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Abstract: The nanocrystalline Mg2Ni-type alloys with nominal compositions of Mg20Ni10−x Cu x (x =0–4) are synthesized by melt-spinning technique. The microstructures of the as-cast and spun alloys are characterized by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys are measured using an automatically controlled Sieverts apparatus. The electrochemical performances are tested by an automatic galvanostatic system. The results show that all the as-spun alloys hold typical nanocrystalline structure. 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 always grows with increasing Cu content. Furthermore, the substitution of Cu for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, involving both the discharge capacity and the electrochemical cycle stability. [Copyright &y& Elsevier]

Abstract: The nanocrystalline and amorphous Mg2Ni-type alloys with nominal compositions of Mg2Ni1−xMnx (x = 0, 0.1, 0.2, 0.3, 0.4) were synthesized by melt spinning technique. The structures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The results show that the as-spun (x = 0) alloy holds a typical nanocrystalline structure, whereas the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass formation in the Mg2Ni-type alloy. The hydrogen absorption capacity of the alloys first increases then decreases with rising Mn content, but the hydrogen desorption capacity of the alloys grows with increasing Mn content. Furthermore, the substitution of Mn for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, involving both the discharge capacity and the electrochemical cycle stability. With an increase in the amount of Mn from 0 to 0.4, the discharge capacity of as-spun (30 m/s) alloy grows from 116.7 to 311.5 mAh/g, and its capacity retaining rate at 20th charging and discharging cycle rises from 36.7 to 78.7%. [ABSTRACT FROM AUTHOR]

Abstract: In order to enhance the glass forming ability of the Mn2Ni-type electrode alloy, Ni in the Mg2Ni compound is partially substituted by Mn. The nanocrystalline and amorphous Mg2Ni-type alloys with nominal compositions of Mg2Ni1−x Mn x (x = 0, 0.1, 0.2, 0.3, 0.4) are fabricated by melt-spinning technique. The spun alloy ribbons with a continuous length, a thickness of about 30 μm and a width of about 25 mm are successfully obtained. The microstructures of the as-spun alloy ribbons are characterized by XRD, SEM and TEM. The electrochemical hydrogen storage characteristics of the as-spun alloy ribbons were tested by an automatic galvanostatic system. The electrochemical impedance spectra (EIS) are plotted by an electrochemical workstation (PARSTAT 2273). The hydrogen diffusion coefficients in the alloys are calculated by virtue of potential-step method. The results show that no amorphous structure is detected in the as-spun Mn-free alloy, whereas the as-spun alloys containing Mn display a nanocrystalline and amorphous structure. The amorphization degree of the alloy increases with rising spinning rate, suggesting that the substitution of Mn for Ni facilitates the glass formation in the Mg2Ni-type alloy. The substitution of Mn for Ni markedly improves the electrochemical hydrogen storage performances of the Mg2Ni-type alloy, enhancing both the discharge capacity and the electrochemical cycle stability. Furthermore, the high rate dischargeability (HRD), electrochemical impedance spectrum and potential-step measurements all indicate that the electrochemical kinetics of the alloy electrodes first increases then decreases with increasing amount of Mn substitution. [Copyright &y& Elsevier]

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: In order to improve the electrochemical hydrogen storage characteristics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Cu, and the nanocrystalline Mg2Ni-type Mg20Ni10−x Cu x (x =0–4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were studied by XRD, SEM and HRTEM. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The results show that the substitution of Cu for Ni does not change the major phase Mg2Ni, but it leads to a significant refinement of the grains of the as-cast alloys. All the as-spun alloys hold nanocrystalline structures and are free of amorphous phase. The discharge capacity of the alloys first increases and then decreases with rising amount of Cu substitution, whereas the electrochemical cycle stability of the alloys monotonously grows with increasing Cu content. [Copyright &y& Elsevier]

