An investigation into the nature of the magnetocrystalline anisotropy of the compound Nd3 (Fe, Mo) 29 and its nitride has been carried out. AC susceptibility measurements, thermomagnetic analysis at low field (0.04T) and 57Fe M

In this paper, the structural and electrochemical properties of the superstoichiometric (Ti0.8Zr0.2) (V0.533Mn0.107Cr0.16Ni0.2)x (x=2, 3, 4, 5, 6) hydrogen storage alloys have been studied systematically. It is found by X-ray diffraction and energy dispersive spectra analysis that all these alloys mainly consist of two phases, a C14 Laves phase with hexagonal structure and a V-based solid solution phase with body-centered cubic structure. The lattice parameters and thus the cell volumes of the two phases all decrease when x is increased. The electrochemical measurements indicate that the maximum discharge capacity, the discharge equilibrium potential, the high rate dischargeability, the cyclic stability, the exchange current density 10, and the limiting current density IL of the alloys all increase with increasing x from 2 to 5. When x reaches 6, the discharge equilibrium potential, the high rate dischargeability, and the cyclic stability are still increasing proportionately, while the maximum discharge capacity, the exchange current density 10, and the limiting current density IL all decrease. Furthermore, the alloy electrodes are activated with more difficulty for the alloys with higher stoichiometry x. Consequently, we believe that the superstoichiometry is an effective way to improve the overall electrochemical properties of the Ti-based Laves-phase hydrogen storage alloys used for the negative electrodes of the Ni-MH secondary batteries.

A novel single-phase Y3 (Fe, Mo) 29 compound with Mo as a new stabilizing element has been synthesized with nominal composition Y1o.sFe86.7Mo2.8 via annealing at 1313K for three days, and then water quenching. The results of thermomagnetic analysis (TMA) show a magnetic ordering temperature of 376K. X-ray diffraction gives lattice parameters a=10.570 Å, b=8.508 Å, c=9.673 Å and β=96.98º. The temperature dependence of the magnetization Ms of Y10.5Fe86.7Mo2.8 in an applied magnetic field up to 7 T and the temperature dependence of the anisotropy field Ba are also reported.

A novel single phase R3 (Fe, M) 29 (R=Nd, Sm and Gd) compound series with M=Mo as a new stabilizing element has been synthesized. A systematic study of the formation and magnetic properties of R3 (Fe, Mo) 29 compounds has been performed. The lattice parameters and magnetic properties incIuding the Curie temperature Tc, saturation magnetization Ms and anisotropy field Ba at 300 and 4.2K are presented.

In our endeavor to improve the cyclic stability of La-Mg-Ni-Co type alloys, La0.7Mg0.3Ni2.652xMn0.1Co0.75Alx (x=0-0.5) hydrogen storage alloys were prepared and the structure and electrochemical properties of these alloys were investigated systematically. X-ray diffraction and Rietveld analyses revealed that the major phases are the (La, Mg) Ni3 phase and the LaNi5 phase. Electrochemical studies indicate that as Ni is progressively substituted by Al, the cyclic stability of alloy electrodes is noticeably improved due to the formation of a dense oxide film on the alloy surface. The capacity retention of the alloy electrodes for 100 cycles increases from 32.0% (x=0) to 73.8% (x=0.3). The maximum discharge capacity decreases with increasing Al content, and the high rate dischargeability, electrochemical impedance spectra, linear polarization, Tafel polarization, and potential-step studies all indicate that the electrochemical kinetics of the alloy electrodes is deteriorated. We ascribe this phenomenon to the increase of the charge-transfer resistance of the alloy electrodes and reduction of the diffusion rate of hydrogen from interior of the bulk to the surface due to the presence of the aforesaid Al-containing oxide film. The optimal content of Al in La0.7Mg0.3Ni2.652xMn0.1Co0.75Alx alloys in this study is in the range from 0.2 to 0.3.