Inert electrode connection

• US 4,500,406 A
• Filed: 12/12/1983
• Issued: 02/19/1985
• Est. Priority Date: 12/12/1983
• Status: Expired due to Fees

• Current Assignee: Aluminum Company of Egypt
• Original Assignee: Aluminum Company of Egypt
• Inventors: Ray, Siba P., Woods, Robert W., Weyand, John D., DeYoung, David H.
• Primary Examiner(s): Niebling, John F.
• Application Number:
  US06/560,602
• Time in Patent Office: 435 Days
• Field of Search: 204/279, 204/280, 204/292, 204/293, 419/6, 419/48, 419/57, 428/548, 428/551, 428/565
• US Class Current: 204/293
• CPC Class Codes: B29C 2043/3628 moving inside a barrel or container like sleeve
• CPC Class Codes: C25C 3/12 Anodes
• CPC Class Codes: C25C 7/025 used in cells for the electrolysis of melts
• CPC Class Codes: Y10T 428/12021 having composition or density gradient or differential porosity

Abstract

An inert electrode connection is disclosed wherein a layer of inert electrode material is bonded to a layer of conductive material by providing at least one intermediate layer of material therebetween comprising a predetermined ratio of inert material to conductive material. In a preferred embodiment, the connection is formed by placing in a die a layer of powdered inert material, at least one layer of a mixture of powdered inert material and conductive material, and a layer of powdered conductive material. The connection is then formed by pressing the material at 15,000-20,000 psi to form a powder compact and then densifying the powder compact in an inert or reducing atmosphere at a temperature of 1200°-1500° C.

Claims

1. An inert electrode suitable for use in an electrolytic reduction cell for the production of aluminum characterized by good electrical conductivity and substantial inertness to the electrolyte in the molten salt bath comprising an interwoven network of a nickel-iron alloy and at least one nickel-iron oxide and having an electrical-mechanical connection thereto capable of carrying electrical current between said electrode and a source of current;

said electrical-mechanical connection comprising a first portion consisting essentially of said inert electrode material, a second portion comprising a conductive metal material selected from the class consisting of nickel and nickel-iron alloys, and at least one region therebetween comprising an electrically conductive gradient of said inert electrode material and said conductive metal material whereby a continuous conductive path of nickel/nickel-iron material will extend from said conductive metal into said molten salt bath while said oxides dispersed throughout the inert electrode will provide sufficient inertness to protect the conductive portions.

2. The inert electrode of claim 1 wherein said gradient, consisting of one or more layers containing a mixture of said interwoven network of nickel-iron alloy and one or more nickel-iron oxides and said conductive metal in various ratios, is formed by bonding the layers together using pressure and heat.

3. The connection of claim 1 wherein said gradient is characterized by the substantial absence of laminations between the layers.

4. The connection of claim 3 wherein said layers initially comprise particulate material to aid in the formation of said gradient.

5. The connection of claim 4 wherein said gradient is formed by pressing said particulate layers together and densifying the resulting compact at an elevated temperature.

6. The connection of claim 5 wherein said compact is formed by pressing together said layers at a pressure of from 15,000 to 20,000 psi.

7. The connection of claim 5 wherein said compact is densified at a temperature of from 1200°

to 1500°

C.

8. The connection of claim 7 wherein said compact is densified in a non-oxidizing atmosphere.

9. The connection of claim 8 wherein said non-oxidizing atmosphere comprises an inert atmosphere.

10. A method of making an inert electrode conductive connection between a conductive member and an inert electrode suitable for use in an electrolytic reduction cell containing a molten salt bath for the production of aluminum, said method comprising:

(a) forming a powder compact under pressure containing the following layers;

(1) a first inert electrode layer consisting of particles containing an interwoven matrix of a nickel-iron alloy and one or more nickel-iron oxides characterized by good electrical conductivity and substantial inertness to the electrolyte in the molten salt bath;

(2) a conductive metal layer consisting of particles of a metal selected from the class consisting of nickel and nickel-iron alloys; and

(3) at least one conductive layer of a mixture of particles of said inert electrode material and said conductive metal; and

(b) heating the layers to from a gradient between said inert electrode layer and said conductive metal layer.

11. The method of claim 10 wherein said powder compact is pressed at a pressure of from 15,000 to 20,000 psi.

12. The method of claim 11 wherein said powder compact is heated to a temperature of from 1200°

to 1500°

C. to densify said compact.

13. The method of claim 12 wherein said powder compact is densified in a non-oxidizing atmosphere.

14. The method of claim 13 wherein said non-oxidizing atmosphere comprises an inert atmosphere.

15. The method of claim 14 wherein said conductive layer comprises nickel powder having a particle size range of 10 to 100 μ

m and said inert electrode layer comprises a mixture containing powdered oxides of nickel and iron, said mixture having a particle size range of 1/2 to 50 μ

m.

16. The method of claim 15 wherein an intermediate layer having a ratio of 50 wt.% particulate nickel powder and 50 wt.% particulate inert electrode material comprising oxides of iron and nickel is placed between said nickel powder layer and said inert electrode layer.

17. The method of claim 16 wherein a plurality of intermediate layers are placed between said nickel layer and said inert electrode layer, and the ratios of the mixtures in said intermediate layers are varied to assist in forming the gradient between the nickel layer and the inert electrode layer.