# US 5,211,741 A · Flaked tantalum powder

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- Number: US 5,211,741 A
- Document ID: US5211741A
- Status: Granted
- Kind: A
- Application number: 07/738,852
- Filed: 1991-07-31
- Granted: 1993-05-18
- Earliest claimed: 1987-11-30
- Assignees: Cabot Corporation
- Inventors: James A. Fife
- Web page: https://patentgrep.com/patent/US5211741A

## CPC

- H01G 9/0525: {Powder therefor}
- C22C 1/045: {Alloys based on refractory metals}
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

The invention relates to flaked tantalum powders suitable for use in electrodes and capacitors. The tantalum powders have a mean particle size of about 2 to 55 micrometers, a BET surface area greater than about 0.5 m.sup.2 /g, and an aspect ratio between about 2 and 50. The powders are in the form of fractured flakes, which contain substantially no tapering of their peripheral edges.

## Claims

### Claim 1

A flaked tantalum powder comprised of reduced size flakes without substantial tapering of the peripheral edges thereof and having a mean particle size in the range of about 2 to about 55 micrometers and a BET surface area greater than about 0.5 m.sup.2 /g; and as aspect ratio between about 2 and about 50.

### Claim 2 (depends on 1)

The flaked tantalum powder of claim 1 wherein the tantalum is chemically reduced tantalum.

### Claim 3 (depends on 2)

The flaked tantalum powder of claim 2, wherein the mean particle size of the reduced size flake is less than about 45 micrometers.

### Claim 4 (depends on 1)

The flaked tantalum powder of claim 1 wherein the tantalum is ingot derived tantalum and said flakes have a BET surface area greater than about 0.7 m.sup.2 /g.

### Claim 5 (depends on 1)

The flaked tantalum powder of claim 1 wherein the mean particle size of the reduced size flake is less than about 45 micrometers.

### Claim 6 (depends on 1)

An electrode having low leakage and a high breakdown voltage prepared with the powder of claim 1.

### Claim 7 (depends on 1)

A flaked tantalum powder of claim 1, wherein the BET surface area in the range of about 0.5 to about 5.0 m.sup.2 /g.

### Claim 8 (depends on 1, 7)

The flaked tantalum powder of claim 1 or 7, wherein the mean particle size of the reduced size flake is in the range of about 5 to about 20 micrometers.

### Claim 9 (depends on 1, 7)

A flaked tantalum powder of claim 1 or 7, wherein the mean particle size is in the range of about 5 to 20 micrometers.

### Claim 10 (depends on 9)

A low density pellet prepared from the reduced size flake of claim 9.

### Claim 11 (depends on 10)

A capacitor prepared from the pellet of claim 10.

### Claim 12 (depends on 7)

The flaked tantalum powder of claim 7 wherein the BET surface area of the reduced size flake is in the range of about 0.5 to about 1.5 m.sup.2 /g.

### Claim 13 (depends on 12)

The flaked tantalum powder of claim 12 wherein the aspect ratio (D/T) of the reduced size flake is in the range of about 5 to about 20.

### Claim 14 (depends on 7)

The flaked tantalum powder of claim 7 wherein the tantalum is chemically reduced tantalum.

### Claim 15 (depends on 14)

The flaked tantalum powder of claim 14, wherein the mean particle size of the reduced size flake is less than about 45 micrometers.

### Claim 16 (depends on 7)

The flaked tantalum powder of claim 7 wherein the tantalum is ingot derived tantalum.

### Claim 17 (depends on 7)

The flaked tantalum powder of claim 7 wherein the mean particle size of the reduced size flake is less than about 45 micrometers.

### Claim 18 (depends on 7)

An electrode having low leakage and a high breakdown voltage prepared with the powder of claim 7.