Reactor and method for production of nanostructures

• US 9,630,162 B1
• Filed: 04/04/2012
• Issued: 04/25/2017
• Est. Priority Date: 10/09/2007
• Status: Active Grant

• Current Assignee: University of Louisville
• Original Assignee: University of Louisville
• Inventors: Sunkara, Mahendra Kumar, Kim, Jeong H., Kumar, Vivekanand
• Primary Examiner(s): Hendricks, Keith
• Assistant Examiner(s): Raphael, Colleen M
• Application Number:
  US13/439,592
• Time in Patent Office: 1,847 Days
• Field of Search: 20415751, 20415744, 20415743, 422186-187, 4235921-59419
• CPC Class Codes: B01J 12/02 for obtaining at least one reaction product which, at normal temperature, is in the solid state
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 13/14 Methods for preparing oxides or hydroxides in general particular individual oxides or hydroxides, see the relevant groups of subclasses C01B - C01G or C25B, according to the element combined with the oxygen or hydroxy group
• CPC Class Codes: C01B 13/32 by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process
• CPC Class Codes: C01F 7/424 using a plasma
• CPC Class Codes: C01G 1/02 Oxides
• CPC Class Codes: C01G 19/02 Oxides
• CPC Class Codes: C01G 23/047 Titanium dioxide
• CPC Class Codes: C01G 23/07 Producing by vapour phase processes, e.g. halide oxidation
• CPC Class Codes: C01G 25/02 Oxides
• CPC Class Codes: C01G 9/00 Compounds of zinc
• CPC Class Codes: C01G 9/02 Oxides; Hydroxides
• CPC Class Codes: C01G 9/03 Processes of production using dry methods, e.g. vapour phase processes
• CPC Class Codes: C01P 2002/82 by IR- or Raman-data
• CPC Class Codes: C01P 2004/03 obtained by SEM
• 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: C01P 2004/17 Nanostrips, nanoribbons or nanobelts, i.e. solid nanofibres with two significantly differing dimensions between 1-100 nanometer
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: H01J 37/32192 Microwave generated discharge H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H01J 37/32449 : Gas control, e.g. control of the gas flow
• CPC Class Codes: H01J 37/32834 : Exhausting
• CPC Class Codes: H05H 1/46 : using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence
• CPC Class Codes: H05H 1/4622 : using waveguides
• CPC Class Codes: H05H 2245/50 : Production of nanostructures

Abstract

A reactor and method for production of nanostructures, including metal oxide nanowires or nanoparticles, are provided. The reactor includes a regulated metal powder delivery system in communication with a dielectric tube; a plasma-forming gas inlet, whereby a plasma-forming gas is delivered substantially longitudinally into the dielectric tube; a sheath gas inlet, whereby a sheath gas is delivered into the dielectric tube; and a microwave energy generator coupled to the dielectric tube, whereby microwave energy is delivered into a plasma-forming gas. The method for producing nanostructures includes providing a reactor to form nanostructures and collecting the formed nanostructures, optionally from a filter located downstream of the dielectric tube.

Claims

1. A method for producing metal oxide nanowires, the method comprising:

a. providing a reactor having;

1) a dielectric tube, wherein the dielectric tube defines an inlet end, an exit end, and a longitudinal axis traversing from the inlet end to the exit end;

2) a microwave energy generator in communication with the dielectric tube, wherein the microwave energy generator is configured to deliver microwave energy into the dielectric tube;

3) a plasma-forming gas inlet in communication with the dielectric tube, and configured to deliver a plasma-forming gas into the dielectric tube substantially parallel to the longitudinal axis;

4) a sheath gas inlet in communication with the dielectric tube, and configured to deliver a sheath gas into the dielectric tube substantially parallel to the longitudinal axis;

5) a metal powder delivery system mounted at the inlet end and in communication with the dielectric tube, wherein the metal powder delivery system is oriented relative to the dielectric tube such that metal powder can be gravity-fed into the dielectric tube substantially parallel to the longitudinal axis; and

,

6) a product collector mounted at the outlet end and in communication with the dielectric tube, wherein the product collector is oriented relative to the dielectric tube such that a product formed in the dielectric tube can be received by and retained in the product collector;

b. delivering a plasma-forming gas and a sheath gas to the dielectric tube via the plasma-forming gas inlet and the sheath gas inlet, respectively;

c. applying a microwave energy to the plasma-forming gas in the dielectric tube to form a plasma;

d. delivering a metal powder having a particle diameter of less than about 1 micron up to about 45 microns into the dielectric tube from the metal powder delivery system such that the metal powder reacts at temperatures close to the metal'"'"'s melting point within the plasma along the longitudinal axis of the dielectric tube to produce metal oxide nanowires; and

,

e. collecting the metal oxide nanowires produced in Step d) in the product collector;

wherein the metal oxide nanowire is defined as a nanoparticle having a first dimension and a second dimension wherein the first dimension is greater than the second dimension.

2. The method of claim 1 wherein the metal powder is reacted within the plasma in the absence of a substrate or a catalyst or a template.

3. The method of claim 1 wherein the metal powder is delivered into the dielectric tube at a flow rate of up to about 200 grams/hour.

4. The method of claim 1 wherein the microwave power delivered to the dielectric tube is from 300 W to 3 kW.

5. The method of claim 1 wherein the metal powder is selected from a group consisting of tin, zinc, tungsten, titanium, iron, gallium, indium, bismuth, niobium, aluminum, vanadium, copper, and combinations thereof.

6. The method of claim 1 wherein the plasma-forming gas comprises argon, an oxidative gas, water vapor, hydrogen gas, or combinations thereof.

7. The method of claim 1 wherein the sheath gas is delivered into the dielectric tube to form a helical sheath gas path.

8. The method of claim 1 wherein the sheath gas comprises air.

9. The method of claim 1 further comprising the step of separating the nanowires from a stream of the nanowires and unreacted metal powder.

10. The method of claim 1 wherein the product collector further comprises a filter bag, and the step of collecting the metal oxide nanowires comprises collecting the metal oxide nanowires from the filter bag.

11. The method of claim 1 further comprising the step of recycling unreacted metal powder into the plasma.