Method and apparatus for producing complex carbon molecules

• US 6,171,451 B1
• Filed: 09/13/1999
• Issued: 01/09/2001
• Est. Priority Date: 01/13/1997
• Status: Expired due to Fees

• Current Assignee: Daimlerchrysler Aerospace
• Original Assignee: Daimlerchrysler Aerospace
• Inventors: Jurczyk, Brian E., Miley, George H., Sved, John
• Primary Examiner(s): Mayekar, Kishor
• Application Number:
  US09/341,458
• Time in Patent Office: 484 Days
• Field of Search: 204/173, 422/186.04, 423/445.B
• US Class Current: 204/173
• CPC Class Codes: B01J 12/002 carried out in the plasma state generating or handling plasma H05H1/00
• CPC Class Codes: B01J 19/088 giving rise to electric discharges for heating purposes H05B7/00; for the production of ozone C01B13/11, H01T19/00
• CPC Class Codes: B01J 19/285 Shaking or vibrating reactors; reactions under the influence of low-frequency vibrations or pulsations for sonic and ultrasonic vibrations B01J19/10
• CPC Class Codes: B01J 2219/0809 employing two or more electrodes
• CPC Class Codes: B01J 2219/0879 Solid
• CPC Class Codes: B01J 2219/0883 Gas-gas
• CPC Class Codes: B01J 2219/0894 Processes carried out in the presence of a plasma
• CPC Class Codes: B01J 2219/1942 spherical
• CPC Class Codes: B01J 3/006 Processes utilising sub-atmospheric pressure; Apparatus therefor
• CPC Class Codes: B01J 3/03 Pressure vessels, or vacuum vessels, having closure members or seals specially adapted therefor
• 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 32/15 Nano-sized carbon materials
• CPC Class Codes: C01B 32/154 Preparation

Abstract

A device (100) for producing fullerenes includes an IEC vacuum chamber (110) which has a central grid-like electrode (112) and a conductive outer shell (111) that are connected to a pulsed source of high voltage (114) and provide an electric field within the chamber (110). The applied voltage supports the creation of a plasma at the inner core of the chamber near the electrode (112). A carbon-based gas, which is introduced into the chamber (110), possibly along with an inert buffer gas, id dissociated into component carbon and hydrogen ions that are separated and the carbon ions recombined into fullerenes that appears as a soot. The device (100) includes a soot extraction mechanism for removing and collecting the fullerenes.

Claims

1. Apparatus for producing complex carbon molecules comprising:

a. a vacuum vessel for containment of at least low pressure gases and plasma, said vessel comprising;

(i) a wall portion having at least one opening that can be hermetically sealed to allow removal of solid phase reaction produces from within said vessel, and

(ii) a first conductive structure providing a conductive surface within said vessel;

b. a second conductive structure, formed as a grid within said vacuum vessel and internal of said first conductive structure, and being highly transparent to flowing ions and electrons, said second conductive structure being operative as a cathode when biased to a negative voltage relative to said first conductive structure;

c. means for flowing at a controlled rate a neutral gas mixture of a carbon-based gas and a buffer gas into said vessel;

d. means of maintaining a low pressure within said vessel by extraction of unreacted gases and gaseous reaction products;

e. a high-voltage feed-through insulator system which provides electrical power at a negative voltage from a power source to said second conductive structure at a value sufficient to create a plasma discharge;

f. a high-voltage power source capable of at least one of continuous regulated direct current and repetitive pulsed current operation, at a power level sufficient to create a plasma discharge capable of dissociating said carbon-based gas into carbon and associated species.

2. The apparatus as recited in claim 1 further comprising:

a means of carbon soot extraction for removal and collection of said complex carbon molecules.

3. The apparatus as recited in claim 2 further comprising:

a means to “

wash down”

accumulated carbon soot from within the vessel.

4. The apparatus as recited in claim 1 wherein said carbon-based gas comprises at least one of methane, ethane, butane, pentane, propane, benzene, ethylene, propylene, butane, acetylene, carbon monoxide, and carbon dioxide.

5. The apparatus as recited in claim 4 wherein said buffer gas primarily comprises at least one of xenon, argon and helium.

6. The apparatus according to claim 1 further comprising:

a. at least one enlarged second opening in said second conductive structure operative to distort a local electrical potential surface and at least one third opening in said first conductive structure aligned with a corresponding one of said at least one second opening such that a plasma jet is formed and flows outward from a volume within said second conductive structure through said second and corresponding first openings;

b. said vacuum vessel having within a wall portion at least one first opening to allow said plasma jet to escape from within said chamber and carry with it reaction products including ions and molecular species.

c. said at least one wall opening in said vacuum vessel being aligned with corresponding ones of said at least one aligned opening in said first conductive structure and said at least one enlarged opening to allow plasma formed within said vessel to emerge from the vessel as a plasma jet;

d. at least one third conductive structure, being substantially cylindrical, transparent, grid and defined by a longitudinal axis passing through centers of said corresponding openings in said vacuum vessel wall, first conductive structure and second conductive structure, said third conductive structure being biased to the same voltage as said second conductive structure when acting as a cathode, but electrically insulated from said first conductive structure, such that said third conductive structure is operative as a guide channel for said plasma jet.

