Voltage-current characteristics of an anodic arc producing carbon nanotubes

Voltage-current (V-I) characteristics of the carbon nanotube producing anodic arc are measured for different gap sizes (up to 13 mm), anode compositions, and background He pressures (in the range of about 300-500 Torr). Are is supported by the erosion of 6.35 mm hollow anode packed with composition of Ni, Y, and carbon powders. Experiments were carried out for the arc currents in the range of about 10-100 A. It is shown that V-I characteristics have a V-type shape with minimum point corresponded to arc current of about 25-30 A and arc voltage of 20-25 V at the gap of 2.5 mm. V-I characteristic shifts 15-25 V to higher arc voltages with increasing gap from 2.5 to 13 mm, while the position of voltage minimum shifts by about 15 A to higher arc currents. The increase in the metallic catalyst fraction in the anode composition (from C: Ni: Y = 56:4: 1 to 36:4: 1) results in the slight decrease in the arc voltage (about a few volts) and slight shift of the minimum position to higher arc currents (5-10 A). Anode erosion rate increases from below 5 mg/s to about 44 mg/s with arc current increase from 40 A to about 100 A. 0 2008 American Institute of Physics. [DOI: 10.1063/1.2986572]