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 μs, in open air at selected locations on the sample. The samples were 10 × 10 mm² graphite plates, carbon-coated 200 mesh copper grids, and Ni-coated glass slides. The counter-electrodes were graphite in the form of 1 × 4 mm² bars or 4 mm diameter rods with a cone tip of 28°, or 0.1 mm diameter steel rods. Randomly oriented MWNTs (typically 5-15 walls) with a diameter of ∼10 nm and lengths of up to 3 μm were produced on the samples with a single 0.2 μs pulse, implying linear growth rates of up to 15 ms^-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.