7. The apparatus according to claim 6 further comprising a plurality of electron emitters disposed inside said vacuum chamber for providing a source of electrons, said electron emitters being electrically insulated from said first conductive structure and said second conductive structure, said emitters being disposed proximate to at least one of said aligned openings to prevent negative charge build-up of a contained plasma during plasma jet generation.

8. The apparatus according to claim 6 further comprising a high volume insulator means for maintaining the electric potential difference between the negatively-biased third structure and said first conductive structure.

9. The apparatus according to claim 8 wherein said insulator means is structured to cover said first conductive structure proximate said first opening and lines the inside of said first opening through which the plasma jet passes.

10. The apparatus according to claim 6 wherein said first conductive structure and said second conductive structure are substantially spherical and further comprising an intermediate conductive structure that lies between said first and second conductive structures, said intermediate structure being highly transparent to ion and electron flows and being biased to a voltage that is positive relative to the first conductive structure potential.

11. The apparatus according to claim 10 wherein said intermediate structure is spherically shaped and has a grid construction.

12. The apparatus according to claim 11 wherein said high-voltage feed-through insulator system is operative to permit electrical power at a high negative voltage to be provided to said second conductive structure, and provides electrical power at a low positive voltage to said intermediate conductive structure.

13. The apparatus according to claim 10 wherein said intermediate conductive structure comprises an electron guide grid operative to localize electron paths around the grid, thus, enhancing the ionization rate of a background neutral gas, a portion of said electron guide grid having at least one fourth opening which is aligned with corresponding ones of said first, second and third openings for passing a plasma jet.

14. The apparatus according to claim 13, wherein said high-voltage feed-through insulator system provides insulation at least from said first opening to said fourth opening.

15. The apparatus according to claim 10 wherein said intermediate conductive structure comprises a partial sphere which does not extend uniformly within the entire device.

16. The apparatus according to claim 10 wherein said electron emitters are disposed in a space between said first conductive structure and said intermediate conductive structure.

17. The apparatus according to claim 10 wherein said intermediate conductive structure is maintained at a positive potential in a range of 100 V to 1000 V.

18. The apparatus according to claim 10 wherein said second conductive structure is biased in a range of −

0.1 Kv to −

150 Kv.

19. The apparatus according to claim 10 wherein said second conductive structure comprises polygonal grid elements.

20. The apparatus according to claim 6 further comprising electrically insulated support means for maintaining the relative positions of said first conductive structure, said second conductive structure and said intermediate conductive structure.

21. The apparatus according to claim 6 which operates with an electrical current to the second conductive structure of 0.005 to 10 Amperes.

22. The apparatus according to claim 6 which produces a single narrow plasma jet having a thickness in a range of 1-5 cm, wherein said first conductive structure comprises a spherical vacuum chamber having a diameter within a range of 20-40 cm, said second conductive structure comprises a spherical grid having a diameter within a range of 4-25 cm smaller than said chamber, said first opening comprising one of a circular or a polygonal hole.

23. The apparatus according to claim 6 wherein said cathode grid has one or more openings enlarged to increase the enclosed area by >

10% compared to neighboring openings such that the local electric field is distorted extracting ions and electrons to form a plasma jet flowing from inside said cathode grid out through said at least one enlarged second opening.

24. The apparatus according to claim 6 wherein said grid, biased to act as a cathode, interacts with the flowing ions and electrons to create a potential structure which traps and re-circulates ions and electrons until they can escape through the said enlarged opening in the grid due to the associated local electric potential distortions.

25. The apparatus according to claim 6 further comprising a second vessel which is conditioned to provide a pressure lower or equal to that of said vacuum vessel and the plasma jet from operation of said vacuum vessel apparatus flows into the second vessel where, after cooling and further recombination, microparticles and/or complex carbon molecules will precipitate into a collection location.

26. The apparatus of claim 25 where said second vessel is adapted to be coupled to a plurality of vacuum vessels such that the plasma jets from each vacuum vessel flows into said second vessel.

27. The. apparatus of claim 26 wherein the second vessel incorporates an opening with appropriate vacuum valving such that accumulated complex carbon molecules products can be removed periodically or continuously.

28. The apparatus according to claim 26 wherein said vacuum vessels are operable at internal pressures at least within a range of 0.1 to 100 mTorr.

