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Abstract: The nanocrystalline Mg2Ni-type electrode alloys with nominal compositions of Mg20Ni10−x Cu x (x = 0, 1, 2, 3, 4) were synthesized by the melt spinning technique. The microstructures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The results show that all the as-spun alloys hold typical nanocrystalline structure instead of an amorphous phase. The melt spinning does not modify the major phase Mg2Ni, but it leads to the formation of crystal defects such as stacking faults, dislocations, sub-grain boundary and twin-grain boundary. The melt spinning significantly improves the electrochemical hydrogen storage capacity of the alloys, whereas it slightly impairs the electrochemical cycle stability of the alloys. The substitution of Cu for Ni significantly ameliorates the electrochemical hydrogen storage performances of the alloys, involving both the electrochemical hydrogen storage capacity and the electrochemical charging and discharging stability. [Copyright &y& Elsevier]

Abstract: The electrode alloys La0.7Mg0.3Co0.45Ni2.55− x Fe x (x =0, 0.1, 0.2, 0.3, 0.4) are fabricated by casting and rapid quenching techniques. The effects of the substitution of Fe for Ni on the cycle stabilities as well as the structures of the alloys have been investigated thoroughly. The results indicate that the substitution of Fe for Ni significantly enhances the cycle stability of the alloys. Furthermore, the positive impact of such substitution on the cycle stability has been observed to be more pronounced for the as-quenched alloy as compared to that for the as-cast one. Scanning electron microscopy (SEM) studies demonstrate that all the alloys exhibit a multiphase structure comprising of two major phases (La, Mg)Ni3 and LaNi5 along with a residual phase of LaNi2. The substitution of Fe for Ni has been observed to facilitate the formation of a like amorphous structure in the as-quenched alloy. With an increase in Fe contents, a significant grain refinement of the as-quenched alloy and an obvious enlargement in the lattice constants and the cell volumes of the alloys have been noticed. [Copyright &y& Elsevier]

Abstract: In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Cu, and the nanocrystalline Mg2Ni-type Mg20Ni10−xCux (x = 0, 1, 2, 3, 4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were studied by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus. The results show that the substitution of Cu for Ni does not change the major phase Mg2Ni. The hydrogen absorption capacity of the alloys first increases and then decreases with rising Cu content, but the hydrogen desorption capacity of the alloys grows with increasing Cu content. The melt spinning significantly improves the hydrogenation and dehydrogenation capacity and kinetics of the alloys. [Copyright &y& Elsevier]

Abstract: Nanocrystalline and amorphous Mg2Ni-type alloys with nominal compositions of Mg20Ni10-xCox (x=0, 1, 2, 3, 4) were synthesized by melt-spinning technique. The microstructures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The electrochemical hydrogen storage characteristics of the as-cast and spun alloys were measured. The obtained results show that the substitution of Co for Ni does not change the major phase of Mg2Ni, but it leads to the formation of secondary phase MgCo2 and Mg. No amorphous phase forms in the as-spun alloy (x=0), whereas the as-spun alloy (x=4) holds a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni significantly heightens the glass forming ability of the Mg2Ni-type alloy. The substitution of Co for Ni and melt spinning significantly improve the electrochemical hydrogen storage performances of the alloys. When Co content x increases from 0 to 4, the maximum discharge capacity of the as-cast alloy increases from 30.3 to 113.3mAh/g, and from 135.5 to 402.5mAh/g for as-spun (30m/s) alloy. The capacity retaining rate of the as-cast alloy after 20 cycles rises from 36.71 to 37.04%, and from 27.06 to 83.35% for as-spun (30m/s) alloy, respectively. [Copyright &y& Elsevier]

Abstract: Nanocrystalline and amorphous Mg2Ni-type electrode alloys with nominal compositions of Mg20Ni10−x Co x (x =0, 1, 2, 3, 4) were synthesized by melt-spinning technique. The microstructures of the as-spun alloy ribbons were characterized by XRD, SEM and HRTEM. The electrochemical properties of the alloys were measured. The experimental results showed that the substitution of Co for Ni did not change the major phase of Mg2Ni, but it led to the formation of secondary phase MgCo2. No amorphous phase formed in the as-spun alloy (x =0), whereas the as-spun alloy (x =4) held a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni significantly enhances the glass forming ability of the Mg2Ni-type alloy. The substitution of Co for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, involving both the discharge capacity and the cycle stability, for which the increased glass forming ability by Co substitution is mainly responsible. [Copyright &y& Elsevier]

