Microstructures and mechanical properties of Mg-8Gd-0.6Zr-xNd (x=0, 1, 2 and 3 mass%) alloys

Mg-8Gd-0.6Zr-xNd (x = 0, 1, 2 and 3 mass%) alloys were prepared by metal mould casting method, and the microstructures, age hardening responses and mechanical properties have been investigated. The microhardness of the as-cast alloys is increased with increasing Nd content. The age hardening behavior and mechanical properties are enhanced significantly by adding Nd element. The peak ageing hardness of the Mg-8Gd-0.6Zr-3Nd alloy is 103, it is about 1.3 times more than that of the Mg-8Gd-0.6Zr alloy. The aged Mg-8Gd-0.6Zr-3Nd alloy exhibits maximum ultimate tensile strength and yield strength, and the values are 271 and 205 MPa at room temperature, 205 MPa and 150 MPa at 250 degrees C, respectively. Which are about 2 times higher than those of Mg-8Gd-0.6Zr alloy. The improved hardness and strength are mainly attributed to the fine dispersiveness Of Mg5RE and Mg12RE precipitates in the alloy.

Structure and mechanical properties of Mg-Zn-RE system alloys

The lightest density of Mg has stimulated renewed interest in Mg based alloys for applications in the automotive, aerospace and communications industries. However, Mg in the pure form has relatively low strength, limited ductility and is susceptible to corrosion. Great efforts have been made to improve the mechanical properties of Mg alloys. Alloying Mg with other elements is one of the most important methods. An important class of Mg alloys is the Mg-Zn-RE system (RE = rare earth elements). In recent few decades, a series of new Mg-Zn-RE system alloys have been obtained, and detailed the structure and mechanical properties of the alloys. In this paper, the structure and mechanical properties of the Mg-Zn-RE alloys have been summarized. It showed that these alloys have high strength and they are prospected to be widely used in the future.

Structure and electrochemical characteristics of TiV1.1Mn0.9Nix (x=0.1-0.7) alloys

The structure and electrochemical properties of TiV1.1Mn0.9Nix (x = 0.1-0.7) solid solution electrode alloys have been investigated. It is found that these alloys mainly consist of a solid solution phase with body centered cubic (bcc) structure and a C14 Laves secondary phase. The solid solution alloys show easy activation behavior, high temperature dischargeability, high discharge capacity and favorable high-rate dischargeability as a negative electrode material in Ni-MH battery. The maximum discharge capacity is 502 mAh g(-1) at 303 K when x = 0.4. Electrochemical impedance spectroscopy (EIS) test shows that the charge-transfer resistance at the surface of the alloy electrodes decreases obviously with increasing Ni content.

Microstructure and some dynamic performances of Ti0.17Zr0.08V0.34RE0.01Cr0.1Ni0.3 (RE = Ce, Dy) hydrogen storage electrode alloys

Microstructure and some dynamic performances of Ti0.17Zr0.08V0.34RE0.01Cr0.1Ni0.3 (RE=Ce, Dy) hydrogen storage electrode alloys have been investigated using XRD, FESEM-EDS, ICP-MS and EIS measurements. The alloy is composed of V-based solid solution phase with a dendritic shape and a continuous C14 Laves phase with a network shape surrounding the dendrite. Pressure-composition isotherm curves indicate that the alloy with Dy addition has a lower equilibrium hydrogen pressure and a wider plateau region. The alloy electrode with Dy addition has higher discharge capacity, while the alloy electrode with Ce addition has better activation and higher cycle stability. The alloy electrode with Ce addition has better electrochemical activity with higher exchange current density (127.5 mA g(-1)), lower charge transfer resistance (1.37 Omega) and lower apparent activation energy (30.5 kJ mol(-1)). The capacity degradation behavior for the alloy electrode is attributed to two main factors: one is the dissolutions of V and Zr element to KOH solution, and another is the larger charge transfer resistance which increases with increasing cycle number.