29. The apparatus according to claim 26 wherein said apparatus comprises a device for mechanically concentrating the soot particles within the said reaction vessels and within the shared second gas containment vessel.

30. The apparatus according to claim 26 wherein said apparatus further comprises individual isolation valves between the vacuum vessel and at least one shared second gas containment vessel.

31. The apparatus according to claim 26 wherein said apparatus further comprises a “

wash down”

system to spray an appropriate liquid onto the internal surfaces of the gas containment vessels in order to remove accumulated soot.

32. The apparatus according to claim 26 wherein said apparatus uses a plurality of pulsed power source in parallel with the steady-state direct current power supply during generation of plasma jets.

33. The apparatus of claim 25 further comprising mechanical means for increasing the compaction of the soot particles.

34. The apparatus of claim 25 further comprising means for removing the compacted soot from the second gas containment vessel without the disturbance of the continuous or quasi continuous production process or gas pressure within the second and first gas containment vessels.

35. The apparatus according to claim 6 where said apparatus further comprises plural valved access ports for inserting or removing components and accumulated solid reaction product.

36. The apparatus according to claim 6 wherein said apparatus comprises at least one access port for visual/optical-microscopic inspections of the plasma discharge and jets.

37. The apparatus according to claim 6 wherein said apparatus further includes an electrostatic deceleration means consisting of two hollow electrodes position coaxially about the jet and within the second chamber wherein a first hollow electrode is at ground potential and the second hollow electrode is positively biased at a voltage of between 10 and 30 kV such that the voltage applied is optimized to decelerate remaining charged particles, both electrodes being of the same diameter and mounted for correct electrical insulation.

38. The apparatus of claim 6 wherein said carbon-based gas comprises at least one of linear hydrocarbons, aromatic hydrocarbons or carbons halides.

39. The apparatus as recited in claim 6 wherein said buffer gas primarily comprises at least one of nitrogen, oxygen, or a noble gas.

40. The apparatus according to claim 1 where said vacuum vessel, said first conductive structure and said second conductive structure are substantially spherical in shape with their centers co-located and said second conductive structure composed of wire or ribbon structures with greater than 80% transparency.

41. The apparatus according to claim 40 wherein said second conductive structure is biased to act as a cathode and interacts with the flowing ions and electrons to create a spherically symmetric electrical potential structure such that ions with different change-to-mass ratio are preferentially concentrated in different spherical shell regions within the potential structure.

42. The apparatus according to claim 41, wherein carbon and hydrogen or oxygen atoms, formed by dissociation of said carbon-based gas species during a plasma discharge operation, are partially separated by preferential concentration in different spherical shell regions within the electrical potential structure formed within the spherical grid volume.

43. The apparatus according to claim 42, wherein carbon atoms are concentrated in a small spherical volume at the center of the spherical grid volume.

44. The apparatus according to claim 41, further comprising means to rapidly turn off the cathode voltage such that carbon ions in the plasma concentrated near the center of the spherical grid volume recombine, providing complex carbon molecules.

45. The apparatus according to claim 44, wherein the cathode grid voltage is repeatively pulsed at rates from 1-100 Hz, providing continuous production of complex carbon molecules.

46. The apparatus according to claim 1 wherein said first conductive structure is biased at one of ground or a zero electrical potential, and said second conductive structure is biased to a negative potential.

47. The apparatus according to claim 1 which operates with a neutral gas pressure between 0.1 and 100 mTorr.

48. The apparatus according to claim 1, wherein said vacuum vessel and said first conductive structure are a single structure and said single structure and said second structure are substantially spherical, wherein said apparatus produces a plurality of individual narrow plasma jets, wherein the vessel defined by said first conductive structure has a diameter within the range of 20-40 cm, the grid defined by said second conductive structure comprises a plural-ring electrical grid and said geometric transparency is greater than 85%.

49. The apparatus according to claim 48 wherein said grid has a diameter of 5-20 cm smaller than that of the surrounding first conductive structure.

50. A method for producing complex carbon molecules comprising:

a. establishing an enclosed volume for containment of at least a low pressure gas and plasma;

b. providing within said enclosed volume a first conductive structure and a second conductive structure formed as a grid within said first conductive structure that is highly transparent to flowing ions and electrons;

c. flowing at a controlled rate a neutral gas mixture of a carbon based gas and a buffer gas;

d. biasing said second conductive structure to a negative voltage relative to said first conductive structure and applying one of continuous regulated direct current or repetitive pulsed current to said first conductive structure;

e. applying electrical power at a negative voltage to said second conductive structure at a value sufficient to create a plasma discharge and cause a reaction comprising a dissociation of said carbon based gas, and creating an electrical potential structure within the enclosed volume such that higher mass reaction products are preferentially concentrated at the center of the volume; and

f. causing said gaseous reaction products to recombine to form a carbon soot containing fullerenes within said volume.

