Single-pulse arc production of carbon nanotubes in ambient air

Multi-wall nanotubes (MWNTs) of carbon were produced by pulsed arc discharges between a room temperature sample and a counter-electrode, with peak currents of 7-100 A, and pulse lengths of 0.2-26 mus, in open air at selected locations on the sample. The samples were 10 x 10 mm(2) graphite plates, carbon-coated 200 mesh copper grids, and Ni-coated glass slides. The counter-electrodes were graphite in the form of 1 x 4 mm(2) bars or 4 mm diameter rods with a cone tip of 28degrees, or 0.1 mm diameter steel rods. Randomly oriented MWNTs (typically 5-15 walls) with a diameter of similar to10 nm and lengths of up to 3 mum were produced on the samples with a single 0.2 mus pulse, implying linear growth rates of up to 15 m s(-1). MWNTs were produced with both polarities and with all types of counter-electrodes used when the substrate contained carbon. Near vertically oriented MWNTs were deposited on the Ni/glass samples using a graphite counter-electrode. The simplicity, rapidity and selectivity of the process may facilitate wider study and practical application.