Preparation of Pd-Cu alloy composite membranes

Pd-Cu alloy composite membranes are not susceptible to the mechanical, embrittlement, and poisoning problems that have prevented widespread industrial use of Pd for high temperature H2 separation. In addition, the H2 permeability was confirmed to be higher than pure Pd membrane and the 

Moreover, thin (less than 2 pm thickness) and pinhole-free Pd-Cu alloy composite membranes with a diffusion barrier have been fabricated on mesoporous stainless steel supports (MSSS) by vacuum electro-deposition (Nam and Lee, 2001). The deposition film was fabricated by multilayer coating and diffusion treatment and the formation of Pd-Cu alloys was achieved by annealing the as-deposited membranes at 450°C in nitrogen atmosphere. To improve the structural stability of Pd alloy/Ni-MSSS composite membranes, a thin intermediate layer of silica by sol-gel method was introduced as a diffusion barrier between Pd-Cu active layer and a modified MSSS substrate. The composition and phase structures of the alloy film were studied by energy dispersive analysis (EDS) and XRD the typical Pd-Cu plating had a composition of 63% Pd and 37%Cu and the atomic inter-diffusion of Pd and Cu resulted in Pd-Cu alloys in an fee structure. The electron probe microanalyser (EPMA) profiling analysis indicated that the improved membranes were structurally stable. The Pd-Cu alloy composite membrane obtained in this study yielded excellent separation performance with H2 permeance of 2.5 x 10 cm /(cm cmHg s) and Hj/Nj selectivity above 70000 at 450°C. 

Electroless plating was used to prepare Pd-Cu composite membranes by successive deposition of Pd and then Cu onto various tubular porous ceramic 

Dual sputtering deposition technique was used to prepare submicron thin Pd-Cu alloy films, which allowed a high composition control of the layer (Hoang et al, 2004). The composition, surface morphology and phase structure of the sputtered layers were investigated by EDS, X-ray, XPS, SEM, TEM and XRD. For example, the XRD data proved that the Pd-Cu layers were an alloy of Pd and Cu. Subsequently, the characterized Pd-Cu alloy layers were deposited on a silicon support structure to create a 750 nm thin Pd-Cu membrane for H2 separation. The reported membrane obtained a high H2 flux of 1.6 moF(m s) at a temperature of452°C, while the selectivity was at least 500 for H2/He. 

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