Claims
- 1. A non-consumable electrode suitable for use as an anode in the electrolysis of molten salts, produced by the process of:
- (a) forming a first conductive ceramic material to produce a core having a substantially flat working surface and a non-working surface;
- (b) forming a physically adherent coating over said non-working surface of said core, on at least the portion thereof which is to be exposed to the electrolyte bath in the cell, said coating consisting of a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 1.0.times.10.sup.-6 /.degree. C.,
- (2) an essentially matched strinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto; and
- (c) sintering the coated core thus formed to produce a monolithic ceramic electrode having a substantially flat working surface and a non-working surface, said non-working surface having an impervious coating thereon, at least in the portion thereof exposed to the electrolyte bath, of higher resistivity than the core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said electrode is conducted into the electrolyte bath through said flat working surface.
- 2. A non-consumable anode for a Hall-Heroult cell having a molten electrolyte bath at cell operating temperature produced by the process of:
- (a) forming an elongated core having two ends from a first conductive ceramic material;
- (b) forming a physically adherent coating over said core with a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 1.0.times.10.sup.-6 /.degree. C.,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto;
- (c) producing a substantially flat uncoated working surface on only one end of the coated core by removing the coating therefrom; and
- (d) sintering the coated core having a substantially flat uncoated working surface to produce an integral monolithic body with an impervious coating layer, thereby forming a ceramic anode having a substantially flat working surface and a non-working surface, said non-working surface having a coating of higher resistivity than said core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said anode is conducted into said electrolyte bath through said flat working surface.
- 3. A non-consumable anode for a Hall-Heroult cell having a molten electrolyte bath at cell operating temperature produced by the process of:
- (a) isostatically pressing a first conductive ceramic material to produce a core having a substantially flat working surface and a non-working surface;
- (b) isostatically pressing a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 1.0.times.10.sup.-6 /.degree. C.,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto to form a physically adherent coating over said non-working surface of said core, on at least the portion thereof which is to be exposed to the electrolyte bath in the cell; and
- (c) sintering the coated core thus formed to produce a monolithic ceramic anode having a substantially flat working surface and a non-working surface, said non-working surface having an impervious coating thereon, at least in the portion thereof exposed to the electrolyte bath, of higher resistivity than the core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said anode is conducted into the electrolyte bath through said flat working surface.
- 4. A non-consumable anode for a Hall-Heroult cell having a molten electrolyte bath at cell operating temperature manufactured by the process of:
- (a) producing an elongated core having two ends by isostatically pressing a first conductive ceramic material;
- (b) forming a physically adherent coating over said core by isostatically pressing on the surface thereof a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 1.0.times.10.sup.-6 /.degree. C.,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto;
- (c) producing a substantially flat uncoated working surface on only one end of the coated core by removing the coating therefrom; and
- (d) sintering the coated core having a substantially flat uncoated working surface to produce an integral monolithic body with an impervious coating layer, thereby forming a ceramic anode having a substantially flat working surface and a non-working surface, said non-working surface having a coating of higher resistivity than said core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said anode is conducted into said electrolyte bath through said flat working surface.
- 5. A process for producing a non-consumable electrode suitable for use as an anode in the electrolysis of molten salts, which comprises:
- (a) forming an elongated core having two ends from a first conductive ceramic material;
- (b) forming a physically adherent coating over said core with a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 1.0.times.10 .sup.-6 /.degree. C.,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto;
- (c) producing a substantially flat uncoated working surface on only one end of the coated core by removing the coating therefrom; and
- (d) sintering the coated core having a substantially flat uncoated working surface to produce an integral monolithic body with an impervious coating layer, thereby forming a ceramic electrode having a substantially flat working surface and a non-working surface, said non-working surface having a coating of higher resistivity than said core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said electrode is conducted into said electrolyte bath through said flat working surface.
- 6. A non-consumable electrode suitable for use as an anode in the electrolysis of molten salts, produced by the process of:
- (a) forming a first conductive ceramic material to produce a core having a substantially flat working surface and a non-working surface;
- (b) forming a physically adherent coating over said non-working surface of said core, on at least the portion thereof which is to be exposed to the electrolyte bath in the cell, said coating consisting of a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 0.5%,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto; and
- (c) sintering the coated core thus formed to produce a monolithic ceramic electrode having a substantially flat working surface and a non-working surface, said non-working surface having an impervious coating thereon, at least in the portion thereof exposed to the electrolyte bath, of higher resistivity than the core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said electrode is conducted into the electrolyte bath through said flat working surface.
