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The LaNi 3.8 Al 1.0 Mn 0.2 hydrogen storage alloy annealed at different temperatures ( T =1173, 1223, 1273, 1323 K) was investigated to examine the effect of annealing temperature on the crystal structure, the activation and the hydrogen absorption/desorption performance. It is found that the non-CaCu 5 phases becomes tinier and more dispersive after annealing. All the alloys consist of the same matrix phase with CaCu 5 type structure. Although it is more difficult to activate the annealed alloy than the as-cast alloy, the activation becomes easier with the increase of annealing temperature for the annealed alloy. The plateau pressure decreases at first with the increase of annealing temperature, when T ≤1223 K and then increases. Changes in both the lattice strain and the pressure plateau slope factor of S f in the alloys show the same trends with that of the annealing temperature, exhibiting a maximum at T =1223 K. It is also found that the absolute value of the enthalpy increases with the increase of annealing temperature, when T ≤1223 K and then decreases, showing the same change trend as that of the cell volume. Moreover, the pulverization resistance and kinetics of the alloy are improved by annealing. The pulverization resistance is weakened at first with the increase of annealing temperature when T ≤1223 K and then increases, but the kinetics of the alloy is almost not influenced by the annealing temperature. [ABSTRACT FROM AUTHOR]

Ti-Zr-Ni-based icosahedral quasicrystals (IQCs) are a type of hydrogen storage materials with promising application in the fields of hydrogen energy and nuclear fusion energy. In the present paper, the preparation of Ti 39 Zr 38 Ni 17 Pd 6 IQC and its deuterium storage properties were investigated by XRD, TEM, XPS analysis and a gas-solid reaction system. Results show that the saturation concentration of absorbing deuterium for the alloy at room temperature reaches near 11 mmol·D 2 /g·M (D 2 means deuterium molecular and M the metal), exceeding those of Zr 2 Fe and ZrCo alloys. After a few absorption/desorption cycles, no phase transformation is observed, but the quasilattice displays a remarkable expansion of 6.37% after full D intake. The binding energy rise of 0.2 eV for Ti and 0.6 eV for Zr, caused by the introduction of saturated deuterium atoms, provides the evidence of the preferential location of deuterium near Zr and Ti in quasicrystals of this kind. The possible existence of a lower D desorption equilibrium pressure with <1 kPa at about 350 °C reflects higher thermodynamic stability of deuterium in the IQC than in ZrCo alloy. The advantages in hydrogen volume, thermal and structural stabilities suggest that the quasicrystals of this type could be a candidate to replace Zr 2 Fe and ZrCo in nuclear fusion field. [ABSTRACT FROM AUTHOR]

The effects of Co partial substitution for Ni on the microstructures and the electrochemical properties of the LaNi3.8-type phase LaNi3.8-xCox (x=0.0, 0.2, 0.4, 0.6) alloys were systematically studied. All the alloys mainly consist of LaNi5-type phase, rhombohedral Ce5Co19-type phase and hexagonal Pr5Co19-type phase. With increasing Co content, the relative abundance of each phase changes while the cell volume increases monotonously, which lower the hydrogen desorption pressure down to the desirable range (0.01~0.1 MPa) for hydride electrode of Ni/MH battery. All the Co-containing alloys display an enhanced cycle ability compared to LaNi3.8 alloy. The LaNi3.4Co0.4 alloy has the biggest discharge capacity, which is consistence with the solid hydrogen desorption capacity of the alloy. The LaNi3.6Co0.2 alloy exhibits the best rate performance corresponding to its maximum exchange current density (Io) and minimum charge transfer resistance (Rct). [ABSTRACT FROM AUTHOR]

Abstract: Amorphous Ti3Ni2 (Ti2Ni/TiNi) alloy has been prepared by mechanical milling of crystalline Ti3Ni2 alloy, and its electrochemical properties were investigated. The results of charge and discharge test show that the amorphous Ti3Ni2 alloy can resolve the problem of extremely short cycle life of crystalline Ti3Ni2 alloy at high temperature (333 K). The capacity retention rate of amorphous Ti3Ni2 alloy is greatly increased to 88.83% at 333 K compared with the retention rate of its crystalline counterpart 39.47% after 19 cycles. Based on analysis of Tafel polarization, linear polarization, and electrochemical impedance spectroscopy, it is found that the major reason for the improvement is the presence of amorphous Ti3Ni2 alloy, which has much better corrosion resistance compared with its crystalline counterpart. [Copyright &y& Elsevier]

Abstract: Structures and electrochemical properties of TiMn2-5x (V4Fe) x (x=0.30,0.35) alloys were investigated. The results of XRD analysis show that the alloys are mainly composed of body centered cubic (bcc) phase, whose lattice parameters are enhanced with the increase of V and Fe content. The SEM images of the alloys show that there are some colonies in the matrix phase. The proportion of colony to the matrix decreases with increasing of V and Fe content. The electrochemical measurements show that TiMn0.25(V4Fe)0.35 alloy has unfavorable activation performance until temperature reaches 327 K, while TiMn0.50(V4Fe)0.30 alloy shows better activation performance, but passivation phenomenon was found in the process of charging at low temperature, which can be eliminated by heating to high temperature. The PCT curves of alloys show that the TiMn0.50(V4Fe)0..30 alloy has a good comprehensive performance, with a favorable plateau pressure at room temperature and wide plateau. The enthalpy and entropy in hydrogen desorption of TiMn0.50(V4Fe)0..30 alloy were also calculated and they are −36.1 kJ/mol, −126.9 J/(mol·K), respectively. [Copyright &y& Elsevier]

