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

Mechanism and life study on polyaniline anti-corrosion coating

Solvent free polyaniline emeraldine base(EB) corrosion protection coating was prepared, employing aliphatic polyamine as solvent of EB as well as hardener of epoxy resin. This coating passed 2000h of salt fog test when the EB loading was about 1 wt%. The interaction between EB and iron indicated that EB acted as a "quasi-catalyst" to cause the formation of densed iron oxide film in the interface.

Preparation of W-Al alloys by mechanical alloying

W1-xAlx (x=0-0.86) alloys were synthesized by mechanically alloying the pure metal powder mixtures at designated compositions by conventional high-energy ball milling. The W-Al alloys were stable under high pressure and high temperature. The alloys were lighter than W. The hardness and oxidation resistance of the alloys was greatly improved compared to both W and Al. (C) 2002 Elsevier Science B.V. All rights reserved.

Electrochemical characteristic of LaNi-based hydrogen storage alloys

Effect of purity of alloy components on the electrode performance of LaNi2 alloys was investigated. The results showed the purity of components had less effect on discharge capacity and self-discharge of LaNi2 alloys. Partial substitution of Al or Mn for Ni greatly improved discharge properties of LaNi2-xAlx, or LaNi2-yMny alloys as negative electrodes in MFl-Ni battery, 0.15less than or equal toxless than or equal to0.25; 0.15less than or equal toyless than or equal to0.25. In addition, surface treatment of LaNi1.8Al0.2 alloy electrode was performed by polymerizing cis-butenedioate with Co-60- gamma -ray radiation, which. had better affect on self-discharge and cycle life of the alloy electrodes at low temperature(-28 C-degrees).

Polyaniline as marine antifouling and corrosion-prevention agent

Conductive polyaniline was found to have special marine antifouling property. The coating from conducting polyaniline and epoxy resin(or polyurethane) can last 6-9 months in Southern China sea, i.e., less than 10% of the coating surface was fouled during this period. The conducting polyaniline has special synergetic antifouling effect on other antifouling agents like cuprous oxide or 4, 4'-dichlorodiphenyltrichloroethane. The conductivity of the polyaniline was found to be extremely important for its antifouling effect. Moreover, employing aliphatic polyamine as solvent of emeraldine base and curing agent of epoxy resin, a new technique to process corrosion prevention coating containing emeraldine base was developed, therefrom the emeraldine base and epoxy resin was in molecular level blending. This technique was solvent free and extremely effective, i.e., only 1wt% of emeraldine base in the coating can have good corrosion prevention property.

Binary alloys of nylon 1010 and ethylene-propylene copolymer: Chemical, morphological, and mechanical analysis

The modification of ethylene-propylene copolymer (EPM) has been accomplished by melt grafting of maleic anhydride (MAH) molecules promoted by radical initiators. The resulting EPM-g-MAH and EPM have been used to obtain binary nylon 1010/EPM or nylon 1010/EPM-g-MAH blends by melt mixing. It was found that the EPM-g-MAH copolymer used as the second component has a profound effect upon the properties of the resulting blends. This behavior has been attributed to a series of chemical and physicochemical interactions taking place between the two components. The interactions are due to the presence of the anhydride functionality on the copolymer and do not occur when this functionality is absent. The interaction has been confirmed by Fourier-transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and scanning electron microscopic.

Truly chlorine-resistant polyamide reverse osmosis composite membrane

Truly chlorine-resistant polyamide reverse osmosis composite membranes were prepared by cross-linking the interface of the composite membrane. Such membranes possessed chlorine resistance one order of magnitude more than those of the commercially used polyamide composite membranes. The effect of the degree of cross-linking on chlorine resistance was also described. (C) 1996 John Wiley & Sons, Inc.

INHIBITION OF CORROSION BY HEXADECYL TRIMETHYL AMMONIUM BROMIDE LANGMUIR-BLODGETT MONOLAYERS ON CARBON-STEEL

Langmuir-Blodgett (LB) monolayers of hexadecyl trimethyl ammonium bromide (HTAB) were deposited onto a carbon steel surface to investigate the inhibition of corrosion by measurement of the polarization resistance and cyclic voltammetry. The corrosion proc

XPS STUDY OF CORROSION BEHAVIOUR OF TITANIUM IN H2C2O4 SOLUTION

The corrosion behaviour of titanium substance and the XPS characterization of Ti surface in the H2C2O4 solution have been first studied by X-ray photoelectron spectroscopy, The experimental results show that there am mile Ti-2 and Ti2+ on sample surface in 10% H2C2O4 solution for two boars corrosion at 80 degrees C, but if corrosion is extended to 4 hones, the surface composition is mainly TiO2 with a small amount of Ti2+. This result corresponds to the structure of TiH1.642 composion in sample surface found by XRD analysis. Since bath TiO2 and the surface coating RuO2 are of Gald-Redstone structure, therefore electrode materials of Ti-Ru are stable in chemical industry.