Method for making cohesive assemblies of carbon
View Patent ↗Cohesive assemblies comprising carbon are prepared by obtaining carbon in the form of powder, particles, flakes, or loose agglomerates, dispersing the carbon in a liquid halogen by mechanical mixing and/or sonication, and substantially removing the liquid halogen, typically by evaporation, whereby the cohesive assembly of carbon is formed. The method is especially suitable for preparing free-standing, monolithic assemblies of carbon nanotubes in the form of films, wafers, or discs, having high carbon packing density and low electrical resistivity. The assemblies have various potential applications, such as electrodes in batteries or supercapacitors or as electromagnetic interference shielding materials.
1. A method for preparing a cohesive assembly comprising carbon, comprising the steps of:
obtaining carbon in the form of powder, particles, flakes, or loose agglomerates,
dispersing the carbon in a liquid comprising a liquid halogen, wherein the carbon and the liquid halogen have a ratio of between 5 and 20 milligrams of carbon per milliliter of liquid halogen,
substantially removing the liquid halogen, and
allowing the dispersed carbon to self-assemble into a monolithic cohesive assembly of the carbon having a distinct shape and size.
2. The method of claim 1 , wherein the carbon comprises carbon nanotubes, graphite, expanded graphite, amorphous carbon, or a combination thereof.
3. The method of claim 1 , wherein the carbon comprises carbon nanotubes.
4. The method of claim 3 , wherein the carbon nanotubes comprise single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, or a combination thereof.
5. The method of claim 1 , wherein the halogen is chlorine, bromine, iodine, an interhalogen compound, or a combination thereof.
6. The method of claim 5 , wherein the halogen is bromine or iodine.
7. The method of claim 1 , wherein the carbon is double-walled carbon nanotubes and the liquid halogen is bromine.
8. The method of claim 7 , wherein the carbon and the liquid halogen have a ratio of between 8 and 15 mg of carbon per milliliter of bromine.
9. The method of claim 1 , wherein the carbon is dispersed in the liquid halogen by mechanical mixing, sonication, microfluidization, or a combination thereof.
10. The method of claim 9 , wherein the carbon comprising double-walled carbon nanotubes is dispersed in the liquid halogen by mechanical mixing.
11. The method of claim 9 , wherein the carbon comprising single-walled carbon nanotubes is dispersed in the liquid halogen by mechanical mixing followed by sonication.
12. The method of claim 1 , wherein the carbon is dispersed in the liquid halogen containing a surfactant less than 1% (w/w) relative to the carbon.
13. The method of claim 1 , wherein the liquid halogen is substantially removed by evaporation.
14. The method of claim 13 , wherein the evaporation occurs at a pressure between 0.01 and 760 Torr.
15. The method of claim 13 , wherein the liquid halogen is heated between about 20° C. and about 180° C.
16. The method of claim 1 , further comprising heating the cohesive assembly formed to remove residual halogen that is chemically or physically bonded to the carbon of the assembly.
17. The method of claim 1 , wherein the cohesive assembly has a carbon packing density of at least 0.5 g/cm 3 .
18. The method of claim 17 , wherein the cohesive assembly has a carbon packing density of at least 1.0 g/cm 3 .
19. The method of claim 1 , wherein the cohesive assembly has electrical resistivity lower than 10 −1 Ω-cm.
20. The method of claim 1 , wherein the carbon is DWCNT or expanded graphite.