Process for the simultaneous and selective preparation of single-walled and multi-walled carbon nanotubes

A process for the simultaneous and selective growth of single walled and multiwalled carbon nanotubes which comprises:

• preparing a graphite electrode rod containing catalyst selected from Fe, Co, Ni, and a mixture thereof, acting as an anode;
• preparing another graphite electrode rod, acting as a cathode, each electrode having a distal and a proximal end;
• placing the above said two electrodes parallel to each other and their axis being substantially aligned such that their distal ends are at least 1 mm apart and in a closed and evacuated arc discharge chamber;
• creating a DC-arc discharge inside the above said chamber by applying a DC-current voltage in the range of 10-50 V, at an arc current of 50-200 amp, under inert gas pressure of 120-500 torr;
• and
• followed by cooling the said two electrodes by maintaining a temperature gradient by using a cooling assembly having a cooling coil surrounding the said two electrodes, to obtain simultaneously the desired deposition of the multiwalled carbon nanotubes at the cathode and the single walled carbon nanotubes in the chamber;
• wherein the proximal end of the graphite electrode acting as the cathode is connected to an electrically insulated shaft extending out of the chamber.