Hydriding-Dehydriding Properties of Mg-Rich Mg-Ni-Nd Alloys with Refined Microstructures

Abstract

The hydriding/dehydriding characteristics, pressure-composition isotherms and X-ray diffractographs of Mg-rich Mg-Ni-Nd alloys fabricated by different solidifying processes (mold-casting, water-quenching, or melt-spinning) are compared and discussed in relation with their microstructures observed by SEM. Among them, the alloy prepared by melt-spinning and subsequent annealing presents best hydrogen-storage properties. It can quickly absorb hydrogen up to ∼5.0 mass% above 423 K and can wholly desorb it above 453 K with moderate speeds. These enhanced absorption/desorption kinetics are exclusively caused by a refined microstructure of the alloy involving Mg 2 Ni and Nd 2 H 5 precipitates in a Mg matrix as well as by a catalytic action of the Nd-hydride.

Hydride stability and hydrogen desorption characteristics in melt-spun and nanocrystallized Mg–Ni–La alloy

“…This enhanced kinetics is supposed to be due to combined effects of a catalytic action of the additives and facilitation of hydrogen transport through the nanostructure of the material. A similar improvement has also been attained for Mg-rich alloys prepared by melt spinning [11][12][13]. Amorphized and then crystallized alloys readily absorb and desorb ∼5 wt% hydrogen repeatedly at temperatures even below 200 • C. This favorable feature has been attributed to enhanced hydrogen transport along * Tel.…”

Hydriding kinetics of the La1.5Ni0.5Mg17–H system prepared by hydriding combustion synthesis

“…From these results, it can be concluded that the hydriding rates of different stage in the two-phase region are similar. In measuring for the overall kinetics of La 1.5 Ni 0.5 Mg 17 , it was found that this alloy exhibits an excellent hydriding/ dehydriding kinetics and can absorb 4.09 and desorb 3.98 mass% H within 300 s at 473 K. While other alloys such as Mg -Ni-Nd alloy only reaches about 4.6 mass% H in absorption and 4.0 mass% H in desorption in a 2000 sduration at the same temperature [12]. For comparison with the results of Mg -Ni -RE (RE ¼ Ce, Nd, Y, La or La-rich mischmetal) [13 -17] [18]), their hydrogen capacities decreased dramatically after several cycles and these alloys cannot desorb more hydrogen at low temperature.…”

Hydrogen-storage properties of amorphous Mg–Ni–Nd alloys

“…Another possible reason for the higher H-capacity of the (Mg 60 Ni 25 ) 90 Nd 10 could be the higher rare earth (Nd) content (10 at.%) in this alloy as compared to the Mg 75 Ni 20 Mm 5 alloy. An optimum Nd content not only provides more amorphous phase and brings a refined microstructure for Mg-Ni-Nd alloys which enhances absorption kinetics [11] but also effectively works as catalysts for the hydrogenation of Mg. Spassov et al [9] observed an improvement in the hydrogenation kinetics of Mg 63 Ni 30 Y 7 alloy due to the catalytic effect of yttrium.…”

“…possesses maximum hydrogen capacity (4.0 wt.% H) at room temperature. Furthermore, Tanaka et al [10,11] found that Mgrich Mg-Ni-Nd alloys can quickly absorb hydrogen up to 5.0 wt.% above 423 • C. In this way, the present paper is devoted to an investigation of the hydrogenation characteristics of rapidly quenched (Mg 60 Ni 25 ) 100−x Nd x (x = 2, 5, 10, 15) alloys with a composition close to that possessing the best H-storage characteristics found by Spassov et al so far, but replacing Mm by Nd.…”