- 7. The electrode of claim 6 wherein the core consists of 98.0-98.5 wt. % SnO.sub.2, 0.1-0.5 wt. % CuO and 1.0-1.5 wt. % Sb.sub.2 O.sub.3.
- 8. The electrode of claim 7 wherein the core consists of 98.5 wt. % SnO.sub.2, 0.5 wt. % CuO and 1.0 wt. % Sb.sub.2 O.sub.3.
- 9. The electrode of claims 6, 7 or 8 wherein the coating consists of an Fe.sub.2 O.sub.3 -doped SnO.sub.2 composition.
- 10. The electrode of claim 9 wherein the coating consists of 98.00-99.75 wt. % SnO.sub.2 and 0.25-2.00 wt. % Fe.sub.2 O.sub.3.
- 11. A non-consumable anode for a Hall-Heroult cell having a molten electrolyte bath at cell operating temperature produced by the process of:
- (a) forming an elongated core having two ends from a first conductive ceramic material;
- (b) forming a physically adherent coating over said core with a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 0.5%,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto;
- (c) producing a substantially flat uncoated working surface on only one end of the coated core by removing the coating therefrom; and
- (d) sintering the coated core having a substantially flat uncoated working surface to produce an integral monolithic body with an impervious coating layer, thereby forming a ceramic anode having a substantially flat working surface and a non-working surface, said non-working surface having a coating of higher resistivity than said core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said anode is conducted into said electrolyte bath through said flat working surface.
- 12. The anode of claim 11 wherein the core consists of 98.0-98.5 wt. % SnO.sub.2, 0.1-0.5 wt. % CuO and 1.0-1.5 wt. % Sb.sub.2 O.sub.3.
- 13. The anode of claim 12 wherein the core consists of 98.5 wt. % SnO.sub.2, 0.5 wt. % CuO and 1.0 wt. % Sb.sub.2 O.sub.3.
- 14. The anode of claims 11, 12 or 13 wherein the coating consists of an Fe.sub.2 O.sub.3 -doped SnO.sub.2 composition.
- 15. The anode of claim 14 wherein the coating consists of 98.00-99.75 wt. % SnO.sub.2 and 0.25-2.00 wt. % Fe.sub.2 O.sub.3.
- 16. A non-consumable anode for a Hall-Heroult cell having a molten electrolyte bath at cell operating temperature produced by the process of:
- (a) isostatically pressing a first conductive ceramic material to produce a core having a substantially flat working surface and a non-working surface;
- (b) isostatically pressing a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 0.5%,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto to form a physically adherent coating over said non-working surface of said core, on at least the portion thereof which is to be exposed to the electrolyte bath in the cell; and
- (c) sintering the coated core thus formed to produce a monolithic ceramic anode having a substantially flat working surface and a non-working surface, said non-working surface having an impervious coating thereon, at least in the portion thereof exposed to the electrolyte bath, of higher resistivity than the core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said anode is conducted into the electrolyte bath through said flat working surface.
- 17. The anode of claim 16 wherein the core consists of 98.0-98.5 wt. % SnO.sub.2, 0.1-0.5 wt. % CuO and 1.0-1.5 wt. % Sb.sub.2 O.sub.3.
- 18. The anode of claim 17 wherein the core consists of 98.5 wt. % SnO.sub.2, 0.5 wt. % CuO and 1.0 wt. % Sb.sub.2 O.sub.3.
- 19. The anode of claims 16, 17 or 18 wherein the coating consists of an Fe.sub.2 O.sub.3 -doped SnO.sub.2 composition.
- 20. The anode of claim 19 wherein the coating consists of 98.00-99.75 wt. % SnO.sub.2 and 0.25-2.00 wt. % Fe.sub.2 O.sub.3.
- 21. A non-consumable anode for a Hall-Heroult cell having a molten electrolyte bath at cell operating temperature manufactured by the process of:
- (a) producing an elongated core having two ends by isostatically pressing a first conductive ceramic material;
- (b) forming a physically adherent coating over said core by isostatically pressing on the surface thereof a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 0.5%,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto;
- (c) producing a substantially flat uncoated working surface on only one end of the coated core by removing the coating therefrom; and
- (d) sintering the coated core having a substantially flat uncoated working surface to produce an integral monolithic body with an impervious coating layer, thereby forming a ceramic anode having a substantially flat working surface and a non-working surface, said non-working surface having a coating of higher resistivity than said core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said anode is conducted into said electrolyte bath through said flat working surface.