Effect of Y for enhanced age hardening response and mechanical properties of Mg-Gd-Y-Zr alloys

In this study, compositional dependence of age hardening response and tensile properties were investigated for Mg-10G(d-x)Y-0.4Zr (x = 1, 3, 5 wt.%) alloys. With increasing Y content, the age hardening response of the alloys enhanced and tensile properties increased. The Mg-10Gd-5Y-0.4Zr alloy exhibited maximum tensile strength and yield strength at aged-peak hardness, and the values were 302 MPa and 289 MPa at room temperature, and 340 MPa and 267 MPa at 250 degrees C, respectively. The strong peak age hardening was attributed to the precipitation of prismatic beta' plates in a triangular arrangement. The cubic shaped beta phase was also observed at grain boundaries. The remarkable improvement in strength is associated with a uniform and high dense distribution of beta' and cubic shaped beta precipitate phases in Mg matrix. Elongation of Mg-10Gd-0.4Zr alloys decreased with increasing Y content, and the elongation of Mg-10Gd-5Y-0.4Zr alloy was less than 3% below 250 degrees C, whereas the alloys containing I wt.% and 3 wt.% Y exhibited higher elongation than 5% at room temperature.

Preparation of W-Al-Mo ternary alloys by mechanical alloying

Single phase WxAl(50)Mo(50)-X (X=40, 30, 20 and 10) powders have been synthesized directly by mechanical alloying (MA). The structural evolutions during MA and subsequent as-milled powders by annealing at 1400 degrees C have been analyzed using X-ray diffraction (XRD). Different from the Mo50Al50 alloy, W40Al50Mo10 and W30Al50Mo20 alloys were stable at 1400 degrees C under vacuum. The results of high-pressure sintering indicated that the microhardnesses of two compositions, namely W40Al50Mo10 and W30Al50Mo20 alloys have higher values compared with W50Al50 alloy.

Grain boundary conductivity of high purity neodymium-doped ceria nanosystem with and without the doping of molybdenum oxide

Solid solutions of Ce1-xNdxO2-x/2 (0.05 <= x <= 0.2) and (Ce1-xNdx)(0.95)MO0.05O2-delta (0.05 <= x <= 0.2) have been synthesized by a modified sol-gel method. Both materials have very low content of SiO2 (similar to 27 ppm). Their structures and ionic conductivities were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and electrochemical impedance spectroscopy (M). The XRD patterns indicate that these materials are single phases with a cubic fluorite structure. The powders calcined at 300 degrees C with a crystal size of 5.7 nm have good sinterability, and the relative density could reach above 96% after being sintered at 1450 degrees C. With the addition Of MoO3, the sintering temperature could be decreased to 1250 degrees C. Impedance spectroscopy measurement in the temperature range of 250-800 degrees C indicates that a sharp increase of conductivity is observed when a small amount of Nd2O3 is added into ceria, of which Ce0.85Nd0.15O1.925 (15NDC) shows the highest conductivity. With the addition of a small amount Of MoO3, the grain boundary conductivity of 15NDC at 600 degrees C increases from 2.56 S m(-1) to 5.62 S m(-1).

Effect of La/Ce ratio on the structure and electrochemical characteristics of La0.7-xCexMg0.3Ni2.8Co0.5 (x=0. 1-0.5) hydrogen storage alloys

The effect of La/Ce ratio on the structure and electrochemical characteristics of the La0.7-xCexMg0.3Ni2.8Co0.5 (x = 0.1, 0.2, 0.3, 0.4, 0.5) alloys has been studied systematically. The result of the Rietveld analyses shows that, except for small amount of impurity phases including LaNi and LaNi2, all these alloys mainly consist of two phases: the La(La, Mg)(2)Ni-9 phase with the rhombohedral PuNi3-type structure and the LaNi5 phase with the hexagonal CaCU5-type structure. The abundance of the La(La, Mg)(2)Ni-9 phase decreases with increasing cerium content whereas the LaNi5 phase increases with increasing Ce content, moreover, both the a and cell volumes of the two phases decrease with the increase of Ce content. The maximum discharge capacity decreases from 367.5 mAh g(-1) (x = 0.1) to 68.3 mAh g(-1) (x = 0.5) but the cycling life gradually improve. As the discharge current density is 1200 mA g(-1), the HRD increases from 55.4% (x = 0.1) to 67.5% (x = 0.3) and then decreases to 52.1% (x = 0.5). The cell volume reduction with increasing x is detrimental to hydrogen diffusion D and accordingly decreases the low temperature dischargeability of the La0.7-xCexMg0.3Ni2.8Co0.5 (x = 0.1-0.5) alloy electrodes.