Abstract: In order to improve the electrochemical cycle stability of the La–Mg–Ni system A2B7-type electrode alloys, La in the alloy was partially substituted by Pr and the melt spinning technology was used for preparing La0.75−x Pr x Mg0.25Ni3.2Co0.2Al0.1 (x =0, 0.1, 0.2, 0.3, 0.4) electrode alloys. The microstructures and electrochemical performances of the as-cast and spun alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the as-cast and spun alloys have a multiphase structure which consists of two main phases (La, Mg)Ni3 and LaNi5 as well as a residual phase LaNi2. The substitution of Pr for La leads to an obvious increase of the (La, Mg)Ni3 phase and a decrease of the LaNi5 phase in the alloys. The results of the electrochemical measurement indicate that the cycle stability of the alloy monotonously rises with increasing Pr content. When Pr content rises from 0 to 0.4, the capacity retaining rate after 100 cycles increases from 65.32 to 79.36% for the as-cast alloy, and from 73.97 to 93.08% for as-spun (20ms−1) alloy. The melt spinning significantly improves the cycle stability of the alloys. When the spinning rate grows from 0 (as-cast was defined as spinning rate of 0ms−1) to 20ms−1, the capacity retaining rate after 100 cycles increases from 65.32 to 73.97% for the (x =0) alloy, and from 79.36 to 93.08% for the (x =0.4) alloy. [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: In order to improve the electrochemical cycle stability of the La–Mg–Ni system A2B7-type electrode alloys, La in the alloy was partially substituted by Zr and the melt-spinning technology was used for preparing La0.75−x Zr x Mg0.25Ni3.2Co0.2Al0.1 (x =0, 0.05, 0.1, 0.15, 0.2) electrode alloys. The microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD, SEM and TEM showed that the as-cast and quenched alloys have a multiphase structure which is composed of two main phases (La, Mg)Ni3 and LaNi5 as well as a residual phase LaNi2. The substitution of Zr for La leads to an obvious increase of the LaNi5 phase in the alloys, and it also helps the formation of a like amorphous structure in the as-quenched alloy. The results of the electrochemical measurement indicated that the substitution of Zr for La obviously decreased the discharge capacity of the as-cast and quenched alloys, but it significantly improved their cycle stability. The discharge capacity of the alloys (x ≤0.1) first increased and then decreased with the variety of the quenching rate. The cycle stability of the alloys monotonously rose with increasing quenching rate. [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: Mg2Ni-type hydrogen storage alloys Mg20−x La x Ni10 (x =0, 2) were prepared by casting and rapid quenching. The structures and morphologies of the as-cast and quenched alloys were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). Thermal stability of the as-quenched alloys was researched by differential scanning calorimetry (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus, and their electrochemical properties were measured by a tri-electrode open cell. The results showed that the no amorphous phase formed in the as-quenched La-free alloy, but the as-quenched alloys containing La held a major amorphous phase. The quenching rate induced a light influence on the crystallization temperature of the amorphous phase, and it significantly improved the initial hydrogenation rate and the hydrogen absorption capacity of the alloys. The discharge capacity and the cycle stability of the alloys grew with the increase of the quenching rate. When the quenching rate increased from 0 (as-cast was defined at a quenching rate of 0ms−1) to 30ms−1, the hydrogen absorption capacity of the alloys for x =0 and 2 at 200°C and 1.5MPa in 10min changed from 1.21 to 3.10wt.% and from 1.26 to 2.60wt.%, the maximum discharge capacity from 30.26 to 135.51mAhg−1 and from 197.23 to 406.51mAhg−1 at a current density of 20mAg−1, and the capacity retaining rate at 20th cycle from 36.71 to 27.06% and from 37.26 to 78.33%, respectively. [Copyright &y& Elsevier]

