Characterization of Pd–Ag membranes after exposure to hydrogen flux at high temperatures

MARÍA L. BOSKO, DAVID YEPES, SILVIA IRUSTA, PIERRE ELOY, PATRICIO RUIZ, EDUARDO A.LOMBARDO, LAURA M. CORNAGLIA

JOURNAL OF MEMBRANE SCIENCE

ELSEVIER

Año: 2007 vol. 306 p. 56 - 65

0376-7388

Pd-Ag  films were deposited  by sequential electroless plating   on    porous stainless steel tubes. Two different  intermediate layers  of   a-Fe2O3   and g-Al2O3 oxides were employed  as  diffusion barriers to modify the  stainless steel porous size and to  avoid the  intermetallic  diffusion  of Fe and Ni through the  Pd-Ag layer. The  membranes were tested in a gas permeation system to determine the  hydrogen permeability and selectivity at temperatures between  673 and 923 K. After the high temperature treatments, they were  characterized by  XRD, XPS,  SEM, AFM and EPMA.  The  Pd-Ag/PSS membranes had a good thermal resistance.   After annealing  at 923 K, the Auger depth profiles did not  show the presence of Fe in the Pd-Ag/ g-Al2O3 membranes. However,  iron was detected  in the surface layer after long-term hydrogen permeation measurements at   temperatures  between 673 and 923 K, indicating that the g-Al2O3 layer did not completely block  the intermetallic diffusion under these severe conditions.