HYDROGEN PERMEABILITY OF PALLADIUM-COPPERALLOY COMPOSITE MEMBRANES OVER A WIDE RANGEOF TEMPERATURES AND PRESSURES

摘要

The permeability of Pd-Cu alloys containing 40, 53, 60, and 80 wt% Pd has beenrndetermined over the 623-1173 K temperature range for H2 partial pressurerndifferences as great as 2.6 Mpa. Pure palladium and copper membranes were alsornevaluated. Each alloy was evaluated under conditions of fcc structure stability orrnmetastability. The fcc permeability increased steadily with the proportion ofrnpalladium, approaching the permeability of pure palladium. The 53wt%Pd-rn47wt%Cu and 60wt%Pd-40wt%Cu alloys were also evaluated at temperaturesrnwithin the bcc stability region. For both alloys, the bcc permeability was severalrntimes greater than the fcc permeability. However, the 60wt%Pd-40wt%Cu bccrnpermeability at 623 K was the highest reaching about 70% of the permeability ofrnpure palladium. These bcc alloys were subjected to temperature increases duringrntesting that resulted in transition from bcc to fcc, followed by temperaturerndecreases that should revert the alloys back to bcc. The permeabilities droppedrnabruptly during the transition from bcc to fcc. On cooling to the bcc stabilityrnregion, the 60wt%Pd-40wt%Cu alloy slowly regained a bcc permeability whilernthe 53wt%Pd-47wt%Cu did not during the test period. None of the Pd-Cu alloysrnsubjected to testing at 1173 K failed, however all showed some decline inrnpermeability that was attributed to intermetallic diffusion between the membranernalloy and support.