Process for the synthesis, separation and purification of powder materials

• US 20070130656A1
• Filed: 08/19/2004
• Published: 06/07/2007
• Est. Priority Date: 08/28/2003
• Status: Active Grant

• Current Assignee: Tekna Plasma Systems Inc.
• Original Assignee: Tekna Plasma Systemes
• Inventors: Jurewicz, Jerzy, Boulos, Maher, Normand, Christian, Nessim, Christine
• Granted Patent: US 7,572,315 B2
• Time in Patent Office: Days
• US Class Current: 423/138
• 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 19/10 employing sonic or ultrasonic vibrations
• CPC Class Codes: B01J 2/04 in a gaseous medium if combined with suspending the material in a gas, e.g. fluidised beds B01J2/16
• CPC Class Codes: B01J 2219/0869 Feeding or evacuating the reactor
• CPC Class Codes: B01J 2219/0871 Heating or cooling of the reactor
• CPC Class Codes: B01J 2219/0877 Liquid
• CPC Class Codes: B01J 2219/0879 Solid
• CPC Class Codes: B01J 2219/0898 Hot plasma
• CPC Class Codes: B22F 1/054 Nanosized particles
• CPC Class Codes: B22F 1/14 Treatment of metallic powder mixing with lubricating or binding agents or with organic material B22F1/10
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy

Abstract

The invention concerns a process for the spheroidisation, densification and purification of powders through the combined action of plasma processing, and ultra-sound treatment of the plasma-processed powder. The ultra-sound treatment allows for the separation of the nanosized condensed powder, referred to as ‘soot’, from the plasma melted and partially vaporized powder. The process can also be used for the synthesis of nanopowders through the partial vaporization of the feed material, followed by the rapid condensation of the formed vapour cloud giving rise to the formation of a fine aerosol of nanopowder. In the latter case, the ultra-sound treatment step serves for the separation of the formed nanopowder form the partially vaporized feed material.

Claims

1. A process for the purification of a material comprising:

providing powder particles of the material including impurities;

plasma heating and melting of said powder particles of the material and release of said impurities in vapour phase through a plasma stream, yielding molten particle droplets of the material mixed in said plasma stream and vaporized impurities;

cooling of said molten particle droplets of the material mixed in said plasma stream with said vaporized impurities, yielding a mixture of purified powder particles of the material and soot;

exposing said mixture of purified powder particles of the material and soot material to ultrasound vibrations in a sonification medium, yielding separated purified powder particles of the material and soot in said sonification medium; and

recovering said purified powder particles of the material from said sonification medium and said soot.

2. A process as recited in claim 1, wherein said sonification medium is selected from the group consisting of water, acetone, alcohol and air.

3. A process as recited in claim 1, wherein recovering said purified powder particles of the material from said sonification medium and said soot includes separation of said purified powder particles of the material by wet sieving, differential sedimentation under normal gravitational forces, or by intense centrifugation.

4. A process as recited in claim 1, wherein recovering said purified powder particles of the material from said sonification medium includes filtration of the sonification medium.

5. A process as recited in claim 1, wherein said plasma heating and melting of said powder particles of the material through a plasma stream is achieved by injecting said powder particles in an inductively coupled radio frequency plasma stream using a carrier gas.

6. A process as recited in claim 1, wherein said plasma heating and melting of said powder particles of the material through a plasma stream is performed under a pressure selected from the group consisting of atmospheric, low pressure, ‘

soft vacuum’

, and above atmospheric pressure.

7. A process as recited in claim 1, wherein said plasma stream is achieved under condition selected from the group consisting of an inert, an oxidizing or a reducing atmosphere.

8. A process as recited in claim 1, wherein said powder particles of the material being provided in raw form.

9. A process as recited in claim 1, wherein said ultrasound vibrations are produced using an ultrasound generator characterized by having an intensity in the range of about 100 W to about 10 kW.

10. A process as recited in claim 1, wherein said cooling of said molten particle droplets of the material mixed in said plasma stream is achieved by rapid quenching of said molten particle droplets of the material mixed in said plasma stream.

11. A process as recited in claim 10, wherein said rapid quenching is achieved through the injection of a cold gas stream, an atomized liquid stream, or contact with a cold surface.

12. A process as recited in claim 1, wherein the material is selected from the group consisting of a ceramic, a pure metal an alloy and a composite.

13. A process as recited in claim 12, wherein said metal is selected from the group consisting of silicon, chromium, molybdenum tungsten, tantalum and ruthenium.

14. A process as recited in claim 1 for improving the flow properties of said powder material.

15. The use of a process as recited in claim 1 for lowering the oxygen content of the powder particles.

16. A process as recited in claim 1 for the purification of powder material for the manufacture of solar cells or sputtering target.

17. A process for the separation of nanopowder mixed with a coarse powder by exposing the nanopowder mixed with the coarse powder to ultrasound vibrations in a sonification medium.

18. A process as recited in claim 17, wherein said sonification medium is selected from the group consisting of water, acetone, alcohol and air.

19. A process as recited in claim 17, wherein said ultrasound vibrations are produced using an ultrasound generator characterized by having an intensity in the range of about 100 W to about 10 kW.

20. A process for the synthesis of a material nanopowder comprising:

i) providing the material in powder form;

ii) plasma heating, melting and vaporization of said powder of the material through a plasma stream, yielding the material in vapour form mixed with partially vaporized particles in said plasma stream;

iii) running the material in vapour form mixed partially vaporized particles in said plasma stream through a quench stream, yielding a mixture of formed material nanopowder and residual coarse material powder; and

iv) exposing said mixture of formed material nanopowder and residual coarse material powder to ultrasound vibrations in a sonification medium, yielding separated nanopowder particles of said material and coarse powder of said material.

21. A process as recited in claim 20, further comprising v) recovering at least one of said separated nanopowder particles of said material and said residual coarse powder of said material.

22. A process as recited in claim 21, wherein step v) includes separation said separated nanopowder particles of said material and coarse powder of said material by wet sieving, differential sedimentation under normal gravitational forces, or by intense centrifugation.

23. A process as recited in claim 21, wherein step v) includes filtration of the sonification medium.

24. A process as recited in claim 20, wherein said sonification medium is selected from the group consisting of water, acetone, alcohol and air.

25. A process as recited in claim 20, wherein said sonification includes the production of ultrasound vibrations characterized by having an intensity in the range of about 100 W to about 10 kW.

26. A process as recited in claim 20, wherein said plasma heating and melting of said powder of the material through said plasma stream is achieved by injecting said powder in an inductively coupled radio frequency plasma stream using a carrier gas.

27. A process as recited in claim 26, wherein said plasma heating and melting of said powder particles of the material through a plasma stream is performed under a pressure selected from the group consisting of atmospheric, low pressure, ‘

soft vacuum’

, and above atmospheric pressure.

28. A process as recited in claim 26, wherein said plasma stream is achieved under condition selected from the group consisting of an inert, an oxidizing or a reducing atmosphere.

29. A process as recited in claim 20, wherein the material is selected from the group consisting of, though not limited to, a ceramic, a pure metal, an alloy or a composite.