Uphill F ffects on Hydrogen Diffusion Coefficients in Pd77Ag23 Alloy Membranes Influences Due To Gorsky Effect And Lattice Strain Gradient Factors

The choice of palladium (Pd) and Pd alloys selected for use in hydrogen permeation membranes is determined by the values for hydrogen solubility and hydrogen diffusion coefficients, DH, with high values being preferred (1-5). Using pure Pd membranes at temperatures # < 300 deg C can be complicate...

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Bibliographic Details
Published in:Platinum metals review 2003-01, Vol.47 (1), p.32-36
Main Authors: Tong, B X O, Lewis, F A, Bell, S E J, Cermak, J
Format: Article
Language:English
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Summary:The choice of palladium (Pd) and Pd alloys selected for use in hydrogen permeation membranes is determined by the values for hydrogen solubility and hydrogen diffusion coefficients, DH, with high values being preferred (1-5). Using pure Pd membranes at temperatures # < 300 deg C can be complicated by the possible involvement of the *a DB *b phase hydride transition regions, with the likely consequent formation of irreversible distortions (1-10). However, the problems of phase transition and related hysteresis effects can be much reduced by using membranes made of carefully chosen Pd alloys. For example, Pd-Ag (palladium-silver) alloys in the composition range Pd77Ag23 to Pd75Ag25; have been successfully used as hydrogen purification membranes over a wide range of equilibration conditions with respect to hydrogen pressure, p, hydrogen content, n (n = H/M atomic ratio, where M is metal) and temperature, T, (from p-c(n)-T relations). Relationships between n and DH, have been derived by using both electrochemical and gas-phase equilibration techniques (6-10).
ISSN:0032-1400