The effect of rapid solidification on structure and electrochemical performance of the LaNi4.5Co0.25Al0.25 hydrogen storage alloy was investigated by X-ray powder diffraction and a simulated battery test, including maximum capacity, cycling stability, self-discharge, and high-rate discharge ability(HRD). All the melt-spun alloys were single-phase with the CaCu5-type structure(space group P6/mmm). In comparison to the as-cast alloy, the rapidly quenched alloys manifested an improved homogeneity of composition and expanded lattice parameters. The electrochemical measurements showed that the activation property, cycling stability and self-discharge of the alloy electrodes were also improved for the rapid solidified alloys. The HRD of the as-cast alloy was better than those of all the rapidly solidified alloys. As the quenching rate increased, the HRD and exchange current density first decreased and then increased.
Phase equilibria in the Fe-Nb-Zr system at 1,200 °C were determined by X-ray diffraction (XRD) and scanning electron microscope (SEM) coupled with energydispersive X-ray spectroscopy (EDS) techniques. Extensive NbFe2 domain was proposed in the current work. This compound existed in the composition range from 35 at% to 73 at% Fe, 12 at% to 32 at% Nb, and 0 to 32 at% Zr. In the present work, four three-phase regions (1)-(Nb,Zr)+NbFe2+NbFe2, (2)-(Nb,Zr)+NbFe2+Liquid, (3)NbFe2+Liquid+ZrFe2, and(4)ZrFe2+Fe+NbFe2, were established.
The isothermal section of the phase diagram of the Gd-Sm-Co ternary system at 773K was investigated by X-ray powder diffraction(XRD),differential thermal analysis(DTA),optical microscopy and scanning electron microscopy(SEM) techniques.The result shows that the isothermal section consists of 12 single-phase regions,16 two-phase regions and 5 three-phase regions.Five pairs of corresponding compounds of Gd-Co and Sm-Co systems,i.e.,Gd2Co17 and Sm2Co17,Gd2Co7 and Sm2Co7,GdCo3 and SmCo3,GdCo2 and SmCo2,Gd3Co and SmCo form continuous series of solid solutions.The maximum solid solubility of Sm in Gd 4Co3 and Gd12Co7 were about 7.2 at.% and 47.8 at.% Sm,respectively.The maximum solid solubility of Gd in Sm5Co19 and Sm5Co2 were about 4.7 at.% and 7.6 at.% Gd,respectively.The binary compounds Sm9Co4,GdCo5 and SmCo5 were not observed at 773K.No ternary compound was found.
The nano-crystalline La_(0.1)Bi_(0.9)FeO_3 compound was successfully synthesized by starch-based combustion method. The crystal structure and magnetic behavior were studied by temperature-dependent X-ray diffraction(XRD), scanning electron microscopy(SEM), differential scanning calorimetry(DSC) and magnetic measurements. The La_(0.1)Bi_(0.9)FeO_3 compounds crystallized in a rhombohedrally distorted perovskite structure with space group R3 c. The substitution of La for Bi reduced the rhombohedral distortion. The structural phase transitions in La_(0.1)Bi_(0.9)FeO_3 driven by temperature showed that the extraordinary two-phase coexistence state of BiF eO 3 and LaF eO 3 was observed in a narrow temperature range of 630–700 oC. The magnetization of the La_(0.1)Bi_(0.9)FeO_3 sample was improved by heat treatment in the temperature range. When the heat treatment temperatures rose from 25 to 600 oC, the remanence(Mr) and coercivity(Hc) of the La_(0.1)Bi_(0.9)FeO_3 compound almost remained the same, and increased rapidly to 0.134 emu/g and 7.1 KOe on further increasing the heat treatment temperature to 650 oC.
