Low energy milling to produce flake powders

Patent metadata

Field	Value
Publication number	US-9514890-B2
Application number	US-201414205698-A
Country	US
Kind code	B2
Filing date	Mar 12, 2014
Priority date	Mar 13, 2013
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A method for increasing surface area of a valve metal particle is provided as is an improved valve metal particle provided thereby. The method includes charging a mill apparatus with a valve metal powder and a media wherein the media has an average diameter of at least 0.01 cm to no more than 0.3175 cm. The valve metal powder is then milled at an average kinetic energy of no more than 3,000 ergs per media particle to obtain a milled powder.

First claim

The invention claimed is:

1. A capacitor comprising as an anode
a tantalum powder formed by the method of:
charging a mill apparatus with a valve metal powder and a media wherein said media has an average diameter of at least 0.01 cm to no more than 0.3175 cm; and
milling at an average kinetic energy of no more than 3,000 ergs per media particle to obtain a milled powder
wherein said milled powder has a BET surface area of greater than 4 M 2 /g and an aspect ratio of at least 3 and no more than 30 ppm metallic impurity.

2. The capacitor of claim 1 comprising milling at an average kinetic energy of no more than 1,000 ergs per media particle.

3. The capacitor of claim 2 comprising milling at an average kinetic energy of no more than 100 ergs per media particle.

4. The capacitor of claim 3 comprising milling at an average kinetic energy of no more than 5 ergs per media particle.

5. The capacitor of claim 4 comprising milling at an average kinetic energy of no more than 2 ergs per media particle.

6. The capacitor of claim 5 comprising milling at an average kinetic energy of no more than 1 erg per media particle.

7. The capacitor of claim 1 wherein said media comprises a material selected from the group consisting of steel, zirconia, yttria stabilized zirconia, 440 stainless steel, glass, tungsten carbide, tantalum, niobium, tantalum nitride, niobium nitride, tantalum carbide and mixtures thereof.

8. The capacitor of claim 1 wherein said media is spherical.

9. The capacitor of claim 1 wherein said milled powder has a BET surface area of greater than 5 M 2 /g.

10. The capacitor of claim 9 wherein said milled powder has a BET surface area of greater than 6 M 2 /g.

11. The capacitor of claim 10 wherein said milled powder has a BET surface area of greater than 7 M 2 /g.

12. The capacitor of claim 11 wherein said milled powder has a BET surface area of greater than 8 M 2 /g.

13. The capacitor of claim 12 wherein said milled powder has a BET surface area of greater than 9 M 2 /g.

14. The capacitor of claim 1 wherein said milled powder has no more than 30 ppm impurity selected from iron, nickel and chromium.

15. The capacitor of claim 1 wherein said milled powder has no more than 30 ppm impurity selected from iron, nickel, chromium, silicon and zirconium.

16. The capacitor of claim 1 wherein said tantalum powder has a CV/g of less than 30,000 micro-farad volts per gram.

17. The capacitor of claim 16 wherein said tantalum powder has a CV/g of less than 50,000 micro-farad volts per gram.

18. The capacitor of claim 17 wherein said tantalum powder has a CV/g of less than 100,000 micro-farad volts per gram.

19. The capacitor of claim 1 wherein said milled powder has a CV/g of at least 180,000 micro-farad volts per gram.

20. The capacitor of claim 19 wherein said milled powder has a CV/g of at least 200,000 micro-farad volts per gram.

21. The capacitor of claim 20 wherein said milled powder has a CV/g of at least 250,000 micro-farad volts per gram.

22. The capacitor of claim 1 wherein said average kinetic energy is achieved at a rotation rate of a drive shaft of no more than 120 RPM.

23. The capacitor of claim 1 wherein said mill apparatus is selected from the group consisting of attitor mill, jar mill, vibratory ball mill and a horizontal stirred ball mill.

