A hot isostatic pressing technique was used to prepare bulk polycrystalline samples of the hydrogen-absorbing materials LaAlxNi5−x. Ultrasonic methods were used to measure the elastic moduli of these alloys. Small corrections were made for porosity so that values expected for the theoretical density were found. The various moduli decrease somewhat with increasing x; the porosity-corrected bulk and shear moduli are 137.4 GPa and 59.2 GPa, respectively, at x=0 and decrease to 126.6 GPa and 54.1 GPa, respectively, at x=1. Poisson’s ratio is independent of x within experimental error at 0.31, a value typical for metals. Debye temperatures calculated from the porosity-corrected elastic constants ranged from 360 to 365 K, and were in good agreement with those reported from heat capacity measurements. The present measurements on LaAlxNi5−x were combined with earlier heat capacity measurements of the hydrides, LaAlxNi5−xHy, to estimate the elastic moduli of the latter materials. The estimated hydride moduli were substantially lower than those of the hydrogen-free metal. These estimated moduli were used to calculate the elastic energy associated with coherent, ellipsoidal hydride precipitates. The minimum elastic energy was found for low aspect ratio, i.e., a plate as opposed to a sphere or needle.

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Roles of hydrogenation, annealing and field in the structure and magnetic entropy change of Tb-based bulk metallic glasses AIP Advances 3, 032134 (2013); 10.1063/1.4797619 Effects of alloying elements and temperature on the elastic properties of dilute Ni-base superalloys from firstprinciples calculations J. Appl. Phys. 112, 053515 (2012); 10.1063/1.4749406 Testing facility for hydrogen storage materials designed to simulate application based conditions Rev. Sci. Instrum. 82, 045107 (2011); 10.1063/1.3571302 Assessing plastic shear resistance of bulk metallic glasses under nanoindentation

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Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 ‘Energy Storage and Conversion based on Hydrogen’ of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group ‘Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage’. The following topics are covered by the review: multiscale modelling of hydrides and hydrogen sorption mechanisms; synthesis and processing techniques; catalysts for hydrogen sorption in Mg; Mg-based nanostructures and new compounds; hydrides based on intermetallic TiFe alloys, high entropy alloys, Laves phases, and Pd-containing alloys. Finally, an outlook is presented on current worldwide investments and future research directions for hydrogen-based energy storage.