High tensile strength carbon nanotube film and process for making the same

Abstract

A conductive carbon nanotube film having high tensile strength and initial tensile modulus comprises primarily oxidized small-diameter carbon nanotubes wherein the diameter of the small-diameter carbon nanotubes are at most about 3 nm. A method for making the film comprises refluxing an aqueous mixture comprising carbon nanotubes and an oxidizing agent to form a refluxed nanotube dispersion; forming a carbon nanotube film from the refluxed carbon nanotube dispersion; optionally removing nitric acid or other oxidizing agent from the carbon nanotube film; drying the carbon nanotube film; and heat-treating the carbon nanotube film to form a heat-treated carbon nanotube film. The method can also comprise sonicating the nanotubes prior to or after refluxing. A heat-treated small-diameter carbon nanotube film can have a tensile strength of over 70 MPa and an initial tensile modulus of about 5 GPa.

1 . A method for making a conductive carbon nanotube film, comprising: 
 (a) refluxing an aqueous mixture comprising carbon nanotubes and an oxidizing agent to form a refluxed nanotube dispersion;    (b) forming a carbon nanotube film from the refluxed nanotube dispersion;    (c) drying the carbon nanotube film; and    (d) heat-treating the carbon nanotube film to form a heat-treated carbon nanotube film.    
     
     
         2 . The method of  claim 1 , wherein the carbon nanotubes are purified.  
     
     
         3 . The method of  claim 1 , wherein the carbon nanotubes comprise single-wall carbon nanotubes.  
     
     
         4 . The method of  claim 1 , wherein the carbon nanotubes comprise multi-wall carbon nanotubes, wherein the multi-wall carbon nanotubes have diameters at most about 3 nm.  
     
     
         5 . The method of  claim 1 , wherein the oxidizing agent is nitric acid.  
     
     
         6 . The method of  claim 5 , wherein the concentration of nitric acid in the aqueous mixture is in the range of about 3 Molar and about 10 Molar.  
     
     
         7 . The method of  claim 5 , wherein the concentration of nitric acid in the aqueous mixture is in the range of about 3 Molar and about 6 Molar.  
     
     
         8 . The method of  claim 5 , wherein the concentration of nitric acid in the aqueous mixture is in the range of about 6 Molar and about 10 Molar.  
     
     
         9 . The method of  claim 1 , wherein the oxidizing agent is selected from the group consisting of ozone, potassium persulfate, a mixture of nitric acid and sulfuric acid, a mixture of nitric acid and hydrogen peroxide, steam, carbon dioxide, halogens, halogen-containing compounds, and combinations thereof.  
     
     
         10 . The method of  claim 1 , further comprising removing the oxidizing agent from the carbon nanotube film.  
     
     
         11 . The method of  claim 10 , wherein the removing is done by washing with a solvent selected from the group consisting of acetone, alcohol, water and a combination thereof.  
     
     
         12 . The method of  claim 1 , wherein the forming is done by filtering the carbon nanotubes.  
     
     
         13 . The method of  claim 1 , wherein the forming is done on an adsorbent or non-adsorbent surface.  
     
     
         14 . The method of  claim 1 , wherein the drying is done in a vacuum.  
     
     
         15 . The method of  claim 1 , wherein the drying is done in an atmosphere selected from the group consisting of a vacuum, nitrogen and inert gas.  
     
     
         16 . The method of  claim 1 , wherein the drying is done at a temperature in the range of about 15° C. and about 200° C.  
     
     
         17 . The method of  claim 1 , wherein the heat-treating is done in an oxygen-containing atmosphere.  
     
     
         18 . The method of  claim 1 , wherein the heat-treating is done in an inert atmosphere.  
     
     
         19 . The method of  claim 1 , wherein the heat-treating is done at a temperature in the range of at least about 200° C. and about 1000° C.  
     
     
         20 . The method of  claim 1 , wherein the heat-treated carbon nanotube film has a tensile strength of at least about 15 MPa.  
     
     
         21 . The method of  claim 1 , wherein the heat-treated carbon nanotube film has a tensile strength of at least about 25 MPa.  
     
     
         22 . The method of  claim 1 , wherein the heat-treated carbon nanotube film has a tensile strength of at least about 50 MPa.  
     
     
         23 . The method of  claim 1 , wherein the heat-treated carbon nanotube film has a tensile strength of at least about 70 MPa.  
     
