Hydrogen permeation through Pd/Fe and Pd/Ni multilayer systems

Different sets of Pd/Fe and Pd/Ni multilayer systems, consisting of different numbers of individual layers, have been prepared on Pd substrates by ion-beam sputtering. The gas permeation of hydrogen through the multilayers was measured for various pressures and temperatures. After in situ surface cleaning the specimens, the permeation follows Sieverts’ law indicating a diffusion-controlled process. Comparing the experimental results with the permeation calculated using the parameters obtained for bulk materials show, that the hydrogen permeation through Pd/Fe multilayers is suppressed, whereas, the permeation through Pd–Ni system is enhanced. In the case of the Pd–Fe system, the hydrogen atoms may additionally be trapped at dislocations lowering the permeation. For the Pd/Ni multilayers, the small grain size of the Ni layers leads to an enhanced permeation by grain boundary diffusion. For both multilayer systems, no strong influence of the interfacial layers was observed.