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

Abstract

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 °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 × 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 °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 °C has been found out. Values of hydrogen permeability of 1–2 × 10 −8 mol m −1 s −1 Pa −0.5 have been measured in the temperature range 200–400 °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.