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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 in the alloy and La2Mg(Ni0.85Co0.15)9Cr x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The obtained results show that Cr addition engenders an inappreciable influence on the phase composition of the as-cast and quenched alloys, but it changes the phase abundance of the alloys significant. The Cr addition markedly enhances the cycle stability of the as-cast and quenched alloys, but it decreases the discharge capacity. When Cr content increased from 0 to 0.4, the discharge capacity of the as-cast alloy decreased from 396.3 to 355.6mAh/g, and the cycle life prolonged from 72 to 97 cycles. For the as-quenched (30m/s) alloys, the discharge capacity reduced from 364.2 to 334.2mAh/g, and the cycle life extended from 100 to 131 cycles. [Copyright &y& Elsevier]

In order to further reduce the cost of AB5 type rare-earth-based hydrogen storage alloy, a low-Co AB5 type hydrogen storage alloy was prepared by substituting Cr, Si, Cu for Co and adjusting of the composition. The result showed that the effect of the three kinds of substituting elements on cycle life increased in the sequence Si>Cr>Cu; and on the discharge capacity in the sequence Cu>Cr>Si. An overall favorable effect becomes possible by adding small quantities of Cr, Cu, Si. The discharge capacity and activation property as well as rate discharge capability of low-Co mischmetal based hydrogen storage electrode alloy reached the requirements of practical use when applying nonstoichiometric compositions. [Copyright &y& Elsevier]

We theoretically investigate the Autler–Townes (AT) splitting in the photoelectron spectrum of four-level ladder K2 molecule driven by a pump 1-pump 2-probe pulse via employing the time-dependent wave packet approach. The effects of the pump-1 laser intensity and wavelength on AT splitting are studied for the first time. The magnitude of AT splitting increases with increasing the pump-1 laser intensity. The triple splitting with asymmetric profile occurs due to the nonresonant excitation. The triple structure is transformed into a double structure (near-resonant region), and then becomes a peak (far-off resonant region) progressively as the pump-1 laser is detuned from the resonance wavelength, which can be explained in terms of the asymmetric excitation/population of dressed states. The splitting between adjacent peaks and the splitting between the two sideband peaks in the triplet do not change with the pump-1 pulse wavelength. The three peaks shift toward lower energy with the same shift 1/4*Δ1 as the pump-1 wavelength changes in near-resonant region. The asymptotic behaviors of AT splitting with the pump-1 laser intensity are interesting in the threshold points of the near-resonant region and the far-off resonant region. [ABSTRACT FROM AUTHOR]

In order to improve the electrochemical characteristics of AB2 Laves phase electrode alloys, the rapid quenching technology was used in the preparation of AB2 type Ti- and Ti-Zr-based electrode alloys. The effects of the rapid quenching on the electrochemical characteristics and microstructures of AB2 Laves phase electrode alloys were investigated comprehensively. The experimental results showed that the effects of the rapid quenching on the electrochemical properties and microstructures of AB2 Laves phase electrode alloys were closely relevant with the compositions of the alloys. For Ti-based alloy, the capacity of the as-quenched alloy was enhanced obviously with the increase of the quenching rate, and a maximum capacity could be obtained at a certain quenching rate. The rapid quenching had little effect on the activation capability and improved the cycle stability slightly. For Ti-Zr-based alloy, the cycle stability was exalted significantly and the capacity and activation capability were reduced dramatically with the increase of the quenching rate. The main reason why the rapid quenching can modify the electrochemical performances of AB2 Laves phase electrode alloys was that it has obviously changed the microstructures of the alloys. [Copyright &y& Elsevier]

Low Co AB5-type MmNi3.8Co0.4Mn0.6Al0.2Bx (x=0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by cast and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were analysed and measured. The effects of boron additive and rapid quenching technique on the microstructures and electrochemical properties of as-cast and quenched alloys were investigated comprehensively. The experimental results showed that the microstructure of as-cast MmNi3.8Co0.4Mn0.6Al0.2Bx (x=0, 0.1, 0.2, 0.3, 0.4) alloys was composed of CaCu5-type main phase and a small amount of CeCo4B-type secondary phase. The abundance of the secondary phase increases with the increase of boron context x. The rapid quenching techniques were used in the preparation of the alloys. The amount of secondary phase in the alloys decreased with the increase of quenching rate. Rapid quenching made lattice constants increase slightly. The effects of rapid quenching on the electrochemical performances of the alloys are very significant. The discharge capacity of the alloys decreased obviously and the cycle stability increased dramatically with the increase of quenching rate. Rapid quenching made the activation capability of the alloys lowered. However, the activate performance and high rate discharge capability as well as discharge voltage characteristic of the alloys were modified obviously with the increase of boron content x. [Copyright &y& Elsevier]

