Abstract:
A tubular hydrogen permeable metal membrane and fabrication process comprises obtaining a metal alloy foil having two surfaces, coating the surfaces with a metal or metal alloy catalytic layer to produce a hydrogen permeable metal membrane, sizing the membrane into a sheet with two long edges, wrapping the membrane around an elongated expandable rod with the two long edges aligned and overlapping to facilitate welding of the two together, placing the foil wrapped rod into a surrounding fixture housing with the two aligned and overlapping foil edges accessible through an elongated aperture in the surrounding fixture housing, expanding the elongated expandable rod within the surrounding fixture housing to tighten the foil about the expanded rod, welding the two long overlapping foil edges to one another generating a tubular membrane, and removing the tubular membrane from within the surrounding fixture housing and the expandable rod from with the tubular membrane.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with Government support under Contract Number W-7405 ENG-36, awarded by the United States Department of Energy to the Regents of the University of California. The Government has certain rights in this invention. 
    
    
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not Applicable 
     This invention pertains generally to a tubular hydrogen permeable metal foil membrane suitable for hydrogen purification procedures and a method of fabrication. More particularly, the subject invention concerns fabrication process of a thin catalytic-layer coated metal foil membrane formed into a tube and utilized for the purpose of hydrogen purification at elevated temperatures such as those found in membrane reactors. 
     DESCRIPTION OF RELATED ART 
     The production of highly purified hydrogen gas is a desired goal for many obvious reasons. The chemical and petrochemical industries handle vast quantities of hydrogen for use in reactions. Purification of this hydrogen is often required. The semiconductor manufacturing industry uses large amounts of hydrogen for depositing materials by chemical vapor deposition processes. The automotive industry is researching ways of reforming fuel on board vehicles, particularly in membrane reactors, to generate hydrogen for electricity production in fuel cells to power electric motors. The hydrogen must be pure so that the fuel cell is not poisoned. Specifically, efficient utilization of coal for chemical and electricity production may be accomplished with the aid of membrane reactors to produce pure hydrogen (see www.netl.doe.gov in relation to DOE Vision 21 Processes). The membrane reactor carries out the water-gas shift reaction to produce purified hydrogen from gasified coal. The hydrogen gas generated from reacting carbon monoxide and water to produce carbon dioxide and hydrogen is removed from the reaction by means of a hydrogen permeable membrane which when results in shifting the equilibrium towards the carbon dioxide and hydrogen products, thereby yielding high conversion values. The membrane-extracted pure hydrogen produces electricity via a fuel cell or chemicals in another suitable reactor and the effluent from the membrane reactor can be further combusted to produce electricity or heat. This water-gas shift scheme has the further advantage of producing a high pressure CO 2 -rich stream that may more easily be sequestrated. Commercialization of membrane reactor technology will require durable, cost effective, and highly hydrogen permeable membrane materials. The subject invention is a hydrogen permeable metal foil membrane, and method of fabrication, ideally suited for use in a water-gas shift reactor and in processes that require purified hydrogen gas. 
     Coating a suitable support material (Group IVB and VB elements and alloys of those elements) with catalytically active Pd or Pt or Pd alloy or Pt alloy film is necessary to minimize the use of costly Pd and Pt in a membrane. Pd and Pt alloy films are necessary to reduce the hydrogen embrittlement experienced by pure Pd and Pt films. Some research has indicated that Pd—Cu alloys (particularly 40 weight %) are sulfur tolerant, have increased hydrogen permeability compared to pure Pd, and also resist hydrogen embrittlement. Group V-B metals have been considered since the 1960s as alternatives to Pd alloys for hydrogen separation membranes. These metals are still attractive due to the intrinsically lower cost compared to Pd or Pt and high hydrogen permeability. A Pd or Pt coating is necessary on Group V-B metals foils to protect them from oxidation and impurities found in hydrogen streams as well as to facilitate hydrogen entry and exit from the metal. The foils serve as solid supports for Pd or Pt enabling very thin coatings (&lt;1 μm) of the Pd or Pt and their alloys. 
     Metal membranes that are selectively permeable to hydrogen are disclosed in various patents and publications (see Tables 1 and 2, immediately below). The purpose of the invention is to create a hydrogen separating membrane that has an advantageous configuration for integrating into processes such as hydrogen separations, and membrane reactors. 
     A variety of materials have been developed, including Group IV-B and V-B alloys for the primary foil (support layer) and Pd, Pt, Pd alloys, and Pt alloys for the thin catalytic coating. Methods for depositing the catalytic coating include ion-milling the surfaces of the refractory metal foil (the primary foil or support layer) to remove contaminants and oxide layers followed by deposition of the Pd, Pt, Pd alloys, and Pt alloys onto both sides of the foil without breaking the vacuum. This type of sandwich (e.g. palladium/refractory/palladium) membrane is primarily used in the form of a flat sheet. A gas-tight seal is made to a flat sheet of membrane material: through the use of gaskets and compression fittings; diffusion bonding, brazing or welding to a frame or mesh; welding/brazing across the end of a tube. Baake et al. (see Table 1 below) have produced tubular membranes by coating Group IV-B and V-B metal sheets with palladium alloys and then reworking these into tubes. Buxbaum et al. (see Table 1 below) have coated Group IV-B and V-B metal tubes with palladium using electroless and electrolytic deposition. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Prior Art Patent References 
               
             
          
           
               
                 Patent 
                 Issued 
                 Inventors 
                 Title 
                 Relevance to Subject Invention 
               
               
                   
               
               
                 U.S. Pat. No. 2958391 
                 Nov. 1, 1960 
                 De Rosset 
                 Purification of 
                 Palladium film supported by 
               
               
                   
                   
                   
                 hydrogen 
                 porous metal. 
               
               
                   
                   
                   
                 utilizing 
               
               
                   
                   
                   
                 hydrogen- 
               
               
                   
                   
                   
                 permeable 
               
               
                   
                   
                   
                 membranes 
               
               
                 U.S. Pat. No. 3350845 
                 Nov. 7, 1967 
                 McKinley 
                 Metal alloy for 
                 Palladium-copper alloy 
               
               
                   
                   
                   
                 hydrogen 
                 hydrogen separating 
               
               
                   
                   
                   
                 separation and 
                 membrane material. 
               
