STRUCTURALLY STABLE COMPOSITE PD-AG ALLOY MEMBRANES - INTRODUCTION OFA DIFFUSION BARRIER

This work investigates the improvement of the structural stability of Pd-Ag alloy membranes by introduction of a diffusion barrier. Asymmetr ic Pd-Ag films were deposited on porous stainless steel (SS) substrate by electroless plating. The formation of these alloys was achieved by annealing the as-deposited membranes at temperatures higher than Tamm an temperatures of the alloy components in a hydrogen atmosphere. The composite Pd-Bg membranes were characterized using XRD and Auger elect ron depth profiling. The atomic interdiffusion oi silver and palladium resulted in Pd-Ag alloys ill an fee structure. To improve the structu ral stability of Pd-Ag alloy/SS membranes, an ultrathin intermediate l ayer of titanium nitride being 0.1 mu m thick was introduced as a diff usion barrier between Pd-Ag and the SS substrate. The Auger electron d epth profiling analysis indicated that the improved membranes were the rmally stable at temperatures as high as 973 K, and practical for the catalytic membrane reactor use. An estimation of diffusion coefficient s revealed that the presence of hydrogen in the annealing atmosphere f avoured the Pd-Ag interdiffusion and thus the formation of Pd-Ag alloy s.