- 22. The anode of claim 21 wherein the core consists of 98.0-98.5 wt. % SnO.sub.2, 0.1-0.5 wt. % CuO and 1.0-1.5 wt. % Sb.sub.2 O.sub.3.
- 23. The anode of claim 22 wherein the core consists of 98.5 wt. % SnO.sub.2, 0.5 wt. % CuO and 1.0 wt. % Sb.sub.2 O.sub.3.
- 24. The anode of claims 21, 22 or 23 wherein the coating consists of an Fe.sub.2 O.sub.3 -doped SnO.sub.2 composition.
- 25. The anode of claim 24 wherein the coating consists of 98.00-99.75 wt. % SnO.sub.2 and 0.25-2.00 wt. % Fe.sub.2 O.sub.3.
- 26. A non-consumable anode for a Hall-Heroult cell having a molten electrolyte bath at cell operating temperature produced by the process of:
- (a) isostatically pressing a first conductive ceramic material consisting of a mixture of 98.5 wt. % SnO.sub.2, 0.5 wt. % CuO and 1.0 wt. % Sb.sub.2 O.sub.3 to produce a core having a substantially flat working surface and a non-working surface;
- (b) isostatically pressing a second conductive ceramic material consisting of 98.0 wt. % SnO.sub.2 and 2.0 wt. % Fe.sub.2 O.sub.3 to form a physically adherent coating over said non-working surface of said core on at least the portion thereof which is to be exposed to the electrolyte bath in the cell; and
- (c) sintering the coated core thus formed to produce a monolithic ceramic anode having a substantially flat working surface and a non-working surface, said non-working surface having an impervious coating thereon, at least in the portion thereof exposed to the electrolyte bath, of higher resistivity than the core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said anode is conducted into the electrolyte bath through said flat working surface.
- 27. A process for producing a non-consumable electrode suitable for use as an anode in the electrolysis of molten salts, which comprises:
- (a) forming an elongated core having two ends from a first conductive ceramic material;
- (b) forming a physically adherent coating over said core with a second conductive ceramic material having, as compared to said first conductive ceramic material,
- (1) a coefficient of thermal expansion differing by no more than about 0.5%,
- (2) an essentially matched shrinkage during sintering,
- (3) a higher electrical resistivity, and capable of being chemical diffusion bonded thereto;
- (c) producing a sustantially flat uncoated working surface on only one end of the coated core by removing the coating therefrom; and
- (d) sintering the coated core having a substantially flat uncoated working surface to produce an integral monolithic body with an impervious coating layer, thereby forming a ceramic electrode having a substantially flat working surface and a non-working surface, said non-working surface having a coating of higher resistivity than said core and chemical diffusion bonded thereto, whereby substantially all of the current applied to said electrode is conducted into said electrolyte bath through said flat working surface.
- 28. The process of claim 27 wherein the electrode core consists of 98.0-98.5 wt. % SnO.sub.2, 0.1-0.5 wt. % CuO and 1.0-1.5 wt. % Sb.sub.2 O.sub.3.
- 29. The process of claim 28 wherein the electrode core consists of 98.5 wt. % SnO.sub.2, 0.5 wt. % CuO and 1.0 wt. % Sb.sub.2 O.sub.3.
- 30. The process of claims 27, 28 or 29 wherein the electrode coating consists of an Fe.sub.2 O.sub.3 -doped SnO.sub.2 composition.
- 31. The process of claim 30 wherein the electrode coating consists of 98.00-99.75 wt. % SnO.sub.2 and 0.25-2.00 wt. % Fe.sub.2 O.sub.3.
DESCRIPTION
This application is a continuation-in-part of application Ser. No. 241,535, filed Mar. 9, 1981, abandoned.
US Referenced Citations (12)
Non-Patent Literature Citations (2)
Entry |
Belyaev & Studentsov, Legkie Metal 6, No. 3, 17-24 (1937), (C.A. 31 [1937], 8384). |
Belyaev, Legkie Metal 7, No. 1, 7-20 (1938), (C.A. 32 [1938], 6553). |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
241535 |
Mar 1981 |
|