24. A capacitor comprising:
an anode comprising a tantalum powder comprising:
a CV/g of at least 180,000 micro-farad volts per gram;
a BET surface area of greater than 4 M 2 /g;
no more than 30 ppm metallic impurity; and
an aspect ratio of at least 3;
a dielectric on said anode; and
a cathode on said dielectric.

25. The capacitor of claim 24 comprising no more than 30 ppm impurity selected from iron, nickel, chromium, silicon and zirconium.

26. The capacitor of claim 24 comprising no more than 30 ppm impurity selected from iron, nickel and chromium.

27. The capacitor of claim 24 wherein said tantalum powder is a milled powder with a BET surface area of greater than 5 M 2 /g.

28. The capacitor of claim 27 wherein said milled powder has a BET surface area of greater than 6 M 2 /g.

29. The capacitor of claim 28 wherein said milled powder has a BET surface area of at least 7 M 2 /g.

30. The capacitor of claim 28 wherein said milled powder has a BET surface area of at least 8 M 2 /g.

31. The capacitor of claim 28 wherein said milled powder has a BET surface area of at least 9 M 2 /g.

32. The capacitor of claim 24 wherein said milled powder has a CV/g of at least 200,000 micro-farad volts per gram.

33. The capacitor of claim 32 wherein said milled powder has a CV/g of at least 250,000 micro-farad volts per gram.

34. A capacitor comprising as an anode a tantalum powder formed by the method of:
charging a mill apparatus with a tantalum powder and a media wherein said media has an average diameter of at least 0.01 cm to no more than 0.3175 cm;
milling at an average kinetic energy of no more than 3,000 ergs per media particle to obtain a milled powder;
herein said milled powder has no more than 30 ppm metallic impurity; and
an aspect ratio of at least 3.

35. The capacitor of claim 34 comprising milling at an average kinetic energy of no more than 1,000 ergs per media particle.

36. The capacitor of claim 35 comprising milling at an average kinetic energy of no more than 100 ergs per media particle.

37. The capacitor of claim 34 wherein said media comprises a material selected from the group consisting of steel, zirconia, yttria stabilized zirconia, 440 stainless steel, glass, tungsten carbide, tantalum, niobium, tantalum nitride, niobium nitride, tantalum carbide and mixtures thereof.

38. The capacitor of claim 34 wherein said media is spherical.

39. The capacitor of claim 34 wherein said milled powder has a BET surface area of greater than 4 M 2 /g.

40. The capacitor of claim 39 wherein said milled powder has a BET surface area of greater than 5 M 2 /g.

41. The capacitor of claim 40 wherein said milled powder has a BET surface area of greater than 6 M 2 /g.

42. The capacitor of claim 41 wherein said milled powder has a BET surface area of greater than 7 M 2 /g.

43. The capacitor of claim 42 wherein said milled powder has a BET surface area of greater than 8 M 2 /g.

44. The capacitor of claim 43 wherein said milled powder has a BET surface area of greater than 9 M 2 /g.

45. The capacitor of claim 34 wherein said milled powder has no more than 30 ppm impurity selected from iron, nickel and chromium.

46. The capacitor of claim 34 wherein said milled powder has no more than 30 ppm impurity selected from iron, nickel, chromium, silicon and zirconium.

47. The capacitor of claim 34 wherein said tantalum powder has a CV/g of less than 50,000 micro-farad volts per gram.

48. The capacitor of claim 47 wherein said tantalum powder has a CV/g of less than 100,000 micro-farad volts per gram.

49. The capacitor of claim 34 wherein said milled powder has a CV/g

Assignees

• Kemet Electronics Corp

Inventors

• Jones Brady A
• Dufur Matthew W
• Fife James Allan

Classifications

• B22F1/068

  Flake-like particles · CPC title

• B22F1/05

  Metallic powder characterised by the size or surface area of the particles · CPC title

• Y10T428/12014

  having metal particles · CPC title

• B22F2301/20

  Refractory metals · CPC title

• H01G9/0029

  Processes of manufacture · CPC title