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Membranes 2018, 8(4), 92; https://doi.org/10.3390/membranes8040092

New Insight to the Effects of Heat Treatment in Air on the Permeation Properties of Thin Pd77%Ag23% Membranes

1
Department of Chemical Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
2
SINTEF Industry, P.O. Box 124 Blindern, N-0314 Oslo, Norway
*
Author to whom correspondence should be addressed.
Received: 22 August 2018 / Revised: 13 September 2018 / Accepted: 16 September 2018 / Published: 10 October 2018
(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)
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Abstract

Sputtered Pd77%Ag23% membranes of thickness 2.2–8.5 µm were subjected to a three-step heat treatment in air (HTA) to investigate the relation between thickness and the reported beneficial effects of HTA on hydrogen transport. The permeability experiments were complimented by volumetric hydrogen sorption measurements and atomic force microscopy (AFM) imaging in order to relate the observed effects to changes in hydrogen solubility and/or structure. The results show that the HTA—essentially an oxidation-reduction cycle—mainly affects the thinner membranes, with the hydrogen flux increasing stepwise upon HTA of each membrane side. The hydrogen solubility is found to remain constant upon HTA, and the change must therefore be attributed to improved transport kinetics. The HTA procedure appears to shift the transition from the surface to bulk-limited transport to lower thickness, roughly from ~5 to ≤2.2 µm under the conditions applied here. Although the surface topography results indicate that HTA influences the surface roughness and increases the effective membrane surface area, this cannot be the sole explanation for the observed hydrogen flux increase. This is because considerable surface roughening occurs during hydrogen permeation (no HTA) as well, but not accompanied by the same hydrogen flux enhancement. The latter effect is particularly pronounced for thinner membranes, implying that the structural changes may be dependent on the magnitude of the hydrogen flux. View Full-Text
Keywords: Pd-Ag membranes; hydrogen permeation; surface characterization; solubility; heat treatment Pd-Ag membranes; hydrogen permeation; surface characterization; solubility; heat treatment
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Vicinanza, N.; Svenum, I.-H.; Peters, T.; Bredesen, R.; Venvik, H. New Insight to the Effects of Heat Treatment in Air on the Permeation Properties of Thin Pd77%Ag23% Membranes. Membranes 2018, 8, 92.

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