Claims
- 1. A method of forming a coating of a precious metal on a ceramic substrate, the method comprising a step of forming a ceramic substrate having pores at a surface of the substrate; a step of forming a solution of a salt of a first metal in an organic solvent which wets the ceramic; a step of forming nucleation sites on the surface of the substrate, said step of forming nucleation sites including wicking the solution into the pores at the surface of the substrate; and thereafter an electroless plating step of plating the precious metal onto the surface from an aqueous plating bath.
- 2. The method of claim 1 wherein the organic solvent is volatile.
- 3. The method of claim 1 wherein the organic solvent is acetone.
- 4. The method of claim 1 wherein the first metal and the precious metal are the same.
- 5. The method of claim 1 including a step, after wicking the solution into the pores at the surface of the substrate, of heating the substrate to drive off the solvent and reduce the salt to a 0.01 to 0.5 micron layer of the first metal with numerous unplated areas.
- 6. The method of claim 1 wherein the substrate is a body of an automotive lambda oxygen sensor.
- 7. The method of claim 6 the method further comprises forming an elongate body formed of a solid electrolyte compact, thereafter a step of drilling an axial cavity in the body, and thereafter a step of firing the body to densify it.
- 8. The method of claim 7 wherein the body is formed by uniaxially compressing a zirconia powder into a thimble having a tapered bore, and then drilling out the tapered bore to form a substantially cylindrical cavity.
- 9. The method of claim 1 wherein wicking the solution into the pores of the body comprises dipping the body in a solution of platinum salt in a volatile solvent.
- 10. The method of claim 9 wherein the platinum salt is hexachloroplatinic acid.
- 11. A method of forming a solid electrolyte cell portion of an automotive lamda oxygen sensor, the method comprising forming a solid thimble-shaped ceramic body, depositing a porous layer on an outer surface of the body, activating the porous layer on the first surface of the body to form a plurality of growth points for a conductive layer on the first surface, growing a first electrode by electroless plating of a conductive layer on the activated porous layer on the outer surface of the body, and forming a second electrode on an inner surface of the body.
- 12. The method of claim 11 wherein the body is formed by uniaxially compressing a zirconia powder into a thimble.
- 13. The method of claim 11 wherein activating the porous layer on the first surface comprises wicking a metal salt carried by a volatile liquid into the porous layer.
- 14. The method of claim 11 wherein growing a first electrode comprises immersion of the porous layer on the first surface in an unstable solution of a salt of a metal.
- 15. The method of claim 14 wherein the unstable solution further comprises a reducing agent
- 16. The method of claim 15 wherein the reducing agent comprises hydrazine.
- 17. The method of claim 15 wherein the salt is hexachloroplatinic acid.
- 18. The method of claim 15 wherein the solution comprises a platinum salt in a volatile solvent.
- 19. The method of claim 18 wherein the volatile solvent comprises acetone.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a division of copending application Ser. No. 10/044,704, filed Nov. 9, 2001, which is a division of application Ser. No. 08/953,864, filed Oct. 16, 1997, including continued prosecution application filed May 10, 2000, now U.S. Pat. No. 6,315,880.
Divisions (2)
|
Number |
Date |
Country |
Parent |
10044704 |
Nov 2001 |
US |
Child |
10789847 |
Feb 2004 |
US |
Parent |
08953864 |
Oct 1997 |
US |
Child |
10044704 |
Nov 2001 |
US |