Carbon nanotube and process for producing the same

Abstract

The carbon nanotube of the present invention has an outer diameter of not more than 500 nm and a length of not less than 50 nm, and comprises a wall which is made of carbon and includes an outside region of an amorphous structure and an inside region of a crystalline structure. The carbon nanotube of the present invention is a novel carbon nanotube which allows functional groups to be readily bonded to the surface thereof since the outside region of the wall has an amorphous structure, and can exhibit a high electrical conductivity and a high strength since the inside region of the wall has a crystalline structure.

1 . A carbon nanotube having an outer diameter of not more than 500 nm and a length of not less than 50 nm, and comprising a wall including an outside region of an amorphous structure and an inside region of a crystalline structure, wherein said carbon nanotube has a ratio of B to A (B/A) of not less than 1.20 wherein A and B are values obtained by an image analysis conducted according to the following procedures using a transmission electron microscope image of the carbon nanotube which has a magnification of not less than 1,000,000 times and a distance between adjacent picture elements of not more than 0.06 nm, and respectively have the following definitions: 
 (1) Drawing two parallel lines (referred to as “line 1” and “line 2”, respectively) on the wall of the carbon nanotube observed on the transmission electron microscope image in the thickness direction of the wall, said lines being spaced by 3 nm apart from each other;    (2) plotting a distance (L) extending from a crossing point between the line 1 and an outside surface of the wall in the thickness direction of the wall, on an abscissa, and plotting an integrated value (P) of densities of picture elements existing on a line perpendicular to the line 1 which extends from a point on the line 1 corresponding to the distance (L) plotted on the abscissa until contacting with the line 2, on an ordinate, to prepare a graph showing relationship between the distance (L) and the integrated value (P) of densities of picture elements, and    (3) in the graph, A is defined as an average value of differences between adjacent maximum and minimum values of the integrated value (P) of densities of picture elements in a thickness region of up to 20% when measured from the outside surface of the wall, and B is defined as an average value of differences of adjacent maximum and minimum values of the integrated value (P) of densities of picture elements in a thickness region of 50 to 100% when measured from the outside surface of the wall.    
     
     
         2 . (canceled)  
     
     
         3 . A carbon nanotube according to  claim 1 , wherein said carbon nanotube has a ratio of D to C (D/C) of not less than 1.20 wherein C and D are values obtained by an image analysis conducted according to the following procedures using a transmission electron microscope image of the carbon nanotube which has a magnification of not less than 1,000,000 times and a distance between adjacent picture elements of not more than 0.06 nm, and respectively have the following definitions: 
 (1) Drawing two parallel lines (referred to as “line 1” and “line 2”, respectively) on the wall of the carbon nanotube observed on the transmission electron microscope image in the thickness direction of the wall, said lines being spaced by 3 nm apart from each other;    (2) plotting a distance (L) extending from a crossing point between the line 1 and an outside surface of the wall in the thickness direction of the wall, on an abscissa, and plotting an integrated value (P) of densities of picture elements existing on a line perpendicular to the line 1 which extends from a point on the line 1 corresponding to the distance (L) plotted on the abscissa until contacting with the line 2, on an ordinate, to prepare a graph showing relationship between the distance (L) and the integrated value (P) of densities of picture elements; and    (3) in the graph, C is defined as an average value of differences between adjacent maximum and minimum values of the integrated value (P) of densities of picture elements in a thickness region of up to 1.5 nm when measured from the outside surface of the wall, and D is defined as an average value of differences of adjacent maximum and minimum values of the integrated value (P) of densities of picture elements in a thickness region extending inwardly from 2.0 nm when measured from the outside surface of the wall.    
     
     
         4 . A carbon nanotube according to  claim 1 , wherein a total content of transition metal elements, Group 13 elements and lanthanoid elements in the carbon nanotube is not more than 0.5% by weight.  
     
