Process for producing single-wall carbon nanotubes uniform in diameter and laser ablation apparatus used therein

Abstract

Single-wall carbon nanotubes are produced from carbon vapor in the presence of nickel-cobalt catalyst vapor, and the carbon vapor and the nickel-cobalt catalyst vapor are constantly generated from a carbon pellet and a nickel-cobalt pellet under radiation of YAG laser beams so that the single-wall carbon nanotubes are constant in diameter.

What is claimed is:  
     
         1 . A process for producing carbon nanotubes, comprising the steps of: 
 a) preparing a source of carbon vapor and a source of catalyst vapor physically separated from each other;    b) radiating laser beams to said source of carbon vapor and said source of catalyst vapor so as to generate a carbon vapor/cluster and a catalyst vapor/cluster;    c) allowing said carbon vapor/cluster to be mixed with said catalyst vapor/cluster so as to form said carbon vapor/cluster into carbon nanotubes.    
     
     
         2 . The process as set forth in    claim 1   , in which said source of carbon vapor and said source of catalyst vapor are provided as a carbon pellet and a catalyst pellet, respectively.  
     
     
         3 . The process as set forth in    claim 2   , in which said carbon pellet is formed of graphite, and said catalyst pellet is formed of material selected from the group consisting of nickel, cobalt, platinum, palladium and alloys containing at least two of said nickel, said cobalt, said platinum and said palladium.  
     
     
         4 . The process as set forth in    claim 2   , in which a spacer is provided between said carbon pellet and said catalyst pellet.  
     
     
         5 . The process as set forth in    claim 1   , in which a YAG laser forms said laser beams.  
     
     
         6 . The process as set forth in    claim 5   , in which said YAG laser forms laser pulse trains for said laser beams, respectively, and said laser pulse trains have a wavelength of 532 nanometers, a frequency of 10 Hz, a pulse width of 7 to 10 nanoseconds and a power of 1.2 to 9.1 J/pulse.  
     
     
         7 . The process as set forth in    claim 1   , in which a carrier gas flows through said source of carbon vapor and said source of catalyst vapor so as to mix said carbon vapor/cluster with said catalyst vapor/cluster in said step c).  
     
     
         8 . The process as set forth in    claim 7   , in which said carrier gas is an inert gas, and said inert gas flows at 0.2 to 0.5 litter per minute at 500 to 600 torr.  
     
     
         9 . The process as set forth in    claim 1   , in which said carbon vapor/cluster is formed into said carbon nanotubes at 1200 degrees in centigrade.  
     
     
         10 . A laser ablation system for producing carbon nanotubes, comprising: 
 a reactor having an air-tight chamber where a source of carbon vapor and a source of catalyst vapor are separately provided;    a laser beam generator provided for said reactor and radiating laser beams to said source of carbon vapor and said source of catalyst vapor for producing a carbon vapor/cluster and a catalyst vapor/cluster from said source of carbon vapor and said source of catalyst vapor, respectively;    an evacuating sub-system connected to said reactor for evacuating a gaseous mixture from said air-tight chamber;    a carrier gas supply sub-system connected to said reactor supplying carrier gas to said air-tight chamber for forming a carrier gas flow in said air-tight chamber; and    a collector provided in said carrier gas flow and capturing carbon nanotubes formed from said carbon vapor/cluster in the presence of said catalyst vapor/cluster and carried on said carrier gas flow.    
     
     
         11 . The laser ablation system as set forth in    claim 10   , in which said reactor is formed of a material selected from the group consisting of quartz and ceramics.  
     
     
         12 . The laser ablation system as set forth in    claim 10   , in which said laser beam generator produces laser pulse trains from a YAG laser for said laser beams, and the laser pulse trains have a wavelength of 532 nanometers, a frequency of 10 Hz, a pulse width of 7 to 10 nanoseconds and a power of 1.2 to 9.1 J/pulse.  
     
     
         13 . The laser ablation system as set forth in    claim 12   , further comprising a heater for heating said air-tight chamber to at least 1200 degrees in centigrade.  
     
     
         14 . The laser ablation system as set forth in    claim 10   , in which a carbon pellet and a catalyst pellet serve as said source of carbon vapor and said source of catalyst vapor, respectively.  
     
     
         15 . The laser ablation system as set forth in    claim 14   , in which said catalyst pellet is formed of a material selected from the group consisting of nickel, cobalt, platinum, palladium and alloys containing at least two metals of said nickel, said cobalt, said platinum and said palladium.  
     
     
         16 . The laser ablation system as set forth in    claim 10   , in which said carrier gas supply system includes a source of inert gas, and said evacuating sub-system and said carrier gas supply system cooperate with each other so as to flow an inert gas at 0.2 to 0.5 litter per minute at 500 to 600 torr in said air-tight chamber.