Method for production of carbon nanostructures

• US 8,252,264 B2
• Filed: 04/07/2009
• Issued: 08/28/2012
• Est. Priority Date: 04/09/2008
• Status: Active Grant

• Current Assignee: Scnte, LLC
• Original Assignee: Riehl-Johnson Holdings, LLC
• Inventors: Riehl, Bill L., Riehl, Jim R., Riehl, Lee R.
• Primary Examiner(s): Hendrickson, Stuart
• Assistant Examiner(s): Rump, Richard M
• Application Number:
  US12/936,433
• Publication Number:
  US 20110033367A1
• Time in Patent Office: 1,239 Days
• Field of Search: 423/445.B, 423/447.1, 423/447.3, 423/DIG.40, 977/742, 977842-843
• US Class Current: 423/447.1
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 2202/02 Single-walled nanotubes
• CPC Class Codes: C01B 2202/06 Multi-walled nanotubes
• CPC Class Codes: C01B 2202/08 Aligned nanotubes
• CPC Class Codes: C01B 32/16 Preparation
• CPC Class Codes: C01B 32/18 Nanoonions; Nanoscrolls; Nanohorns; Nanocones; Nanowalls
• CPC Class Codes: D01F 9/127 by thermal decomposition of hydrocarbon gases or vapours or other carbon-containing compounds in the form of gas or vapour, e.g. carbon monoxide, alcohols

Abstract

A process for the production of carbon nanostructures by an oxidation-reduction method is described. The growth of carbon nanorods, nanotubes, and nanoclusters on planar and non planar substrates, and free standing is demonstrated. In one embodiment a reactive gas is generated in situ and reacted with a carbide while the byproducts are removed, thereby adjusting the equilibrium to favor the formation of the carbon nanostructured product.

Claims

1. A process for producing carbon nanostructures comprising the steps of:

introducing a reactive gas into a reactor containing a carbide substrate, the reactive gas comprising a carbon oxide;

reacting the reactive gas with the carbide substrate by a reaction that converts carbon in the carbide substrate to elemental carbon nanostructures and produces a gaseous byproduct; and

removing the gaseous byproduct from the reactor in a manner that shifts the reaction equilibrium to favor the formation of the carbon nanostructures.

2. The process of claim 1 wherein the reactor comprises carbon.

3. The process of claim 1 wherein the carbon oxide is formed in situ in the reactor by introducing an oxygen containing gas into the reactor.

4. The process of claim 1 wherein the reactive gas includes at least one of air and an inert gas.

5. The process of claim 1, wherein the reactive gas is present at a partial pressure greater than about 0.01 Torr.

6. The process of claim 1, wherein the reactive gas is present at a partial pressure of at least about 0.0001 Torr.

7. The process of claim 1, wherein the carbide substrate includes particles of carbide.

8. The process of claim 7, wherein the particles of carbide are agitated as they are reacted with the reactive gas.

9. The process of claim 1, wherein the carbide substrate comprises a graphite tray coated with a carbide powder having a particle size of about 10 nm to 50 μ

m.

10. The process of claim 1, wherein the carbide substrate comprises a porous or non-porous carbide.

11. The process of claim 10, wherein the carbide substrate comprises monocrystalline carbide, polycrystalline carbide or amorphous carbide or a mixture thereof.

12. The process of claim 11, wherein the carbide substrate is monolithic.

13. The process of claim 1, wherein the carbide substrate is reacted at a temperature of about −

20°

C. to 3000°

C.

14. The process according to claim 1, wherein the carbide substrate is reacted at a temperature of about 900°

C. to 1900°

C.

15. The process according to claim 1, wherein the carbide substrate is reacted at a temperature of about 1400°

C. to 1700°

C.

16. The process of claim 1, wherein the step of reacting the carbide substrate occurs at a pressure in excess of 10⁻

4 Torr.

17. The process of claim 16, wherein the pressure is at least about 1 Torr.

18. The process of claim 1, wherein the reaction of the carbide substrate is conducted under conditions of pressure and temperature that yield solid carbon nanorods.

19. The process of claim 18, wherein the reactive gas is introduced at a rate that favors the formation of the solid carbon nanorods.

20. The process of claim 19, wherein the rate of introduction of the reactive gas is about 1 sccm to 50 sccm per liter of reactor volume at a temperature of about 1600°

C. to 1700°

C. to yield larger diameter solid carbon nanorods.

21. The process of claim 19, wherein the temperature is about 1400°

C. to 1550°

C. to yield smaller diameter solid carbon nanorods.

22. The process of claim 19, wherein the reactive gas is introduced at a rate of about 20 sccm per liter of reactor volume.

23. The process of claim 1, wherein the reaction of the carbide substrate is conducted under conditions of pressure and temperature that yield carbon nanotubes.

24. The process according to claim 23, wherein the reactive gas is introduced at a rate that favors the formation of the carbon nanotubes.

25. The process according to claim 24, wherein the reactive gas is introduced at a rate of about 0.1 sccm per liter of reactor volume.

26. The process of claim 23, wherein the carbon nanotubes are single walled, multiwalled, or a combination thereof.

27. The process according to claim 26, wherein the reaction of the carbide substrate is conducted at temperatures of about 1200°

C. to 1500°

C. to favor formation of single walled carbon nanotubes.

28. The process of claim 23, wherein the carbon nanotubes are free standing.

29. The process of claim 1, further comprising the step of removing passivating compounds from the surface of the carbide substrate before reacting the carbide substrate to form the carbon nanostructures.

30. The process of claim 1, further comprising the step of annealing the carbide substrate prior to said reacting step.

31. The process of claim 30, wherein the carbide substrate comprises monocrystalline carbide, polycrystalline carbide, or amorphous carbide.