FULLERENE SYNTHESIS IN HELIUM FLOW AT ATMOSPHERIC PRESSURE

We present results obtained on carbon structures formed as condensates from a carbon-helium plasma under atmospheric pressure, when the plasma is maintained by an alternating current (AC) of 44 kHz, of 50 Hz, and by direct current (DC), respectively. It was found that the kind of current (AC or DC) has no pronounced influence on the kind of produced substances (re-crystallized graphite, soot, fullerenes) but a significant influence on their relative abundance ratios. The relative abundances of the obtained fullerenes (C60, C70 etc.) remain about constant independent of the kind of current applied. We observed that by applying AC of 44 kHz, the most efficient fullerene production was obtained in a chamber with diameter 20 cm and height 15 cm. Under these conditions, the plasma in the chamber is stratified, indicating that a kind of resonance is taking place which also may be responsible for the high fullerene productivity. No such effects occurred at AC or 50 Hz DC. At 44 kHz AC, the obtained productivity is 16 mg of soot per minute and the soot contains fullerene (9% weight) and the re-crystallized graphite (7%).