Metal/metal oxide sensor apparatus and methods regarding same

• US 20020180609A1
• Filed: 05/17/2002
• Published: 12/05/2002
• Est. Priority Date: 05/18/2001
• Status: Abandoned Application

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Zhang, Zhong, Ding, Kang, Seyfried, W.E. Jr.
• Application Number:
  US10/150,734
• Publication Number:
  US 20020180609A1
• Time in Patent Office: Days
• US Class Current: 340/633
• CPC Class Codes: G01N 27/302 pH sensitive, e.g. quinhydron, antimony or hydrogen electrodes ion selective electrodes G01N27/333, glass electrodes G01N27/36
• CPC Class Codes: G01N 27/333 Ion-selective electrodes or membranes glass electrodes G01N27/36
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence

Abstract

Various pH sensor apparatus, and methods of providing such apparatus, include using a hydrogen ion (H⁺) sensitive element formed of a corrosion-resistant metal, such as titanium or zirconium. The pH sensitive element makes use of a discontinuous metal oxide layer, e.g., titanium dioxide, formed on a surface of the metal hydrogen ion (H⁺) sensitive element (e.g., titanium wire core element). Preferably, the discontinuous metal oxide layer is formed by thermal treatment in the presence of an oxygen containing media. The pH sensor apparatus may be used with any of a range of standard reference electrodes for providing the pH measurement. Further, a pH sensor apparatus can be used as a reference electrode with a hydrogen sensing electrode, e.g., a fine gold wire, for measuring dissolved hydrogen (H₂) concentrations.

Claims

1. A method for use in providing an electrochemical pH sensing apparatus, the method comprising:

providing an electrically conductive electrode element, wherein the conductive electrode element comprises a surface, wherein at least the surface of the conductive electrode element comprises titanium (Ti); and

oxidizing at least a portion of the surface of the conductive electrode element resulting in the formation of a discontinuous titanium oxide (TiO_x) layer, wherein oxidizing the at least a portion of the surface of the conductive electrode element comprises thermally treating the at least a portion of the surface of the conductive electrode element in the presence of at least one oxygen containing media.

2. The method of claim 1, wherein oxidizing the at least a portion of the surface of the conductive electrode element comprises thermally treating the surface of the conductive electrode element at a temperature in the range of about 300 degrees centigrade to about 880 degrees centigrade.

3. The method of claim 1, wherein oxidizing the at least a portion of the surface of the conductive electrode element comprises thermally treating the surface of the conductive electrode element in the presence of at least one liquid oxygen containing media.

4. The method of claim 3, wherein oxidizing the at least a portion of the surface of the conductive electrode element comprises thermally treating the surface of the conductive electrode element in the presence of at least one liquid alkali element carbonate or peroxide.

5. The method of claim 4, wherein oxidizing the at least a portion of the surface of the conductive electrode element comprises thermally treating the surface of the conductive electrode element in the presence of at least one liquid alkali element carbonate or peroxide selected from the group consisting essentially of Na₂CO₃, Li₂CO₃, and Na₂O₃.

6. The method of claim 1, wherein oxidizing the at least a portion of the surface of the conductive electrode element comprises thermally treating the surface of the conductive electrode element in the presence of at least one oxygen containing media for a time period less than about 2 hours.

7. The method of claim 1, wherein the discontinuous titanium oxide (TiO_x) layer is formed such that less than 10 percent of the surface of the conductive electrode element is exposed.

8. The method of claim 1, wherein the conductive electrode element comprises a titanium wire, and further wherein oxidizing the at least a portion of the surface of the conductive electrode element comprises oxidizing the titanium wire resulting in the formation of the discontinuous titanium oxide (TiO_x) layer on a surface of the wire.

9. The method of claim 8, wherein oxidizing the at least a portion of the surface of the conductive electrode element comprises thermally treating a surface of the titanium wire at a temperature in the range of 500 degrees centigrade to 880 degrees centigrade in the presence of at least one oxygen containing media selected from a group consisting essentially of an alkali element carbonate or peroxide for a time period less than 2 hours.

10. The method of claim 8, wherein the method further comprises:

electrically insulating the oxidized titanium wire resulting in an insulated portion of the oxidized titanium wire and a sensing portion at a distal end of the oxidized titanium wire; and

providing a conductive support housing about at least a portion of the insulated portion of the oxidized titanium wire.

11. A method for use in providing an electrochemical pH sensing apparatus, the method comprising:

providing an electrically conductive elongated wire element comprising a surface extending from a first end to a second distal end thereof, wherein at least the surface of the conductive elongated wire element comprises a metal (M);

forming a discontinuous metal oxide (M_xO_y) layer on at least a portion of the surface proximate the second distal end of the conductive elongated wire element;

providing an insulating layer on at least a portion of the conductive elongated wire element resulting in an insulated portion of the conductive elongated wire element and a sensing portion at the second distal end of the conductive elongated wire element, wherein the sensing portion comprises exposed metal through the discontinuous metal oxide layer; and

providing a conductive support housing about at least a portion of the insulated portion.