Abstract: In order to improve the hydrogenation and dehydrogenation performances of the Mg2Ni-type alloys, Mg in the alloy was partially substituted by element La, and rapid quenching technology was used for the preparation of the Mg20−x La x Ni10 (x =0, 2, 4, 6) hydrogen storage alloys. The structures and morphologies of the as-cast and quenched alloys were studied by XRD and high-resolution transmission electronic microscope (HRTEM). Thermal stability of the as-quenched alloys was researched by differential scanning calorimetry (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus. The 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, which is attributed to the fact that the substitution of La for Mg significantly heightens the glass forming ability of the Mg2Ni-type alloy. The quenching rate induced a light influence on the crystallization temperature of the amorphous phase, but it significantly improved the hydrogenation and dehydrogenation capacities and the kinetics of the alloys. When the quenching rate increases from 0 (as-cast was defined as quenching rate of 0m/s) to 30m/s, the hydrogen capacity of the alloys (x =0) at 200°C and 1.5MPa in 10min rises from 1.21 to 3.10wt.%, and from 1.26 to 2.60wt.% for the alloy (x =2). The hydrogen desorption capacity of the alloy (x =0) in 10min increases from 0.23 to 0.99wt.%, and from 1.48 to 2.46wt.% for the alloy (x =2), respectively. [Copyright &y& Elsevier]

Abstract: In order to enhance the glass forming ability of the Mg2Ni-type hydrogen storage alloy, the Mg in the alloy was partially substituted by La. The alloys Mg20−x La x Ni10 (x =0, 2, 4, 6) were prepared by casting and rapid quenching. The structures and morphologies of the as-cast and the quenched alloys were studied by XRD, SEM and HRTEM. It was found that no amorphous phase was formed in the as-quenched La-free alloy. But the as-quenched alloys containing La held a major amorphous phase, confirming that the substitution of La for Mg significantly enhances the glass forming ability of the alloys. When La content x ≤2, the major phase in the as-cast alloys is Mg2Ni phase, but with the further increase of La content, the major phase of the as-cast alloys changes into (La,Mg)Ni3 +LaMg3 phase. Thermal stability of the as-quenched alloys was studied by DSC, showing that La content engenders a negligible influence on the crystallization temperature of the amorphous phase. The hydrogen absorption and desorption kinetics of the as-cast and the quenched alloys were measured by an automatically controlled Sieverts apparatus. The results showed that the hydrogen absorption and desorption capacities and kinetics of the as-cast alloys clearly rise with increasing La content. For La content x =2, the as-quenched alloy displays an optimal hydrogen desorption kinetics at 200°C. The electrochemical measurement showed that the discharge capacities of the as-cast alloys rose with the increase of La content, but those of the as-quenched alloys obtained the maximum values with the variation of La content. The cycle stability of the as-cast and the quenched alloys significantly improved with increasing La content. [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 improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Fe, Mn and Al, and the electrode alloys La0.7Mg0.3Ni2.55−x Co0.45M x (M=Fe, Mn, Al; x =0, 0.1) were prepared by casting and rapid quenching. The effects of the substitution of Fe, Mn and Al for Ni and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM indicate that element substitution has no influence on the phase compositions of the alloys, but it changes the phase abundances of the alloys. Particularly, the substitution of Al and Mn obviously raises the amount of the LaNi2 phase. The substitution of Al and Fe leads to a significant refinement of the as-quenched alloy''s grains. The substitution of Al strongly restrains the formation of an amorphous in the as-quenched alloy, but the substitution of Fe is quite helpful for the formation of an amorphous phase. The effects of the substitution of Fe, Mn and Al on the cycle stabilities of the as-cast and quenched alloys are different. The positive influence of the substitution elements on the cycle stabilities of the as-cast alloys is in proper order Al>Fe>Mn, and for as-quenched alloys, the order is Fe>Al>Mn. Rapid quenching engenders an inappreciable influence on the phase composition, but it markedly enhances the cycle stabilities of the alloys. [Copyright &y& Elsevier]

Abstract: The La0.75Mg0.25Ni2.5Co x (x =0, 0.2, 0.4, 0.6, 0.8, 1.0) hydrogen storage alloys were prepared by vacuum medium-frequency induction furnace under the argon atmosphere. The microstructures and electrochemical performances of the alloys were analyzed and measured. The effects of Co addition on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results by X-ray diffractometer (XRD) showed that alloys were composed of the (La,Mg)Ni3, the LaNi5, LaNi2 and the La2Ni7 phases. With the increase of Co content x, the LaNi2 phase decreases, the (La,Mg)Ni3, the La2Ni7 and the LaNi5 phases increase. The results by the electrochemical measurements indicated that the maximum discharge capacity of the alloys is enhanced and activation performance is improved with the incremental change of Co content. The alloy (x =1.0) has a maximum discharge capacity of 388.7mAh/g. The addition of Co raises the high rate discharge capacity of the alloys. The cycle stability of the alloys first increases and then decreases with the growth of Co content. When Co content is 0.4, the capacity retention rate (S 100) of the alloy reaches a maximum volume of 76.9%. [Copyright &y& Elsevier]

