The mutual destabilization between complex hydrides and lithium amide has been comprehensively reported. In this paper, CeH2 doped Li-Mg-N-H/NaAlH4 composite was successfully synthesized by ball milling Li-Mg-N-H mixture and NaAlH4 in a molar ratio of 1:2. It was found that a total of 5 wt.% of hydrogen could be desorbed from the newly synthesized composite with a three-step reaction. Temperature-programmed-desorption (TPD) measurements showed that the composite ball milled for 10 min began to desorb hydrogen below 100 °C, which was about 75 °C lower than the pristine materials. XRD analysis revealed that NaAlH4 firstly reacted with LiH to yield Na2LiAlH6 and Al below 150 °C, then the newly developed Na2LiAlH6 reacted with Mg(NH2)2 to form NaH, Al, and Li2MgN2H2 in the temperature range of 180-250 °C. From 200 to 300 °C, the newly formed Al and Li2MgN2H2 reacted further to form Li2NH and some stable phase (AlN and Mg3N2). The H-cycling properties of the composite were further investigated by a standard Sievert's type apparatus at 150, 200 and 250 °C, respectively. Finally, the reversibility of the newly synthesized composite was discussed.
La Ni3.8Al1.0Mn0.2 alloy was prepared by vacuum induction melting and melt-spinning.The effects of different preparation techniques of the as-cast,cast then annealed,as-spun and spun then annealed alloys on the microstructure and hydrogen storage properties were investigated.The results indicated that the non-Ca Cu5 phases in the alloy became tinier and more dispersive after annealing or melt-spinning compared to those of the as-cast one.But in the spun then annealed alloy,the non-Ca Cu5 phases disappeared and only a single-phase with Ca Cu5 type structure was found.For all the alloys,the cell volume was increased in an order of as-cast < spun then annealed < cast then annealed < as-spun,and the change of plateau pressure showed the opposite trend with that of the cell volume.The plateau could be flattened after melt-spinning or annealing,and the spun then annealed alloy showed the minimum plateau slope.The absorption kinetics of the alloy was promoted after melt-spinning or annealing.It is suggested that the change in cell volume and compositional homogeneity resulting from different preparation techniques contribute to the difference of the hydrogen storage properties of the investigated alloys.
Al–Ga–Sn, Al–Ga–In and Al–Ga–In–Sn alloys were prepared using arc melting technique. Their microstructures were investigated by X-ray diffraction and scanning electron microscopy with energy dispersed X-ray. Based on microstructure analysis, the phase constituents of alloys at Al grain boundaries were identi?ed. The melting points of Al grain boundary phases were measured using differential scanning calorimeter.The reactivities of Al–water at different water temperatures indicate that liquid Al grain boundary phases promote Al–water reactions of alloys. The melting points of Al grain boundary phases affect the reaction temperatures of Al–water, leading to different reaction temperatures of alloys. The measured H2 generation rate and yields of alloys are related to the compositions of alloys. The theory of microgalvanic cell is used to explain the observed different H2 generation rates of alloys.
