Carbon and Electrospun Nanostructures

Abstract

The present invention is directed to the production of nanostructures, e.g., single wall carbon nanotubes (“SWNT”) and/or multi wall carbon nanotubes (“MWNT”), from solutions containing a polymer, such as polyacrylonitrile (PAN). In particular, the invention is directed to the production of nanostructures, for example, SWNT and/or MWNT, from mixtures, e.g., solutions, containing polyacrylonitrile, polyaniline emeraldine base (PANi) or a salt thereof, an iron salt, e.g., iron chloride, and a solvent. In one embodiment, a mixture containing polyacrylonitrile, polyaniline emeraldine base or a salt thereof, an iron salt, e.g., iron chloride, and a solvent is formed and the mixture is electrospun to form nanofibers. In another embodiment, the electrospun nanofibers are then oxidized, e.g., heated in air, and subsequently pyrolyzed to form carbon nanostructures.

1 . Carbon nanotubes produced by a method, comprising the steps of:
 (a) forming a polymer solution including an organic solvent and a polymer that includes at least one of a polyacrylonitrile and a polyimide;   (b) electrospinning the polymer solution to form nanofibers having diameters in a range of between about 1 nanometer and about 10 nanometers; and   heating and pyrolyzing the nanofibers to form single wall carbon nanotubes.   
     
     
         2 . The carbon nanotubes of  claim 1  wherein the polymer solution includes between about 1 and about 10 weight percent polyacrylonitrile. 
     
     
         3 . The carbon nanotubes of  claim 1  wherein the polymer solution includes between about 3 and about 5 weight percent polyacrylonitrile. 
     
     
         4 . The carbon nanotubes of  claim 1 , wherein the polymer solution further includes a salt. 
     
     
         5 . The carbon nanotubes of  claim 4  wherein the salt is an iron salt. 
     
     
         6 . The carbon nanotubes of  claim 5 , wherein the iron salt includes iron chloride. 
     
     
         7 . The carbon nanotubes of  claim 5  wherein the polymer solution includes greater than zero and up to about 0.5 weight percent iron salt. 
     
     
         8 . The carbon nanotubes of  claim 7  wherein the polymer solution includes between about 0.05 and about 0.15 weight percent an iron salt. 
     
     
         9 . The carbon nanotubes of  claim 1 , wherein the polymer includes a conductive polymer. 
     
     
         10 . The carbon nanotubes of  claim 1 , wherein the conductive polymer includes at least one of polyaniline and polyethylene dioxythiophene. 
     
     
         11 . The carbon nanotubes of  claim 1 , wherein the polymer solution further includes a metal salt. 
     
     
         12 . The carbon nanotubes of  claim 11 , wherein the metal salt is iron chloride. 
     
     
         13 . The carbon nanotubes of  claim 1  wherein the polymer solution includes greater than zero and up to about 1 weight percent polyaniline emeraldine base or a salt thereof. 
     
     
         14 . The carbon nanotubes of  claim 13  wherein the polymer solution includes between about 0.3 and about 0.5 weight percent polyaniline emeraldine base or a salt thereof. 
     
     
         15 . The carbon nanotubes of  claim 1 , wherein the fibers are pyrolyzed at a temperature in the range of between about 900° C. to about 2,400° C. 
     
     
         16 . The carbon nanotubes of  claim 15 , wherein the fibers are pyrolyzed at a temperature in the range of between about 1,000° C. to about 2,000° C. 
     
     
         17 . The carbon nanotubes of  claim 16 , wherein the fibers are pyrolyzed at a temperature in the range of between about 1,100° C. to about 1,600° C. 
     
     
         18 . The carbon nanotubes of  claim 17 , wherein the fibers are pyrolyzed at a temperature in the range of between about 1,300° C. to about 1,500° C. 
     
     
         19 . The carbon nanotubes of  claim 18 , wherein the fibers are pyrolyzed at a temperature in the range of between about 1,300° C. to about 1,400° C. 
     
     
         20 . The carbon nanotubes of  claim 1 , wherein the nanotubes are heated in air at a temperature in a range of between about 300° C. to about 350° C., for a period of time in a range of between about 5 minutes and about 60 minutes, and then placed in a tube furnace with an oxygen-free nitrogen purge, heated to a temperature of about 2,400° C. and then pyrolyzed for a period of time in a range of between about one minute and about five hours.