Abstract: Mg2−x Zr x Ni (x =0, 0.15, 0.3, 0.45 and 0.6) electrode alloys were prepared by mechanical alloying (MA). The effects of substituting Mg with Zr on the microstructures and electrochemical performance of the MA alloys were investigated in detail. The results obtained by XRD and TEM show that the substitution of Zr for Mg is favorable for the formation of an amorphous phase. For a fixed milling time, the amorphous phase in the alloy increases with increasing Zr content. The electrochemical measurements indicate that the substitution of Zr can dramatically enhance the discharge capacity with preferable cycle stability, and markedly improve the discharge voltage characteristics of the alloys. The fact that Zr promotes the formation of an amorphous phase is mainly responsible for these effects. [Copyright &y& Elsevier]

Abstract: The electrode alloys Mg2−x Zr x Ni (x =0, 0.15, 0.3, 0.45 and 0.6) were prepared by mechanical alloying (MA). Mg in the alloy was partially substituted with Zr in order to improve the electrochemical characteristics of the Mg2Ni-type alloy. The microstructures and the electrochemical characteristics of the experimental alloys were measured systemically. The effects of substituting Mg with Zr and MA technique on the microstructures and electrochemical performances of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the substitution of Zr is favourable for the formation of an amorphous phase. For a fixed milling time, the amorphous phase in the alloy grows with increasing Zr content. The electrochemical measurement indicates that the substitution of Zr can dramatically enhance the discharge capacity with preferable cycle stability, and it markedly improves the discharge voltage characteristic of the alloys. For x ≤0.3, the discharge capacity of the alloys monotonically increases with milling time. But for x >0.3, it has a maximum value with the change of milling time. [Copyright &y& Elsevier]

Abstract: A new La–Mg–Ni system (PuNi3-type) La0.7Mg0.3Co0.45Ni2.55−x M x (M=Cu, Al, Mn; x =0, 0.1, 0.2, 0.3, 0.4) electrode alloys were prepared by casting and rapid quenching. The effects of element substitution and rapid quenching on the microstructures and electrochemical performances of the alloys were investigated. The results obtained by XRD, SEM and TEM show that the alloys have a multiphase structure, including the (La, Mg)Ni3, the LaNi5 and the LaNi2 phases. The substitution of Cu for Ni promotes the formation of an amorphous phase in the as-quenched alloy, and a reversal result produced by the substitution of Al for Ni. The electrochemical measurement indicates that the element substitution decreases the discharge capacity of the alloys, whereas it obviously improved the cycle stability of the alloys. The positive influence of three kinds of substitution elements on the cycle life of the alloys is in the sequence Al>Cu>Mn, and the negative influence on the discharge capacity in the sequence Al>Mn>Cu. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partially substituted by Al, and La0.7Mg0.3Ni2.55−x Co0.45Al x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of substituting Ni with Al on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3, the LaNi5 and the LaNi2 phases. The substitution of Al for Ni increases the amount of the LaNi2 phase in the as-cast alloys, but it has an inappreciable influence on the abundance of the LaNi2 phase in the as-quenched alloy. The results obtained by SEM and TEM indicate that the substitution of Al for Ni leads to the grains of the as-quenched alloys coarsen and restrain an amorphous phase formed in the as-quenched alloys. The results of the electrochemical measurement indicate that the capacities of the as-cast and quenched alloys monotonously decrease and their cycle stabilities significantly increase with the increase of Al content. When the amount of substitution Al for Ni increased from 0 to 0.4, the cycle life of the as-cast alloys increased from 72 to 132 cycles, and that of the as-quenched (20ms−1) alloys from 86 to 134 cycles. [Copyright &y& Elsevier]

