Sputtered, electroless, and rolled palladium-ceramic membranes

Three techniques were used to produce palladium-ceramic (Pd-ceramic) compos ite membranes for hydrogen separation and production. They are sputtering, electroless deposition and rolling of thin Pd alloy films over ceramic poro us tubes. After studying and developing the three coating techniques, an ex tensive testing and characterizing work was carried out on these thin film composite membranes. The results show that in the sputtered (0.5-5 mum) and electroless (2.5-20 mum) composite membranes, the thermal cycling of the h ydrogenated metallic layer produces membrane failures. Such failures are ch aracterized by crack formation and metal film peeling. This fact has been e xplained by an evaluation of the shear stresses at the metal-ceramic interf ace due to the differential elongation between the palladium (Pd) coating a nd the ceramic support under thermal cycling and hydrogen loading. The roll ed membranes (50-70 mum), however, because of the particular coating soluti on, have shown a complete hydrogen selectivity and good chemical and physic al stability in long-term tests. (C) 2002 Elsevier Science B.V. All rights reserved.