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The thermobaric and concentrational stresses, which arise during the operation of a membrane element under cyclic conditions, can result in the violation of the integrity of a membrane comprising an element and in failure of the element. Studies of the effect of thermobaric cycling in a hydrogen atmosphere at operating parameters (pressure differential, temperature, time of operation) on the properties of membranes allow us to determine the optimum operation conditions of the membrane element. The stability of the Pd–6 wt % In–0.5 wt % Ru–1 wt % Co membrane structure is estimated using the studied temperature dependence of the specific hydrogen permeability of the membrane during its operation in a hydrogen atmosphere, and the possibility of efficient operation of the membrane under given conditions in a temperature range of 250–600°C is noted. The surface of the Pd–6 wt % In–0.5 wt % Ru–1 wt % Co membrane subjected to thermobaric cycling in a commercial-purity hydrogen atmosphere is studied by atomic force microscopy and X‑ray diffraction analysis.

The purity of hydrogen, which is an alternative energy carrier in powder sources of distributed energy resource systems and, in particular, is the feed stock for fuel cells, should be no less than 99.9999 vol % purity High-purity hydrogen can be prepared only via its separation as a result of selective diffusion through metallic membranes manufactured from specific membrane palladium-based alloys prepared in the form of thin foils. In the present work, the combination of deformation and annealings under different conditions is used to prepare the Pd–7.70 wt % Lu alloy in the form of foil 50 µm thick, whose specific hydrogen permeability is studied in the course of cyclic heating and cooling in a hydrogen atmosphere in a temperature range of 300–500°С. The Pd–7.70 wt % Lu membrane is shown to demonstrate high and stable hydrogen permeability. The evolution of the surface structure of the membrane in the course of its operation in the hydrogen atmosphere is studied by atomic force microscopy using the phase contrast mode.

X-ray diffraction has been used to study the phase composition and determine the lattice parameter of the β- and α-phases in foil of a Pd–Cu solid solution with a composition that ensures reversibility of the β $$ \rightleftarrows $$ α transformations: with the structure of the β- and α-phases and a two-phase structure. The thermal expansion coefficient of the Pd–Cu solid solution has been determined for the first time.

A study of methanol steam reforming (MSR) in the presence of a Ni0.2–Cu0.8/Ce0.3Zr0.7O2-δ catalyst in conventional and membrane reactors has revealed that the hydrogen yield in a reactor with a Pd–Cu membrane is higher than that in a conventional flow reactor. It has been shown that the Pd–Cu alloy membrane exhibits high hydrogen permeability. Methanol steam reforming in the membrane reactor provides the production of high-purity hydrogen, because a stream of pure hydrogen free from any impurities is effluent from the permeate zone. Measurements of the hydrogen permeability of the Pd–Cu alloy foil membrane in the membrane reactor before and after catalysis have been conducted.

We have studied the phase composition and texture of a Pd–Cu solid solution with a nearly equiatomic composition in different steps of the preparation of membrane foil by rolling to 300, 175, 100, and 20 μm and 7-μm-thick foil produced by magnetron sputtering of a target having the same composition as the foil. We have identified orientation relationships between the β- and α-phases in the as-prepared two-phase structures and demonstrated that, after heating to 600°C and subsequent cooling, the ordered solid solutions (β-phase) prepared by the two processes, have identical textures, which can be understood in terms of the transformation mechanism.

The structural state of diffusive membrane filters made from a Pd94Y6 alloy, which have undergone a prolonged relaxation after hydrogenation, is studied. The phase composition and structure dispersity are determined. One of the membranes was subjected to secondary hydrogenation, and the effect of occluded hydrogen on the strain processes in the crystal lattice of the inhomogeneous material was demonstrated. High-resolution scanning electron microscopy is used to study the Ostwald ripening of the surface structure of the diffusion membrane filters after secondary hydrogenation. The fact of grain coalescence of an island structure, which can substantially affect the strength characteristics of the membranes, is found.

The effectiveness of flash lamp processing and ion beam sputtering in surface cleaning of membrane foil from a Pd–Cu solid solution produced by rolling has been assessed using cyclic voltammetry and atomic force microscopy. It has been shown that it is reasonable to use cyclic voltammetry for assessing the degree of foil surface cleaning and that combined surface processing of membrane foil is effective in foil surface cleaning. Ion beam processing reproducing the surface elemental composition corresponding to the original composition of the solid solution and increasing surface roughness is a factor of 1.3 more effective than combined surface processing.

