Phase relations and hydrogen absorption in the lanthanum-nickel system
Abstract
The LaNi system has been reinvestigated in the range 50–100 at. % Ni. The following compounds were observed: LaNi, LaNi1.4, LaNi2, LaNi3, La2Ni7 and LaNi5. For these compounds the lattice constants have been determined. The phase LaNi5 has a relatively large homogeneity region at elevated temperatures. For the compounds LaNix within this region the equilibrium hydrogen pressure, p, of the 40 °C isotherms was found to change from 2.75 atm for LaNi4.9 to about 9.2 atm for LaNi5.4 according to In p = Cx + q with C = 2.4, q = − 10.75.
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Phase forming law and electrochemical properties of A<inf>2</inf>B<inf>7</inf>-type La–Y–Ni-based hydrogen storage alloys with different La/Y ratios
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Study on the evolution of phase and properties for ternary La-Y-Ni-based hydrogen storage alloys with different stoichiometric ratios
2022, Journal of Alloys and CompoundsIn recent years, some progress has been made in the development and application of the highly anticipated La-Y-Ni hydrogen storage alloy system. However, the relationship between the structure and properties of materials has not been studied systematically and thoroughly. In this paper, the evolution law of AB3-, A2B7- and A5B19-type phases for La-Y-Ni-based hydrogen storage alloys was proposed. The single-phase LaY2Ni9 (AB3), La2Y4Ni21 (A2B7) and La5Y10Ni57 (A5B19) alloys were synthesized by powder sintering method at 1173, 1353 and 1423 K, respectively. The XRD and SEM results of the alloys show that LaY2Ni9 alloy has a single PuNi3 phase (3 R), La2Y4Ni21 alloy is composed of Ce2Ni7 phase (2 H) and Gd2CO7 phase (3 R), and La5Y10Ni57 alloy contains Pr5Co19 phase (2 H) and Ce5Co19 phase (3 R). Among the three alloys, the La2Y4Ni21 alloy has the largest hydrogen storage capacity (1.59 wt%) in solid /H2 reaction at 313 K. The target alloys all exhibit excellent electrochemical activation ability. The maximum discharge capacity of LaY2Ni9, La2Y4Ni21 and La5Y10Ni57 alloys decreases gradually, but their cycle stability increases in turn. The high-rate discharge performance of La2Y4Ni21 alloy is the best, because its exchange current density (I0 = 75.55 mA/g) and hydrogen diffusion coefficient (D0 = 2.51 ×10−10 cm2/s) cooperate well. It is hoped that these findings can offer theoretical guidance and technical assistance for the development of La-Y-Ni-based hydrogen storage alloys.
Highlighting the stability control of superlattice structures by fine tuning of subunit volumes
2022, Journal of Alloys and CompoundsABy compounds with superlattice structures are considered as new generation materials for hydrogen storage and very promising as negative electrode for Ni-MH batteries. These compounds can be considered as the stacking of two fundamental layers along the c crystallographic axis: [A2B4] and [AB5]. Binary RNix (R = rare earths) compounds adopting stacking structures absorb large quantity of hydrogen but show poor reversibility. The superlattice structures are built by constraining the ab planes of the [A2B4] subunit to that of the more stable [AB5] one. The volume mismatch between the two subunits is the main cause of the multi-plateau behavior of the binary RNix (R = rare earths) compounds. The multi-element compounds show often improved hydrogen storage properties. In this review we highlight the structural evolution with the element substitution and the correlation between the subunit volume matches and the hydrogenation properties.
Machine-learning enabled thermodynamic model for the design of new rare-earth compounds
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Phase transformations and phase equilibria in the La-Ni and La-Ni-Fe systems. Part 2: Isothermal sections at 750, 600 and 500 °C
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Polyetherimide-LaNi<inf>5</inf> composite films for hydrogen storage applications
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