               
                   
                   
                   
                 purification 
               
               
                 U.S. Pat. No. 3350846 
                 Nov. 7, 1967 
                 Makrides 
                 Separation of 
                 Use of Group VA foils coated 
               
               
                   
                   
                 et al. 
                 hydrogen by 
                 with palladium and palladium 
               
               
                   
                   
                   
                 permeation 
                 alloys. Attachment of foil to end 
               
               
                   
                   
                   
                   
                 of stainless steel tube with 
               
               
                   
                   
                   
                   
                 electron beam welding. 
               
               
                 U.S. Pat. No. 3393098 
                 Jul. 16, 1968 
                 Hartner et 
                 Fuel cell 
                 Group VB metals as hydrogen 
               
               
                   
                   
                 al. 
                 comprising a 
                 membranes. 
               
               
                   
                   
                   
                 hydrogen 
               
               
                   
                   
                   
                 diffusion anode 
               
               
                   
                   
                   
                 having two 
               
               
                   
                   
                   
                 layers of 
               
               
                   
                   
                   
                 dissimilar 
               
               
                   
                   
                   
                 metals and 
               
               
                   
                   
                   
                 method of 
               
               
                   
                   
                   
                 operating same 
               
               
                 U.S. Pat. No. 3957534 
                 May 18, 1976 
                 Linkohr et 
                 Diaphragm for 
                 A TiNi alloy for hydrogen 
               
               
                   
                   
                 al. 
                 the separation 
                 separation. 
               
               
                   
                   
                   
                 of hydrogen 
               
               
                   
                   
                   
                 from hydrogen- 
               
               
                   
                   
                   
                 containing 
               
               
                   
                   
                   
                 gaseous 
               
               
                   
                   
                   
                 mixtures 
               
               
                 U.S. Pat. No. 4468235 
                 Aug. 28, 1984 
                 Hill 
                 Hydrogen 
                 Titanium alloy membrane 
               
               
                   
                   
                   
                 separation 
                 coated with palladium alloy. 
               
               
                   
                   
                   
                 using coated 
               
               
                   
                   
                   
                 titanium alloys 
               
               
                 U.S. Pat. No. 4496373 
                 Jan. 29, 1985 
                 Behr et al. 
                 Diffusion 
                 Palladium alloy coated Group 
               
               
                   
                   
                   
                 membrane and 
                 IV-B and V-B alloys. 
               
               
                   
                   
                   
                 process for 
               
               
                   
                   
                   
                 separating 
               
               
                   
                   
                   
                 hydrogen from 
               
               
                   
                   
                   
                 gas mixture 
               
               
                 U.S. Pat. No. 5139541 
                 Feb. 12, 1992 
                 Edlund 
                 Hydrogen- 
                 Group I-B, III-B, IV-B, V-B and 
               
               
                   
                   
                   
                 permeable 
                 VII-B metal and metal alloy foils 
               
               
                   
                   
                   
                 composite 
                 coated with palladium alloys. 
               
               
                   
                   
                   
                 metal 
               
               
                   
                   
                   
                 membrane 
               
               
                 U.S. Pat. No. 5149420 
                 Sep. 22, 1992 
                 Buxbaum 
                 Method for 
                 Deposition of a palladium layer 
               
               
                   
                   
                 et al. 
                 plating 
                 onto a Group IV-B or V-B 
               
               
                   
                   
                   
                 palladium 
                 metals and their alloys using 
               
               
                   
                   
                   
                   
                 electroless and electrolytic 
               
               
                   
                   
                   
                   
                 plating. 
               
               
                 U.S. Pat. No. 5215729 
                 Jun. 1, 1993 
                 Buxbaum 
                 Composite 
                 Deposition of a palladium layer 
               
               
                   
                   
                   
                 metal 
                 onto a Group IV-B or V-B 
               
               
                   
                   
                   
                 membrane for 
                 metals and their alloys using 
               
               
                   
                   
                   
                 hydrogen 
                 electroless and electrolytic 
               
               
                   
                   
                   
                 extraction 
                 plating. 
               
               
                 U.S. Pat. No. 5217506 
                 Jun. 8, 1993 
                 Edlund 
                 Hydrogen- 
                 Group I-B, III-B, IV-B, V-B and 
               
               
                   
                   
                   
                 permeable 
                 VII-B metal and metal alloy foils 
               
               
                   
                   
                   
                 composite 
                 coated with palladium alloys. 
               
               
                   
                   
                   
                 membrane and 
               
               
                   
                   
                   
                 uses thereof 
               
               
                 U.S. Pat. No. 5259870 
                 Nov. 9, 1993 
                 Edlund 
                 Hydrogen- 
                 Group I-B, III-B, IV-B, V-B and 
               
               
                   
                   
                   
                 permeable 
                 VII-B metal and metal alloy foils 
               
               
                   
                   
                   
                 composite 
                 coated with palladium alloys. 
               
               
                   
                   
                   
                 metal 
               
               
                   
                   
                   
                 membrane 
               
               
                 U.S. Pat. No. 5393325 
                 Feb. 28, 1995 
                 Edlund 
                 Composite 
                 Group I-B, III-B, IV-B, V-B and 
               
               
                   
                   
                   
                 hydrogen 
                 VII-B metal and metal alloy foils 
               
               
                   
                   
                   
                 separation 
                 coated with palladium alloys. 
               
               
                   
                   
                   
                 metal 
               
               
                   
                   
                   
                 membrane 
               
               
                 U.S. Pat. No. 5498278 
                 Mar. 12, 1996 
                 Edlund 
                 Composite 
                 Palladium alloy coated 
               
               
                   
                   
                   
                 hydrogen 
                 refractory metals. 
               
               
                   
                   
                   
                 separation 
               
               
                   
                   
                   
                 element and 
               
               
                   
                   
                   
                 module 
               
               
                 U.S. Pat. No. 5645626 
                 Jul. 8, 1997 
                 Edlund 
                 Composite 
                 Palladium alloy coated 
               
               
                   
                   
                   
                 hydrogen 
                 refractory metals. 
               