Abstract: Effect of Mn substitution for Ni on phase constitution and electrochemical characteristics of La2Mg0.9Al0.1Ni7.5-x Co1.5Mn x (x=0, 0.3, 0.6, 0.9) hydrogen storage alloys was studied. It is found that Mn substitution will change phase composition and phase constitution of the alloys. LaNi3 phase disappears; the components of αLa2Ni7 first increases with Mn content from x=0 to x=0.3 and then decreases from x=0.6 to 0.9. Both component of LaMgNi4 phase and La5Ni19 phase increase as x increases in the alloys. Replacement of Ni by Mn will lower hydrogen storage capacity, maximum electrochemical discharge capacity and activation property of the alloy electrodes. La2Mg0.9Al0.1Ni7.2Co1.5Mn0.3 hydride electrode shows the best cycle stability. The high rate dischargeability of the alloys decreases with the increase of Mn content, which would be attributed to the decrease of exchange current density (I 0) and diffusion coefficient of the hydrogen atom (D). [Copyright &y& Elsevier]

Abstract: The influences of Cu content on the crystal structure, thermodynamic properties and hydrogen storage performance of La0.6Nd0.4Ni4.8Mn0.2Cu x alloys (x=0, 0.1, 0.2, 0.3, 0.4) were investigated and the relationships among the lattice parameter, plateau pressure and Gibbs free energy were analyzed. It was found that with the increase of the Cu content, the lattice parameter a shrunk and c expanded while the cell volume increased when x ≤ 0.2 and then decreased when x ≥ 0.3. The plateau pressure linearly decreased with the increase of a. The Seitz radius decreased with the increase of the Cu content and showed a clear linear relationship with ΔS d/ΔH d and an obvious hyperbolic relationship with ΔS α/ΔH α. [Copyright &y& Elsevier]

Abstract: The microstructure and hydrogen storage property changes with V contents from 5at% to 35at% in Ti-V-Cr alloys were investigated. According to the SEM and XRD results, the microstructure of Ti-V-Cr alloy with 5at% V content consists of Cr1.97Ti1.07 phase, Cr2Ti phase and small amount of Ti phase; Ti-V-Cr alloy with 10at% V content still contains an amount of V based solid solution besides the phases which are the same as the 5at% one; when V content is up to 35at%, the main phase existing in the Ti-V-Cr alloy is only V based solid solution. Accompanying with the changes of the phase constitution and microstructure, hydrogen storage properties of Ti-V-Cr alloy vary remarkably. With the increase of V content, the maximum hydrogen storage capacity of Ti-V-Cr alloy increases continuously, and the hydrogen desorption ability increases too, but the kinetic and activation properties become worse. Among all the alloys studied, (TiCr)65V35 shows the largest hydrogen storage capacity and the highest hydrogen desorption ratio at room temperature; under the condition in the present research, the maximum hydrogen storage capacity and the hydrogen desorption ratio of the (TiCr)65V35 alloy are 2.86% (mass fraction) and 61%, respectively. [Copyright &y& Elsevier]

Abstract: The phase structure and electrochemical properties of La2Mg1−x Al x Ni7.5Co1.5 (x=0.0,0.1,0.3,0.5) alloys were investigated by means of X-ray diffraction (XRD), electron probe X-Ray microanalysis (EPMA) and electrochemical measurements. XRD and EPMA results show that small quantity replacement Mg by Al (x=0.1) does not change phase composition of La2MgNi7.5Co1.5 alloy, the alloy is still constituted with LaNi3 phase and αLa2Ni7 phase, but the abundance of LaNi3 phase decreases obviously and that of αLa2Ni7 increases in the La2Mg0.9Al0.1Ni7.5Co1.5 alloy. The more Al substitution will change phase composition of the alloy, resulting in LaNi3 phase disappearance. Influence of change of Al content on cell parameters of different phases of the La2Mg1−x Al x Ni7.5Co1.5 alloy is different. Moreover, little replacement of Mg by Al (x=0.1) lowers scarcely hydrogen storage capacity and maximum electrochemical discharge capacity of the alloy, but with the increment of Al content in the La2Mg1−x Mg x Ni7.5Co1.5 alloy, hydrogen storage capacity, activation property and maximum electrochemical discharge capacity of the alloys decrease continuously. Al substitution for Mg can improve obviously electrochemical cyclic stability of La2MgNi7.5Co1.5 alloy electrode, and is beneficial to improve high rate dischargeability of the alloy electrode. [Copyright &y& Elsevier]

Abstract: Effects of Fe, Mn and Si on the hydrogen-induced amorphization in LaNi3 were investigated by XRD and electrochemical method. All the LaNi2.5 M 0.5 (M = Ni, Fe, Mn and Si) alloys were prepared by melt-spun plus annealing method and their main phase is LaNi3. It is found that the hydrogen-induced amorphization appears in all the alloys for the first charging cycle. During the discharge process, no plateau is observed in LaNi3 and LaNi2.5Fe0.5 but a plateau in LaNi2.5Mn0.5 and LaNi2.5Si0.5, indicating that a small amount of Mn and Si suppresses the tendency of hydrogen-induced amorphization. [Copyright &y& Elsevier]