     
         24 . The method of  claim 1 , wherein the carbon nanotube film comprises crosslinked carbon nanotubes.  
     
     
         25 . The method of  claim 1 , further comprising sonicating the carbon nanotubes in water before refluxing.  
     
     
         26 . The method of  claim 1 , further comprising sonicating the mixture, the dispersion or both.  
     
     
         27 . The method of  claim 1 , wherein the heat-treated carbon nanotube film comprises primarily single-wall carbon nanotubes.  
     
     
         28 . The method of  claim 1 , wherein the heat-treated carbon nanotube film comprises primarily small-diameter carbon nanotubes having diameters at most about 3 nm.  
     
     
         29 . The method of  claim 1 , wherein the heat-treated carbon nanotube film has a thickness in the range of about 0.1 micron and about 10,000 microns.  
     
     
         30 . The method of  claim 1 , wherein the heat-treated carbon nanotube film has a thickness in the range of about 1 micron and about 1,000 microns.  
     
     
         31 . The method of  claim 1 , wherein the heat-treated carbon nanotube film has a thickness in the range of about 1 micron and about 100 microns.  
     
     
         32 . An film comprising primarily small-diameter carbon nanotubes, wherein the nanotubes have been oxidized, and wherein the film has a thickness in the range of about 0.1 micron and about 10,000 microns and tensile strength of at least about 15 MPa.  
     
     
         33 . The film of  claim 32 , wherein the film has a tensile strength of at least about 25 MPa.  
     
     
         34 . The film of  claim 32 , wherein the film has a tensile strength of at least about 50 MPa.  
     
     
         35 . The film of  claim 32 , wherein the film has a tensile strength of at least about 70 MPa.  
     
     
         36 . The film of  claim 32 , wherein the film has a thickness in the range of about 1 micron and about 1,000 microns.  
     
     
         37 . The film of  claim 32 , wherein the film has a thickness in the range of about 1 micron and about 100 microns.  
     
     
         38 . A film consisting essentially of small-diameter carbon nanotubes, wherein the small-diameter carbon nanotubes are crosslinked.  
     
     
         39 . The film of  claim 38 , wherein the film has a tensile strength of at least about 25 MPa.  
     
     
         40 . The film of  claim 38 , wherein the film has a tensile strength of at least about 50 MPa.  
     
     
         41 . The film of  claim 38 , wherein the film has a tensile strength of at least about 70 MPa.  
     
     
         42 . The film of  claim 38 , wherein the film has a thickness in the range of about 0.1 micron and about 10,000 microns.  
     
     
         43 . The film of  claim 38 , wherein the film has a thickness in the range of about 1 micron and about 1,000 microns.  
     
     
         44 . The film of  claim 38 , wherein the film has a thickness in the range of about 1 micron and about 100 microns.  
     
     
         45 . A conductive carbon nanotube film made by the process comprising: 
 (a) refluxing an aqueous mixture comprising carbon nanotubes and an oxidizing agent to form a refluxed nanotube dispersion;    (b) forming a carbon nanotube film,    (c) drying the carbon nanotube film; and    (d) heat-treating the carbon nanotube film to form a heat-treated carbon nanotube film.    
     
     
         46 . The film of  claim 45 , wherein the carbon nanotubes are purified.  
     
     
         47 . The film of  claim 45 , wherein the carbon nanotubes comprise single-wall carbon nanotubes.  
     
     
         48 . The film of  claim 45 , wherein the carbon nanotubes comprise small-diameter carbon nanotubes, wherein the small-diameter carbon nanotubes have diameters of at most about 3 nm.  
     
     
         49 . The film of  claim 45 , wherein the oxidizing agent is nitric acid.  
     
     
         50 . The film of  claim 45 , wherein the oxidizing agent is removed from the carbon nanotubes.  
     
     
         51 . The film of  claim 45 , wherein the forming is done by filtering.  
     
     
         52 . The film of  claim 45 , wherein the heat-treating is done at a temperature in the range of at least about 200° C. and about 1000° C.  
     
     
         53 . The film of  claim 45 , wherein the heat-treated carbon nanotube film has a thickness in the range of about 0.1 micron and about 10,000 microns.  
     
     
         54 . The film of  claim 45 , wherein the heat-treated carbon nanotube film has a thickness in the range of about 1 micron and about 1,000 microns  
     
     
         55 . The film of  claim 45 , wherein the heat-treated carbon nanotube film has a thickness in the range of about 1 micron and about 100 microns.