               
                   
                   
                   
                 separation 
               
               
                   
                   
                   
                 element and 
               
               
                   
                   
                   
                 module 
               
               
                 U.S. Pat. No. 5738708 
                 Apr. 14, 1998 
                 Peachey 
                 Composite 
                 Method of coating palladium 
               
               
                 WO9640413 
                   
                 et al. 
                 metal 
                 alloys onto the Group IV-B and 
               
               
                   
                   
                   
                 membrane 
                 V-B foil. 
               
               
                 U.S. Pat. No. 5888273 
                 Mar. 30, 1999 
                 Buxbaum 
                 High- 
                 Group V-B metal alloys coated 
               
               
                   
                   
                   
                 temperature 
                 with palladium alloys. 
               
               
                   
                   
                   
                 gas purification 
               
               
                   
                   
                   
                 system 
               
               
                 U.S. Pat. No. 5931987 
                 Mar. 8, 1999 
                 Buxbaum 
                 Apparatus and 
                 Group V-B metal alloys coated 
               
               
                   
                   
                   
                 methods for gas 
                 with palladium alloys. 
               
               
                   
                   
                   
                 extraction 
               
               
                 U.S. Pat. No. 6183543 
                 Feb. 6, 2001 
                 Buxbaum 
                 Apparatus and 
                 Group V-B metal alloys coated 
               
               
                   
                   
                   
                 methods for gas 
                 with palladium alloys. 
               
               
                   
                   
                   
                 extraction 
               
               
                 U.S. Pat. No. 6214090 
                 Apr. 10, 2001 
                 Dye et al. 
                 Thermally 
                 Method of coating palladium 
               
               
                   
                   
                   
                 tolerant 
                 alloys onto the Group IV-B and 
               
               
                   
                   
                   
                 multilayer metal 
                 V-B foil. Metal alloys used as 
               
               
                   
                   
                   
                 membrane 
                 membrane materials. 
               
               
                 U.S. Pat. No. 6267801 
                 Jul. 31, 2001 
                 Baake et 
                 Method for 
                 Palladium alloy coated Group 
               
               
                   
                   
                 al. 
                 producing a 
                 IV-B and V-B metals, formed 
               
               
                   
                   
                   
                 tubular 
                 into a tube by drawing, pressing 
               
               
                   
                   
                   
                 hydrogen 
                 or extrusion. 
               
               
                   
                   
                   
                 permeation 
               
               
                   
                   
                   
                 membrane 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Prior Art Publication References 
               
             
          
           
               
                 Publication 
                 Relevance to Subject Invention 
               
               
                   
               
               
                 1. Holleck, G. L. Hydrogen Diffusion through 
                 Permeation of hydrogen through 
               
               
                 (Palladium-Silver)-Tantalum-(Palladium-Silver) 
                 palladium-silver coated tantalum. 
               
               
                 Composites. J. Phys. Chem. 1970, 74 (9), 1957. 
               
               
                 2. Boes, N.; Züchner, H. Diffusion of Hydrogen and 
                 Permeation of hydrogen through 
               
               
                 Deuterium in Ta, Nb, and V. phys. stat. sol. (a) 
                 tantalum, niobium and vanadium 
               
               
                 1973, 17, K111. 
                 coated with palladium. 
               
               
                 3. Boes, N.; Züchner, H. Application of 
               
               
                 Electrochemical Techniques for Studying Diffusion 
               
               
                 of Hydrogen Isotopes in V, Nb and Ta. Zeitschrift für 
               
               
                 Naturforschung A 1976, 31, 760. 
               
               
                 4. Boes, N.; Züchner, H. Preparation of Hydrogen 
               
               
                 Permeable Foils of V, Nb and Ta by Means of Ultra 
               
               
                 High Vacuum Techniques. Zeitschrift für 
               
               
                 Naturforschung A 1976, 31, 754. 
               
               
                 5. Boes, N.; Züchner, H. Secondary ion mass 
               
               
                 spectrometry and Auger electron spectroscopy 
               
               
                 investigations of Vb metal foils prepared for 
               
               
                 hydrogen permeation measurements. Surf. Tech. 
               
               
                 1978, 7, 401. 
               
               
                 6. Züchner, H. Multilayer problems in studying the 
                 Permeation of hydrogen through 
               
               
                 diffusion of hydrogen in metals by time-lag 
                 tantalum coated with 100 nm of 
               
               
                 techniques. Trans. JIM (Trans. JIM) 1980, 21 
                 palladium. 
               
               
                 (supplement), 101. 
               
               
                 7. Buxbaum, R. E. The Use of Zirconium-Palladium 
                 Palladium coated zirconium. 
               
               
                 Windows for the Separation of Tritium from the 
               
               
                 Liquid Metal Breeder-Blanket of a Fusion Reactor. 
               
               
                 Sep. Sci. Tech. 1983, 18 (12 &amp; 13), 1251. 
               
               
                 8. Hsu, C.; Buxbaum, R. E. Palladium-catalyzed 
                 Palladium coated zirconium, 
               
               
                 oxidative diffusion for tritium extraction from 
                 niobium, or vanadium. 
               
               
                 breeder-blanket fluids at low concentrations. J. Nucl. 
               
               
                 Mater. 1986, 141–143, 238. 
               
               
                 9. Weirich, W.; Biallas, B.; Kügler, B.; Oertel, M.; 
                 Titanium-nickel foil membranes 
               
               
                 Pietsch, M.; Winkelmann, U. Development of a 
                 coated with palladium-copper. 
               
               
                 laboratory cycle for a thermochemical water-splitting 
               
               
                 process (Me/MeH cycle). Int. J. Hydrogen Energy 
               
               
                 1986, 11 (7), 459. 
               
               
                 10. Nishimura, C.; Komaki, M.; Amano, M. 
                 Vanadium-nickel alloys coated 
               
               
                 Hydrogen Permeation Characteristics of Vanadium- 
                 with palladium. 
               
               
                 Nickel Alloys. Mater. Trans., JIM 1991, 32 (5), 501. 
               
               
                 11. Amano, M.; Komaki. M.; Nishimura, C. 
                 Vanadium-nickel alloys coated 
               
               
                 Hydrogen permeation characteristic of palladium- 
                 with palladium. 
               
               
                 plated V—Ni alloy membranes. J. Less-Common Met. 
               
               
                 1991, 172–174, 727. 
               