     
         5 . A carbon nanotube according to  claim 1 , wherein said carbon nanotube is produced by a solid phase method.  
     
     
         6 . A process for producing a carbon nanotube, comprising: 
 melt-spinning particles having an average particle diameter of 10 to 10,000 nm and a Cv value of particle diameter of not more than 30% which are prepared by coating respective heat-decomposable and dissipatable fine resin particles with a carbon precursor resin;    adequately subjecting the resultant melt-spun product to infusibilization treatment; and    heat-calcining the obtained product for carbonization treatment thereof.    
     
     
         7 . A process for producing a carbon nanotube, comprising: 
 dispersing particles having an average particle diameter of 10 to 10,000 nm and a Cv value of particle diameter of not more than 30% which are prepared by coating respective heat-decomposable and dissipatable fine resin particles with a carbon precursor resin, in a matrix resin capable of being decomposed and dissipated by heating to prepare a dispersion;    melt-spinning the obtained dispersion;    adequately subjecting the resultant melt-spun product to infusibilization treatment; and    heat-calcining the obtained product for carbonization treatment thereof.    
     
     
         8 . A process according to  claim 6  or  7 , wherein the heat-decomposable and dissipatable fine resin particles are formed by chemical growth using a polymerization method.  
     
     
         9 . A process according to  claim 6  or  7 , wherein the particles prepared by coating with the carbon precursor resin are formed by chemically coating the fine resin particles with the carbon precursor resin.  
     
     
         10 . A process according to  claim 6  or  7 , wherein the particles prepared by coating the heat-decomposable and dissipatable fine resin particles with the carbon precursor resin, are obtained by polymerizing a monomer of the heat-decomposable and dissipatable resin, and then successively charging a monomer of the carbon precursor resin to the resultant resin to chemically coat the resin with the carbon precursor resin.  
     
     
         11 . A process according to  claim 6  or  7 , wherein the carbonization treatment by heat-calcination after the melt-spinning is conducted at a temperature of not more than 1,500° C.  
     
     
         12 . A process for producing a carbon nanotube, comprising: 
 chemically coating a surface of respective heat-decomposable and dissipatable fine resin particles which are produced by chemical growth using a polymerization method, with a carbon precursor resin;    dispersing the resultant coated particles in a matrix resin capable of being decomposed and dissipated by heating to prepare a dispersion;    melt-spinning the resultant dispersion;    adequately subjecting the resultant melt-spun product to infusibilization treatment; and    heat-calcining the obtained product for carbonization treatment thereof.    
     
     
         13 . A process according to  claim 12 , wherein the carbonization treatment by heat-calcination after the melt-spinning is conducted at a temperature of not more than 1,500° C.  
     
     
         14 . A process for producing a carbon nanotube, comprising: 
 polymerizing a monomer of a heat-decomposable and dissipatable resin;    charging and polymerizing a component containing a monomer of a carbon precursor resin;    further charging and polymerizing the monomer of the heat-decomposable and dissipatable resin to obtain fine particles;    melt-spinning the obtained fine particles;    adequately subjecting the resultant melt-spun product to infusibilization treatment; and    heat-calcining the obtained product for carbonization treatment thereof.    
     
     
         15 . A process according to  claim 14 , wherein the carbonization treatment by heat-calcination after the melt-spinning is conducted at a temperature of not more than 1,500° C.  
     
     
         16 . A process for producing a carbon nanotube, comprising: 
 coating heat-decomposable and dissipatable fine resin particles with a carbon precursor resin;    coating the resultant particles with the heat-decomposable and dissipatable resin;    melt-spinning the obtained coated particles;    adequately subjecting the resultant melt-spun product to infusibilization treatment; and    heat-calcining the obtained product for carbonization treatment thereof.    
     
     
         17 . A process according to  claim 16 , wherein the carbonization treatment by heat-calcination after the melt-spinning is conducted at a temperature of not more than 1,500° C.