Graphite cathode spot produces carbon nanotubes in arc discharge

A dc arc discharge was generated between graphite (C) and molybdenum (Mo) electrodes at 25 kPa of He gas ambient for a period of about 1 s in order to reveal the relation between nanotube growth and arc discharge phenomena. Numerous multiwall carbon nanotubes and nanocapsules were observed at the cathode spot area of the C-cathode. However, almost no nanotubes were observed at the C-anode, Mo-anode, and Mo-cathode. These results clearly indicated that the nanotubes were grown by the cathode spot of the C-cathode. Based on the results, a logical explanation of the growth of soft-core containing nanotubes and a hard-shell in the usual arc with a C-cathode and C-anode electrode system was presented.