12. The method of claim 11, wherein forming a discontinuous metal oxide (M_xO_y) layer on at least a portion of the surface of the conductive elongated wire element comprises electrochemical plating the surface of the conductive elongated wire element with the metal oxide.

13. The method of claim 11, wherein forming a discontinuous metal oxide (M_xO_y) layer on at least a portion of the surface of the conductive elongated wire element comprises thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media.

14. The method of claim 13, wherein thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media comprises thermally treating the surface of the conductive elongated wire element at a temperature in the range of about 300 degrees centigrade to about 880 degrees centigrade.

15. The method of claim 13, wherein thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media comprises thermally treating the surface of the conductive elongated wire element in the presence of at least one liquid alkali element carbonate or peroxide.

16. The method of claim 15, wherein thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media comprises thermally treating the surface of the conductive elongated wire element in the presence of at least one liquid alkali element carbonate or peroxide selected from the group consisting essentially of Na₂CO₃, Li₂CO₃, and Na₂O₃.

17. The method of claim 13, thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media comprises thermally treating the surface of the conductive support element in the presence of at least one oxygen containing media for a time period less than 2 hours.

18. The method of claim 11, wherein forming a discontinuous metal oxide layer on at least a portion of the surface of the conductive elongated wire element comprises forming a discontinuous metal oxide layer such that less than 10 percent of the surface of the conductive elongated wire element is exposed.

19. The method of claim 11, wherein the surface of the conductive elongated wire element comprises at least one of titanium and zirconium.

20. The method of claim 19, wherein the surface of the conductive elongated wire element comprises titanium and the discontinuous metal oxide layer comprises titanium dioxide.

21. The method of claim 11, wherein the conductive elongated wire element comprises a titanium wire.

22. A method for use in providing an electrochemical hydrogen (H₂) sensing apparatus, the method comprising:

providing an electrically conductive elongated wire element comprising a surface extending from a first end to a second end thereof, wherein at least the surface of the conductive elongated wire element comprises a metal (M);

forming a discontinuous metal oxide (M_xO_y) layer on at least a portion of the surface proximate the second end of the conductive elongated wire element, wherein at least a portion of the electrically conductive elongated wire element proximate the second end having the discontinuous metal oxide layer formed thereon is used to provide a reference sensing portion;

providing a conductive layer adjacent to the conductive elongated wire element from the first end to the second end thereof but isolated from the conductive elongate wire element by a first insulating layer, wherein the conductive layer comprises a conductive material proximate at least the second end to provide a hydrogen sensing portion;

providing a second insulating layer over at least the conductive layer such that the reference sensing portion and the hydrogen sensing portion at the second end are exposed; and

providing a conductive support housing about at least a portion of the second insulating layer.

23. The method of claim 22, wherein the conductive material comprises gold.

24. The method of claim 22, wherein the metal (M) comprises titanium.

25. The method of claim 22, wherein forming a discontinuous metal oxide (M_xO_y) layer on at least a portion of the surface of the conductive elongated wire element comprises electrochemical plating the surface of the conductive elongated wire element.

26. The method of claim 22, wherein forming a discontinuous metal oxide (M_xO_y) layer on at least a portion of the surface of the conductive elongated wire element comprises thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media.

27. The method of claim 26, wherein thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media comprises thermally treating the surface of the conductive elongated wire element at a temperature in the range of 300 degrees centigrade to 880 degrees centigrade.

28. The method of claim 26, wherein thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media comprises thermally treating the surface of the conductive elongated wire element in the presence of at least one liquid oxygen containing media.

29. The method of claim 28, wherein thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media comprises thermally treating the surface of the conductive elongated wire element in the presence of at least one liquid alkali element carbonate or peroxide.

30. The method of claim 26, wherein thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media comprises thermally treating the surface of the conductive elongated wire element in the presence of at least one oxygen containing media for a time period less than 2 hours.

31. The method of claim 22, wherein forming a discontinuous metal oxide layer on at least a portion of the surface of the conductive elongated wire element comprises forming a discontinuous metal oxide layer such that less than 10 percent of the surface of the conductive elongated wire element is exposed.

32. The method of claim 22, wherein the conductive elongated wire element comprises a titanium wire.

33. The method of claim 22, wherein the conductive material comprises gold, and further wherein the metal (M) comprises titanium.