               
                 12. Katsuta, H.; McLellan, R. B.; Furukawa, K. Metal 
                 Permeability of palladium coated 
               
               
                 hydrides in energy conversion systems. Trans. JIM 
                 vanadium. 
               
               
                 (Trans. JIM) 1980, 21 (supplement), 113. 
               
               
                 13. Buxbaum, R. E.; Hsu, P. C. Measurement of 
                 Palladium coated zirconium. 
               
               
                 diffusive and surface transport resistances for 
               
               
                 deuterium in palladium-coated zirconium 
               
               
                 membranes. J. Nucl. Mater. 1992, 189 (1), 183. 
               
               
                 14. Buxbaum, R. E.; Marker, T. L. Hydrogen transport 
                 Palladium coated niobium, 
               
               
                 through non-porous membranes of palladium- 
                 tantalum, and vanadium tubes. 
               
               
                 coated niobium, tantalum and vanadium. J. Membr. 
               
               
                 Sci. 1993, 85, 29. 
               
               
                 15. Edlund, D. J.; McCarthy, J. The relationship 
                 Vanadium coated with palladium. 
               
               
                 between intermetallic diffusion and flux decline in 
               
               
                 composite-metal membranes: implications for 
               
               
                 achieving long membrane lifetime. J. Membr. Sci. 
               
               
                 1995, 107, 147. 
               
               
                 16. Buxbaum, R. E.; Kinney, A. B. Hydrogen 
                 Palladium coated niobium and 
               
               
                 Transport through Tubular Membranes of 
                 tantalum tubes. 
               
               
                 Palladium-Coated Tantalum and Niobium. Ind. Eng. 
               
               
                 Chem. Res. 1996, 35, 530. 
               
               
                 17. Buxbaum, R. E.; Subramanian, R.; Park, J. H.; 
                 V—Cr—Ti alloy tubes coated with 
               
               
                 Smith, D. L. Hydrogen transport and embrittlement 
                 palladium. 
               
               
                 for palladium coated vanadium-chromium-titanium 
               
               
                 alloys. J. Nucl. Mater. 1996, 233–237, 510. 
               
               
                 18. Romanenko, O. G.; Tazhibaeva, I. L.; Shestakov, 
                 Hydrogen permeability of a 
               
               
                 V. P.; Klepikov, A. K.; Chikhray, Y. V.; Golossanov, 
                 VCr6Ti5 alloy. 
               
               
                 A. V.; Kolbasov, B. N. Hydrogen gas driven 
               
               
                 permeation through vanadium alloy VCr6Ti5. J. 
               
               
                 Nucl. Mater. 1996, 233–237, 376. 
               
               
                 19. Peachey, N. M.; Dye, R. C. High temperature 
                 Tantalum coated with palladium 
               
               
                 efforts at Los Alamos National Laboratory, 
                 on both sides after ion-milling. 
               
               
                 DE96011306; Los Alamos National Laboratory: Los 
               
               
                 Alamos, New Mexico, US, 1995. 
               
               
                 20. Peachey, N. M.; Snow, R. C.; Dye, R. C. 
               
               
                 Composite Pd/Ta metal membranes for hydrogen 
               
               
                 separation. J. Membr. Sci. 1996, 111, 123. 
               
               
                 21. Moss, T. S.; Dye, R. C. Engineering materials for 
                 Group V-B metal foil coated on 
               
               
                 hydrogen separation, DE97002456; Los Alamos 
                 both sides with palladium after 
               
               
                 National Laboratory: Los Alamos, New Mexico, US, 
                 ion-milling. 
               
               
                 1996. 
               
               
                 22. Moss, T. S.; Dye, R. C. Composite Metal 
               
               
                 Membranes for Hydrogen Separation Applications, 
               
               
                 DE97007586; Los Alamos National Laboratory: Los 
               
               
                 Alamos, New Mexico, US, 1997 
               
               
                 23. Dye, R. C.; Birdsell, S. A.; Snow, R. C.; Moss, 
               
               
                 T. S.; Peachey, N. Advancing the Technology Base 
               
               
                 for High-Temperature Membranes, DE98000093; 
               
               
                 Los Alamos National Laboratory: Los Alamos, New 
               
               
                 Mexico, US, 1997. 
               
               
                 24. Moss, T. S.; Peachey, N. M.; Snow, R. C.; Dye, 
               
               
                 R. C. Multilayer metal membranes for hydrogen 
               
               
                 separation. Int. J. Hydrogen Energy 1998, 23 (2), 
               
               
                 99. 
               
               
                 25. Tosti, S.; Bettinali, L.; Violante, V. Rolled thin Pd 
                 TIG welded a palladium-silver 
               
               
                 and Pd—Ag membranes for hydrogen separation and 
                 alloy foil into the shape of a tube. 
               
               
                 production. Int. J. Hydrogen Energy 2000, 25 (4), 
                 The fixture clamps the foil 
               
               
                 319. 
                 together at the weld seam and 
               
               
                   
                 the foil is wrapped around a brass 
               
               
                   
                 mandrel. The 50 μm palladium- 
               
               
                   
                 silver tube is brazed to a stainless 
               
               
                   
                 steel tube. 
               
               
                 26. Tosti, S.; Bettinali, L.; Castelli, S.; Sarto, F.; 
                 50–70 μm thick palladium-silver 
               
               
                 Scaglione, S.; Violante, V. Sputtered, electroless, 
                 foils TIG arc-welded or diffusion 
               
               
                 and rolled palladium-ceramic membranes. J. 
                 welded into the shape of a tube 
               
               
                 Membr. Sci. 2002, 196, 241. 
                 around tubular porous ceramic 
               
               
                   
                 supports. 
               
