Pd/H system in H_2 plasmas

摘要

The absorption of hydrogen by Pd wire samples has been studied at 299 K and in the H_2 pressure range from 18 to 1800 mbar under both tensile stress and tensile stress under cold H_2 plasma. Plasma is generated in a eorona discharge regime by applying a dc high voltage between a Pd wire and a cylindrical counterelectrode. Positive and negative coronas have been performed. Three independent experimental quantities have been simultaneously measured: ratio x=n_H_(Pd), with n the number of atoms; ratio R/R_0, with R the four-probe resistance of the wire and R_0 the resistance when x=0; and ratio Δl/l_0, with Δl the length change of the wire and l_0 its length when x=0. From the thermodynamic analysis of data, the absorption standard chemical potential, Δμ_(abs)~0, and the excess chemical potential, Δμ~(exc), of hydrogen atoms in Pd have been obtained. At constant T, H_2 pressure, and tensile stress, the x value under cold plasma is always higher.