I.Yu. Zavaliy

Effect of oxygen content on hydrogen storage capacity of Zr-based η-phases

Abstract The hydrogen storage capacity of η-phases Zr 3 V 3 O x and Zr 4 Fe 2 O x has been found to depend substantially on the oxygen content. Increase of the hydrogen storage capacities to H/f.u. ∼10.5 and 9.4 with the decrease of O-content have been observed for Zr 3 V 3 O x and Zr 4 Fe 2 O x , respectively. The hydrogen concentration in the title phases is higher than that in the corresponding ZrV 2 H 4.9 and Zr 2 FeH 4.5 saturated hydrides. The maximum hydrogen storage capacity is observed at x =0.6 for η-Zr 3 V 3 O x and x =0.3 for η-Zr 4 Fe 2 O x . Based on these results, it is believed that other Zr-based oxygen-stabilised η-phases could also display large hydrogen storage capacity due to partial occupation of 16(c) or 8(a) sites by oxygen atoms.

Hydrogen absorption and phase structural characteristics of oxygen-containing ZrV alloys substituted by Hf, Ti, Nb, Fe

Abstract Hydrogen absorption properties of ZrVO alloys where some of the Zr or V is substituted by Ti, Hf, or Nb, Fe, respectively have been investigated. Phase structural characteristics of these alloys and their hydrides have been determined by X-ray powder diffraction. The interdependence of obtained crystallographic and hydrogenation characteristics has been discussed.

(Hf, Zr)2Fe and Zr4Fe2O0.6 compounds and their hydrides : phase equilibria, crystal structure and magnetic properties

Abstract Hydrogen absorption and desorption properties of the (Hf,Zr) 2 Fe quasibinary alloys (Ti 2 Ni structure type) and the oxygen-stabilised compound Zr 4 Fe 2 O 0.6 with the filled-Ti 2 Ni type of structure, have been studied and discussed in relation to their phase-structural and chemical composition. The crystallographic characteristics, hyperfine parameters and magnetic properties of the hydrogenated alloys have been determined.

Hydrogenation of Zr6FeAl2 and crystal structure of Zr6FeAl2D10

Abstract The intermetallic compound Zr6FeAl2 was hydrogenated (deuterated) at room temperature and investigated by X-ray and neutron powder diffraction. The hydride (deuteride) crystallizes with hexagonal symmetry (space group P 6 2c; deuteride : a = 8.1354(4) A , c = 7.0940(6) A , V = 406.62(5) A 3 , Z = 2 , refined composition Zr6FeAl2D9.82(3)). Its metal atom substructure derives from an ordered Fe2P type host structure (space group P 6 2m ) by small atomic displacements that lead to a doubling of the c axis. Deuterium occupies two types of tetrahedral [Zr4], one type of tetrahedral [Zr3Fe] and one type of trigonal bipyramidal [Zr3Fe2] interstices, thus avoiding the neighbourhood of aluminium. The metal-deuterium bond distances are in the range Zr-D = 2.03–2.22 A and Fe-D = 1.73–1.77 A, while the shortest Al-D distance is 2.90 A. The hydrogen sorption properties of Zr6FeAl2 are intermediate to those of Zr2Fe and Zr2Al.

The crystal structure of the oxygen-stabilized η-phase Zr3V3OxD9.6

Abstract Hydrogen storage capacity and crystal structure of hydrogen-free Zr3V3O0.6 and its saturated deuteride, Zr3V3OxD9.6, have been studied using both X-ray and neutron powder diffraction. Experimental data together with the geometrical analysis of the crystal structure of the deuteride indicate that oxygen non-stoichiometry plays a significant role in the 2-fold increase of hydrogen storage capacity of Zr3V3O0.6 compared with the stoichiometric oxygenated Zr3V3O.

Oxide-modified ZrFe alloys: thermodynamic calculations, X-ray analysis and hydrogen absorption properties

Abstract To predict the possibility of formation of η-Zr 4 Fe 2 O x ternary intermetallics of Ti 2 Ni type structure during interaction between ZrFe melt and added oxide, the thermodynamic calculations for ZrFeR x O y systems were done. The influence of oxide addition on the hydrogen absorption properties of Zr 2 Fe alloys was studied.

Hydrogen ordering and H-induced phase transformations in Zr-based intermetallic hydrides

Abstract Crystal chemistry aspects of hydrogen behaviour in the zirconium–iron intermetallic deuterides (hydrides), Zr2FeD1.80–5.00, Zr3FeD1.27–6.70 and Zr4Fe2O0.6H7.80, were studied with a focus on the application of high resolution powder neutron diffraction. The effects of crystal structure, chemical composition of the metal matrices, temperature and hydrogen contents on preferences in the interstices occupation and H ordering were investigated and discussed in relation to the H absorption–desorption properties. The Hydrogenation–Disproportionation–Desorption–Recombination process was successfully applied to all materials studied, including the first reported example of an oxygen-containing compound, Zr4Fe2O0.6.

Interaction of hydrogen with RECu2 and RE(Cu,Ni)2 intermetallic compounds (RE=Y, Pr, Dy, Ho)☆

Hydrogenation of RECu2 (RE=Dy, Ho, Y) at room temperature and pressures of 100–1500-bar H2 has not resulted in the formation of ternary hydrides. The interaction of hydrogen with Pr(Cu1−xNix)2 (x=0, 0.1, 0.17, 0.25, 0.32) at room temperature and pressure of 25 bar resulted in the formation of Pr(Cu1−xNix)2H∼3 hydrides. It was found that the PrCu2H3 and Pr(Cu0.9Ni0.1)2H2.9 hydrides are poorly crystallized, but that an increase of the Ni-content leads to improved crystallinity of the hydrides. The hydrides Pr(Cu0.75Ni0.25)2H∼3 and Pr(Cu0.68Ni0.32)2H∼3 preserve, shortly after the hydrogen absorption, the CeCu2 type structure of their metallic matrix with a hydrogen induced volume expansion up to 28% compared to the parent compound. During long-term exposure in the air they undergo a structural transformation from the orthorhombic CeCu2 to the hexagonal Fe2P type with a hydrogen induced volume expansion up to 16.6% compared to the parent compound.

Hydrogen-Induced Phase Transformations In H-Storing Alloys of Zirconium

Zirconium-based Zr-V and Zr-Fe alloys are known to be highly efficient absorbers of low pressure hydrogen. Their working performance is structure-dependent and can be improved by modifying the composition of the basic alloys with doping elements. Particularly promising in this respect are modifications of oxide materials where both H-sorption capacity and hydrogenation activity can be increased substantially, especially when boron or rare earth oxides are introduced into the matrices of Zr-V and Zr-V-Fe[1–3].

Electrode Materials Based on LaMgNi4–xCox (0 ≤ x ≤ 1) Alloys

The LaMgNi4–xCox (x = 0, 0.33, 0.67, 1) alloys are prepared by sintering and prolonged heat treatment at 500°C, with the main cubic phase of MgCu4Sn type. The alloy samples ball-milled in an argon atmosphere show the glass-forming ability. Electrochemical experiments of the LaMgNi4–xCox electrodes are performed at charge and discharge current densities of 100 mAh. The maximum discharge capacity is exhibited by the powdered alloys (218–302 mAh/g) compared to the ball-milled ones (92–134 mAh/g). The cobalt content of the LaMgNi4–xCox alloys influences the electrode characteristics. The highest discharge capacity is shown by the powdered alloy with x = 0.33. The ball-milled alloys have slightly higher cyclic stability.