Abstract: Nanocrystalline and amorphous Mg2Ni-type Mg20−x La x Ni10 (x =0, 2, 4, 6) electrode alloys were synthesized by the melt-spinning technique. The microstructures of the as-quenched ribbons were characterized by XRD, HRTEM and electron diffraction (ED). The electrode properties of these alloys were measured. The experimental results show that no amorphous phase forms in the as-quenched La-free alloy, but the as-quenched alloys containing La hold a major amorphous phase, confirming that the substitution of La for Mg significantly increases the glass forming ability of the Mg2Ni-type alloys. The discharge capacities of the as-cast alloys increase with rising La content, but those of the as-quenched alloys first increase and then decrease with the variety of La content. The largest discharge capacity reaches around 406.5mAh/g at a discharge current density of 20mA/g for the Mg18La2Ni10 sample quenched at 30m/s. The substitution of La for Mg significantly intensifies the cycle stability of the alloys. When La content grows from 0 to 6, the capacity retaining rate of the as-quenched (15m/s) alloy after 15 cycles rises from 37.18 to 94.93%, and from 35.29 to 95.99% for quenching rate of 30m/s, respectively. Rapid quenching engenders impactful effects on the electrochemical performances of the experimental alloys, involving the increased discharge capacity except x =6 and the strengthened cycle stability, which means that the improvement of electrochemical performances is not only a function of the sample composition but also strongly influenced by the proportion of the nanocrystalline and amorphous phase in the alloys. [Copyright &y& Elsevier]

Abstract: The La–Mg–Ni system PuNi3-type La0.5Ce0.2Mg0.3Co0.4Ni2.6−x Mn x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and quenching. Ni in the alloy was partially substituted by Mn in order to improve the electrochemical characteristics of the alloys. The effects of the substitution of Mn for Ni and rapid quenching on the structures and electrochemical characteristics of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the alloys have multiphase structures which are composed of two major phases (La, Mg)Ni3 and LaNi5 as well as a residual phase LaNi. The substitution of Mn for Ni leads to an obvious increase of the LaNi5 phase and an decrease of the (La, Mg)Ni3 in the alloys. The electrochemical measurements indicate that the discharge capacities of the as-cast and quenched alloys first increase and then decrease with growing Mn content. The substitution of Mn for Ni clearly improves the high rate discharge abilities (HRDs) and the activation capabilities of the as-cast and quenched alloys, but it slightly impairs the cycle stabilities of the alloys. The rapid quenching significantly improves the cycle stabilities of the alloys, and the discharge capacities and HRDs of the alloys have the maximum values with the variety of the quenching rate. [Copyright &y& Elsevier]

Abstract: In order to investigate the influences of the stoichiometric ratios of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structure and the electrochemical performances of the -type electrode alloys, the La–Mg–Ni–Co system (, Co; , 0.2, 0.4, 0.6, 0.8, 1.0) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The obtained results show that the structures and electrochemical performances of the alloys are closely relevant to the M content. All the alloys exhibit a multiphase structure, including , and phases, and the major phase in the alloys changes from to with the variety of M content. The electrochemical performances of the alloys, involving the discharge capacity, the high rate discharge (HRD) ability, the activation capability and the discharge potential characteristics, significantly improve with increasing M content. When M content increases from 0 to 1.0, the discharge capacity rises from 177.7 to 343.62 mAh/g for the alloy , and from 177.7 to 388.7mAh/g for the alloy . The cycle stability of the alloy first mounts up then declines with growing M content. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed M content , the substitution of Co for Ni enhances the discharge capacity from 343.62 to 388.7mAh/g, and the capacity retention ratio after 100 charging–discharging cycles from 51.45% to 61.1%. [Copyright &y& Elsevier]

Abstract: The effects of the substitution of Mn for Ni on the structures and electrochemical characteristics of the as-cast and quenched (, 0.1, 0.2, 0.3, 0.4) alloys were studied systematically. The results obtained by XRD, SEM and TEM indicate that the as-cast and quenched alloys mainly consist of two major phases the and and a residual phase LaNi. With increasing Mn content in the alloys, the abundance of the phase decreases and that of the phase increases and both the lattice parameters and the cell volumes of major phases and increase. The as-quenched alloys display a nanocrystalline structure, and the grain sizes of the alloys are in a range of 20–30nm. The results by the electrochemical measurements indicate that the discharge capacities of the as-cast and quenched alloys first increase and then decrease with the variety of Mn content and obtain the maximum values for a Mn content of . The substitution of Mn for Ni clearly improves the high rate discharge abilities (HRDs) and the activation capabilities of the as-cast and quenched alloys, but it slightly impairs the cycle stabilities of the as-cast and quenched alloys. [Copyright &y& Elsevier]

Abstract: The La–Mg–Ni system -type hydrogen storage alloys (, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. Ni in the alloy was partially substituted by Fe in order to improve the cycle stability of the alloys. The effects of the substitution of Fe for Ni combining rapid quenching on the microstructures and electrochemical performances of the as-cast and -quenched alloys were investigated in detail. The results indicate that the substitution of Fe for Ni obviously decreases the discharge capacity and high rate discharge (HRD) capability as well as the discharge potential of the as-cast and -quenched alloys, but it significantly improves their cycle stabilities. The microstructure of the alloys analyzed by XRD, SEM and TEM shows that the as-cast and -quenched alloys have a multiphase structure which is composed of two major phases (La, Mg) and as well as a residual phase . The substitution of Fe for Ni leads to an obvious increase in the phase in the as-cast alloys, and it also helps the formation of a like amorphous structure in the as-quenched alloy. With the increase of Fe content, the grain sizes of the as-quenched alloys significantly reduce, and the lattice constants and cell volumes of the alloys obviously enlarge. [Copyright &y& Elsevier]