               
                 27. Nishimura, C.; Komaki, M.; Hwang, S.; Amano, 
                 Vanadium-nickel alloy coated 
               
               
                 M. V—Ni alloy membranes for hydrogen purification. 
                 with palladium. 
               
               
                 J. Alloys Compd. 2002, 330–332, 902. 
               
               
                   
               
             
          
         
       
     
     The foregoing patents and other publications reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicant&#39;s acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully submitted, however, that none of these patents teaches or renders obvious, singly or when considered in combination, applicant&#39;s claimed invention. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the invention is to provide a method of fabricating a hydrogen permeable metal membrane. 
     Another object of the invention is a method of fabricating a hydrogen permeable metal membrane from virtually any suitable metal membrane material, whereby the produced membrane is essentially leak-free. 
     A still further object of the invention is to relate a fabrication fixture employed in producing leak-free metal membranes in which an expandable inner rod is utilized in conjunction with a mated outer housing. 
     Further objects of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only: 
         FIG. 1  is a perspective drawing of the subject metal expansion rods shown in their “expanded” position (where the ends are approximately aligned). 
         FIG. 2  is a side view of the subject metal expansion rods shown in their “expanded” but vertically separated, for clarity, position (where the ends are approximately aligned). 
         FIG. 3  is a side view drawing of the subject metal expansion rods shown in their “expanded” position (where the ends are approximately aligned). 
         FIG. 4  is a top view drawing of the subject metal expansion rods shown in their “expanded” position (where the ends are approximately aligned). 
         FIG. 5  is a first end view drawing of the subject metal expansion rods shown in their “expanded” position (where the ends are approximately aligned). 
         FIG. 6  is a second end view drawing of the subject metal expansion rods shown in their “expanded” position (where the ends are approximately aligned). 
         FIG. 7  is a side view drawing of the subject metal expansion rods shown in their “non-expanded” position. 
         FIG. 8  is a side view drawing of the subject metal expansion rods shown in their “intermediate-expanded” position (the opposing ends of each half-rod have been pushed inward). 
         FIG. 9  is an exploded view of the subject apparatus. 
         FIG. 10  is a top view of the top half of the subject surrounding fixture housing. 
         FIG. 11  is a bottom view of the top half of the subject surrounding fixture housing. 
         FIG. 12  is an end view of the top half of the subject surrounding fixture housing. 
         FIG. 13  is top view of the bottom half of the subject surrounding fixture housing. 
         FIG. 14  is an end view of the bottom half of the subject surrounding fixture housing. 
         FIG. 15  is a perspective view of the subject fixture. 
         FIG. 16  is a cross-sectional view of the subject fixture showing the foil surrounding the metal expansion rods with the foil edges overlapping beneath the slit in the top half of the surrounding fixture housing and taken along line  16 — 16  in  FIG. 15 . 
         FIG. 17  is side view of the subject tubular membrane produced by the subject method and mounted in suitable “plumbing” adaptors. 
         FIG. 18  is a photograph (see  FIG. 17  for an equivalent drawing) of the subject tubular membrane produced by the subject method and mounted in suitable “plumbing” adaptors. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus generally shown in  FIG. 1  through  FIG. 18 . It will be appreciated that the apparatus may vary as to configuration and as to details of the parts, and that the method may vary as to the specific steps and sequence, without departing from the basic concepts as disclosed herein. 
     Generally, the subject V-alloy composite membranes comprise a V-Cu foil with a Pd coating. Fabrication of the subject V-alloy composite membranes consisted of the following generalized steps [Peachey, N. M.; Snow, R. C.; Dye, R. C. Composite Pd/Ta metal membranes for hydrogen separation. J. Membr. Sci. 1996, 111, 123, U.S. Pat. No. 5,738,708, and Moss, T. S.; Peachey, N. M.; Snow, R. C.; Dye, R. C. Multilayer metal membranes for hydrogen separation. Int. J. Hydrogen Energy 1998, 23 (2), 99, which are herein incorporated by reference]; 1) melting and rolling alloy foils, 2) cleaning, deposition of Pd, and 3) welding into a tubular shape. High purity (99.9%) powders were mixed and electron beam (e-beam) melted into buttons in a vacuum furnace. The buttons were flipped and re-melted several times to ensure compositional uniformity. The alloys were cold rolled into ˜5×15 cm strips with a nominal thickness of 40 μm. The foils were washed with soap and water, rinsed with methanol, blown dry with nitrogen, mounted by clamping the ends of the foil strip, and loaded into the physical vapor deposition (PVD) chamber. After evacuation, argon was bled into the chamber to a pressure of 1.510–4 Torr and the ion-gun (ion Tech, Teddington, UK) was set to a power of 1 keV and 20–25 mA to ion-mill each side of the foil for 60–90 min. The foil was visually inspected through a window during ion-milling to ensure removal of all remaining macroscopic contaminants. After ion-milling, the chamber was evacuated to 110–7 Torr and the e-beam (Airco-Temescal CV-14 power supply) evaporated Pd onto the foil at 3–5 A/s. A piezoelectric device was used to determine the thickness of metal deposited. Approximately 100 nm of Pd or Pd alloy was deposited onto each side of the foil. A tubular membrane was fabricated by placing the foil in a specially designed fixture and electron beam welding the foil to itself and to stainless steel fittings. The membrane was plumbed into the test system for evaluation. Permeation tests for membranes were conducted by heating at 1° C./min under argon purge (all gases were 99.999% pure) to the desired temperature followed by introduction of pure hydrogen and measurement of the permeation flux at pressure differences across the membrane up to 100 psig. The test bench was described previously [Paglieri, S. N. and S. A. Birdsell. Palladium alloy composite membranes for hydrogen separation. in 15th Annual Conf. Fossil Energy Mater. 2001. Knoxville, Tenn.: Oak Ridge Natl. Lab., which is herein incorporated by reference]. 
     Several tubular V—Cu alloy membranes were fabricated and tested. The foil was determined to contain 2 atom % Cu by AES. This is close to the solubility limit of Cu in V [12]. The first membrane was not coated with Pd and permeated less than 1 sccm of hydrogen at 300° C. and a ΔP across the membrane of 100 psi. Argon did not measurably permeate through the membrane. The membrane survived a cool down to room temperature until it was re-pressurized with argon at ˜100 psig. 