35. The method of claim 34, wherein the conductive material comprises gold.

36. The method of claim 34, wherein the metal core comprises titanium.

37. The method of claim 34, wherein the method further comprises forming the discontinuous metal oxide layer on at least the portion of the surface of the metal core by electrochemical plating the surface of at least a portion of the metal core.

38. The method of claim 34, wherein the method further comprises forming the discontinuous metal oxide layer on at least the portion of the surface of the metal core by thermally treating the surface of the metal core in the presence of at least one oxygen containing media.

39. The method of claim 34, wherein thermally treating the surface of the metal core in the presence of at least one oxygen containing media comprises thermally treating the surface of the metal core in the presence of at least one liquid oxygen containing media.

40. The method of claim 39, wherein thermally treating the surface of the metal core in the presence of at least one oxygen containing media comprises thermally treating the surface of the metal core in the presence of at least one liquid alkali element carbonate or peroxide.

41. The method of claim 34, wherein providing the first conductive portion comprises providing a wire extending along an axis therethrough and a concentric discontinuous metal oxide layer formed on a radial surface of the wire along the axis;

and further wherein providing the second conductive portion comprises providing a concentric layer of conductive material formed radially relative to the axis and separated from the discontinuous metal oxide layer by the isolation material.

42. The method of claim 34, wherein providing the first conductive portion comprises providing a metal core of material from the first end of the elongated electrode assembly to the second end of the elongated electrode assembly with the discontinuous metal oxide layer formed on at least a portion of the surface of the metal core, and further wherein providing the second conductive portion comprises providing a conductive material from the first end of the elongated electrode assembly to the second end of the elongated electrode assembly adjacent to but separated from the metal core and the discontinuous metal oxide layer formed thereon by at least the isolation material.

43. The method of claim 34, wherein the metal core comprises titanium and the conductive material comprises gold.

34. A method of providing an electrochemical hydrogen (H₂) sensing apparatus, the method comprising:

providing an elongated electrode assembly, wherein providing the elongated electrode assembly comprises;

providing a first conductive portion extending from a first end of the elongated electrode assembly to a second end of the elongated electrode assembly, wherein the first conductive portion comprises a metal core having a discontinuous metal oxide layer formed on at least a portion of a surface of the metal core;

providing a second conductive portion extending from the first end of the elongated electrode assembly to the second end of the elongated electrode assembly, wherein the second conductive portion comprises a conductive material for use in sensing hydrogen (H₂); and

providing an isolation material extending from the first end of the elongated electrode assembly to the second end of the elongated electrode assembly electrically isolating the first conductive portion from the second conductive portion; and

providing an insulating material over the elongated electrode assembly resulting in an exposed sensing portion at the second end of the elongated electrode assembly, wherein the exposed sensing portion comprises exposed metal through the discontinuous metal oxide layer of the first conductive portion and exposed conductive material of the second conductive portion; and

providing a conductive support housing about at least a portion of the insulating material.

44. An electrochemical pH sensing apparatus comprising:

an electrically conductive wire core extending between a first end and a second end along an axis, wherein at least a surface of the wire core comprises titanium (Ti);

a discontinuous titanium oxide (TiO_x) layer on at least a portion of the surface of the wire core;

an insulating layer formed relative to the discontinuous titanium oxide layer formed on at least a portion of the wire core so as to provide a sensing portion at the second end of the wire core, wherein the sensing portion comprises exposed titanium through openings in the discontinuous titanium oxide layer; and

a conductive support housing electrically isolated from at least the wire core by the insulating layer.

45. The apparatus of claim 44, wherein the exposed titanium through the discontinuous titanium oxide layer is less than 10 percent.

46. The apparatus of claim 44, wherein the discontinuous titanium oxide layer comprises titanium dioxide.

47. The apparatus of claim 44, wherein the conductive support housing comprises titanium.

49. The apparatus of claim 48, wherein the exposed metal through the discontinuous metal oxide layer is less than 10 percent.

50. The apparatus of claim 48, wherein at least the surface of the wire core comprises at least one of titanium and zirconium.

51. The apparatus of claim 50, wherein the surface of the wire core comprises titanium and the discontinuous metal oxide layer comprises titanium dioxide.

52. The apparatus of claim 48, wherein the discontinuous metal oxide layer, where present, has a thickness of less than 3 micrometers.

48. An electrochemical pH sensing apparatus comprising:

an electrically conductive elongated wire core extending between a first end and a second end along an axis thereof, wherein at least a surface of the wire core comprises a metal (M);

a discontinuous metal oxide (M_xO_y) layer provided on at least a portion of the surface proximate the second end of the wire core;

an insulating layer provided on at least a portion of the discontinuous metal oxide layer resulting in an insulated portion of the wire core and also a sensing portion at the second end of the wire core, wherein the sensing portion comprises exposed metal through openings in the discontinuous metal oxide layer; and

a conductive support housing about at least a portion of the insulated portion.

