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Thin, porous metal sheets and methods for forming them are presented to enable a variety of applications and devices. The thin, porous metal sheets are less than or equal to approximately 200 μm thick, have a porosity between 25% and 75% by volume, and have pores with an average diameter less than o

Thin, porous metal sheets and methods for forming them are presented to enable a variety of applications and devices. The thin, porous metal sheets are less than or equal to approximately 200 μm thick, have a porosity between 25% and 75% by volume, and have pores with an average diameter less than or equal to approximately 2 μm. The thin, porous metal sheets can be fabricated by preparing a slurry having between 10 and 50 wt % solvent and between 20 and 80 wt % powder of a metal precursor. The average particle size in the metal precursor powder should be between 100 nm and 5 μm.

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1. A method of fabricating a thin, porous metal sheet, the method characterized by the steps of: Preparing a slurry comprising between 10 and 50 wt % solvent and between 20 and 80 wt % non-metallic powder of a metal oxide, metal hydride or metalorganic, the non-metallic powder comprising average par

1. A method of fabricating a thin, porous metal sheet, the method characterized by the steps of: Preparing a slurry comprising between 10 and 50 wt % solvent and between 20 and 80 wt % non-metallic powder of a metal oxide, metal hydride or metalorganic, the non-metallic powder comprising average particle sizes from 100 nm to 5 μm;Casting the slurry into a green body having a thickness between 10 and 200 μm;Firing the green body thereby converting the metal oxide, metal hydride or metalorganic into a metallic state and yielding a fired body; andSintering, annealing or flattening the fired body to yield the thin, porous metal sheet having a metallic backbone of networked pore structures in three dimensions with a porosity between 25% and 75% by volume, and with an average pore diameter less than or equal to 2 μm. 2. The method of claim 1, further comprising adding up to 30 wt % of a pore former to the slurry, the pore former comprising average particle sizes between 100 nm and 10 μm, wherein said firing substantially removes the pore former. 3. The method of claim 2, wherein the pore former is selected from the group consisting of carbon black, graphite, coke, starch materials, and combinations thereof. 4. The method of claim 1 further comprising adding up to 15 wt % of organic additives to the slurry, the organic additives selected from the group consisting of dispersants, binders, plasticizers, and combinations thereof, wherein said firing substantially removes the organic additives. 5. The method of claim 1, wherein said firing further comprises heating the green body in a reducing environment at a ramp rate between 0.2 and 10° C./min to a firing temperature between 400 and 1200° C. and maintaining the firing temperature for a period between 30 minutes and 24 hours. 6. The method of claim 1, wherein said preparing the slurry comprises ball-milling constituents of the slurry. 7. The method of claim 1, further comprising ball-milling or attrition milling the metal precursor. 8. The method of claim 1, wherein the thin metal sheet and the metal precursor comprise a metal selected from the group consisting of Ni, NiFe alloy, Ni—Cu alloy, stainless steel alloy, Ti, Ti alloy, and combinations thereof. 9. The method of claim 1, wherein said firing further comprises heating the green body in an oxidizing environment to a first temperature between 800 and 1400° C. followed by heating in a reducing environment to a second temperature between 400 and 1200° C. for a period of 30 minutes to 24 hours. 10. The method of claim 9, wherein a ramp rate to the first temperature is less than or equal to 10° C. per minute. 11. The method of claim 1, wherein said sintering or annealing occur in an inert or reducing environment at temperatures below the metal melting point and approximately equal to a softening point of the metal. 12. The method of claim 1, further comprising depositing a ceramic, an anti-sintering material, or both inside pores of the porous metal body, the ceramic or anti-sintering material having an average particle size between 1 and 200 nm. 13. The method of claim 1, wherein said casting comprises casting the slurry into two or more green body sheets each having a thickness from 10 to 100 μm and laminating the two or more green body sheets into a single laminate, and wherein said firing comprises firing the single laminate to convert the metal precursor into a metallic state and to yield a fired body. 14. The method of claim 13, wherein said laminating comprises laminating together a first green body sheet having pores with an average diameter less than or equal to 10 μm and at least one green body sheet having pores with an average diameter less than or equal to 2 μm, wherein the pores on one side of the thin, porous metal sheet have an