Comparative analysis of carbon plasma in arc and RF reactors

Results on studies of molecular spectra emitted in the initial stages of fullerene formation during the processing of graphite powder in induction RF reactor and evaporation of graphite electrodes in arc reactor are presented in this paper. It was found that C-2 radicals were dominant molecular species in both plasmas. C-2 radicals have an important role in the process of fullerene synthesis. The rotational-vibrational temperatures of C-2 and CN species were calculated by fitting the experimental spectra to the simulated ones. The results of optical emission study of C-2 radicals generated in carbon arc plasma have shown that rotational temperature of C-2 species depends on carbon concentration and current intensity significantly. The optical emission study of induction RF plasma and SEM analysis of graphite powder before and after plasma treatment have shown that evaporation of the processed graphite powder depends on feed rate and composition of gas phase significantly. Based on the obtained results, it was concluded that in the plasma region CN radicals could be formed by the reaction of C-2 species with atomic nitrogen at smaller loads. At larger feed rate of graphite powder, CN species were produced by surface reaction of the hot carbon particles with nitrogen atoms. The presence of nitrogen in induction RF plasma reduces the fullerene yield significantly. The fullerene yield obtained in two different reactors was: 13% in arc reactor and 4.1% in induction RF reactor. However, the fullerene production rate was higher in induction RIF reactor-6.4 g/h versus 1.7 g/h in arc reactor.