Methods to partially reduce certain metal oxides and oxygen reduced metal oxides
View Patent ↗Methods to at least partially reduce valve metal oxides are described wherein the process includes heat treating the valve metal oxide in the presence of a getter material, in an atmosphere which permits the transfer of oxygen atoms from the starting valve metal oxide to the getter material, and for a sufficient time and at a sufficient temperature to form an oxygen reduced valve metal oxide. Valve metal oxides and/or suboxides thereof are also described as well as capacitors containing anodes made from the valve metal oxides and suboxides thereof.
1. A metal oxide powder comprising a valve metal oxide having an atomic ratio of metal to oxygen of 1:less than 2.5, wherein said valve metal oxide has a specific surface area of from about 0.5 to about 10.0 m 2 /g, and said valve metal oxide has an apparent density of less than about 2.0 g/cc, and wherein said valve metal oxide is tantalum oxide or niobium oxide.
2. The metal oxide powder of claim 1 , wherein the ratio is 1:less than 2.0.
3. The metal oxide powder of claim 1 , wherein the ratio is 1:less than 1.5.
4. The metal oxide powder of claim 1 , wherein the ratio is 1:0.167 or 2:2.2.
5. The metal oxide powder of claim 1 , wherein the ratio is 1:1.
6. The metal oxide powder of claim 1 , wherein the ratio is 1:0.5.
7. The metal oxide powder of claim 1 , wherein the valve metal oxide is a tantalum oxide.
8. The metal oxide powder of claim 1 , wherein the valve metal oxide has a micro-porous structure.
9. The metal oxide powder of claim 1 , wherein the valve metal oxide has a pore volume of about 50%.
10. The metal oxide powder of claim 1 , wherein said metal oxide powder has a shape that is nodular, flaked, angular, or combinations thereof.
11. The metal oxide powder of claim 1 , wherein said metal oxide powder has primary particles having a size of 1 micron or less.
12. The metal oxide powder of claim 1 , wherein said specific surface area is from about 1.0 to about 2.0 m 2 /g.
13. The metal oxide powder of claim 1 , wherein said specific surface area is from about 1.5 m 2 /g to 10.0 m 2 /g.
14. The metal oxide powder of claim 1 , wherein said apparent density is from about 0.5 to about 1.5 g/cc.
15. The metal oxide powder of claim 1 , wherein said apparent density is less than 1.5 g/cc.
16. The metal oxide powder of claim 1 , wherein said powder has a capacitance of from about 20,000 to 300,000 CV/g and a DC leakage of less than about 5.0 nA/CV when formed into a capacitor anode with a press density of 3.5 g/cc and sintered at a temperature of 1450° C. for 10 minutes, and formed at a formation voltage of 30 volts and at a formation temperature of 60° C.
17. The metal oxide powder of claim 16 , wherein said capacitance is from about 62,000 CV/g to about 200,000 CV/g.
18. The metal oxide powder of claim 16 , wherein said capacitance is from about 60,000 CV/g to about 150,000 CV/g.
19. The metal oxide powder of claim 11 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
20. The metal oxide powder of claim 16 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
21. The metal oxide powder of claim 17 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
22. The metal oxide powder of claim 18 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
23. The metal oxide powder of claim 19 , wherein said metal oxide powder consists essentially of said niobium oxide.
24. The metal oxide powder of claim 20 , wherein said metal oxide powder consists essentially of said niobium oxide.
25. The metal oxide powder of claim 21 , wherein said metal oxide powder consists essentially of said niobium oxide.
26. The metal oxide powder of claim 22 , wherein said metal oxide powder consists essentially of said niobium oxide.
27. The metal oxide powder of claim 1 , wherein said metal oxide powder consists essentially of NbO.
28. A method to at least partially reduce a metal oxide powder comprising a valve metal oxide, said method comprising heat treating the valve metal oxide in the presence of a getter material and, in an atmosphere which permits the transfer of oxygen atoms from the valve metal oxide to the getter material, for a sufficient time and temperature to form an oxygen reduced metal oxide having an atomic ratio of metal to oxygen of 1:less than 2.5 and a specific surface area of from about 0.5 to about 10.0 m 2 /g, and having an apparent density of less than about 2.0 g/cc, and wherein said valve metal oxide is tantalum oxide or niobium oxide.
29. The method of claim 28 , wherein the valve metal oxide is a tantalum oxide.
30. The method of claim 28 , wherein the valve metal oxide is a tantalum oxide and the oxygen reduced metal oxide is a tantalum suboxide.
31. The method of claim 28 , wherein the oxygen reduced metal oxide has a micro-porous structure.
32. The method of claim 28 , wherein the oxygen reduced metal oxide has a pore volume of about 50%.
33. The method of claim 28 , wherein said atmosphere is a hydrogen atmosphere that is present in an amount of about 10 Torr to about 2000 Torr.
34. The method of claim 28 , wherein the getter material comprises tantalum hydride particles.
35. The method of claim 28 , wherein the getter material comprises capacitor grade tantalum.
36. The method of claim 28 , wherein the getter material is 14/40 mesh tantalum hydride particles.
37. The method of claim 28 , wherein said atmosphere is a hydrogen atmosphere.
38. The method of claim 28 , wherein said heat treating is at a temperature of from about 1000° C. to about 1300° C. and for about 10 to about 90 minutes.
39. The method of claim 28 , wherein said getter material is tantalum.
40. The method of claim 28 , wherein said valve metal oxide powder has a mesh size of from about 60/100 to about 100/325 mesh.
41. The method of claim 28 , wherein said valve metal oxide powder has a mesh size of from about 60/100 to about 200/325 mesh.
42. The method of claim 28 , wherein said valve metal oxide powder has a mesh size of from about −40 to about −325 mesh.
43. The method of claim 28 , further comprising calcining said valve metal oxide prior to said heat treating.
44. The method of claim 28 , further comprising a pre-heat treatment of said valve metal oxide prior to said heat treating to create controlled porosity in said valve metal oxide.
45. The metal oxide powder of claim 40 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
46. The metal oxide powder of claim 41 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
47. The metal oxide powder of claim 42 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
48. The method of claim 43 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
49. The method of claim 44 , wherein said valve metal oxide is niobium oxide and said ratio is 1:less than 1.5.
50. The metal oxide powder of claim 45 , wherein said metal oxide powder consists essentially of said niobium oxide.
51. The metal oxide powder of claim 46 , wherein said metal oxide powder consists essentially of said niobium oxide.
52. The metal oxide powder of claim 47 , wherein said metal oxide powder consists essentially of said niobium oxide.
53. The method of claim 48 , wherein said metal oxide powder consists essentially of said niobium oxide.
54. The method of claim 49 , wherein said metal oxide powder consists essentially of said niobium oxide.