Patent ID: 7846414

Claim:
A process for the manufacture of carbon nanostructures, the carbon nanostructures being selected from carbon nanotubes and carbon nano-onions, comprising the steps of a) providing a high enthalpy metal electrode generated direct current thermal plasma torch having a plasma forming gas feed and a cooled nozzle attached thereto, the torch being connected to a cooled reactor having a quenching zone downstream of the plasma torch for the formation of carbon nanostructures; b) selecting a catalyst metal and providing the catalyst metal to the plasma stream, selecting a torch power at a level of from about 30 kW up to a multi-megawatt level, selecting a flow rate for the plasma forming gas feed, and selecting the reactor pressure so as to provide a plasma torch stream temperature required to vaporize and maintain the selected catalyst metal in the vapor state; c) providing a feed of a carbon containing substance and a carrier gas at a selected flow rate to the plasma stream, and d) the resulting plasma stream containing carbon, carrier gas and metal vapor entering the quenching zone of carbon nanostructure formation, wherein the plasma stream is rapidly cooled at a quenching rate of about 10 7 ° C./s which can be calculated in accordance with the formula ΔT/t, where ΔT is the temperature difference between the temperature of the plasma entering the nozzle T 2 and the temperature of the plasma in the guenching zone T 1 , with the average temperature entering the nozzle T 2 being calculated by the formula T 2 =T 1 +W p /{dot over (m)}C p , where T 1 is room temperature; W p is the energy input to the plasma, {dot over (m)} is the mass flow rate of the carrier gas; C p is the specific heat of the carrier gas; and t is the time for the plasma stream to travel from the plasma torch to the quenching zone, where t can be calculated by the formula t=length of nozzle/velocity of plasma gas entering the nozzle, whereupon metal catalyst nanoparticles acting as nucleation sites and catalyst for the growth of carbon nanostructures are generated in situ from the metal catalyst vapor, which, with atomic carbon from the carbon containing substance, form such structures in a diameter range of from about 2 to about 30 nm, which carbon nanostructures are then collected.