Patent EA-004763-B1 (EA)
Title: Method for removing substance from solid metal or semi-metal compounds
Inventor: FRAY DEREK JOHN
IPC: C23C8/00
Filed: 1999-06-07
Abstract: 1. A method for removing a substance (X) from a solid compound (M<1>X) between the substance and a metal or semi-metal (M<1>), comprising the steps of arranging a cathode comprising the solid compound in contact with an electrolyte (M<2>Y) comprising a fused salt, the electrolyte comprising a cation (M<2>); arranging an anode in contact with the electrolyte; and applying a voltage between the cathode and the anode such that the potential at the cathode is lower than a deposition potential for the cation at a surface of the cathode and such that the substance dissolves in the electrolyte. 2. A method for removing a substance (X) from a solid compound (M<1>X) between the substance and a metal or semi-metal (M<1>), wherein the solid compound is an insulator, comprising the steps of arranging a cathode comprising the solid compound in contact with an electrolyte (M<2>Y) comprising a fused salt, the electrolyte comprising a cation (M<2>); arranging an anode in contact with the electrolyte; and applying a voltage between the cathode and the anode such that the substance dissolves in the electrolyte. 3. A method for removing a substance (X) from a solid compound (M<1>X) between the substance and a metal or semi-metal (M<1>), comprising the steps of arranging a cathode comprising the solid compound in contact with an electrolyte (M<2>Y) comprising a fused salt, the electrolyte comprising a cation (M<2>); arranging an anode in contact with the electrolyte; and applying a voltage between the cathode and the anode such that the substance dissolves in the electrolyte and such that the metal or semi-metal produced by the method contains substantially no deposition of the cation from the electrolyte. 4. A method according to any of claims 1 to 3, in which the cathode comprises the solid compound in contact with a conductor. 5. A method according to claim 4, in which the solid compound is held in the conductor. 6. The method according to any of claims 1 to 5, in which the cathode is formed from the solid compound in powdered form by slip-casting and/or sintering. 7. A method for removing a substance (X) from a solid compound (M<1>X) between the substance and a metal or semi-metal (M<1>), comprising the steps of arranging a cathode, comprising sintered artefacts of the solid compound held in a conductor, in contact with an electrolyte (M<2>Y) comprising a fused salt, the electrolyte comprising a cation (M<2>); arranging an anode in contact with the electrolyte; and applying a voltage between the cathode and the anode such that the substance dissolves in the electrolyte. 8. A method according to claim 5 or 7, in which the conductor is in the form of a basket. 9. A method according to claim 5 or 7, in which the conductor is in the form of a crucible. 10. The method according to any of claims 1, or 3 to 9, wherein the solid compound is an insulator. 11. The method according to any of claims 1 to 10, wherein the solid compound is a surface coating on a body of the metal or semi-metal. 12. The method according to any of claims 1 to 11, characterised in that the metal or semi-metal comprises one or more elements selected from the group consisting of Ti, Si, Ge, Zr, Hf, Sm, U, Al, Mg, Nd, Mo, Cr and Nb. 13. The method according to any of claims 1 to 12, wherein the substance is selected from the group consisting of O, S, C and N. 14. The method according to any of claims 1 to 13, wherein a further metal compound or semi-metal compound (M<N>X) is present, and the electrolysis product is an alloy of the metals and/or semi-metals. 15. The method according to any of claims 1 to 14, wherein the metal, semi-metal or alloy produced by the method comprises one or more elements selected from the group consisting of Ti, Si, Ge, Zr, Hf, Sm, U, Al, Mg, Nd, Mo, Cr, and Nb. 16. The method according to any of claims 1 to 15, wherein the solid compound is applied to a metal substrate prior to treatment. 17. The method according to any of claims 1 to 16, wherein the solid compound is in the form of a porous pellet or powder. 