Free-standing Pd-23wt%Ag membranes, with 5 thicknesses ranging from ∼1.3 to ∼5.0μm, were prepared by magnetron sputtering. The hydrogen permeation was determined before and after heat-treatment in air at 300C. For all of the membranes studied, the heat treatment resulted in enhanced permeation and, for some membranes, the hydrogen flux more than doubled. A permeance of 1.7 x 10-2mol/m2sPa0.5 was observed for ∼1.3μm-thick membranes. Bulk diffusion was the main rate-limiting step after heat treatment in air. The permeability was similar for all of the membranes studied after this treatment, with a mean value of 2.1 x 10-8mol.m/m2sPa0.5. Atomic force microscopy showed that samples which were heat-treated in air had a higher surface roughness, a larger surface area and a larger surface grains than samples not heat-treated in air.
Hydrogen Permeation of Thin, Free-Standing Pd/Ag23% Membranes before and after Heat Treatment in Air. A.L.Mejdell, H.Klette, A.Ramachandran, A.Borg, R.Bredesen: Journal of Membrane Science, 2008, 307[1], 96-104
Table 137
Diffusivity of D in Pd-25%Ag as a Function of Pressure
[D (cm2/s) = α+ βP + γP2]
T (C) | α | β | γ | P (psia) |
300 | 1.23 x 10-5 | 6.37 x 10-8 | 8.90 x 10-12 | 7.6-882 |
400 | 2.64 x 10-5 | 4.05 x 10-8 | 1.92 x 10-11 | 7.7-894 |
500 | 4.80 x 10-5 | 3.66 x 10-8 | -3.80 x 10-12 | 7.5-855 |