Abstract: A new type of hydrogen storage alloy La0.7Mg0.3Ni2.55−x Co0.45Al x (x =0, 0.1, 0.2, 0.3, 0.4) with a PuNi3-type structure (R−3m) were prepared by casting and rapid quenching. The effects of the rapid quenching on the microstructures and electrochemical performances of the specimen alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3 phase, the LaNi5 phase and the LaNi2 phase. The rapid quenching had an inappreciable influence on the phase composition of the alloys, but it obviously changed the phase abundance of the alloys. The rapid quenching can significantly improve the compositional homogeneity and markedly decrease the grain size of the alloys. The results obtained by the electrochemical measurements indicate that the rapid quenching obviously enhanced the cyclic stability of the alloys, but it decreased the discharge capacity and activation capability of the alloys. [Copyright &y& Elsevier]

Abstract: A trace of Cr was added in La–Mg–Ni based (PuNi3-type) electrode alloy and rapid quenching technique was used in order to improve its cycle stability. The electrode alloys La2Mg(Ni0.85Co0.15)9Cr x (x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching, and the effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the as-cast and quenched alloys have a multiphase structure, including two main phases of (La, Mg)Ni3 and LaNi5, a residual phase of LaNi2. The Cr addition has an inappreciable influence on the phase compositions of the alloys, whereas it changes the phase abundance of the alloys. The results obtained by the electrochemical measurement indicate that the Cr addition obviously enhances the cycle stability of the as-cast and quenched alloys and leads to a different extent decrease of the discharge capacity of the alloys. When the amount of Cr addition changes incrementally from 0 to 0.4, the discharge capacity of the as-cast alloy decreases from 396.5 to 355.6mAh/g, and the cycle life increases from 72 to 97 cycles. For the as-quenched (30m/s) alloys, the discharge capacity decreases from 364.6 to 334.2mAh/g, and the cycle life increases from 100 to 131 cycles. The Cr addition improves the discharge voltage characteristic and activation capability of the as-cast alloys, but it slightly decreases the activation capability of the as-quenched alloys. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of the La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Cu. Hydrogen storage alloys La0.7Mg0.3Ni2.55−x Co0.45Cu x (x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The effects of substituting Ni with Cu and the quenching rate on the microstructures and the cycle stability of the as-cast and quenched alloys were investigated in detail. The results obtained by X-ray diffraction show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3 phase, the LaNi5 phase and the LaNi2 phase, and the amount of the LaNi2 phase increased with the increase of the Cu content. The substitution and rapid quenching have an inappreciable influence on the phase compositions of the alloys, but both obviously changed the phase abundances of the alloys. The results derived by transmission electron microscopy confirm that the substitution of Cu for Ni is favourable for the formation of an amorphous phase in the as-quenched alloys. The results obtained by the electrochemical measurement indicate that substituting Ni with Cu improved the cycle stability. When the Cu content increases from 0 to 0.4, the cycle lives of the as-cast and rapidly solidified alloys increased from 72 cycles to 88 cycles and from 100 cycles to 122 cycles, respectively. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Al, and La0.7Mg0.3Ni2.55−x Co0.45Al x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of substituting Ni with Al and rapid quenching on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3 phase, the LaNi5 phase and the LaNi2 phase. The substitution of Al for Ni increases the amount of the LaNi2 phase in the as-cast alloys, but it has an inappreciable influence on the abundance of the LaNi2 phase in the as-quenched alloy. The results obtained by the electrochemical measurement indicate that the capacities of the as-cast and quenched alloys monotonously decrease and their cycle stabilities significantly increase with the increase of Al content. Rapid quenching leads to the decrease of the capacity and an obvious improvement of the cycle stability of the alloys. [Copyright &y& Elsevier]

