| abstract |
Improvements are disclosed for fabrication of composite hydrogen transport membranes, which are used for extraction of hydrogen from gas mixtures. Methods are described for supporting and re-enforcing layers of metals and metal alloys which have high permeability for hydrogen but which are either too thin to be self supporting, too weak to resist desired differential pressures across the membrane, or which become embrittled by hydrogen. In order to minimize stress at internal interfaces, which can lead to formation of dislocations and initiations of cracks, the support material is chosen so as to be lattice matched to the metals and metal alloys. Preferred metals with high permeability for hydrogen include vanadium, niobium, tantalum, palladium, and alloys thereof. In one embodiment, a porous support matrix is fabricated first, and then the pores are blocked by metals and metal alloys which are permeable to hydrogen. In a second embodiment, powders of the preferred metal are first sintered together to form a porous metal matrix, and the pores of the metal matrix are then blocked with materials which make the membrane impervious to gases other than hydrogen. In a third embodiment, cermets (ceramic-metals) are fabricated by sintering together powders of the preferred metals with powders of lattice-matched ceramic to make a dense material impervious to gases other than hydrogen. |