APPARATUS AND METHODS FOR PRODUCING NANOPARTICLES IN A DENSE FLUID MEDIUM

• US 20080169182A1
• Filed: 01/12/2007
• Published: 07/17/2008
• Est. Priority Date: 01/12/2007
• Status: Active Grant

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Jiang, Hongquan, Denes, Ferencz S., Manolache, Sorin O.
• Granted Patent: US 7,862,782 B2
• Time in Patent Office: Days
• US Class Current: 204/164
• 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 2219/0809 employing two or more electrodes
• CPC Class Codes: B01J 2219/083 cylindrical
• CPC Class Codes: B01J 2219/0833 forming part of a full circle
• CPC Class Codes: B01J 2219/0841 Metal
• CPC Class Codes: B01J 2219/0869 Feeding or evacuating the reactor
• CPC Class Codes: B01J 2219/0877 Liquid
• CPC Class Codes: B22F 1/054 Nanosized particles
• CPC Class Codes: B22F 2202/13 Use of plasma
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 9/14 using electric discharge
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 32/05 Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
• CPC Class Codes: C01B 33/021 Preparation chemical coating from the vapour phase C23C16/00

Abstract

An apparatus and method are disclosed for producing nanoparticles in a dense fluid medium. The method is based on the formation of nanoparticles from nanoparticle precursors in a dense fluid medium in which a plasma discharge is created between electrodes submerged in the dense fluid medium. The electrodes define a plasma discharge zone between opposing electrode discharge faces and further define an internal cavitation zone into which a cavitation gas is released, creating bubbles in the dense fluid medium. The result is the efficient production of nanoparticles using a high-frequency, high-voltage electric field to react dense-phase precursors in an atmospheric pressure, low temperature environment.

Claims

1. An apparatus for the synthesis of nanoparticles comprising:

(a) a reaction vessel defining an internal reaction chamber;

(b) a first electrode housed within the reaction chamber comprising;

(i) a first discharge face defining a first central electrode opening; and

(ii) a first electrode wall extending upwardly from the first discharge face and defining a first electrode cavity extending upwardly from the first central electrode opening;

(c) a second electrode housed within the reaction chamber comprising;

(i) a second discharge face defining a second central electrode opening; and

(ii) a second electrode wall extending downwardly from the second discharge face and defining a second electrode cavity extending downwardly from the second central electrode opening;

wherein the first discharge face is disposed opposite and facing the second discharge face and the first central electrode opening is disposed opposite and facing the second central electrode opening, such that the first discharge face and the second discharge face are separated by a gap and the first electrode cavity, the second electrode cavity, and the gap provide a cavitation zone; and

(d) a gas inlet port that opens into the cavitation zone.

2. The apparatus of claim 1 wherein the gas inlet port comprises:

(i) an elongated central member comprising an electrically conductive material, the central member having an outer wall and a longitudinal axis; and

(ii) a hollow elongated insulating member comprising an electrically insulating material, the insulating member having an outer wall and an inner wall disposed coaxially around the central member;

wherein the outer wall of the central member and the inner wall of the insulating member are separated by a channel which provides the gas inlet port.

3. The apparatus of claim 1 wherein the central member has a distal end that extends beyond the distal end of the insulating member, and further wherein the second electrode is mounted to the distal end of the central member.

4. The apparatus of claim 3 wherein the inlet port further comprises a hollow elongated conducting member comprising an electrically conductive material, the conducting member having an outer wall and an inner wall disposed coaxially around the insulating member, and further wherein the first electrode is mounted to the elongated conducting member.

5. The apparatus of claim 1 wherein the first discharge face and the second discharge face are ring-shaped.

6. The apparatus of claim 5 wherein the ring-shaped discharge faces and the gas inlet port share a common longitudinal axis.

7. The apparatus of claim 1, further comprising a reaction vessel outlet channel in fluid communication with the reaction chamber and one or more magnets disposed around the reaction vessel outlet channel.

8. The apparatus of claim 1, further comprising a gas source in communication with the gas inlet port.

9. The apparatus of claim 1, further comprising a voltage source in electrical communication with one or both of the first and second electrodes.

10. The apparatus of claim 1 wherein the height of the gap is adjustable.

11. The apparatus of claim 1 wherein neither the first nor the second electrode is rotatable.

12. A method of producing nanoparticles using the apparatus of claim 1, the method comprising:

(a) introducing a liquid comprising a nanoparticle precursor into the reaction chamber such that the cavitation zone is submerged in the liquid;

(b) introducing a cavitation gas into the cavitation zone through the gas inlet port to create bubbles in the liquid; and

(c) applying an electric potential between the first discharge face and the second discharge face, thereby creating a plurality of plasma discharges between the first discharge face and the second discharge face for a time sufficient to produce nanoparticles from the nanoparticle precursor.

13. The method of claim 12 wherein the nanoparticles comprise semiconductor nanoparticles.

14. The method of claim 13 wherein the nanoparticles are silicon nanoparticles.

15. The method of claim 14 wherein the nanoparticle precursor is liquid SiCl₄.

16. The method of claim 12 wherein the nanoparticles are carbon nanoparticles.

17. The method of claim 16 wherein the precursor is benzene.

18. The method of claim 12 wherein the nanoparticles comprise magnetic nanoparticles.

19. The method of claim 18 wherein the apparatus further comprises a reaction vessel outlet channel in fluid communication with the reaction chamber and one or more magnets disposed around the reaction vessel outlet channel, the method further comprising passing the liquid containing the magnetic nanoparticles through the reaction vessel outlet channel.

20. The method of claim 12 wherein the nanoparticles are hybrid nanoparticles comprising an element derived from the nanoparticle precursor and an element sputtered from the first electrode or the second electrode.

21. The method of claim 20 wherein the element derived from the nanoparticle precursor is carbon.