Low defect nanotube application solutions and fabrics and methods for making same
The present disclosure provides methods for removing defects nanotube application solutions and providing low defect, highly uniform nanotube fabrics. In one aspect, a degassing process is performed on a suspension of nanotubes to remove air bubbles present in the solution. In another aspect, a continuous flow centrifugation (CFC) process is used to remove small scale defects from the solution. In another aspect, a depth filter is used to remove large scale defects from the solution. According to the present disclosure, these three methods can be used alone or combined to realize a low defect nanotube application solutions and fabrics.
1. A method for forming a low defect, uniform nanotube fabric comprising:
contacting a plurality of nanotubes with a liquid medium to obtain a mixture;
purifying said mixture to obtain a purified nanotube solution;
degassing said purified nanotube solution;
performing at least one additional defect reduction processing step on said purified nanotube solution; and
depositing said purified nanotube solution over a material layer to form a nanotube fabric layer
wherein said step of degassing is performed immediately prior to said at least one additional defect reduction processing step; and
wherein said purified nanotube solution remains in a degassed state during said at least one additional defect reduction step.
2. The method of claim 1 wherein said at least one additional defect reduction processing step includes at least one of a degassing process, a continuous flow centrifugation process, a batch centrifugation process, and a depth filter.
3. The method of claim 1 wherein at least one of said at least one defect reduction processing step is repeated at least once.
4. The method of claim 1 wherein said step of degassing prevents the formation of nanotube clumps during the steps of performing, and depositing.
5. The method of claim 1 wherein said one additional defect reduction processing step removes small scale defects from said purified nanotube solution.
6. The method of claim 5 wherein small scale defects are elements within said purified nanotube solution on the order of 100 nanometers to on the order of 300 nanometers.
7. The method of claim 1 wherein said one additional defect reduction step removes large scale defects from said purified nanotube solution.
8. The method of claim 7 wherein large scale defects are elements within said nanotube application solution greater than 2 microns.
9. The method of claim 7 wherein large scale defects are elements within said nanotube application solution greater than 10 microns.
10. The method of claim 7 wherein large scale defects are elements within said nanotube application solution greater than 20 microns.
11. The method of claim 1 wherein said nanotube fabric layer is uniform and substantially free of defects.
12. The method of claim 1 wherein said nanotube fabric layer is substantially free of defects having a diameter of greater than about 2 microns.
13. The method of claim 1 wherein said nanotube fabric layer is substantially free of defects having a diameter of greater than about 10 microns.
14. The method of claim 1 wherein said nanotube fabric layer is substantially free of defects having a diameter of greater than about 20 microns.
15. The method of claim 1 wherein said step of purifying comprises at least one of an acid oxidation process, a cross-flow filtration process, an ion exchange process, and a centrifugation process.
16. The method of claim 15 wherein at least one of said acid oxidation process, said cross-flow filtration process, said ion exchange process, and said centrifugation process is repeated at least once.
17. The method of claim 1 wherein said nanotubes comprise conductive nanotubes.
18. The method of claim 1 wherein said nanotubes comprise semiconductive nanotubes.
19. The method of claim 1 wherein said nanotubes comprise single-walled carbon nanotubes.
20. The method of claim 1 wherein said nanotubes comprise multi-walled carbon nanotubes.
21. The method of claim 1 wherein said purified nanotube solution comprises nanotubes at a concentration of greater than 100 mg/L.
22. The method of claim 1 wherein said purified nanotube solution comprises nanotubes at a concentration of greater than 1000 mg/L.
23. The method of claim 1 wherein said liquid medium is water.