Boron Nitride Nanotubes

• US 20090117021A1
• Filed: 05/14/2008
• Published: 05/07/2009
• Est. Priority Date: 05/15/2007
• Status: Active Grant

• Current Assignee: Jefferson Science Associates, Llc (Government of the United States of America), National Institute of Aerospace Asscoiates, United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: Jefferson Science Associates, Llc (Government of the United States of America), National Institute of Aerospace Asscoiates, U.S.A. as represented by the Administrator of the National Aeronautics and Space Administration
• Inventors: Smith, Michael W., Park, Cheol, Jordan, Kevin
• Granted Patent: US 8,206,674 B2
• Time in Patent Office: Days
• US Class Current: 423/290
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 21/0641 Preparation by direct nitridation of elemental boron
• CPC Class Codes: C01B 35/146 Compounds containing boron and nitrogen, e.g. borazoles ammonium tetrafluoborates C01B35/063; ammonium borates C01B35/12
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/13 Nanotubes
• CPC Class Codes: C01P 2004/133 Multiwall nanotubes
• CPC Class Codes: C01P 2004/16 Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer
• CPC Class Codes: C30B 23/00 Single-crystal growth by condensing evaporated or sublimed materials
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/602 Nanotubes

Abstract

Boron nitride nanotubes are prepared by a process which includes:

• • (a) creating a source of boron vapor;
  • (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and
  • (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

Claims

1. A process for producing boron nitride nanotubes and nanostructures, which process comprises thermally exciting a boron-containing target in a chamber under nitrogen pressure which is elevated above atmospheric.

2. The process of claim 1, wherein the boron-containing target is thermally excited by means of a laser.

3. The process of claim 2, wherein the laser is a member selected from the group consisting of a free electron laser and a carbon dioxide laser.

4. The process of claim 1, wherein the boron-containing target comprises a member selected from the group consisting of compressed boron powder and compressed boron nitride powder.

5. The process of claim 4, wherein the target is cylindrical, rotating, and illuminated on the radius.

6. The process of claim 4, wherein the target is cylindrical, rotating, and illuminated on one face.

7. The process of claim 4, wherein the target is stationary.

8. A process for producing boron nitride nanotubes, which process comprises:

(a) creating a source of boron vapor;

(b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, the nitrogen gas being provided at a pressure elevated above atmospheric; and

(c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

9. The process of claim 8, wherein the pressure of the nitrogen gas is greater than about 2 atmospheres and less than about 250 atmospheres.

10. The process of claim 8, wherein the source of boron vapor is provided by supplying energy to a solid boron-containing target, which energy is sufficient to break bonds in the solid boron-containing target, thereby allowing boron to enter the vapor state.

11. The process of claim 10, wherein the energy supplied to the solid boron-containing target is focused thermal energy.

12. The process of claim 8, wherein the boron nitride nanotubes are formed at the nucleation site in the absence of a catalyst.

13. The process of claim 8, wherein the nucleation site is a surface.

14. The process of claim 13, wherein the surface has an asperity.

15. The process of claim 10, wherein the solid boron-containing target is a plug selected from the group consisting of pressed boron powder and pressed boron nitride powder.

16. The process of claim 8, wherein the nitrogen gas is provided at a pressure from greater than about 2 atmospheres up to about 12 atmospheres.

17. The process of claim 10, wherein the energy is in the form of a laser beam, which is directed at the solid boron-containing target.

18. The process of claim 17, wherein the laser beam is allowed to drill a hole in the solid boron-containing target as the laser beam is directed thereto, thereby creating a stream of boron vapor by laser heating inside the hole.

19. The process of claim 18, wherein the stream of boron vapor is allowed to flow upwardly from the bottom of the hole and through the hole, whence it contacts the nitrogen gas, which is kept under pressure in a synthesis chamber enclosing the solid boron-containing target and containing the nitrogen gas under pressure.

20. The process of claim 19, wherein the nucleation site is the upper periphery of the hole in the solid boron-containing target, where any asperity exists.

21. The process of claim 20, wherein the boron nitride nanotubes are formed at the nucleation site and propagate away therefrom in the direction of flow of the stream of boron vapor.

22. The process of claim 21, wherein the boron nitride nanotubes are prepared at a growth rate of about 10 cm/sec.

23. The process of claim 17, wherein the laser beam emanates from a member of the group consisting of a free electron laser and a carbon dioxide laser.

24. The process of claim 8, wherein the boron nitride nanotubes are crystalline nanotubes having continuous, parallel, substantially defect-free, and sp2 bonded walls, the boron nitride nanotubes being selected from the group consisting of single-walled nanotubes, double-walled nanotubes, few-walled nanotubes, and multi-walled nanotubes.

25. Boron nitride nanotubes prepared according to the process of claim 8.