Comparative analysis of two methods for synthesis of fullerenes at different helium pressures

The results of the effect of helium pressure in the chamber on the amount and composition of the produced fullerenes (C60, C70, etc.) synthesized in the arc plasma with graphite electrodes are presented. The findings obtained when the arc is powered by a direct (DC) and alternating (AC) currents of low frequency were compared in the same chamber with the electrodes located at the same angle to each other. These two methods are drastically different. The complete conversion of graphite into fullerene soot in AC occurs, but a part of the graphite is converted into a cathode deposit that does not contain fullerenes in DC, the relative amount of which increases when decreasing the helium pressure in the chamber. The highest fullerene content in fullerene soot of 10.2 wt.% is produced at a pressure of 127.5 kPa in AC arc, but in DC arc, the highest content of fullerenes in fullerene soot of 8.3 wt.% is produced at a pressure of 33.3 kPa.