Apparatus and method for plasma synthesis of carbon nanotubes

Abstract

Apparatus for plasma synthesis of carbon nanotubes, comprising: a plasma nozzle coupled to a reaction tube or chamber; means for supplying a process gas to the plasma nozzle, the process gas comprising a carbon-containing species; means for supplying radio frequency radiation to the process gas within the plasma nozzle, so as to sustain a plasma within the nozzle in use, and thereby cause cracking of the carbon-containing species; and means for providing a catalyst; wherein the plasma nozzle is arranged such that an afterglow of the plasma extends into the reaction tube/chamber, the cracked carbon-containing species also pass into the reaction tube/chamber, and the cracked carbon-containing species recombine within the afterglow, so as to form carbon nanotubes in the presence of the catalyst. A method of plasma-synthesising carbon nanotubes is also provided.

1 - 84 . (canceled) 
     
     
         85 . An apparatus for plasma synthesis of carbon nanotubes, the apparatus comprising:
 a plasma nozzle coupled to a reaction tube or chamber;   a gas supply for supplying a process gas comprising a carbon-containing species to the plasma nozzle;   a source of radio frequency radiation for supplying radio frequency radiation to the process gas within the plasma nozzle in use, so as to sustain a plasma within the plasma nozzle in use, and thereby cause cracking of the carbon-containing species; and   a provider of a catalyst;   wherein the plasma nozzle is arranged such that, in use, an afterglow of the plasma extends into the reaction tube or the chamber, the cracked carbon-containing species also passes into the reaction tube or the chamber, and the cracked carbon-containing species recombines within the afterglow, so as to form carbon nanotubes in the presence of the catalyst; and   wherein the reaction tube or the chamber is configured to apply cooling to the afterglow on exiting the plasma nozzle.   
     
     
         86 . The apparatus according to  claim 85 , wherein the carbon-containing species comprises a gaseous hydrocarbon, natural gas, CH 4 , C 2 H 6 , C 2 H 4 , C 3 H 8 , C 4 H 10 , a liquid hydrocarbon, a liquefied hydrocarbon, toluene, or ethanol. 
     
     
         87 . The apparatus according to  claim 86 , wherein the apparatus is configured to generate the plasma at substantially atmospheric pressure. 
     
     
         88 . The apparatus according to  claim 86 , wherein the apparatus is configured to generate the plasma at a pressure that is lower than atmospheric pressure. 
     
     
         89 . The apparatus according to  claim 85 , wherein the plasma nozzle is shaped and configured so as to cause, in use, at least one vortex to be formed in the process gas within the plasma nozzle, said at least one vortex being subjected to said radio frequency radiation. 
     
     
         90 . The apparatus according to  claim 89 , wherein the plasma nozzle is shaped and configured so as to cause, in use, multiple vortices to be formed in the process gas within the plasma nozzle, said multiple vortices being subjected to said radio frequency radiation. 
     
     
         91 . The apparatus according to  claim 90 , wherein the plasma nozzle comprises:
 at least one inlet for receiving a stream of the process gas, that forms a first vortex in use;   an open end in communication with the reaction tube or the chamber; and   a vortex-reflecting end opposite the open end;   wherein the plasma nozzle is internally tapered towards the open end such that, in use, a second vortex is created by the vortex-reflecting end, and a third vortex is produced by reflection of the second vortex from the vortex-reflecting end.   
     
     
         92 . The apparatus according to  claim 85 , wherein the source of radio frequency radiation comprises a microwave generator, the microwave generator being coupled to a waveguide arranged to direct the radiation to the plasma nozzle in use. 
     
     
         93 . The apparatus according to  claim 85 , wherein the cooling comprises water cooling or gas cooling. 
     
     
         94 . The apparatus according to  claim 85 , wherein the process gas further comprises a buffer gas, the buffer gas comprising argon, nitrogen, or helium. 
     
     
         95 . The apparatus according to  claim 85 , wherein the process gas further comprises a buffer gas, the buffer gas comprising carbon dioxide. 
     
     
         96 . The apparatus according to  claim 85 , wherein the plasma nozzle is arranged such that the afterglow within the reaction tube or the chamber has an operating temperature of lower than 3500° C., lower than 2000° C., or around 1000° C. 
     
     
         97 . The apparatus according to  claim 85 , wherein a chord central angle of an interface of the plasma nozzle with the reaction tube/chamber is greater than 0°, or between 50° and 180°, or between 150° and 170°. 
     
     
         98 . The apparatus according to  claim 85 , wherein the plasma nozzle is a first plasma nozzle, the apparatus further comprising a plurality of plasma nozzles including the first plasma nozzle, the plurality of plasma nozzles being coupled to the reaction tube or the chamber;
 wherein a chord central angle of an interface of each plasma nozzle with the reaction tube or the chamber is between 0° and 180°, or between 50° and 170°, or between 70° and 160°.   
     
     
         99 . The apparatus according to  claim 85 , wherein the apparatus is configured to deliver a gas around an interface between the plasma nozzle and the reaction tube or the chamber. 
     
     
         100 . The apparatus according to  claim 85 , wherein the apparatus is configured to remove the carbon nanotubes from walls of the reaction tube or the chamber. 
     
     
         101 . The apparatus according to  claim 85 , further comprising a filter coupled to the reaction tube or the chamber, the filter being configured to collect the carbon nanotubes. 
     
     
         102 . The apparatus according to  claim 85 , wherein the provider of the catalyst comprises an injector or an inserter configured to introduce a catalyst precursor into the afterglow, the catalyst precursor providing the said catalyst in use,
 wherein the injector comprises an injector tube,   or wherein the inserter comprises a catalyst wire.   
     
     
         103 . The apparatus according to  claim 85 , wherein the provider of the catalyst comprises an injector configured to introduce a catalyst precursor into the process gas that is supplied to the plasma nozzle, the catalyst precursor providing the catalyst in use. 
     
     
         104 . The apparatus according to  claim 85 , wherein the provider of the catalyst comprises a substrate that is at least partially coated or soaked with a catalyst precursor, the catalyst precursor providing the catalyst in use,
 wherein the substrate is in the form of elongate material that is arranged to be pulled through the reaction tube or the chamber in an incremental or substantially continuous manner.