Electrical resistivity, strain and permeability of Pd-Ag membrane tubes

A Pd-Ag (silver 25 wt.%) permeator tube has been tested in order to measure the electrical resistivity, the strain, and the hydrogen permeability under different hydrogenation conditions in the temperature range 50-400 degrees C. The permeator tube has been assembled into the membrane module in a finger-like configuration: pure hydrogen has been fed in the lumen side of the tube at a pressure of 100-400 kPa while the permeated hydrogen has been recovered in the shell side of the membrane via a nitrogen purge gas stream of 3.70 x 10(-4) mol s(-1) at atmospheric pressure. The electrical resistivity increases with both the temperature and hydrogen pressure but a minimum of the resistivity is present at 100 degrees C. The strain of the hydrogenated material increases with the hydrogen pressure and reduces with the temperature. Moreover, the relationship between the strain and the hydrogen content has been investigated and a power law for isotherms in the temperature range 50-400 degrees C has been found out. Values of hydrogen permeability of 1-2 x 10(-8) mol m(-1) s(-1) Pa-0.5 have been measured in the temperature range 200-400 degrees C: the results showed a modest influence of the hydrogen pressure while the dependence from the temperature follows the Arrhenius' law in agreement with literature. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.