INDUCTION-COUPLED PLASMA SYNTHESIS OF BORON NITRIDE NANOTUBES

• US 20150125374A1
• Filed: 10/31/2014
• Published: 05/07/2015
• Est. Priority Date: 11/01/2013
• Status: Active Grant

• Current Assignee: BNNT, LLC
• Original Assignee: BNNT, LLC
• Inventors: Smith, Michael W., Jordan, Kevin C., Stevens, Jonathan C.
• Granted Patent: US 9,776,865 B2
• Time in Patent Office: Days
• US Class Current: 423/290
• CPC Class Codes: B01J 10/005 carried out at high temperatures in the presence of a molten material
• CPC Class Codes: B01J 19/08 Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor application of shock waves B01J3/08
• 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 2219/0898 Hot plasma
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 21/064 with boron
• CPC Class Codes: C01B 21/0641 Preparation by direct nitridation of elemental boron
• CPC Class Codes: C01P 2004/13 Nanotubes
• CPC Class Codes: C01P 2004/133 Multiwall nanotubes

Abstract

Described herein are processes and apparatus for the large-scale synthesis of boron nitride nanotubes (BNNTs) by induction-coupled plasma (ICP). A boron-containing feedstock may be heated by ICP in the presence of nitrogen gas at an elevated pressure, to form vaporized boron. The vaporized boron may be cooled to form boron droplets, such as nanodroplets. Cooling may take place using a condenser, for example. BNNTs may then form downstream and can be harvested.

Claims

1. A process for synthesizing boron nitride nanotubes (BNNTs), the process comprising:

a. introducing nitrogen gas and a boron-containing feedstock into a chamber;

b. heating the nitrogen gas and boron-containing feedstock with an induction-coupled plasma to form heated reactants;

c. introducing asperities downstream of the heated reactants to trigger formation of BNNTs; and

d. collecting the BNNTs.

2. The process of claim 1, wherein the BNNTs are at least one of single-to-few walled and greater than 50 microns long.

3. The process of claim 1, wherein the asperities comprise a condenser.

4. The process of claim 3, wherein the condenser comprises at least one of a copper rod, a tungsten wire, a network of copper rods, a network of tungsten wires, a grid of copper rods, and a grid of tungsten wires.

5. The process of claim 1, wherein the process proceeds without catalysts, i.e. with no reactive feedstock other than boron and nitrogen.

6. The process of claim 1, wherein the collecting is performed using at least one of a solid surface condenser, collection surfaces, and filters downstream of the growth zone.

7. The process of claim 1, wherein introducing nitrogen gas and a boron-containing feedstock into a chamber is a continuous process.

8. The process of claim 1, wherein collecting BNNTs is a continuous process.

9. The process of claim 1, wherein the chamber is at an elevated pressure of at least 2 atmospheres to about 250 atmospheres.

10. The process of claim 9, wherein the chamber is at an elevated pressure of at least 2 atmospheres to about 12 atmospheres.

11. The process of claim 1, wherein the heated reactants comprise boron nanodroplets.

12. A process for synthesizing BNNTs, the process comprising:

a. dispersing reactants into a chamber at an elevated pressure, wherein the reactants comprise nitrogen gas and a boron-containing feedstock;

b. heating, with an induction-coupled plasma, the reactants to a temperature greater than the vaporization temperature of the boron-containing feedstock, to form vaporized boron;

c. cooling the vaporized boron to form boron droplets;

d. exposing the boron droplets and nitrogen gas to a temperature between boron'"'"'s melting point and below boron'"'"'s boiling point; and

e. harvesting BNNTs.

13. The process of claim 12, wherein the elevated pressure is at least 2 atmospheres to about 250 atmospheres.

14. The process of claim 13, wherein the elevated pressure is at least 2 atmospheres to about 12 atmospheres.

15. The process of claim 12, wherein the reactants consist essentially of nitrogen gas and a boron-containing feedstock.

16. The process of claim 12, wherein the boron-containing feedstock comprises at least one of elemental boron, elemental boron powder, boron nitride, boron nitride powder, cubic boron nitride powder, and hexagonal boron nitride powder.

17. The process of claim 12, wherein cooling the vaporized boron is performed with at least one of a condenser and a plurality of asperities.

18. The process of claim 12, wherein cooling the vaporized boron is performed with a condenser comprising at least one of a copper rod, a tungsten wire, a network of copper rods, a network of tungsten wires, a grid of copper rods, and a grid of tungsten wires.

19. The process of claim 17, wherein cooling the vaporized boron is performed by introducing a plurality of asperities in the form of a condenser.

20. An apparatus for ICP-based BNNT synthesis, the apparatus comprising:

a. a chamber configured to maintain nitrogen gas and a boron-containing feedstock at an elevated pressure;

b. a gas inlet configured to introduce nitrogen gas into the chamber;

c. a feedstock inlet configured to disperse a boron-containing feedstock into the chamber;

d. an induction-coupled plasma head;

e. a nucleation zone;

f. a growth zone; and

g. a collection zone.