Process and apparatus for the production of carbon nanotubes

Abstract

A process for preparing carbon nanotubes comprising locating a substrate ( 1 ) capable of supporting carbon nanotube growth in a localised heating zone within a reaction chamber ( 7 ), said localised heating zone being provided by a heating element ( 2 ) located within the reaction chamber ( 7 ), passing a gaseous carbonaceous material into the reaction chamber ( 7 ) such that the gaseous material passes over and contacts the substrate ( 1 ) in the localised heating zone, whereby the gaseous material undergoes pyrolysis under the influence of the heat to form carbon nanotubes on the substrate ( 1 ). Embodiments of the process prepare multilayer carbon nanotubes and hetero-structured multilayer carbon nanotube films.

The claims defining the invention are as follows:  
     
         1 . A process for preparing carbon nanotubes comprising: 
 locating a substrate capable of supporting carbon nanotube growth in a localised heating zone within a reaction chamber, said localised heating zone being provided by a heating element located within said reaction chamber,    passing a gaseous carbonaceous material into said reaction chamber such that the gaseous material passes over and contacts said substrate in the localised heating zone, whereby said gaseous material undergoes pyrolysis under the influence of said heat to form carbon nanotubes on said substrate.    
     
     
         2 . A process according to  claim 1  wherein the localised heating zone has a temperature greater than 300° C.  
     
     
         3 . A process according to  claim 2  wherein the localised heating zone has a temperature between 400° C. and 800° C.  
     
     
         4 . A process according to  claim 1  wherein the substrate is quartz glass, mesoporous silica, nanoporous alumina, a ceramic plate, glass, graphite or mica.  
     
     
         5 . A process according to  claim 4  wherein the substrate is glass.  
     
     
         6 . A process according to  claim 1  wherein the gaseous carbonaceous material is selected from an alkane, alkene, alkyne or aromatic hydrocarbon.  
     
     
         7 . A process according to  claim 6  wherein the gaseous carbonaceous material is selected from methane, ethylene, benzene or acetylene.  
     
     
         8 . A process according to  claim 7  wherein the gaseous carbonaceous material is acetylene.  
     
     
         9 . A process according to  claim 1  wherein pyrolysis of the carbonaceous material occurs in the presence of a catalyst.  
     
     
         10 . A process according to  claim 9  wherein the catalyst is coated on the substrate.  
     
     
         11 . A process according to  claim 9  or  10  wherein the catalyst comprises a transition metal selected from Ni, Fe, Co, Al, Mn, Pd, Cr or alloys thereof.  
     
     
         12 . A process according to  claim 11  wherein the catalyst comprises Ni.  
     
     
         13 . A process according to  claim 1  wherein the pyrolysis conditions are controlled to provide aligned carbon nanotubes.  
     
     
         14 . A process according to  claim 1  wherein the pyrolysis conditions are controlled to provide non-aligned carbon nanotubes.  
     
     
         15 . A process according to  claim 1  wherein the pyrolysis conditions are controlled to provide homogeneous carbon nanotube growth on the substrate.  
     
     
         16 . A process according to  claim 1  wherein the pyrolysis conditions are controlled to provide patterned carbon nanotube growth on the substrate.  
     
     
         17 . A process for preparing multilayer carbon nanotube materials comprising: 
 (a) synthesising a first layer of carbon nanotubes on a substrate under a first set of pyrolysis conditions to provide a nanotube coated substrate;    (b) synthesising a second layer of carbon nanotubes on the nanotube coated substrate under a second set of pyrolysis conditions,    wherein at least one of steps (a) and (b) is performed using a process of  claim 1 .    
     
     
         18 . A process according to  claim 17  wherein step (b) is repeated at least once.  
     
     
         19 . A process according to  claim 17  wherein the pyrolysis conditions of step (a) are the same as the pyrolysis conditions of step (b).  
     
     
         20 . A process according to  claim 17  wherein the pyrolysis conditions of step (a) are different from the pyrolysis conditions of step (b).  
     
     
         21 . A process for the preparation of a hetero-structured multilayer carbon nanotube film comprising: 
 (a) synthesising a first layer of carbon nanotubes on a substrate under a first set of pyrolysis conditions to provide a nanotube coated substrate;    (b) coating a layer of pyrolysis resistant material onto the nanotube coated substrate to provide a hetero-structured multilayer substrate;    (c) synthesising a second layer of carbon nanotubes on the hetero-structured multilayer substrate under a second set of pyrolysis conditions,    wherein at least one of steps (a) and (c) is performed using a process of  claim 1 .    
     
     
         22 . A process according to  claim 21  wherein steps (b) and (c) are repeated at least once.  
     
     
         23 . A process according to  claim 21  wherein the pyrolysis conditions of step (a) are the same as the pyrolysis conditions of step (c).  
     
     
         24 . A process according to  claim 21  wherein the pyrolysis conditions of step (a) are different from the pyrolysis conditions of step (c).  
     
     
         25 . A process according to  claim 21  wherein the pyrolysis resistant material is a metal, a semiconductor or a polymer.  
     
     
         26 . A process according to  claim 25  wherein the pyrolysis resistant material is a metal.  
     
     
         27 . A reactor for preparing carbon nanotubes comprising: 
 a reaction chamber,    at least one support means located within said reaction chamber capable of supporting a substrate, said substrate being capable of supporting carbon nanotube growth,    at least one heating element located within said reaction chamber capable of providing localised heating to said substrate within said reaction chamber,    means for passing a gaseous carbonaceous material into said reaction chamber such that it passes over and contacts said substrate.    
     
     
         28 . A reactor according to  claim 27  wherein the reaction chamber is formed from metal, glass, plastic or a combination thereof.  
     
     
         29 . A reactor according to  claim 28  wherein the reaction chamber is formed from glass or comprises at least one glass panel.  
     
     
         30 . A reactor according to  claim 27  wherein the heating element comprises resistant wires, an induction field, microwave radiation or infrared radiation.  
     
     
         31 . A reactor according to  claim 27  wherein the heating element is located within the substrate support.  
     
     
         32 . A reactor according to  claim 31  wherein the heating element and substrate support comprise a ceramic plate into which resistant wires have been inserted.  
     
     
         33 . A reactor according to  claim 27  wherein the means for passing a gaseous carbonaceous material into the reaction chamber is at least one gas conduit.  
     
     
         34 . A reactor according to  claim 33  wherein the at least one gas conduit is located above the substrate.  
     
     
         35 . A reactor according to  claim 33  wherein the at least one gas conduit is located to allow the gaseous carbonaceous material to flow across the surface of the substrate.  
     
     
         36 . A reactor according to  claim 27  comprising multiple support means.  
     
     
         37 . A reactor according to  claim 27  comprising multiple heating elements.  
     
     
         38 . A reactor according to  claim 27  further comprising a pre-heating zone.  
     
     
         39 . A reactor according to  claim 38  wherein the pre-heating zone is located in a separate chamber from the reaction chamber.  
     
     
         40 . A reactor according to  claim 27  further comprising a cooling zone.  
     
     
         41 . A reactor according to  claim 40  wherein the cooling zone is located in a separate chamber from the reaction chamber.  
     
     
         42 . A reactor according to  claim 27  further comprising a means of transferring a substrate from a pre-heating zone to a support means and/or from the support means to a cooling zone.  
     
     
         43 . Carbon nanotubes prepared by the process of any one of  claims 1  to  16 .  
     
     
         44 . Multilayer carbon nanotubes prepared by the process of any one of  claims 17  to  20 .  
     
     
         45 . Hetero-structured multilayer carbon nanotube films prepared by the process of any one of  claims 21  to  26 .