Production of carbon nanotubes

• US 20040253167A1
• Filed: 08/04/2004
• Published: 12/16/2004
• Est. Priority Date: 07/27/2001
• Status: Active Grant

• Current Assignee: University of Surrey
• Original Assignee: University of Surrey
• Inventors: Silva, Sembukutiarachilage Ravi, Boskovic, Bojan O., Haq, Sajad
• Granted Patent: US 8,715,790 B2
• Time in Patent Office: Days
• 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 32/162 characterised by catalysts

Abstract

A method of forming carbon nanotubes by plasma enhanced chemical vapour deposition using a carbon containing gas plasma, wherein the carbon nanotubes are not formed on a substrate at a temperature 300° C. or above.

Claims

1. A method of forming a carbon nanotubes by plasma enhanced chemical vapour deposition using a carbon containing gas plasma, wherein the carbon nonotubes are either formed on a substrate placed within a chamber wherein the substrate temperature is less than 300°

C., or are formed within the chamber and subsequently deposited on a substrate external to the chamber.

2. A method to claim 1 wherein the substrate is not separately heated.

3. A method according to claim 2 wherein the substrate is kept at a temperature below 300°

C.

4. A method according to claim 3 wherein the substrate is kept at a temperature of 200°

C. or below.

5. A method according to claim 4 wherein the substrate is kept at a temperature of 150°

C. or below.

6. A method according to claim 5 wherein the substrate is kept at a temperature of 100°

C. or below.

7. A method according to claim 6 wherein the substrate is kept at a temperature of 50°

C. or below.

8. A method according to claim 7 wherein the substrate is kept at substantially room temperature.

9. A method according to claim 1 further comprising the step of cooling the substrate during the formation of the carbon nanotubes.

10. A method according to claim 9 wherein the substrate is kept at a temperature below 0°

C.

11. A method according to claim 9 further comprising the step of cooling the substrate with liquid nitrogen.

12. A method according to claim 1 further comprising the step of growing carbon nanotubes within a chamber on a substrate that is placed within the chamber.

13. A method according to claim 12 further comprising the step of placing a catalyst on a surface of the substrate.

14. A method according to claim 13 wherein the catalyst is placed directly on the substrate surface.

15. A method according to claim 13 wherein the carbon nanotubes are grown from the catalyst as deposited on the substrate.

16. A method according to claim 1 wherein the substrate is placed on an earthed electrode of a plasma generator, within the sheathed region of the plasma.

17. A method according to claim 16 wherein the potential difference between the substrate/catalyst and the plasma is less than 100 volts.

18. A method according to claim 17 wherein the potential difference between the material/catalyst and the plasma is less than 70 volts.

19. A method according to claim 18 wherein the potential difference between the material/catalyst and the plasma is less than 40 volts.

20. A method according to claim 16 effected within a plasma chamber further comprising the step of cooling the electrodes.

21. A method according to claim 20 wherein the electrode is cooled by water.

22. A method according to claim 1 further comprising the step of growing the carbon nanotubes within a chamber and then depositing the carbon nanotubes on a substrate that is external to the chamber.

23. A method according to claim 22 further comprising the step of injecting a catalyst into the chamber.

24. A method according to claim 13 wherein the catalyst is a metal.

25. A method according to claim 24 wherein the metal is a transition metal.

26. A method according to claim 25 wherein the transition metal includes a metal, or mixture of metals, from the group comprising nickel (Ni), cobalt (Co) and iron (Fe).

27. A method according to claim 23 wherein the catalyst is in the form of a powder.

28. A method according to claim 23 wherein the catalyst is in the form of a gas.

29. A method according to claim 13 wherein the catalyst is in the form of a powder, film or island arrays.

30. A method according to claim 29 wherein the island arrays are etched island arrays of which the particle sized is between 2nm and 100 nm.

31. A method according to claim 27 wherein the powder has a particle size from 1 μ

m to 10 μ

m.

32. A method according to any preceding claim 1 wherein the substrate is of organic material.

33. A method according to claim 1 wherein the substrate is a fabric.

34. A method according to claim 1 wherein the substrate is a plastics material.

35. A method according to claim 1 wherein the substrate is a polymer.

36. A method according to claim 1 wherein the substrate is paper.

37. A method according to claim 1 wherein the plasma is of an ionised gas or gas mixture.

38. A method according to claim 1 wherein the plasma is in the form of a beam.

39. A method according to claim 1 wherein the plasma is generated by radio-frequency energy.

40. A method according to claim 1 wherein the plasma is generated by radio-frequency energy combined with microwave energy.

41. A method according to claim 1 wherein the plasma is generated by microwave energy.

42. A method according to claim 1 wherein the plasma is generated using a pulsed supply.

43. A method according to claim 1 wherein the plasma is generated by a primary power source and combined with at least one secondary power source.

44. A method according to claim 1 wherein the carbon containing gas is a hydrocarbon gas.

45. A method according to claim 44 wherein the hydrocarbon gas is methane, acetylene, ethylene or any mixture of the said gases.

46. A method according to claim 1 wherein the carbon containing gas is carbon monoxide or carbon dioxide.

47. A method according to claim 1 wherein the carbon containing gas is non-destructive and non-etching of the substrate or chamber when in a plasma state.

48. A method according to claim 1 wherein the carbon containing gas is combined with a carrier gas.

49. A method according to claim 48 wherein the carrier gas is from the group comprising nitrogen, hydrogen, argon and ammonia.

50. A method according to claim 1 further comprising the step of performing the method in a vacuum chamber constructed to generate, maintain and withstand a gaseous plasma.

51. A method according to claim 1 further comprising the step of inserting the carbon nanotubes into a liquid with will cause them to self-organise into ropes.

52. A method according to claim 51 wherein the liquid is water.

53. A method according to claim 1 subsequently followed by an acid treatment step for removal of excess catalyst particles.

54. A method according to claim 53 subsequently followed by a wash step to remove the acid.

55. A method according to claim 1 wherein a proportion of formed nanotubes are in at least one of the following forms:

bi-directional, branched, multiple-coaxial, coiled or densely packed ropes of nanotubes.

56. A carbon nanotube formed by a method according to claim 55 wherein the carbon nanotube comprises a substantially Y-shaped junction.

57. A carbon nanotube formed by a method according to claim 55 wherein the carbon nanotube comprises a substantially H-shaped junction.

58. A rope of carbon nanotubes obtained by a method according to claim 55.

59. A method of providing a pattern of carbon nanotubes on a fabric or organic material.

60. A method of forming ropes of partially aligned carbon nanotubes, comprising placing said nanotubes in a liquid selected so that the nanotubes self-orgnaise into bundles.

61. A method according to claim 60 wherein the liquid is a nitric acid solution.

62. A method according to claim 61 including the step of diluting the solution with water.

63. A method according to claim 62 wherein the ropes are formed in the diluted solution.

64. A method according to claim 60 in which said liquid comprises water.