18. A method for forming an alloy of two or more metal or semi-metal components (M<1>, M<N>), comprising the steps of providing solid compounds (M<1>X, M<N>Z) of each of the components with another substance or substances (X, Z); mixing the solid compounds together; providing an electrolyte (M<2>Y) comprising a fused salt, the electrolyte comprising a cation (M<2>); arranging a cathode comprising the mixed solid compounds in contact with the electrolyte; arranging an anode in contact with the electrolyte; and applying a voltage between the cathode and the anode such that the potential at the cathode is lower than a deposition potential for the cation at a surface of the cathode and such that the substance or substances dissolve(s) in the electrolyte. 19. A method for forming an alloy of two or more metal or semi-metal components (M<1>, M<N>), comprising the steps of providing solid compounds (M<1>X, M<N>Z) of each of the components with another substance or substances (X, Z), at least one of the compounds being an insulator; mixing the solid compounds together; providing an electrolyte (M<2>Y) comprising a fused salt, the electrolyte comprising a cation (M<2>); arranging a cathode comprising the mixed solid compounds in contact with the electrolyte; arranging an anode in contact with the electrolyte; and applying a voltage between the cathode and the anode such that the substance or substances dissolve(s) in the electrolyte. 20. A method for forming an alloy of two or more metal or semi-metal components (M<1>, M<N>), comprising the steps of providing solid compounds (M<1>X, M<N>Z) of each of the components with another substance or substances (X, Z); mixing the solid compounds together; providing an electrolyte (M<2>Y) comprising a fused salt, the electrolyte comprising a cation (M<2>); arranging a cathode comprising the mixed solid compounds in contact with the electrolyte; arranging an anode in contact with the electrolyte; and applying a voltage between the cathode and the anode such that the substance or substances dissolve(s) in the electrolyte, and such that the alloy produced by the method contains substantially no deposition of the cation from the electrolyte. 21. A method according to any of claims 18 to 20, in which the mixed solid compounds are sintered before being contacted with the electrolyte. 22. A method for forming an alloy of two or more metal or semi-metal components (M<1>, M<N>), comprising the steps of providing solid compounds (M<1>X, M<N>Z) of each of the components with another substance or substances (X, Z); mixing and sintering the solid compounds together; providing an electrolyte (M<2>Y) comprising a fused salt, the electrolyte comprising a cation (M<2>); arranging a cathode, comprising sintered artefacts of the solid compounds held in a conductor, in contact with an electrolyte; arranging an anode in contact with the electrolyte; and applying a voltage between the cathode and the anode such that the substance or substances dissolve(s) in the electrolyte. 23. A method according to any of claims 1 to 22, in which the cation is selected from the group consisting of Ca, Ba, Li, Sr and Cs, and the metal or semi-metal produced by the method contains substantially no deposited Ca, Ba, Li, Sr or Cs, respectively. 24. The method according to any of claims 1 to 23, wherein electrolysis is carried out at a temperature from 700 degree C to 1000 degree C. 25. The method according to any of claims 1 to 24, wherein the cation is selected from the group consisting of Ca, Ba, Li, Cs and Sr; and the electrolyte comprises an anion (Y), which is Cl. 26. The method according to any of claims 1 to 25, wherein the current flow at an initial stage of electrolysis does not exceed a predetermined limit. 27. The method according to any of claims 1 to 26, wherein electrolysis is carried out in two stages, an electrolyte provided in a second stage containing a lower concentration of the substance (X) than an electrolyte provided in a previous stage. 28. The method according to any of claims 1 to 27, wherein electrolysis is conducted with a potential below the decomposition potential of the electrolyte. 29. The method according to any of claims 1 to 28, the electrolysis is conducted under conditions such that reaction of the substance rather than deposition of the cation occurs at the cathode surface. 30. An apparatus for carrying out the method as defined in claim 8, 9 or 10, comprising a cathode comprising a conductor for holding the sintered artefacts of the solid compound (M<1>X); a container for the electrolyte (M<2>Y); and a source of a potential for application to the cathode. 31. A metal or semi-metal fabricated according to the method of any of claims 1 to 17 or 23 to 29. 32. An alloy fabricated according to the method of any of claims 18 to 29.