The high-grade leak-tight foils 10–20 μm in thickness were obtained from effective alloys (wt %) Pd–6 In–0.5 Ru, Pd–6 Ru, and Pd–40 Cu by using advanced technology. For the Pd–40% wt Cu alloy, the foil with ordered β phase with the CsCl structure, exhibiting maximum hydrogen permeability in the Pd–Cu system, was formed by the combination of deformation and annealing conditions. The mechanical properties and hydrogen permeability of the obtained foil membranes as compared with the foils of 50 μm in thickness and also their performance for pure hydrogen at the membranes work in the commercially pure hydrogen medium were investigated. The concentration dilatation of the foils in hydrogen was investigated at various temperatures. Data on dilatation of palladium membrane alloys are of paramount importance to design of membrane filter elements and choice of their optimal usage conditions because these data determine the operational life of membrane. The Pd–6 wt % In–0.5 wt % Ru–1.25 wt % Co alloy with improved strength characteristics and lower temperature of α ↔ β hydride transition was developed on the basis of the Pd– 6 wt % In–0.5 wt % Ru alloy.

The β $$ \rightleftarrows $$ α phase transformations in foil of the Pd–52 at % Cu solid solution prepared by rolling have been studied using X-ray diffractometry and resistivity measurements during thermal heating–cooling cycles or lamp processing (LP) using light from high-power pulsed xenon lamps, followed by cooling. The results demonstrate that complete ordering of the two-phase (α + β) as-prepared (as-rolled) foil follows the sequence (α + β) → β → α → β in the first heating–cooling cycle and β → α → β in the second and subsequent cycles. When a radiative energy critical for a given thickness of foil with an ordered structure is delivered to the foil surface, an irreversible β → α phase transformation occurs, whose rate can be three orders of magnitude higher than the rate characteristic of the disordering process during Joule heating. After LP, the reversibility of the β $$ \rightleftarrows $$ α phase transformations, inherent in the initial, ordered structure, is observed in a second thermal cycle: heating to 700°C and cooling. The sequence of phase transitions is α → β → α → β in the first cycle and β → α → β in the second and subsequent cycles. The localization of light in the skin layer and finite thermal conductivity offer the possibility of producing a structure with a phase composition gradient at subcritical irradiation times. The fact that the LP-stabilized α-phase persists up to 300°C makes it possible to compare the mechanical properties of foil samples having identical elemental compositions but different (ordered and disordered) structures.

The peculiarities of joining a palladium alloy foil to 12Cr18Ni10Ti stainless steel by diffusion and resistance welding are considered. It is shown that both technologies can be realized only using an intermediate nickel layer with a thickness of 0.1 mm, which provides uniform strength and joint tightness and also prevents the formation of brittle intermetallic compounds. Diffusion welding allows one to obtain high-quality joints of palladium alloy to stainless steel, but this process proceeds at relatively high (950°C) temperatures and takes a long time. Resistance welding does not have these disadvantages, but the outcome significantly depends on the correct choice of welding conditions, upon which the spot weld nugget must be displaced as much as possible toward the stainless steel and the intermediate nickel layer. The connection of the palladium alloy to the intermediate layer occurs owing to mutual diffusion occurring during the passage of the welding pulse.

Diffusion filtering metallic palladium–yttrium membranes are subjected to hydrogenation from a gas phase and are studied by X-ray diffraction using synchrotron radiation. Boundaries of the formation of hydrogen-enriched phases are improved for a range of alloying component content, which is critical for their formation. The effect of the initial state of the alloy on conditions of hydride phase formation in the system is demonstrated. The content of hydrogen occluded in the membrane structure and hydrogen-induced lattice dilatations are determined. The parameters of the alloy substructure are calculated.

β $$ \rightleftarrows $$ α transformations in a thin ~4 µm foil of the PdCu solid solution have been studied by X-ray powder diffraction and measurement of electrical resistance in heating–cooling cycles during heat treatment or rapid photon treatment by radiation of high-power pulsed xenon lamps. It has been found that a single rapid photon treatment for 0.3 s (the radiation energy dose delivered to the sample is 10 J cm–2) leads to a complete disordering of the solid solution at a rate 400 times higher than in that achieved under heat treatment conditions (heating rate of 15 K min–1).

Composite membranes with a thin selective layer based on the Pd–46 at % Cu or Pd–5 at % Pb solid solution on the surface of a bilayer heterostructure with two-level porosity in the form of Kh18N10T steel/nanoporous titanium oxide (steel/rutile) are fabricated. The structure of the selective 4-μm-thick layer is found to have no through pores, and a metal does not penetrate into the nanopores in titanium oxide. The selective layer in both versions has a fine submicrocrystalline granular structure, which is caused by the presence of a second component in the Pd–Pb layer and by a two-phase composition of the Pd–Cu layer. In the temperature range 200–300°C, the hydrogen permeability of the membrane based on the two-phase Pd–Cu solid solution is higher than the membrane based on the Pd–Pb solid solution by a factor of 1.7–2.0.

