Ingots of palladium alloys with 5, 8, 12, 16, and 20 wt % Pb, which correspond to the Pd-based solid solution region, are prepared by arc melting in a protective atmosphere. Foils 50 μm thick are prepared from the ingots subjected to cold rolling and intermediate vacuum annealing. The membrane characteristics of the foils, which include the strength, the hydrogen permeability, the corrosion resistance, the α ⇄ β hydride transition temperature, and the crystal lattice parameters, have been studied. The Pd–8 wt % Pb alloy is shown to exhibit the maximum specific hydrogen permeability (2.6 N m3 mm/(m2 h MPa0.5)) at 500°C, an adequate plasticity (δ = 12%), a high strength (\({\sigma _{{u_{hard}}}}\) = 550 MPa, \({\sigma _{{u_{ann}}}}\) = 230 MPa), and corrosion resistance against one of the hydrocarbon-conversion products (CO2), which allow us to recommend this alloy for application as the membranes in filtration membrane elements.
Owing to exceptionally high selectivity, membranes based on palladium alloys are widely used for obtaining high-purity hydrogen. An important issue for providing high hydrogen permeability of the membranes is to form the required phase composition. The structural organization of the solid solutions consisting of Cu–36.4 at .% Pd and Cu–50 at .% Pd were studied by X-ray diffraction (XRD), electron diffraction (ED), high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDXS). It was found that the former composition can be ordered in the temperature range of 300–400 °C and in the heating (up to 800 °C)–cooling cycle. In the presence of excess Cu atoms (27.2%), this structure can be represented by CsCl type structural units (β-phase) and distributed body center cubic (BCC) copper structural units in the corresponding concentration dose. The formation of a single crystal ordered phase within the mosaic blocks of the disordered phase was established. Experimental evidence was obtained for the separation of the α-phase solid solution in the elemental composition; the very low rate of ordering inherent in this system was attributed to this effect. The hydrogen permeability of a foil of the equiatomic composition was described.
1 November 2021 in Moscow University Physics Bulletin
The microstructure of the membrane alloy Pd-9.1 at $$\%$$ Y has been studied by X-ray diffraction using synchrotron radiation and transmission electron mic