Zr-based intermetallic diffusion barrier for stainless steel supported palladium membrane

Electroless-plated palladium membranes were prepared on 316L stainless steel supports with Zr-based intermetallic diffusion barriers, i.e., Zr, ZrO₂ and ZrN. A dc magnetron sputtering method was used to deposit Zr films. The ZrO₂ thin films were obtained from oxidation of Zr thin films in air at 500°C for 1 hour. The ZrN thin films were grown by dc reactive magnetron sputtering at nitrogen flow rate of 2 sccm to obtain stoichiometriccomposition. The prepared films were characterized by XRD, EDS and SEM for phase structure, elemental composition, and surface morphology, respectively. SEM-EDS line scan was used to investigate palladium membranes with and without the diffusion barriers under hydrogen atmosphere at 400-600°C for 24 hours. It was found that ZrO₂ intermetallic diffusion barrier was more effective than ZrN and Zr. The hydrogen permeation flux obtained from palladium membranes with the diffusion barriers was higher than that without, with increasing order, Zr 0.5 µm < ZrN 0.5 µm < ZrO₂ 0.17 µm < ZrO₂ 0.5 µm. Thus, ZrO₂ thin film is the most suitable intermetallic diffusion barrier due not only to prevent the metal migration into palladium membranes but also giving high hydrogen permeance.