HYDROGEN PERMEABILITY OF Pd53Cu FILM ALLOYS OF VARIOUS PHASE COMPOSITION

The purpose of this work was to reveal the infl uence of the phase composition and the crystallographic orientation of fi lm samples of Pd-Cu solid solution on the parameters of extraction and injection of atomic hydrogen in aqueous solution of sulphuric acid. The study was carried out using a two-step cathode-anode chronoamperometry method. The fi lms of the Pd53Cu alloy of various thickness were obtained by magnetron sputtering. They were characterised by the same phase (100% of theβ -phase of a solid solution) and chemical composition. It was confi rmed that during the initial period (≤ 4 s, the injection of atomic hydrogen proceeds in a mixed diffusion-phase-boundary regime, which later transforms into a purely diffusion mode. The kinetic and diffusion parameters of the stages of phase-boundary penetration of hydrogen and its subsequent solid-phase diffusion were calculated by the cathodic and anodic current decays. It was established that regardless of the thickness of the sample, an increase in the β phase fraction in the alloy leads to a marked increase in the diffusion coeffi cient of atomic hydrogen and, consequently, to an increase in the hydrogen permeability constant. The crystallographic orientation only affects the stage of phase-boundary penetration of hydrogen into the fi lm alloy. The data obtained confi rm the preferential movement of hydrogen along the grain body rather than over the interphase boundaries.