     The subject invention is a hydrogen separating membrane that has an advantageous configuration for integrating into processes such as hydrogen separations, and membrane reactors. Further, the subject invention is concerned with the formation of a leak free metal membrane and its attachment to connective plumbing for the purpose of hydrogen purification at elevated temperatures. A difficulty that is often encountered in the development of hydrogen separating metal membranes is the formation of the material into a configuration suitable for long-term operation at high temperatures and pressures. Tubes are a favorable geometry for membranes due to strength, high surface-to-volume ratio, and fewer mass transfer limitations. Tubes are also easier to manifold and manufacture into process equipment and if one tube breaks it can be isolated or replaced. 
     For the subject invention, a thin metal foil is welded into a tube to form a hydrogen separating membrane. The foil material is from Groups IV-B and V-B of the Periodic Table such as, but not limited to; vanadium, niobium, tantalum, titanium, or zirconium or alloys comprised of the aforementioned metals combined with each other or containing copper, nickel or silver. 
     In forming the tubular membrane, a specific fixture clamps the seam together during the process of welding the foil and contains a halved copper rod that acts as both a heat sink and a means by which the foil is mounted in the fixture during welding. Once the foil is welded into a tubular shape, it is welded or brazed (usually using silver or other suitable material) to other metals to form a leak-free seal. 
     Foils of Group IV-B and V-B metals or their alloys are placed in a vacuum chamber, ion-milled using an ion gun and an inert gas such as argon and then coated with palladium and palladium alloys. Usually, electron beam (e-beam) evaporation is used for the deposition of palladium, although other physical vapor deposition processes may also be used. Other methods such as chemical vapor deposition (CVD), electrodeposition, or electroless plating may also be employed for deposition of the palladium coating. The foils are ideally between 5 and 100 μm thick while the thickness of the palladium or palladium alloy layer is preferably about 1,000 Å thick. Therefore, the Group IVB or VB metal foil serves as a support for the thin but continuous palladium or palladium alloy film. 
     Group IV-B or V-B metals have intrinsically high hydrogen solubilities and permeabilities although they are readily oxidized and the surface is passivated because of their reactivity. A protective coating of a metal that is catalytically active for the dissociation of hydrogen into atoms is required on both sides of the foil in order to inhibit contamination and facilitate the entry and exit of hydrogen through the foil. Due to high hydrogen solubility, Group IV-B or V-B metals are subject to hydrogen embrittlement during operation as a membrane and particularly during thermal cycling. In order to decrease the solubility of hydrogen in these metals (and therefore lessen the problem of embrittlement) these metals are alloyed with each other or with Group I-A metals such as copper, nickel, or silver. Likewise, pure palladium also embrittles and alloying it with other metals such as silver, copper, yttrium, ruthenium, or gold is required to prevent hydrogen embrittlement of the palladium coating. 
     As mentioned above, a fixture is required in order to weld the foil into the shape of a tube. The fixture clamps the two edges of the foil together during welding so that a continuous and gas-tight seam may be formed. A rod made of a material with high heat conductivity such as copper, brass, or graphite is sliced diagonally to slide and wedge the foil into a cylindrical shape and press the seam together during welding. The halved rod also serves the function of a heat sink, to absorb energy during welding. Otherwise, the thin foil will melt, and pinholes will be formed. The foil, welded to itself into the shape of a tube, is removed from the fixture and slipped over the end of a plumbing tube, made of stainless steel, for example. The foil may be welded directly to the tube or an interlayer of silver may be deposited onto the stainless steel tube and the foil brazed to the coated tube. The silver layer should be between about 10 and 20 μm thick. Electron beam welding is used during all of these steps to maintain precise control over beam power and avoid creating holes in the thin foil. E-beam welding is also performed under vacuum, eliminating the likelihood that the refractory metal foil will oxidize during welding. TIG (Tungsten Inert Gas) welding may also be employed to weld the foil to itself and to the plumbing tubes. 
     Some uses of the tubular membrane include ultra high hydrogen purification to parts per billion (ppb) levels of impurities, and use as a membrane reactor for gaseous or liquid hydrogenations and dehydrogenations. When used as a membrane reactor the membrane removes hydrogen from the reaction space and increases the reaction yield. The surface of the membrane itself can be catalytic towards the desired reaction or catalyst can be packed around it. 
     Detailed Description of the Subject Fabrication Fixture Utilized in the Subject Tubular Foil Membrane Fabrication Procedure 
     Metal Expansion Rod: As seen in  FIGS. 1–8 , the two-part metal expansion rod  5 , around which the alloy foil is formed and made taut comprises two halves  10  and  15 . Although a copper rod is generally used, other equivalent heat-sink suitable and structurally supportive metals and alloys are acceptable. Thus, by way of example and not by way of limitation, a 0.635 cm (0.25 inch) diameter copper rod was sliced in half diagonally using wire EDM (electrical discharge machining) or other suitable separation means.  FIG. 1  shows a diagonal cut along a solid rod&#39;s long axis generated the two halves  10  and  15  .  FIG. 2  illustrates that the two halves  10  and  15  are freely separable from one another, with an aligned side view seen in  FIG. 3  and an aligned top or bottom view seen in  FIG. 4 . Opposing end views are depicted in  FIGS. 5 and 6 . When the membrane foil is wrapped around both halves of the copper rod  10  and  15  the foil is loosely formed into the shape of a cylinder. Once mounted and secured in the surrounding fixture housing  20  (see immediately below), by pushing together on the two halves  10  and  15  of the copper rod  5  (see  FIGS. 7 and 8  in which  FIG. 7  shows an earlier position in the expansion process and  FIG. 8  shows a later position in the expansion process in which the outer diameter of the rod  5  is enlarged over earlier positions), the foil is tightened against the fixture housing , eventually enabling a hermetic seam to be welded. 