Abstract: La–Mg–Ni system (PuNi3-type) La0.7Mg0.3Ni2.55−x Co0.45Cu x (x =0, 0.2, 0.4) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The effects of substituting Ni with Cu and rapid quenching on microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The microstructures of the as-cast and quenched alloys were systematically determined by XRD, SEM and TEM. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase and the LaNi5 phase as well as the LaNi2 phase. The substitution and the rapid quenching do not have a large influence on the phase compositions of the alloys, but both changed the phase abundances of the alloys obviously. The results obtained by the electrochemical measurement indicate that the substitution decreased the discharge capacities of the as-cast and quenched alloys, whereas it improved the cycle stability and discharge voltage characteristic of the as-cast and quenched alloys. The rapid quenching significantly enhanced the cycle stability of the alloys, but it notably decreased the discharge capacity of the alloys. [Copyright &y& Elsevier]

Abstract: In order to improve the electrochemical performances of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, a trace of boron was added in La2Mg(Ni0.85Co0.15)9 and rapid quenching techniques were used. La2Mg(Ni0.85Co0.15)9 B x (x =0, 0.05, 0.1, 0.15, 0.2) hydrogen storage alloys were prepared by casting and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were determined and measured. The effects of the boron content and the quenching rate on the microstructures and electrochemical performances of the alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3 structure), the LaNi5 phase and the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloys containing boron. The Ni2B phase in the alloys containing boron nearly disappears after rapid quenching and the relative amount of each phase in the alloys changes with the variety of the quenching rate. The addition of boron obviously enhances the cycle stability of the as-cast and quenched alloys. The effects of boron content on the capacities of the as-cast and quenched alloys are different. The capacities of the as-cast alloys monotonously decrease with the increase of boron content, whereas the capacities of the as-quenched alloys have a maximum value with the change of boron content. The as-cast and quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]

Abstract: The La–Mg–Ni-based (PuNi3-type) La2Mg(Ni0.85Co0.15)9 (, Cr, Ti; ) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were analyzed and measured. The effects of B, Cr, Ti and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type structure) and the LaNi5 phase as well as the small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloy containing boron, and the Ni2B phase in the alloy nearly disappears after rapid quenching. The relative amount of each phase in the alloys depends on the composition of the alloys and the quenching rate. The addition of B, Cr enhances the cycle stability of the as-cast alloys, while the addition of Ti reduces the cycle stability of the as-cast alloy. The addition of B, Cr, Ti decreases the discharge capacities of the alloys. Rapid quenching increase the cycle lives of the alloys, but the effect of rapid quenching on the discharge capacity of the alloys is different. Except the alloy containing boron, the capacities of the alloys decrease monotonously with the increase of the quenching rate. The capacity of the alloy containing boron has a maximum value with the increase of the quenching rate. The as-cast and quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]

Abstract: The rare-earth-based AB5-type Mm(NiMnSiAl)4.3Co0.6−x Fe x (x =0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) hydrogen storage alloys were prepared by casting and rapid quenching. The microstructures of the as-cast and quenched alloys were analysed by XRD, SEM and TEM, and electrochemical cycle stabilities of the alloys were measured. The effects of substituting Co with Fe on microstructures and cycle stabilities of the as-cast and quenched alloys were investigated in detail. The obtained results show that the effects of substituting Co with Fe on the phase structures of the as-cast and quenched alloys are imperceptible, but its effects on cycle stabilities of the alloys are notable. Substituting Co with Fe improves slightly the cycle stabilities of the as-cast alloys, but it can significantly enhance the cycle lives of the as-quenched alloys, which is mainly attributed to the grain refinement of the alloys caused by substituting Co with Fe. [Copyright &y& Elsevier]

Abstract: The PuNi3-type La2Mg (Ni0.85Co0.15)9M x (M=B, Cr, Ti; x =0, 0.1) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The electrochemical cycle stabilities and microstructures of the as-cast and quenched alloys were measured and determined. The effects of B, Cr, Ti and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type) and the LaNi5 phase as well as a small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloy containing boron, and the Ni2B phase in the alloy nearly disappears after rapid quenching. The relative amount of each phase in the alloys changes with varying quenching rate. The addition of B, Cr enhances the cycle stabilities of the alloys, whereas the addition of Ti reduces the cycle stabilities of the alloys. Rapid quenching increases the cycle stabilities of the alloys, the cycle stabilities of the alloys increase monotonously with the increase of the quenching rate. [Copyright &y& Elsevier]