Synthesis and characterization of the nanoporous ultrathin multilayer films based on molybdenum polyoxometalate (Mo-36)(n)

Ultrathin multilayer films of the wheel-shaped molybdenum polyoxometalate cluster (Mo-36)(n) and poly(allylamine hydrochloride) (PAH) have been prepared by the layer-by-layer (LbL) self-assembly method. The ((Mo-36)(n)/PAH)(m) multilayer films have been characterized by Xray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). UV-VIS measurements reveal regular film growth with each (Mo-36)(n) adsorption. The electrochemical behavior of the film at room temperature was investigated.

Morphology-controllable synthesis and characterization of single-crystal molybdenum trioxide

Molybdenum trioxide nanobelts and prism-like particles with good crystallinity and high surface areas have been prepared by a facile hydrothermal method, and the morphology could be controlled by using different inorganic salts, such as KNO3, Ca(NO3)(2), La(NO3)(3), etc. The possible growth mechanism of molybdenum trioxide prism-like particles is discussed on the basis of the presence of HI and the modification of metal cations. The as-prepared nanomaterials are characterized by means of powder X-ray diffraction (PXRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and ultraviolet and visible spectroscopy (UV-vis). TEM and HRTEM micrographs show that the molybdenum trioxide nanobelts and prism-like particles have a relatively high degree of crystallinity and uniformity. BET specific surface areas of the as-prepared molybdenum trioxide nanocrystals are 67-79 m(2)g(-1). XPS analysis indicates that the hexavalent molybdenum is predominant in the nanocrystals. UV-vis spectra reveal that the direct band gap energy of the annealed molybdenum trioxide prism-like particles shows a pronounced blue shift compared to that of bulk MoO3 powder.

Crystallographic and electrochemical characteristics of La0.7Mg0.3Ni3.5-x (Al0.5Mo0.5)(x) (x=0-0.8) hydrogen storage alloys

The crystal structure, hydrogen storage property and electrochemical characteristics of the La0.7Mg0.3Ni3.5-x(Al0.5Mo0.5), (x=0-0.8) alloys have been investigated systematically. It can be found that with X-ray powder diffraction and Rietveld analysis the alloys are of multiphase alloy and consisted of impurity LaNi phase and two main crystallographic phases, namely the La(La, Mg)(2)Ni-9 phase and the LaNi5 phase, and the lattice parameter and the cell volume of both the La(La, Mg)(2)Ni-9 phase and the LaNi5 phase increases with increasing A] and Mo content in the alloys. The P-C isotherms curves indicate that the hydrogen storage capacity of the alloy first increases and then decreases with increasing x, and the equilibrium pressure decreases with increasing x. The electrochemical measurements show that the maximum discharge capacity first increases from 354.2 (v = 0) to 397.6 mAh g(-1) (x = 0.6) and then decreases to 370.4 mAh g(-1) (x= 0.8). The high-rate dischargeability of the alloy electrode increases lineally from 55.7% (x=0) to 73.8% (x=0.8) at the discharge current density of 1200 mA g(-1). Moreover, the exchange current density of the alloy electrodes also increases monotonously with increasing x.

