Carbon nanotube structures and methods for production thereof
A method and system for substantially reducing iron and organic impurities in carbon nanotube materials.
1. A method for treating a nanofibrous macrostructure, the method comprising:
(a) providing a nanofibrous macrostructure, the nanofibrous macrostructure being defined by a plurality of substantially non-aligned nanotubes;
(b) exposing the nanotubes within the nanofibrous macrostructure to a first electrochemical treatment to form an electrochemically treated nanofibrous macrostructure, wherein the first electrochemical treatment is an anodic treatment comprising contacting the nanofibrous macrostructure with a first electrolyte solution and subjecting the nanofibrous macrostructure to electrical energy in a range from 20 to 100 Amperes-minute per gram of the nanofibrous macrostructure and stretching the nanofibrous macrostructure while exposing the nanotubes to the first treatment
wherein the nanofibrous macrostructure is not heated to a temperature in a range from 300 to 800° C. prior to exposing the nanotubes within the nanofibrous macrostructure to the first electrochemical treatment; and
(c) exposing the electrochemically treated nanofibrous macrostructure to a second electrochemical treatment which is a cathodic treatment by contacting the electrochemically treated nanofibrous macrostructure with a second electrolyte solution and subjecting the electrochemically treated nanofibrous macrostructure to electrical energy.
2. The method of claim 1 , wherein the step of stretching the nanofibrous macrostructure substantially aligns the nanotubes relative to one another within the stretched nanofibrous macrostructure.
3. The method of claim 1 , wherein, in the step of providing, the nanofibrous macrostructure is a non-woven sheet of nanotubes.
4. The method of claim 1 , wherein, in the step of providing, the nanofibrous macrostructure is a yarn.
5. The method of claim 1 , wherein the step of providing, the nanotubes are carbon nanotubes.
6. The method of claim 1 , wherein, in the step of providing, the nanotubes include one of single wall nanotubes, dual wall nanotubes, multiwall nanotubes, or a combination thereof.
7. The method of claim 1 wherein the step of exposing is in an electrochemical cell.
8. The method of claim 1 wherein the first electrolyte solution is an organic electrolyte solution.
9. The method of claim 1 further comprising washing the nanofibrous macrostructure.
10. The method of claim 1 wherein the impurities comprise non-CNT carbonaceous contaminant, hydrocarbon, catalyst, and combination thereof.
11. The method of claim 10 wherein the catalyst is iron.
12. The method of claim 1 further comprising collecting the electrochemically treated and stretched nanofibrous macrostructure.
13. The method of claim 1 wherein the second electrochemical treatment comprises subjecting the nanofibrous macrostructure to electrical energy in a range from 20 to 400 Amperes-minute per gram of the nanofibrous macrostructure.
14. The method of claim 1 , further comprising exposing the nanofibrous structure to an acid having an H 0 value of less than −12, and optionally subjecting the nanofibrous structure to additional stretching.
15. The method of claim 1 wherein the acid is a super acid and comprises one of chlorosulfonic acid, triflic acid, fluorosulfuric acid, fluoroantimonic acid, fuming sulfuric acid or a combination thereof.