbon powders up to a rate of 10 g/min, which is high enough quantity to produce the C_<60> cluster with a high rate.3) Among the experiments carried out under several conditions with respects to the gas sort, pressure and the power of plasma, Ar/He noble gas plasma showed the most highest C_<60> synthesis rate, while the dissociative CO_2 gas plasma showed no synthesis of C_<60>. The results indicate that a strong quenching effect of the radical C atom and C_2 molecule is essential for the synthesis of such high order fullurene materials.