Composite wire microelectrode and method of making same

• US 5,580,431 A
• Filed: 07/20/1995
• Issued: 12/03/1996
• Est. Priority Date: 07/20/1995
• Status: Expired due to Fees

• Current Assignee: Brookhaven Science Associates, LLC (Government of the United States of America)
• Original Assignee: Associated Universities, Inc.
• Inventors: Aldykiewicz, Antonio J. Jr., Isaacs, Hugh S.
• Primary Examiner(s): Bell, Bruce F.
• Application Number:
  US08/507,591
• Time in Patent Office: 502 Days
• Field of Search: 204/403, 204/416, 204/290 R, 204/290 F, 204/404, 128/642, 420/417, 420/422, 420/425, 420/426, 420/427
• US Class Current: 205/656
• CPC Class Codes: G01N 17/02 Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement

Abstract

A composite wire microelectrode for making electro-chemical measurements, and method of making same. The microelectrode includes an inner conductive sensing wire and an outer tube that is oxidized to form a dielectric, self-healing oxide layer around the sensing wire.

Claims

1. A composite wire microelectrode for making electro-chemical or related measurements, comprising;

an inner electrically conductive metal sensing wire and,

an outer tube formed of a metal or metal alloy taken from the group consisting of tantalum, niobium, zirconium, hafnium and titanium;

said tube being mechanically compressed around a covered portion of the sensing wire to form a rugged support for it, and the outer surface of said tube being oxidized to form a dielectric layer that insulates said covered portion of the sensing wire.

2. A microelectrode as defined in claim 1 wherein said tube comprises a swaged portion compressed down onto the sensing wire.

3. A microelectrode as defined in claim 2 wherein said tube swaged portion comprises rolled portions that compress set portions of its axial length onto the sensing wire.

4. A microelectrode as defined in claim 3 wherein said set portions comprise substantially the full longitudinal axial length of said tube.

5. A microelectrode as defined in claim 1 wherein the composite wire microelectrode comprises a reduced drawn down cross-sectional diameter of the inner sensing wire to a set diameter in the range of 0.5 to 10 μ

m.

6. A microelectrode as defined in claim 1 wherein said dielectric layer comprises an electrochemically formed oxide formed from reaction with one or more electrolytes such as borates, organic acids, sulfates, nitrates, alkalies or mineral acids.

7. A microelectrode as defined in claim 1 wherein one end of said outer tube comprises a conically tapered section with an end of the sensing wire exposed at the apex of said conical section.

8. A microelectrode as defined in claim 7 made by a method wherein said one end of the tube is dissolved by immersing it in an acid or in a solution of acid and hydrogen peroxide, thereby to form said conically tapered section.

9. A method as defined in claim 8 wherein said acid is hydrofluoric acid or nitric acid.

10. A microelectrode as defined in claim 1 made by a method wherein said outer tube is dissolved by immersing it in an electrolyte and applying an electric voltage to the tube across the electrolyte.

11. A method as defined in claim 10 wherein said applied voltage is either ac or dc, and wherein said electrolyte is a fluoride.