Tantalum powders and methods of producing same
View Patent ↗Methods of forming tantalum powders and other valve metal powders are described. The method involves high impact milling a starting powder in a fluid medium and optionally a milling media using a high energy mill. The methods of the present invention have the ability to reduce DC leakage and/or increase capacitance capabilities of valve metal powders when formed into capacitor anodes. The methods of present invention further reduce the milling time necessary to form high surface area valve metal powders and leads to reducing contaminant levels in the valve metal powders. The process is particularly well-suited for forming metal flakes, such as tantalum or niobium flakes, of high purity.
1. A tantalum powder, wherein said tantalum powder has a BET surface area of at least 1.5 m 2 /g, and wherein when said tantalum powder is formed into an electrolytic capacitor anode, said anode has a capacitance of at least about 190,000 CV/g, when formed at a V f of 20 V and sintered at 1400° C. for 10 minutes.
2. The tantalum powder of claim 1 , wherein said tantalum powder is flaked, nodular, angular, or combinations thereof.
3. The tantalum powder of claim 1 , wherein said anode has a capacitance of from about 190,000 to about 285,000 CV/g.
4. A capacitor anode comprising the tantalum powder of claim 3 .
5. The capacitor anode of claim 4 , wherein said tantalum powder is sintered at a temperature of from about 1200 to about 1750° C.
6. The capacitor anode of claim 4 , wherein said anode has a DC leakage of less than about 5.0 na/CV.
7. The capacitor anode of claim 4 , wherein said anode has a DC leakage of from about 0.5 to about 2.0 na/CV.
8. The tantalum powder of claim 1 , wherein said tantalum powder has a BET surface area of from about 1.5 to about 8 m 2 /g.
9. A capacitor anode comprising the tantalum powder of claim 8 .
10. The capacitor anode of claim 9 , wherein said tantalum powder is sintered at a temperature of from about 1200 to about 1750° C.
11. The capacitor anode of claim 9 , wherein said anode has a DC leakage of less than about 5.0 na/CV.
12. The capacitor anode of claim 9 , wherein said anode has a DC leakage of from about 0.5 to about 2.0 na/CV.
13. The tantalum powder of claim 1 , wherein said tantalum powder has a BET surface area of from about 1.7 to about 5 m 2 /g.
14. A capacitor anode comprising the tantalum powder of claim 13 .
15. The capacitor anode of claim 14 , wherein said tantalum powder is sintered at a temperature of from about 1200 to about 1750° C.
16. The capacitor anode of claim 14 , wherein said anode has a DC leakage of less than about 5.0 na/CV.
17. The capacitor anode of claim 14 , wherein said anode has a DC leakage of from about 0.5 to about 2.0 na/CV.
18. The tantalum powder of claim 1 , wherein said tantalum powder has a BET surface area of at least 5 m 2 /g, and wherein said anode has a capacitance of from about 200,000 to about 285,000 CV/g.
19. A capacitor anode comprising the tantalum powder of claim 1 .
20. The capacitor anode of claim 19 , wherein said tantalum powder is sintered at a temperature of from about 1200 to about 1750° C.
21. The capacitor anode of claim 19 , wherein said anode has a DC leakage of less than about 5.0 na/CV.
22. The capacitor anode of claim 19 , wherein said anode has a DC leakage of from about 0.5 to about 2 na/CV.