51. The method as recited in claim 50 further comprising the step of collecting and compacting said carbon soot for collection.

52. The method as recited in claim 51 wherein said carbon-based gas comprises at least one of methane and benzene.

53. The method as recited in claim 51 wherein said buffer gas primarily comprises at least one of xenon, argon and helium.

54. The method according to claim 51 wherein said second conductive surface distorts a local electrical potential surface such that a plasma jet is formed and flows out from inside said second conductive structure.

55. The method according to claim 54 further comprising an added conductive structure that defines a path from within the enclosed volume to allow a plasma jet to escape carry with it reaction products including fullerenes.

56. The method according to claim 55 wherein said path as defined by a longitudinal axis being orthogonal to a surface of said first conductive structure and said second conductive structure.

57. The method of claim 56 further comprising suppressing the electrical potential along said longitudinal axis for providing a guide-channel for a plasma jet escaping from within said second conductive structure.

58. The method of claim 55 comprising emitting electrons inside said volume to prevent negative charge build-up of a contained plasma.

59. The method according to claim 54 wherein said first conductive structure and said second conductive structure are substantially spherical, and further comprising providing an intermediate spherical-shaped grid structure that lies between said first and second conductive structures, said intermediate grid structure being highly transparent to ion and electron flows, biasing said intermediate conductive structure to a voltage that is positive relative to a first conductive structure potential such that said intermediate conductive structure provides a guide path for electrons from emitters located on, but electrically insulated from, the first conductive surface, thus providing an intense ionization region along the electron guide path.

60. The method according to claim 59 further comprising electrically insulating said first, second and intermediate structures and providing electrical power at a high negative voltage to said second conductive structure, and electrical power at a low positive voltage to said intermediate structure.

61. The method according to claim 59 wherein said intermediate electron grid guide is biased positive in a range of 100 V to 1000 V.

62. The method according to claim 59 wherein said second conductive structure is biased range of −

0.1 Kv to −

150 Kv.

63. The method according to claim 59 further comprising providing a second vessel conditioned to provide a lower or equal pressure compared to said enclosed volume and in communication with said enclosed volume such that matter ejected from said enclosed volume as hot ionized or neutrally charged gas containing a substantial fraction of the carbon “

soot”

is accumulated within the second vessel.

64. The method as recited in claim 50 further comprising washing accumulated carbon soot from associated electrical components.

65. The method of claim 50 wherein said carbon-based gas comprises at least one of linear hydrocarbons, aromatic hydrocarbons or carbons halides.

66. The method as recited in claim 50 wherein said buffer gas primarily comprises at least one of nitrogen, oxygen, or a noble gas.

67. A method for complex carbon molecule production, using one or more vessels producing intense heating of carbonaceous gas, containment of the more massive atomic and molecular species, separation of the less massive atomic or molecular species, a plasma jet of the various species, ejection of the jet from the plasma producing vessel into a “

soot”

collection vessel equipped with a “

soot”

removal apparatus which preserves the lower operating pressure of said vessels, said method comprising;

a. operating a first conductive structure as a first gas containment vessel with a wall portion having at least a first opening to allow a plasma jet to escape from within said vessel;

b. forming a second conductive structure as a grid within said first conductive structure that is highly transparent to flowing ions and electrons, said second conductive structure being operative to act like a cathode grid when biased to a negative voltage and having a second opening in said grid-type structure, said second opening being enlarged and operative to distort a local electrical potential surface such that a plasma jet flows out from inside the grid through said second opening;

c. flowing at a controlled rate a neutral gas mixture containing carbonaceous species and non-chemically reactive buffer gas into said gas containment vessel;

d. providing electrical power at a negative voltage from a power source to said cathode grid at a value sufficient to create a plasma discharge;

e. causing plasma formed within said vessel to emerge from the vessel as a plasma jet and enters a second vessel;

f. a second gas containment vessel to which one or more of said first gas containment vessels are hermetically attached such that the jets emerging from the vessels are directed into the second vessel; and

g. decelerating the jet plumes within the second gas containment vessel so that the micro-particles or large fullerene molecules or “

soot”

will precipitate as fullerene particles.

68. The method of claim 67 further comprising biasing said first conductive structure at one of ground or a zero electrical voltage and said second conductive structure to a negative potential.

69. The method of claim 68 further comprising biasing a path for said jet to the same voltage as said second conductive structure when acting as a cathode.

70. The method of claim 67 further comprising compacting and removing complex carbon particles from the second gas containment vessel.

71. The method of claim 70 further comprising a continuous or quasi continuous production process.