     Surrounding Fixture Housing: The fixture housing  20  comprises two mating sections  25  and  30 . Although various types of materials may be utilized to form the two sections  25  and  30 , an acceptable material is aluminum. The bottom section  30  of the fixture was machined from a rectangular block of aluminum and consisted of a trough  35  formed in the bottom section  30  of the fixture (a trough of 0.3175 cm (0.125 inch) radius has been shown to function, as would other equivalent radii). Apertures  37  were tapped into the edges of the bottom section  30  of the fixture to anchor the top section  25  of the fixture with suitable/standard attachment means. The top section  25  of the fixture was machined from a rectangular aluminum block with apertures  39  around the edges to receive anchoring means such as screws  40  that anchor into the corresponding apertures  37  in the bottom section of the fixture  30 . An upper trough  42  is formed in the upper surface of the upper section  25  of the fixture. A slit  44  is placed in the upper fixture section  25 , within the upper trough  42 . Often the (0.028 inch is acceptable) slit  44  is machined into and through a length of the top fixture section  25 , although other methods of introducing the slit are acceptable. The slit  44  is where an electron beam, or other equivalent welding means, will eventually weld the foil to itself to form a leak-free seam. A groove  46  is formed in the lower surface of the upper section of the fixture  25 . This groove  46  may be of many standard shapes, often “V-shaped,” as seen in the subject figures. 
     Assembled Fixture Housing and Metal Expansion Rod:  FIGS. 15 and 16  show the assembled apparatus, both parts of the fixture housing  25  and  30  and both parts of the metal expansion rod  10  and  15  in their expanded positions. Included is a metal foil  50  wrapped around the expanded rod halves  10  and  15 , with its eventual seam edges  55  overlapping and showing through the slit  44 . 
     Detailed Description of Subject Tubular Foil Membrane Fabrication Procedure 
     1. The alloy foil  50  is cleaned, dried, placed in the vacuum coating chamber, ion-milled on both sides, and without breaking vacuum, coated on both sides with a layer of palladium (usually the thickness is between 100–10,000 Å, although 1000 Å is typically used) (see U.S. Pat. No. 5,738,708 by Peachey et al. and the publication by Moss et al. in International J. of Hydrogen Energy, 23 (2), (1998)). 
     2. The foil  50  is cut to the proper dimensions and rolled around the metal expansion rod  5  halves  10  and  15 . The foil  50  when formed into a tube should overlap itself so that it can be welded to itself along its future seam edges  55 , through slit  44 , to produce a welded seam  65 . 
     3. The wrapped metal expansion rod  5  is placed in the two-piece fixture housing  20  and the two halves  25  and  30  screwed together to secure the foil overlapping region  55  so as to be welding accessible through slit  44  formed in the top half of the fixture  25 . The two halves  10  and  15  of the metal expansion rod  5  are then pushed together to tighten the overlapping foil  50  together along and beneath the slit  44  so that during welding a continuous seam  65  is formed. 
     4. The assembled fixture (housing halves  25  and  30  and metal expansion rods halves  10  and  15 ) with the foil  50  securely tightened about the rod  5  and inside the housing fixture  20 , with the future seam  65  (the overlapping foil edges region  55 ) exposed, is placed in a suitable welding device, often an electron welder, and the associated vacuum chamber is then evacuated. For an electron welder apparatus, the electron beam at relatively low power is slowly guided along overlapping foil edges region  55  to weld a seam. Visual inspection during the process helps to prevent the formation of holes in the thin foil  50  due to excessive heat buildup and conversely ensures enough power is supplied to form a continuous weld along the overlapping foil edges region  55 . It is stressed that any suitable seam-forming device is contemplated, for example TIG or a laser welder with an inert gas blanket would also work to weld the foil using the subject fixture. 
     5. The assembled fixture (housing halves  25  and  30  and metal expansion rod halves  10  and  15  ) with the welded overlapping foil edges region  55  now forming a seam  65 , is removed from the vacuum chamber and the foil (welded to itself into the shape of a tube or cylinder) is removed from the subject fixture. The produced metal membrane tube is then fitted with suitable “plumbing” adaptors to be utilized in any desired application. For example, the ends of the foil tube are slipped over tubing or VOR gland fittings. The fit should be snug enough to facilitate the formation of a continuous weld. The foil tube with its fittings/tubes is loaded into an electron beam welder vacuum chamber (or equivalent), evacuated, and welded while rotating the tube. For example, while vanadium alloy is easily welded to a stainless steel fitting/tube, a silver braze coating on the fitting/tube can be used to braze the foil to the fitting/tube and may help in adhesion of the vanadium alloy foil during hydrogen permeation testing. The silver-brazed fittings are prepared by milling down the OD of the tube, cleaning, and coating with silver to a thickness of ˜15 μm using PVD (although other deposition methods may be used). 
     EXPERIMENTAL EXAMPLES 
     Example 1 
     Non-Catalytic Coated Reference Structure 
     Vanadium and copper were electron-beam melted on a water-cooled copper hearth. The produced button was flipped and re-melted several times to ensure compositional uniformity of 25 weight % copper. The resulting button was cold rolled into an ˜5×15 cm (˜2×5.9 inch) strip with a nominal thickness of 40 μm (˜1.6 mil). The foil was washed with soap and water, rinsed with methanol, and blown dry with nitrogen. 
     A piece of the foil was placed into a subject fixture and welded to itself to form a tube. The bottom half of the fixture was machined from a rectangular block of aluminum and consisted of a 0.3175 cm (0.125 inch) radius trough bored along a block. The foil was wrapped around the both halves of the copper expansion rod (0.635 cm (0.25 inch) diameter copper rod) into the shape of a cylinder and placed in the trough. The top of the fixture was a rectangular aluminum block. A (0.028 inch) slit was machined along the length of the top fixture where the electron beam welded the foil to itself to form a leak-free seam. The electron-beam welder was at a power of 0.55 A when the foil was welded to itself to form a 0.635 cm (0.25 inch) cylinder. 
     The tubing ends of stainless steel 0.635 cm (0.25 inch) VCR glands were machined down, PVD coated with 15 microns (0.59 mil) of silver, and placed inside the ends of the cylindrical foil tube. The glands fit tightly so that no fixture was needed during welding. The ends of the foil cylinder were brazed to the VCR glands using electron-beam welding at a power of 0.62 A. The resulting membrane module was cleaned with acetone and ethanol, attached to VCR fittings attached to a gas manifold, and the membrane tube lumen was pressurized with argon to 44 psia with no detectable leakage. The membrane was heated to 300° C. at 1° C./minute. Hydrogen permeation through the membrane was &lt;1 sccm (cm 3  (STP)/minute) at 40 psia. The membrane was exposed to hydrogen flowing at 200 sccm for 24 hours and then cooled to 25° C. 
