Fullerene synthesis in the graphite electrode arc process: local plasma characteristics and correlation with yield

In order to optimize the fullerene synthesis process based on an electric arc with graphite electrodes, an experimental study using a reactor geometry optimized for plasma spectroscopy is performed to correlate the arc properties with the fullerene formation. Emission spectroscopy studies based on the use of the Swan C 2 (0,0) rotational system emission spectra were carried out to determine the plasma temperature. The self-absorption effect in the d 3 Π g , v ' = 0 → a 3 Π u , v '' = 0 C 2 band was used for column density determination of C 2 molecules and temperatures under various arc discharge conditions. Discharge parameters (pressure, arc current, electrode gap length) are optimized with respect both to the anode erosion rate and the weight percentage of toluene extractable fullerenes in the soot. Local plasma discharge conditions (temperature and density fields) are evaluated and correlated with the C 60 yield. Steep temperature gradients around the arc fringes are shown to provide optimal conditions for C 60 production.