Characterization of intermetallic diffusion barrier and alloy formation for Pd/Cu and Pd/Ag porous stainless steel composite membranes

The formation of the intermetallic diffusion barrier layer by the controlled in-situ oxidation method for Pd and Pd/alloy porous stainless steel composite membranes was investigated. SEM and EDS results showed the existence of an oxide layer as the intermetallic diffusion barrier for oxidation temperatures higher than 600 degreesC. At oxidation temperatures lower than 600 degreesC, there might still be an oxide layer at the membrane-substrate interface although it was too thin to be detected by SEM and EDS. The alloy formation study showed that annealing at 500 degreesC under helium atmosphere did not produce alloys with uniform compositions either for Pd/Ag or Pd/Cu membranes. However, annealing at 600 degreesC gave a uniform Pd/Cu-porous stainless steel (PSS) composite membrane, with no detectable presence of elements from the PSS substrate, further demonstrating the oxide layer as an effective intermetallic diffusion barrier.