     The membrane was then pressurized with argon to 114 psia and &lt;1 sccm leakage was observed. 
     Example 2 
     Catalytic Coated Structure (same as Example 1 Except the Foil is Coated with Palladium to Make the Hydrogen Separating Membrane, the Coated Foil is Welded Directly to the Stainless Steel VCR Gland Fittings Instead of Brazed to Silver Coated Fittings, and the Membrane is Tested for Pinholes and Hydrogen Permeability) 
     Vanadium and copper were electron-beam melted on a water-cooled copper hearth. The button was flipped and re-melted several times to ensure compositional uniformity of 25 weight % copper. The resulting button was cold rolled into a 5×15 cm (2×5.9 inch) strip with a nominal thickness of 40 μm (1.6 mil). The foil was washed with soap and water, rinsed with methanol, and blown dry with nitrogen. The foil was mounted by clamping the ends of the foil strip, and loaded into the physical vapor deposition (PVD) chamber. After evacuation to 1·10 −6  Torr, argon was bled into the chamber to a pressure of 1.5·10 −4  Torr and the ion-gun (ion Tech, Teddington, UK) was set to a power of 1 keV and 20–25 mA to ion-mill each side of the foil for 60–90 min. The foil was visually inspected through a window during ion-milling to ensure removal of all remaining macroscopic contaminants. Without breaking vacuum, the chamber was evacuated to 1·10 −6  Torr and a 1000 Å (3.9 microinch) layer of palladium was deposited on each side by e-beam evaporation (Airco-Temescal CV-14 power supply) at 3–5 Å/s. A quartz crystal was used to monitor the thickness of metal deposited. 
     A piece of the foil was placed into a fixture and welded to itself to form a tube. The bottom half of the fixture was machined from a rectangular block of aluminum and consisted of a 0.3175 cm (0.125 inch) radius trough bored along a block. Holes were tapped into the edges of the block to screw down the top of the fixture. The foil was wrapped around both halves of the copper rod into the shape of a cylinder and placed in the trough. The top of the fixture was a rectangular aluminum block with holes around the edges to put screws through to attach to the bottom fixture. A (0.028 inch) slit was machined along the length of the top fixture where the electron beam welded the foil to itself to form a leak-free seam. A 0.635 cm (0.25 inch) diameter copper rod was sliced in half diagonally using wire EDM (electrical discharge machining). By pushing together on the two halves of the copper rod, the foil could be tightened against the fixture, enabling a hermetic seam to be welded. The electron-beam welder was at a power of 0.55 A when the foil was welded to itself to form a 0.635 cm (0.25 inch) cylinder. 
     The tubing ends of stainless steel 0.635 cm (0.25 inch) VCR glands were machined down and placed inside the ends of the cylindrical foil tube. The glands fit tightly so that no fixture was needed during welding. The ends of the foil cylinder were brazed to the VCR gland fittings using electron-beam welding at a power of 0.62 A. The resulting membrane module was cleaned with acetone and ethanol, attached to VCR fittings attached to a gas manifold, and the membrane tube lumen was pressurized with argon to 55 psia &lt;1 sccm leakage was observed. The membrane was heated to 300° C. at 1° C./minute. Both sides of the membrane were purged with argon. The membrane lumen was pressurized to 56 psia with flowing hydrogen at 150 sccm and the hydrogen permeation through the membrane was 3.5 sccm. 
     Example 3 
     Catalytic Coated Structure (Same as Example 2 Except Changes in Hydrogen Permeability Testing Parameters). 
     Vanadium and copper were electron-beam melted on a water-cooled copper hearth. The button was flipped and re-melted several times to ensure compositional uniformity of 25 weight % copper. The resulting button was cold rolled into a 5×15 cm (2×5.9 inch) strip with a nominal thickness of 40 μm (1.6 mil). The foil was washed with soap and water, rinsed with methanol, and blown dry with nitrogen. The foil was mounted by clamping the ends of the foil strip, and loaded into the physical vapor deposition (PVD) chamber. After evacuation to 1·10 −6  Torr, argon was bled into the chamber to a pressure of 1.5·10 −4  Torr and the ion-gun (Ion Tech, Teddington, UK) was set to a power of 1 keV and 20–25 mA to ion-mill each side of the foil for 60–90 min. The foil was visually inspected through a window during ion-milling to ensure removal of all remaining macroscopic contaminants. Without breaking vacuum, the chamber was evacuated to 1·10 −6  Torr and a 1000 Å (3.9 microinch) layer of palladium was deposited on each side by e-beam evaporation (Airco-Temescal CV-14 power supply) at 3–5 Å/s. A quartz crystal was used to monitor the thickness of metal deposited. 
     A piece of the foil was placed into a fixture and welded to itself to form a tube. The bottom half of the fixture was machined from a rectangular block of aluminum and consisted of a 0.3175 cm (0.125 inch) radius trough bored along a block. Holes were tapped into the edges of the block to screw down the top of the fixture. The foil was wrapped around both halves of the copper rod into the shape of a cylinder and placed in the trough. The top of the fixture was a rectangular aluminum block with holes around the edges to put screws through to attach to the bottom fixture. A (0028 inch) slit was machined along the length of the top fixture where the electron beam welded the foil to itself to form a leak-free seam. A 0.635 cm (0.25 inch) diameter copper rod was sliced in half diagonally using wire EDM (electrical discharge machining). By pushing together on the two halves of the copper rod, the foil could be tightened against the fixture, enabling a hermetic seam to be welded. The electron-beam welder was at a power of 0.55 A when the foil was welded to itself to form a 0.635 cm (0.25 inch) cylinder. 
     The tubing ends of stainless steel 0.635 cm (0.25 inch) VCR glands were machined down and placed inside the ends of the cylindrical foil tube. The glands fit tightly so that no fixture was needed during welding. The ends of the foil cylinder were brazed to the VCR gland fittings using electron-beam welding at a power of 0.62 A. The resulting membrane module was cleaned with acetone and ethanol attached to VCR fittings attached to a gas manifold, and the membrane tube lumen was pressurized with argon to 30 psia with no detectable leakage. The membrane was heated to 350° C. at 1° C./minute. Both sides of the membrane were purged with argon. The membrane lumen was pressurized to 17 psia with flowing hydrogen at 50 sccm and the hydrogen permeation through the membrane was 4 sccm. 
       FIG. 17  (a drawing) and  18  (an equivalent photograph of the drawing seen in  FIG. 17 ) depict a tubular vanadium-copper membrane  60 , with a weld seam  65  (along the overlapping foil edges region  55 ), produced by the subject method and fitted, on each end, to appropriate “plumbing” fittings  70  and  75  that mate with suitable usage or test devices. 
     Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”