Influence of surface coating on the performance of V-Cu, V-Ti, and Ta membranes for hydrogen separation
- Stephen N.
- David R.
- Robert C.
- Craig R.
- Ronny C.
- Frank M.
- Stephen A.
Foils of V{sub 0.95}Ti{sub 0.05}, V{sub 1-x}Cu{sub x} (x = 0.01-0.12, atom fraction) and Ta coated with thin films of Pd or Pd alloys (Pd-Cu or Pd-Ag), and other metal interlayers were fabricated and tested for hydrogen permeability and stability at temperatures from 320-450 C. Vanadium-alloy or Ta foils were ion-milled and coatings between 30 and 250 nm thick were applied to both sides in-situ via electron beam evaporation. Membranes were between 40 and 75 {mu}m thick and were completely permselective for hydrogen. Pt or Ni surface coatings on VTi{sub 5} foils reduced the permeability by at least an order of magnitude while the membrane coated with the thinnest Pd layer (30 nm) exhibited the fastest hydrogen flux decline at 450 C. The hydrogen flux through a 75 {mu}m thick Pd/V{sub 0.99}Cu{sub 0.01}/Pd composite membrane with 100 nm Pd per side was 0.66 mol (STP)/m{sup 2} {center_dot} s at 350 C and a transmembrane pressure differential ({Delta}P) of 3.5 atm compared to 0.44 mol (STP)/m{sup 2} {center_dot} s for a 71 {mu}m thick Pd/V{sub 0.88}Cu{sub 0.12}/Pd membrane at the same conditions. Foils of Ta were coated with layers of Ti, Mo and Pd to increase the hydrogen flux stability during operation above 400 C. Although the hydrogen flux through the coated Ta foils was generally an order of magnitude less than through the vanadium-alloy membranes, the hydrogen flux stability was greater. Metallic interdiffusion at different temperatures between various surface coatings and foils was characterized with AES depth profiles. Methods are being developed for welding the thin foil membranes into modules for testing.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 977669
- Report Number(s):
- LA-UR-04-3859; TRN: US201012%%646
- Resource Relation:
- Conference: Submitted to: 8th International Confernece on Inorganic Membranes, Cincinnati, Ohio, July 18-22, 2004
- Country of Publication:
- United States
- Language:
- English
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