Plasma synthesis of hollow nanostructures

Abstract

A method is described for the continuous production of nanotubes comprising forming a plasma jet, introducing into the plasma jet a metal catalyst or metal catalyst precursor to produce vaporised catalyst metal, directing one or more streams of quenching gas into the plasma to quench the plasma and passing the resulting gaseous mixture through a furnace, one or more nanotube forming materials being added whereby nanotubes are formed therefrom under the influcence of the metal catalyst and are grown to a desired length during passage through the furnace, and collecting the nanotubes so formed.

1 . A method for the continuous production of nanotubes comprising forming a plasma jet, introducing into the plasma jet a metal catalyst or metal catalyst precursor to produce vaporised catalyst metal, directing one or more streams of quenching gas into the plasma to quench the plasma and passing the resulting gaseous mixture through a furnace, one or more nanotube forming materials being added whereby nanotubes are formed therefrom under the influence of the metal catalyst and are grown to a desired length during passage through the furnace, and collecting the nanotubes so formed.  
     
     
         2 . A method as claimed in  claim 1 , wherein the nanotube forming material is a carbon containing material and the product is carbon nanotubes.  
     
     
         3 . A method as claimed in  claim 2 , wherein the nanotube forming material is carbon containing material and the product is predominantly carbon nanotubes.  
     
     
         4 . A method as claimed in  claim 1 , wherein the nanotube forming material is a carbon containing material and the product contains multi wall nanotubes.  
     
     
         5 . A method as claimed in  claim 2 , wherein the nanotube forming material is carbon monoxide, carbon particulates, a normally liquid or gaseouse hydro carbon, or an oxygen containing hydrocarbon derivative.  
     
     
         6 . A method as claimed in  claim 1 , wherein the catalyst precursor material acts as a nanotube forming material and vice versa.  
     
     
         7 . A method as claimed in  claim 2 , wherein the nanotube forming material further comprises non-carbon dopant elements.  
     
     
         8 . A method as claimed in  claim 1 , wherein the nanotube forming material comprises borazine, boron powder plus nitrogen gas, boranes plus nitrogen gas, tunsten oxide powder plus hydrogen disulphide gas, or tungsten disulphide powder.  
     
     
         9 . A method as claimed in  claim 1 , wherein the nanotube forming material is added upstream of the plasma jet.  
     
     
         10 . A method as claimed in  claim 1 , wherein the nanotube forming material is added as or with the quenching gas, or is added downstream of the plasma jet separately from the quenching gas.  
     
     
         11 . A method as claimed in  claim 1 , wherein the metal catalyst or catalyst precursor is or contains copper, chromium, molybdenum, tungsten, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, yttrium, a lanthanide or an actinide, or a mixture of two or more thereof.  
     
     
         12 . A method as claimed in  claim 1 , wherein the temperature within the furnace is from 700 to 1200° C.  
     
     
         13 . A method as claimed in  claim 1 , wherein the introduced materials have a residence time within the furnace of from 5 to 30 seconds.  
     
     
         14 . A method as claimed in  claim 1 , wherein the plasma is generated by an inductively coupled plasma 15 torch.  
     
     
         15 . A method as claimed in  claim 1 , wherein said quenching gas is directed radially into said plasma jet from multiple directions to induce full mixing of the plasma and quenching gas to produce uniform conditions within the mixture thereof.  
     
     
         16 . A method as claimed in  claim 12 , where the symmetric array of nozzles are directed at an angle to the radial direction to induce a turbulent vortex where mixing of the plasma and quenching gas occurs.