Electrochemical characteristics and microstructure of Zr0.9Ti0.1Ni1.1Mn0.6V0.3-LaNi5 composite hydrogen storage alloys

AB(2-x)%LaNi5 (x =0, 1, 5, 10) composite alloys were prepared by melting Zr0.9Ti0.1Ni1.1Mn0.6V0.3 with a small amount of LaNi5 alloy as addition. The microstructure and electrochemical characteristics of the composite alloys were investigated by means of XRD, SEM, EDS and electrochemical measurements. It was shown that LaNi5 addition does not change the basic hexagonal C14 Laves phase of AB(2) alloys, but some second phases have segregated. It was found that the addition of LaNi5 greatly improves the activation property, high-rate dischargeability (HRD) and charge-discharge cycling stability of AB(2) Laves phase alloy. At current density of 1200 mA/g, HRD of the alloy increases from 38.92% (x =0) to 60.09% (x = 10). The capacity retention of the alloy after 200 charge-discharge cycles increases from 57. 10% (x = 0) to 83.86% (x = 5) and 67.31% (x = 10). The improvement of the electrochemical characteristics caused by LaNi5 addition seems to be related to formation of the second phases.

Microstructures and tensile properties of Mg-8Gd-0.6Zr-xNd-yY (x+y=3, mass%) alloys

Mg-8Gd-0.6Zr-xNd-yY (mass%) alloys which containing different Nd:Y mass ratio of 3:0, 2:1, 1:2 and 0:3 with a constant x + y = 3 were prepared by metal mould casting method, and the microstructure, aging behaviour and tensile properties have been investigated. The fibrous eutectic areas along the boundaries enlarge clearly in the as-cast alloys containing Y element, and the fine grain boundaries and dispersed precipitation are observed in the aged alloys. The Mg-8Gd-0.6Zr-2Nd-Y alloy exhibits notably age-hardening behaviour and the highest mechanical property. The ultimate tensile strength and yield strength of Mg-8Gd-0.6Zr-2Nd-Y alloy in the peak aged hardness are 293 and 221 MPa at room temperature, 248 and 191 MPa at 230 degrees C. The improvement of age-hardening response and tensile properties is mainly attributed to the quadrate-like stable Mg5RE precipitate, which forms readily and orderly in aged Mg-8Gd-0.6Zr-2Nd-Y alloy.

The structure and electrochemical characteristics of La0.67Mg0.33 (Ni0.8Co0.1Mn0.1)(x) (x=2.5-5.0) multiphase alloys for nickel-metal hydride batteries

This paper presents results concerning structure and electrochemical characteristics of the La0.67Mg0.33 (Ni0.8Co0.1Mn0.1) (x) (x=2.5-5.0) alloy. It can be found from the result of the Rietveld analyses that the structures of the alloys change obviously with increasing x from 2.5 to 5.0. The main phase of the alloys with x=2.5-3.5 is LaMg2Ni9 phase with a PuNi3-type rhombohedral structure, but the main phase of the alloys with x=4.0-5.0 is LaNi(5)phase with a CaCu5-type hexagonal structure. Furthermore, the phase ratio, lattice parameter and cell volume of the LaMg2Ni9 phase and the LaNi5 phase change with increasing x. The electrochemical studies show that the maximum discharge capacity increases from 214.7 mAh/g (x=2.5) to 391.1 mAh/g (x=3.5) and then decreases to 238.5 mAh/g (x=5.0). As the discharge current density is 1,200 mA/g, the high rate dischargeability (HRD) increases from 51.1% (x=2.5) to 83.7% (x=3.5) and then decreases to 71.6% (x=5.0). Moreover, the exchange current density (I-0) of the alloy electrodes first increases and then decrease with increasing x from 2.5 to 5.0, which is consistent with the variation of the HRD. The cell volume reduces with increasing x in the alloys, which is detrimental to hydrogen diffusion and accordingly decreases the low-temperature dischargeability of the alloy electrodes.

Structures and electrochemical characteristics of several kinds of alloys

The structures and the electrochemical characteristics of La0.7-xCexMg0.3Ni2.8Co0.5 (x = 0.1-0.5) alloy, Ti0.25-xZrxV0.35Cr0.1Ni0.3 (x = 0.05-0.15) alloy and AB(3