Abstract: In order to improve the electrochemical cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, a trace of Cr was added and rapid quenching techniques were employed. The electrochemical performances and microstructures of the as-cast and -quenched alloys were determined and measured. The effects of Cr content and quenching rate on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast and -quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type structure) and the LaNi5 phase as well as the LaNi2 phase. The amount of the LaNi2 phase increases with the increase of Cr content. The addition of Cr enhances the cycle stability of the as-cast and -quenched alloys, but decreases the discharge capacities of the alloys. The cycle lives of the alloys increase with the increase of the quenching rate. The as-cast and -quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]

Abstract: The microstructures of the rare-earth-based AB5-type Mm(NiMnSiAl)4.3Co0.6-xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) hydrogen storage alloys were analysed by XRD, SEM and TEM, and electrochemical characteristics of the as-cast and quenched alloys were measured. The effects of substituting Co with Fe on microstructures and electrochemical characteristics of the as-cast and quenched alloys were investigated in detail. The obtained results show that the effects of substituting Co with Fe on the phase structures of the as-cast and quenched alloys are imperceptible, but its effects on electrochemical characteristics of the alloys are notable. The discharge capacities decrease, but the cycle lives of the alloys were improved with the increase of the amount of Fe substitution. Especially, substituting Co with Fe can significantly enhance the cycle lives of the as-quenched alloys, which is mainly attributed to the grain refinement caused by substituting Co with Fe. [Copyright &y& Elsevier]

Abstract: In order to enhance the electrochemical capacity of the Co-free AB5-type electrode alloy, Mm in the alloys was substituted with La and Co-free LaxMm1-x(NiMnSiAlFe)4.9 (x = 0, 0.45, 0.75, 1.0) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of the substituting Mm with La on the electrochemical performances of the as-cast and quenched alloys were investigated in detail. The obtained results show that substituting Mm with La can enhance markedly the capacities of the as-cast and quenched alloys. When the amount of substituting Mm with La, x increased from 0 to 1.0, the maximum capacity of the as-cast alloys at 0.2C rate increased from 273.45 to 304.47mAhg-1, and the capacity retaining rate (Rh) increased from 59.16 to 59.86%. The capacity of the as-quenched alloys with a quenching rate of 10ms-1 increased from 236.83 to 300.31mAhg-1, and the capacity retaining rate (Rh) decreased from 78.69 to 62.29%. The substituting Mm with La had an insignificant effect on the activation capabilities of the as-cast and quenched alloys. [Copyright &y& Elsevier]

In order to improve the electrochemical performance of rare-earth-based AB5-type electrode alloy, the AB5-type Mm(NiMnSiAl)4.3Co0.6-xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) electrode alloys were quenched by melt-spinning. The phase structures and microstructure morphologies of the as-cast and quenched alloys were analyzed by XRD, SEM and TEM. The effects of the rapid quenching on the microstructures and electrochemical performances of the alloys were investigated in detail. The obtained results show that the as-quenched alloys have an excellent activation performance and can be completely activated through two to five charge–discharge cycles. The effect of the rapid quenching on the capacities of the alloys with Fe content x ≤ 0.2 is minor, and the capacities and high rate discharge abilities of the alloys with Fe content x > 0.2 decrease significantly with the increase of quenching rate. The cycle lives of the alloys increase greatly with the increase of the quenching rate. [Copyright &y& Elsevier]

The rare-earth Mg-based La2Mg(Ni0.85Co0.15)9Bx (x=0–0.2) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were determined and measured systematically. The effects of boron content and quenching rate on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type structure), the LaNi5 phase as well as of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloys containing boron, and when the quenching rate is larger than 15 m/s, the Ni2B phase in the alloys nearly disappears. The relative amount of each phase in the alloys depends on the composition of the alloys and the quenching rate. The addition of boron enhances the cycle stability of the as-cast and quenching alloys, but decreases the discharge capacity of the alloys. The capacity of the alloys without boron monotonously decreases with increasing quenching rate, but for the alloys containing boron, the capacities have a maximum value when varying the quenching rate. The cycle lives of the as-quenched alloys increase with increasing quenching rate. The as-cast and quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]