Continuous carbon nanotube production in underwater AC electric arc

Home-made apparatus for underwater electric arc discharge nanotube growth

TEM image of multi wall carbon nanotubes produced by AC arc-discharge under water.

We developed a simple, low cost and continuous growth method for the production of well graphitized multi-wall carbon nanotubes. In our procedure we combine the underwater growth with the use of an AC power supply and computer control.
An AC electric arc is generated between two identical carbon rods of 6 mm in diameter, submerged in deionized water. Two computer controlled stepper motors are used to regulate the distance between the electrodes. At a voltage of 40 V the arc is stable in the range of 85–45 A. At lower current values higher fraction of carbon nanotubes is obtained in the product.

There is no product on the electrodes, the deposit peels off the actual cathode into the water in the next half cycle when the role of the electrodes is reversed. No vacuum is needed, a continuous flow of water makes easy the removal of the product from the system. This makes our method suitable for up-scaling.