average pore diameter less than or equal to 10 μm and the pores of the opposite side have an average diameter less than or equal to 2 μm. 15. The method of claim 13, wherein the slurry composition for each green body differs, thereby yielding a thin, porous metal sheet having a graded composition, a graded pore structure, or both. 16. A method of fabricating a thin, porous metal sheet, the method characterized by the steps of: Preparing a slurry comprising between 10 and 50 wt % solvent, up to 30 wt % pore former comprising average particle sizes between 100 nm and 10 μm, and between 20 and 80 wt % non-metallic powder of a metal precursor comprising average particle sizes between 100 nm and 5 μm, wherein the metal precursor comprises metal oxide;Casting the slurry into a green body having a thickness between 10 and 200 um;Firing the green body to convert the metal precursor into a metallic state, to remove the pore former, and to yield a fired body, said firing comprising heating the green body in an oxidizing environment to a first temperature between 800 and 1400° C. followed by heating in a reducing environment to a second temperature between 400 and 1200° C. for a period of 30 minutes to 24 hours; and, thereby,Yielding a metallic backbone of networked pore structures in three dimensions with a porosity between 25% and 75% by volume, and with an average pore diameter less than or equal to 2 μm. 17. The method of claim 16, further comprising sintering, annealing or flattening the fired body to enhance surface smoothness, mechanical strength, or both. 18. A method of fabricating a thin, porous metal sheet, the method characterized by the steps of: preparing a slurry comprising between 10 and 50 wt % solvent, up to 30 wt. % pore former comprising average particle sizes between 10 nm and 5 μm, and between 20 and 80 wt % non-ductile, metal element-containing particles with an average particle size between 100 nm and 5 μm;casting the slurry into a green body having a thickness between 10 and 200 um;drying the green body to substantially free of volatile solvent;removing the organics and pore formers, reducing the metal element-containing particles into metal particles, and sintering metal particles by heating the green tape in hydrogen gas at a temperature within the range from 400 and 1200° C. for a period of 30 minutes to 24 hours; and, thereby,yielding a metallic backbone of networked pore structures in three dimensions with a porosity between 25% and 75% by volume, and with an average pore diameter less than or equal to 2 μm. 19. The method of claim 18, wherein the non-ductile, metal element-containing particles are metal oxides, metalorganic, or metal hydride. 20. The method of claim 18, wherein the pore former is selected from the group consisting of carbon black, graphite, coke, and combinations thereof, wherein the pore former can be removed concomitantly during reduction of the metal element-containing particle by heating in hydrogen gas at high temperatures. 21. The method of claim 18, further comprising adding up to 15 wt % of organic additives to the slurry, the organic additives selected from the group consisting of dispersants, binders, plasticizers, and combinations thereof, wherein said heating in hydrogen gas substantially removes the organic additives. 22. The method of claim 18, wherein the hydrogen gas stream contains 70% hydrogen. 23. The method of claim 18, wherein said preparing the slurry comprises ball-milling constituents of the slurry in a sequence of mixing the pore former, dispersant and solvent first, followed with an addition of the metal element-containing particles. 24. The method of claim 18, the non-ductile, metal element-containing particles are prepared by ball-milling or attrition milling of the same materials comprising large agglomerates with particle sizes above 5 μm. 25. The method of claim 18, wherein a ramp rate from the room temperature to hydrogen reaction temperature is less than or equal to 10° C. per minute, preferably less than 2° C./min. 26. The method of claim 18, wherein said casting comprises casting the slurry into two or more green body sheets each having a thickness from 10 to 100 μm and laminating the two or more green body sheets into a single laminate, and wherein said firing comprises firing the single laminate to convert the metal precursor into a metallic state and to yield a fired body. 27. The method of claim 26, wherein said laminating comprises laminating together a first green body sheet having pores with an average diameter less than or equal to 10 μm and at least one green body sheet having pores with an average diameter less than or equal to 2 μm, wherein the pores on one side of the thin, porous metal sheet have an average pore diameter less than or equal to 10 μm and the pores of the opposite side have an average diameter less than or equal to 2 μm. 28. The method of claim 26, wherein the slurry composition for each green body differs, thereby yielding a thin, porous metal sheet having a graded composition, a graded pore structure, or both.