Methods for providing thin hydrogen separation membranes and associated uses
The present disclosure is generally related to providing thin hydrogen separation membranes coated on porous substrates that are useful in membrane steam reformers and methods for making same. These reformers can be integrated with protein exchange membrane (PEM) fuel cells to form power systems.
1. A method for providing a hydrogen separation membrane upon a porous metallic substrate, comprising;
providing the substrate having a surface;
subjecting said surface to at least one surface treatment comprising a polishing step whereby the surface is smoothed and whereby bulk properties of the substrate remain unchanged; and
forming said hydrogen separation membrane upon said surface of the substrate by performing a plurality of deposition cycles, each deposition cycle comprising
disposing upon said surface a composition,
forming a coating on said surface of the substrate by a laser direct-write process utilizing said composition,
subjecting the coating to soft baking, and
subjecting the coating to sintering;
wherein said hydrogen separation membrane provides permeance of hydrogen therethrough;
wherein said composition is a metallic ink having a metallic component and a carrier component, said metallic component comprising at least at least one of palladium, a palladium alloy, and a palladium and silver alloy;
wherein the soft baking substantially removes the carrier component from the coating; and
wherein the sintering substantially densifies and mends the metallic component of the coating to provide substantially complete coverage of the surface without substantial openings or defects in the coating.
2. The method of claim 1 , wherein said composition providing said coating is comprised of at least one of palladium or palladium alloy.
3. The method of claim 1 , further comprising the step of providing a diffusion barrier upon said surface after subjecting said surface to said surface treatment, wherein said diffusion barrier is configured to allow diffusion of hydrogen and prevent diffusion of intermetallic constituents.
4. The method of claim 3 , further comprising the step of etching said provided diffusion barrier prior to disposing said composition upon said surface.
5. The method of claim 1 , wherein said polishing step utilizes a method selected from the group consisting of shot peening, ion-beam treatment, plasma deposition of metals and vapor deposition of metals.
6. The method of claim 4 , wherein said etching step employs etching with at least one of nitric acid, hydrochloric acid and pickling solutions.
7. The method of claim 1 , wherein said hydrogen separation membrane, disposed upon said substrate, is less than about 20 microns thick.
8. The method of claim 1 , wherein said hydrogen separation membrane, disposed upon said substrate, is about 2 to about 10 microns thick.
9. The method of claim 1 , wherein said hydrogen separation membrane, disposed upon said substrate, is about 5 to about 10 microns thick.
10. The method of claim 1 , wherein said metallic component of said metallic ink is produced by an aerosol decomposition process.
11. The method of claim 1 , wherein said metallic component has a palladium content of about 70 to about 78% by weight.
12. The method of claim 1 , wherein said metallic component has a palladium content of about 75 to 77% by weight.
13. The method of claim 1 , wherein said metallic component of said metallic ink comprises about 25% palladium and silver mix and about 75% carrier, by weight respectively, wherein said palladium and silver mix is provided in a ratio of about 75% palladium to about 25% silver, by weight respectively.
14. The method of claim 1 , wherein said metallic component of said metallic ink comprises about 5% to 50% palladium and silver mix and about 50% to 95% carrier, by weight respectively, wherein said palladium and silver mix is provided in a ratio of about 70% to 78% palladium to about 22% to 30% silver, by weight respectively.
15. The method of claim 1 , wherein at least one of said soft baking and said sintering is carried out in an environment having a partial pressure of oxygen between about 10 −2 atm and 10 −5 atm.
16. The method of claim 1 , wherein at least one of said soft baking and said sintering is carried out in a lean hydrogen gas atmosphere having less than about 10% hydrogen by weight.
17. The method of claim 1 , wherein said sintering comprises localized sintering of the coating and not an underlying support, wherein said localized sintering of the coating utilizes an ion or laser beam.