The microstructures of the as-cast and quenched Ti0.5Zr0.5Mn0.2Cr0.5V0.2Ni0.95 alloy is composed of the C15 main phase and traces of the C14 phase and Zr7Ni10 phase. The ratio of the three phases, which could be varied by different quenching rates, influences the electrochemical characteristics of the alloys. An amorphous phase was formed easily in the Ti0.5Zr0.5Mn0.2Cr0.5V0.2Ni0.95 alloy, a larger quantity of the amorphous phase being formed in the as-quenched alloy. The amorphous phase could significantly enhance the cycle stability of the alloy and strongly decrease the discharge capacity and the activation performance of the alloy. The cycle life of the as-quenched alloy obtained with a quenching rate of 26 m/s is larger than 1000 cycles, which is five to six times as large as that of the as-cast alloy. Its maximum discharge capacity is less than 200 mAh/g, and the alloy could be activated completely in about 180 charge–discharge cycles. [Copyright &y& Elsevier]

In order to modify the cycle stability of low-Co AB5-type alloy, a trace of boron was added in MmNi3.8Co0.4Mn0.6Al0.2 hydrogen storage alloy. The low-Co AB5-type alloys MmNi3.8Co0.4Mn0.6Al0.2Bx(x=0, 0.1, 0.2, 0.3, 0.4) were prepared by cast and rapid quenching. The cycle lives and microstructures of the as-cast and quenched alloys were measured and analyzed. The effects of boron additive on the microstructures and cycle lives of as-cast and quenched alloys were investigated comprehensively. The obtained results showed that the addition of boron could dramatically enhance the cycle lives of the as-cast and quenched alloys. When boron content x increases from 0 to 0.4, the cycle lives of the as-cast alloys were increased from 118 to 183 cycles, and for as-quenched alloys with quenching rate of 38 m/s from 310 to 566 cycles. [Copyright &y& Elsevier]

The rapidly quenched treatment produced significant effects on the electrochemical characteristics of Mm(NiMnAlCu)4.9Co0.2 alloy. It made the activation capability and the discharge capacity decrease, while the cycle stability improved and the degree of the effects increased with increase of the quenching rate. The results of X-ray diffraction analysis showed that the structures of the main phase and secondary phase of Mm(NiMnAlCu)4.9Co0.2 alloy are both of the CaCu5 type, but the lattice constants of two structures have a little difference. The amount of the secondary phase in the as-quenched alloy is very little, and rapidly quenched treatment made the structure of the alloy more homogeneous. The lattice constants of the main phase of the as-quenched alloy are larger than that of the as-cast one. Amorphous and crystal co-exist in the alloy with quenching rate of 15 m/s. The Co content was reduced from 10.0 wt.% to 2.8 wt.% through suitable rapidly quenched treatment, and it is not necessary to add other expensive elements in the alloy. [Copyright &y& Elsevier]

Abstract: In order to improve the hydrogen storage characteristics of the Mg2Ni-type alloys, Ni in the alloy is partially substituted by element Mn, and melt-spinning technology is used for the preparation of the Mg2Ni1−x Mn x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys. 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 by an automatically controlled Sieverts apparatus. The electrochemical performances are tested by an automatic galvanostatic system. The results show that the as-spun Mn-free alloy holds typical nanocrystalline structure, whereas the as-spun alloys containing Mn displays a nanocrystalline and amorphous structure. The hydrogen absorption and desorption capacities and kinetics of the alloys increase with rising spinning rate. Additionally, melt spinning markedly improves the electrochemical hydrogen storage capacity and cycle stability of the alloys containing Mn. With an increase in the spinning rate from 0 (As-casts is defined as spinning rate of 0m/s) to 30m/s, the discharge capacity of the (x =0.3) alloy mounts up from 92.3 to 211.1mAh/g, and its capacity retaining rate at 20th charging and discharging cycle grows from 36.21% to 76.02%. [Copyright &y& Elsevier]

Abstract: The melt-spinning technique is applied to the preparation of 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). The as-spun alloy ribbons possessing a continuous length, a thickness of about 30μm and a width of about 25mm were prepared. The structures of the as-spun alloy ribbons are characterized by XRD and TEM. The electrochemical performances of the as-spun alloy ribbons are measured by an automatic galvanostatic system. The results show that no amorphous structure is detected in the as-spun Mg2Ni alloy, whereas the as-spun Mg2Ni0.6Mn0.4 alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni notably intensifies the amorphous forming ability of the Mg2Ni-type alloy. The amorphization degree of the as-spun alloys containing Mn increases with increasing spinning rate. The melt spinning also significantly enhances the electrochemical performances such as the discharge capacity and the electrochemical cycle stability of the Mn-containing alloys. Furthermore, the high rate dischargeability (HRD) of the (x ≤0.1) alloys increases with an increase in the spinning rate, while for the (x ≥0.2) alloys, the HRD exhibits a maximum value at a particular spinning rate, and it varies with the change in Mn contents of the alloys. [Copyright &y& Elsevier]