53. An electrochemical hydrogen (H₂) sensing apparatus comprising:

an electrically conductive elongated wire core element extending between a first and second end of the apparatus along an axis thereof, wherein at least a surface of the wire core element comprises a metal (M);

a discontinuous metal oxide (M_xO_y) layer formed on at least a portion of the surface of the wire core element proximate the second end;

a conductive layer extending along the axis, wherein the conductive layer comprises a conductive material for use in sensing hydrogen;

a first insulating layer located to electrically isolate the conductive layer from the conductive elongated wire core element;

a second insulating layer formed over at least a portion of the conductive layer resulting in a sensing portion at the second end of the apparatus, wherein the sensing portion comprises at least a portion of the conductive wire core element having the discontinuous metal oxide layer formed thereon and exposed conductive material; and

a conductive support housing about at least a portion of the second insulating layer.

54. The apparatus of claim 53, wherein the conductive material comprises gold.

55. The apparatus of claim 53, wherein the metal (M) comprises titanium.

56. The apparatus of claim 55, wherein the discontinuous metal oxide layer comprises titanium dioxide.

57. The apparatus of claim 53, wherein the discontinuous metal oxide layer comprises a discontinuous metal oxide layer formed such that less than 10 percent of the surface of the wire core element is exposed through openings in the discontinuous metal oxide layer.

59. The apparatus of claim 58, wherein the conductive material comprises gold.

60. The apparatus of claim 58, wherein the metal core comprises titanium.

61. The apparatus of claim 58, wherein the discontinuous metal oxide layer comprises a discontinuous metal oxide layer formed such that less than 10 percent of the surface of the wire core element is exposed through the openings in the discontinuous metal oxide.

62. The apparatus of claim 58, wherein the first conductive portion comprises a wire extending along an axis of the elongated electrode assembly and a concentric discontinuous metal oxide layer formed on a radial surface of the wire along the axis;

and further wherein the second conductive portion comprises a concentric layer of conductive material formed radially relative to the axis and separated from the discontinuous metal oxide layer by the isolation material.

63. The apparatus of claim 58, wherein the metal core comprises titanium and the conductive material comprises gold.

64. The apparatus of claim 58, wherein the first conductive portion is provided adjacent to but separated from the second conductive portion by at least the isolation material.

58. An electrochemical hydrogen (H₂) sensing apparatus comprising:

an elongated electrode assembly, wherein the elongated electrode assembly comprises;

a first conductive portion extending from a first end of the elongated electrode assembly to a second end of the elongated electrode assembly, wherein the first conductive portion comprises a metal core with a discontinuous metal oxide layer formed on at least a portion of a surface of the metal core;

a second conductive portion extending from the first end of the elongated electrode assembly to the second end of the elongated electrode assembly, wherein the second conductive portion comprises a conductive material for use in sensing hydrogen; and

an isolation material extending from the first end of the elongated electrode assembly to the second end of the elongated electrode assembly electrically isolating the first conductive portion from the second conductive portion; and

an insulating material formed over the elongated electrode assembly resulting in a sensing portion at the first end of the elongated electrode assembly, wherein the sensing portion comprises exposed metal through openings in the discontinuous metal oxide layer of the first conductive portion and exposed conductive material of the second conductive portion; and

a conductive support housing provided about at least a portion of the insulating material.

65. An electrochemical pH sensing electrode apparatus, the apparatus comprising:

an electrically conductive electrode element, wherein the conductive electrode element comprises a surface, wherein at least the surface of the conductive electrode element comprises one of titanium (Ti) and zirconium (Zr); and

a discontinuous oxide layer on at least a portion of the surface of the conductive electrode element, wherein the discontinuous oxide layer comprises one of titanium oxide (TiO_x) and zirconium oxide (ZrO_x), and further wherein openings in the discontinuous oxide layer allow for sensing of hydrogen ions at the surface of the conductive electrode element for use in determining pH of a composition when immersed therein.

66. The apparatus of claim 65, wherein less than 10 percent of the surface of the conductive electrode element is exposed through the openings in the discontinuous oxide layer.

67. The apparatus of claim 65, wherein the conductive electrode element comprises titanium and the discontinuous oxide layer comprises titanium dioxide.

68. The apparatus of claim 65, wherein the apparatus further comprises:

an insulating layer provided on at least a portion of the discontinuous oxide layer resulting in an insulated portion of the conductive electrode element and also a sensing portion, wherein the sensing portion comprises exposed titanium (Ti) or zirconium (Zr) through the openings in the discontinuous oxide layer; and

a conductive support housing about at least a portion of the insulated portion.