Zr-based intermetallic diffusion barriers for stainless steel supported palladium membranes

Electroless-plated palladium membranes were prepared on stainless steel supports with thin Zr, ZrO2 and ZrN films as intermetallic diffusion barriers. DC magnetron sputtering, and reactive DC magnetron sputtering in the presence of a 2 sccm nitrogen flow rate, were used to deposit the Zr films or ZrN films, respectively. ZrO2 films were obtained from oxidation of Zr films in air at 500 °C. The as-prepared films were characterized by X-ray diffraction (XRD), electro dispersive spectrometry (EDS) and scanning electron microscopy (SEM) for their phase structure, elemental composition and surface morphology, respectively. The presence of the Zr-based membrane barriers significantly reduced the intermetallic diffusion of Fe, Cr and Ni into the palladium membrane, as determined by SEM–EDS line scans, and increased the hydrogen permeation flux in the order of Zr < ZrN < ZrO2 for the same 0.5 μm thickness. The results indicated that both ZrO2 and ZrN thin (0.5 μm) films are promising intermetallic diffusion barriers, not only for preventing the metal migration into the palladium membrane but also in giving a high hydrogen permeance.