Hydrogen permeability measurement through Pd, Ni and Fe membranes

An ultrahigh vacuum apparatus for the measurement of hydrogen gas permeation through metal membranes has been developed to perform studies in the ranges of low pressure and medium temperature. The sealing of the hydrogen gas at the specimen is done by gold O-rings which yield vacuum tightness. The hydrogen permeation is measured for pure Pd, Ni and Fe membranes over a pressure range of 0.1-100 mbar and a temperature range of 50-440 degreesC. The results are compared with data in the literature. It shows that the permeation is exceedingly affected by the surface contamination on the specimens in the case of Pd. The contaminants are taken off from the Pd surface by short aging around 200-300 degreesC in air. After cleaning the surface, the permeation amount increases and agrees well with the literature data. The activation enthalpies for permeation are (0.144 +/-0.003), (0.600 +/-0.003) and (0.382 +/-0.004) eV for Pd, Ni and Fe, respectively, in the present investigation. For Ni and Fe, such a special treatment to clean the surface is not necessary. (C) 2001 Elsevier Science B.V. All rights reserved.