Thin samples (about 4 μm in thickness) of membrane foil of a Pd–Cu solid solution have been grown on the surface of a SiO2/Si heterostructure by magnetron sputtering. The key features of \(\beta \rightleftharpoons \alpha \) phase transformations have been identified using X-ray diffraction, Auger electron spectroscopy, energy dispersive X-ray microanalysis, and resistivity measurements during a heating–cooling cycle. The results demonstrate that the phase transformations are reversible only in solid solutions containing an excess of copper in the concentration range corresponding to limiting temperatures near the temperature stability limit of the β-phase. Thermal conditions of membrane element operation have been found that ensure stability of the ordered atomic structure of the foil and, accordingly, its high performance. The \(\beta \rightleftharpoons \alpha \) phase transformation has been shown to be reversible after holding the foil at t = 830°C, in a state with a disordered atomic structure, which ensures restoration of its high hydrogen permeability after diffusion bonding to the case of a membrane element.

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.

The possibility of obtaining thick films (3 to 7 µm) of solid solution Pd–6 wt % Ru by magnetron sputtering of a target having the corresponding composition is shown. The structure, phase composition, and surface morphology of films condensed on the surface of oxidized silicon, fluorphlogopite, and anodic aluminum oxide at 300–950 K are studied. A general trend of formation of a gradient grain structure of thick films (with a high grain dispersity level at the initial growth stage) and subsequent selective growth of grains and subgrains having an anisotropic shape and primary orientation is independent of the structure and morphology of the substrate surface.

Among Pdbased membrane alloys (1), the Pd-Cu system has long attracted attention for deep hydrogen purification. This system is distinguished by the for� mation of a CsCltype ordered solid solution ( β phase) (2) in a rather narrow composition range close to Pd- 40 wt % Cu. It is accepted (3) that the CsCltype lattice, as compared to the less dense fcc lattice of the disordered solid solution ( α) phase), and, respectively, the shorter distance between octahedral voids (involved in hydro� gen diffusion) are responsible for a lower barrier for diffusion and a manyfold enhancement of hydrogen permeability. According to the results of numerous experimental studies summarized in (3), the hydrogen diffusion activation energy is 0.035 eV in the ordered solid solution, 0.325 eV in the disordered solid solu� tion, and 0.23 eV in palladium. The hydrogen diffu� sion coefficient at 300 K in the β phase is almost four orders of magnitude higher than in the α phase and two orders of magnitude higher than in Pd (3). Thus, the first, major, way of improving the perfor� mance of a Pd-Cu alloy membrane is to increase hydrogen permeability through ordering of the solid solution. The kinetics and mechanism of solid solu� tion ordering have been studied for more than three

The possibility of the formation of a thin foil in the process of magnetron sputtering of the membrane alloy Pd-Ru (6 wt %) is shown. Data on its structure, mechanical properties, and hydrogen permeability are obtained.

Magnetron sputtering is used to prepare thin (down to 7 μm) Pd-Cu and Pd-Ru membrane foils deposited on the surface of a SiO2/Si heterostructure at 300 and 700 K. Condensed foils (CFs) of an ordered Pd-Cu solid solution (β phase with a CsCl-type structure) and a Pd-Ru solid solution (fcc lattice) are synthesized for the first time. The foils of both alloys are characterized by a gradient granular structure due to selective development of 〈110〉 and 〈112〉 textures and a 〈111〉 texture in the Pd-Cu and Pd-Ru foils during their deposition, respectively. The hardness of the free surface of both foils removed from the substrate is determined by nanoindentation. The hardness is 3.0–3.6 GPa and is 20–50% lower than that of the contact surface (at the interface with the substrate) owing to the gradient structure. The hydrogen permeability of the Pd-Cu CF (β phase) is higher than that of the Pd CF by almost an order of magnitude (effect of a less dense crystal lattice) and is 5–7 times higher than those of the Pd-Ru CF and the Pd-Cu foil prepared by rolling.

The main stages of formation of thin-film membranes with a functional layer of palladium-ruthenium alloy on a foil carrier made of corrosion-resistant steel with directed pores are studied. Selective etching agents and etching modes are determined, and a project of a technological route for the production of such composite hydrogen-permeable membranes is developed.

X-ray diffraction analysis is used to study the effect of hydrogenation on the structural state of Pd-8.3 at % Y foil. The decomposition of the single-phase Pd-8.3 at % Y alloy into two phases that was found experimentally after its saturation with hydrogen and subsequent relaxation at room temperature for 840 h indicates a substantial increase in the coefficient of diffusion of yttrium in the alloy under study. Such an increase in the mobility of yttrium atoms is likely to be related to the high contents of hydrogen and vacancies introduced into the matrix of the alloy under study during the hydrogenation.