Hydrogen permeability measurement through Pd, Ni and Fe membranes

An ultrahigh vacuum apparatus for the measurement of hydrogen gas permeatio n through metal membranes has been developed to perform studies in the rang es 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 h ydrogen permeation is measured for pure Pd, Ni and Fe membranes over a pres sure 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 permeat ion is exceedingly affected by the surface contamination on the specimens i n the case of Pd. The contaminants are taken off from the Pd surface by sho rt aging around 200-300 degreesC in air. After cleaning the surface, the pe rmeation amount increases and agrees well with the literature data. The act ivation enthalpies for permeation are (0.144 +/-0.003), (0.600 +/-0.003) an d (0.382 +/-0.004) eV for Pd, Ni and Fe, respectively, in the present inves tigation. For Ni and Fe, such a special treatment to clean the surface is n ot necessary. (C) 2001 Elsevier Science B.V. All rights reserved.