Efficient boron nitride nanotube formation via combined laser-gas flow levitation

• US 20120168299A1
• Filed: 09/22/2011
• Published: 07/05/2012
• Est. Priority Date: 01/04/2011
• Status: Active Grant

• Current Assignee: Jefferson Science Associates, Llc, United States of America As REP By The Administrator of The National Aeronautics & Space, United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States of America As REP By The Administrator of The National Aeronautics & Space
• Inventors: Jordan, Kevin, Smith, Michael W., Whitney, R. Roy
• Granted Patent: US 8,673,120 B2
• Time in Patent Office: Days
• US Class Current: 204/157.41
• CPC Class Codes: B01J 19/121 Coherent waves, e.g. laser beams lasers per se H01S3/00
• CPC Class Codes: B01J 2219/0879 Solid
• 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 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: C04B 2235/3856 Carbonitrides, e.g. titanium carbonitride, zirconium carbonitride
• CPC Class Codes: C04B 2235/421 Boron
• CPC Class Codes: C04B 2235/46 Gases other than oxygen used as reactant, e.g. nitrogen used to make a nitride phase
• CPC Class Codes: C04B 2235/5284 Hollow fibers, e.g. nanotubes
• CPC Class Codes: C04B 2235/6587 Influencing the atmosphere by vaporising a solid material, e.g. by using a burying of sacrificial powder
• CPC Class Codes: C04B 35/6229 based on boron nitride

Abstract

A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B_xC_yN_z. The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B_xC_yN_z.

Claims

1. A process for producing boron nitride nanotubes, the process comprising the steps;

a. providing a boron ball target, a first laser beam having an adjustable power level and a gas flow comprising nitrogen;

b. positioning the boron ball target in a reaction position above the first laser beam and in the gas flow, the reaction position comprising a vertical reaction position and a horizontal reaction position;

c. adjusting the power level of the first laser beam to provide sufficient force from the first laser beam to the boron ball target to balance the force of gravity and the force of a light from above the boron ball target acting downward on the boron ball target and maintain the boron ball target in the vertical reaction position;

d. heating the boron ball target with the first laser beam wherein the heating evaporates a portion of the boron ball target and forms a boron vapor plume;

e. adjusting the power level of the first laser beam to maintain the heated boron ball target balanced in the reaction position as the boron vapor plume moves upward from the boron ball target;

f. providing at least one second laser beam positioned above and to the side of the boron ball target, wherein the at least one second laser beam exerts a second laser beam force on the boron ball target to maintain the boron ball target in the horizontal reaction position; and

g. forming a plurality of boron nitride nanotubes as the upward moving boron vapor plume contacts the nitrogen in the gas flow.

2. The process of claim 1, wherein the steps are performed in sequence.

3. The process of claim 1, wherein the boron ball target has attached whiskers which are positioned mechanically to position the boron ball target above the first laser beam.

4. The process of claim 1, wherein the boron ball target is positioned above the first laser beam by propelling the boron ball upward in a near parabolic arc of motion with a top wherein the top of the near parabolic arc of motion is at the reaction position.

5. The process of claim 1, wherein the heated boron ball target is acted upon by the forces of gravity, light, gas flow including buoyancy and evaporation and the forces are balanced such that the net force acting on the heated boron ball target is zero.

6. The process of claim 1, further comprising collecting the boron nitride nanotubes.

7. The process of claim 1, wherein the first laser beam is provided by a first laser and the at least one second laser beam is provided by at least one second laser.

8. The process of claim 1, wherein the first laser beam and the at least one second laser beam are provided by a single laser and wherein the single laser produces a single laser beam and wherein a first portion of the single laser beam forms the first laser beam and a second portion of the single laser beam forms the at least one second laser beam.

9. The process of claim 1, where in the gas flow is at a pressure of about 15 to about 20,000 psi.

10. A process for producing boron-carbon-nitrogen nanotubes of the general formula B_xC_yN_z the process comprising the steps;

a. providing a boron ball target, a first laser beam having an adjustable power level, a gas flow comprising nitrogen, and a carbon source;

b. positioning the boron ball target in a reaction position above the first laser beam and in the gas flow, the reaction position comprising a vertical reaction position and a horizontal reaction position;

c. adjusting the power level of the first laser beam to provide sufficient force from the first laser beam to the boron ball target to balance the force of gravity and the force of a light from above the boron ball target acting downward on the boron ball target and maintain the boron ball target in the reaction position;

d. heating the boron ball target with the first laser beam wherein the heating evaporates a portion of the boron ball target and forms a boron vapor plume and vaporizes the carbon source to form carbon atoms;

e. adjusting the power level of the first laser beam to maintain the heated boron ball target balanced in the reaction position as the boron vapor plume moves upward from the boron ball target;

f. providing at least one second laser beam positioned above and to the side of the boron ball target, wherein the at least one second laser beam exerts a second laser beam force on the boron ball target to maintain the boron ball target in the horizontal reaction position; and

g. forming a plurality of boron-carbon-nitrogen nanotubes of the general formula B_xC_yN_z as the upward moving boron vapor plume contacts the nitrogen in the gas flow and carbon atoms.

11. The process of claim 10, wherein the steps are performed in sequence.

12. The process of claim 10, wherein the boron ball target has attached whiskers which are positioned mechanically to position the boron ball target above the first laser beam.

13. The process of claim 10, wherein the boron ball target is positioned above the first laser beam by propelling the boron ball upward in a near parabolic arc of motion with a top wherein the top of the near parabolic arc of motion is at the reaction position.

14. The process of claim 10, wherein the heated boron ball target is acted upon by the forces of gravity, light, gas flow and evaporation and the forces are balanced such that the net force acting on the heated boron ball target is zero.

15. The process of claim 10, further comprising collecting the boron-carbon-nitrogen nanotubes of the general formula B_xC_yN_z.

16. The process of claim 10, wherein the first laser beam is provided by a first laser and the at least one second laser beam is provided by at least one second laser.

17. The process of claim 10, wherein the first laser beam and the at least one second laser beam are provided by a single laser and wherein the single laser produces a single laser beam and wherein a first portion of the single laser beam forms the first laser beam and a second portion of the single laser beam forms the at least one second laser beam.

18. The process of claim 10, wherein the boron ball target comprises boron and a carbon source.

19. The process of claim 10, wherein the carbon source is a carbon rich gas and the carbon rich gas is mixed with the nitrogen in the gas flow.