Material for electrodes of low temperature plasma generators

• US 20070249256A1
• Filed: 06/15/2007
• Published: 10/25/2007
• Est. Priority Date: 11/30/2000
• Status: Active Grant

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Rutberg, Philip, Safronov, Alexi, Shekalov, Valentin, Ribin, Valeri, Caplan, Malcom, Vinogradov, Sergel
• Granted Patent: US 7,462,089 B2
• Time in Patent Office: Days
• US Class Current: 445/49
• CPC Class Codes: B22F 1/09 Mixtures of metallic powders
• CPC Class Codes: B22F 1/12 Metallic powder containing non-metallic particles containing lubricating or binding agents or organic material B22F1/10
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/02 Compacting only
• CPC Class Codes: B22F 3/14 simultaneously
• CPC Class Codes: B22F 3/17 by forging
• CPC Class Codes: B22F 5/10 of articles with cavities or holes, not otherwise provided for in the preceding subgroups
• CPC Class Codes: C22C 32/0021 Matrix based on noble metals, Cu or alloys thereof
• CPC Class Codes: H01J 37/32009 Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources plasma generation in general H05H1/24
• CPC Class Codes: H01J 37/32541 Shape
• CPC Class Codes: H01J 37/3255 Material

Abstract

Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y₂O₃ is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron: 3-30; Y₂O₃:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y₂O₃ provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, and municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

Claims

1. A method for producing electrodes of low temperature plasma generators, comprising:

providing a mixture of dry metal powders of (Cu+Fe) and Y₂O₃,

compacting the mixture of powders in a mold, baking the compacted mixture,

forging the baked compacted mixture to form an electrode, and

mechanically processing the electrode to a finish member having ultimate dimensions.

2. The method of claim 1, wherein compacting the mixture of powders is carried out such that cross-section areas of the compacted powders and the finish member related as 4:

1-8;

1.

3. The method of claim 1, wherein baking the compacted mixture is carried out in a shielding-reducing medium.

4. The method of claim 3, wherein the shielding-reducing medium comprises hydrogen, dissociated ammonia.

5. The method of claim 3, wherein the baking is carried out in a temperature range of about 900-1050°

C.

6. The method of claim 5, wherein the baking is carried out in a time period of about 20 min-4 hours.

7. The method of claim 3, wherein forging the baked compacted mixture is carried out in a temperature range of about 850-950°

C.

8. The method of claim 7, wherein the forging is carried out to form an electrode having an allowance on diameter of about 2-3 mm.

9. The method of claim 3, wherein mechanical processing of the member is carried out to produce an electrode having a length of about 260 mm and diameter of about 25 mm.

10. The method of claim 2, wherein the compacted powders have a length of about 90 mm and width of about 60 mm, and the finish member has a length of about 280 mm and width of about 29 mm.

11. The method of claim 1, additionally including forming at least one cooling channel in the thus formed electrode.

12. The method of claim 1, additionally including forming the mixture to create a composition of about 3-30% of Fe, about 0.05-0.1% of Y₂O₃, and the remainder of Cu.

13. The method of claim 12, wherein mixing of the Fe, Y₂O₃ and Cu powders is carried out in three steps sequentially:

mixing of about 10 g of about Cu, 5 g of Fe, and about 5 g Of Y₂O₃, adding to the resulting composition of about 80 g of Fe, 200 g of Cu and mix once more, and adding to the resulting composition about 1410 g of Fe and about 3290 g of Cu and mix once more.

14. The method of claim 1, wherein compacting is carried out at a compaction pressure of about 300-400 Mpa (3-4 t/cm²).

15. The method of claim 1, wherein forging is carried out in swages of about 5 mm in a pass to the diameter with intermediate heating after each pass.

16. The method of claim 15, wherein forging is carried out at a temperature range of about 900-950°

C. with a time of exposure of about 60 minutes at forging temperature.