18. The method of claim 1 , wherein said substrate is cylindrical or tubular.
19. The method of claim 1 , wherein the plurality of deposition cycles comprises three deposition cycles.
20. The method of claim 1 , wherein the plurality of deposition cycles comprises five deposition cycles.
21. The method of claim 1 , wherein subjecting the layer of the coating to soft baking comprises soft baking at about 150 degrees C. to less than about 350 degrees C.
22. The method of claim 1 , wherein subjecting the coating to sintering comprises sintering the coating at about 850 degrees C. to about 1000 degrees C.
23. The method of claim 1 , wherein subjecting the coating to sintering comprises conducting the sintering in N 2 by
heating at a rate of about 3 degrees C. per minute to a soak temperature of 850° C. or 900° C. or 950° C.;
soaking for 1 hour; then
cooling at a rate of about 3 degrees C. per minute.
24. The method of claim 1 , wherein subjecting the coating to sintering comprises
heating at a rate of about 10 to about 100 degrees C. per minute; and
soaking for about 2 to about 10 hours at about 900 degrees C. to about 1000 degrees C.
25. The method of claim 1 , wherein the formed hydrogen separation membrane substantially uniformly covers the surface edge-to-edge.
26. A hydrogen separation membrane comprising:
a coating disposed upon a surface of a substrate;
wherein said coating transports hydrogen;
wherein the substrate is of a porous metal, said surface of the substrate being polished by a surface treatment whereby the surface is smoothed and whereby bulk properties of the substrate remain unchanged;
wherein said coating is provided to said substrate by a laser direct-write process utilizing a metallic ink having a metallic component and a carrier component, said metallic component comprising at least at least one of palladium, a palladium alloy, and a palladium and silver alloy; and wherein said coating is subject to thermal processing
wherein the thermal processing comprises
soft baking, the soft baking rendering the coating substantially free of the carrier component, and
sintering, the sintering rendering the metallic component densitied and mended to provide substantially complete coverage of the surface without substantial openings or defects in the coating.
27. The hydrogen separation membrane of claim 26 , wherein said polished substrate is treated to include a diffusion barrier between said polished substrate and said coating, wherein said diffusion barrier is configured to allow diffusion of hydrogen and prevent diffusion of intermetallic constituents.
28. The hydrogen separation membrane of claim 27 , wherein said diffusion barrier is etched.
29. The hydrogen separation membrane of claim 26 , wherein said polishing is accomplished by at least one of shot peening, ion-beam treatment, plasma deposition of metals and vapor deposition of metals.
30. The hydrogen separation membrane of claim 26 , wherein said coating has a thickness of less than about 20 microns.
31. The hydrogen separation membrane of claim 26 , wherein said coating has a thickness of between about 2 to 10 microns.
32. The hydrogen separation membrane of claim 26 , wherein said metallic component of said metallic ink is provided by an aerosol decomposition process.
33. The hydrogen separation membrane of claim 26 , wherein said metallic component of said ink is comprised of an alloy having between about 70 to about 78% palladium by weight.
34. The hydrogen separation membrane of claim 26 , wherein said metallic component of said ink is comprised of an alloy having between about 75 to about 77% palladium by weight.
35. The hydrogen separation membrane of claim 26 , wherein said metallic component of said metallic ink is comprised of about 25% palladium and silver mix and about 75% carrier, by weight respectively, wherein said palladium and silver mix is provided in a ratio of about 75% palladium to about 25% silver, by weight respectively.
36. The hydrogen separation membrane of claim 26 , wherein said metallic component of said metallic ink is comprised of about 50% palladium and silver mix and about 50% carrier, by weight respectively, wherein said palladium and silver mix is provided in a ratio of about 70% palladium to about 30% silver, by weight respectively.
37. The hydrogen separation membrane of claim 26 , wherein said substrate is cylindrical or tubular.
38. The hydrogen separation membrane of claim 26 , wherein the sintering comprises localized sintering which sinters the coating and not an underlying support, wherein said localized sintering of the coating utilizes an ion or laser beam.
39. The hydrogen separation membrane of claim 26 , wherein the coating substantially uniformly covers the surface of the substrate edge-to-edge.