LaNi5 Alloy Research Articles

Crystallographic and electrochemical characteristics of melt-spun Ti–Zr–Ni–La alloys

Ti-based icosahedral quasicrystalline phase (I-phase) exhibited excellent hydrogen storage property for special structure. Unfortunately, the application as the negative electrode material of the nickel-metal hydride batteries was limited due to the poor electrochemical kinetics. Meanwhile, rare-earth element was beneficial to the electrochemical properties of Ti, Zr-based alloy. In present work, Ti 45Zr 30Ni 25La x ( x = 3, 5 and 7) alloys were prepared by melt-spinning. The effect of adding La on the electrochemical performance of melt-spun alloys was investigated in detail. The phase structure of the melt-spun alloys was analyzed by XRD and DSC. The results showed that the amorphous forming ability increased with increasing x value. The maximum discharge capacity decreased from 109 mAh g −1 to 99 mAh g −1 with increasing x value. High-rate dischargeability and cycling stability were improved by adding La, which may be resulted from the increase of amorphous phase in the alloy electrodes.

水素化により駆動する La-Ni 合金薄膜の運動曲げ歪における操作温度の影響

Hydrogenation operates the bending motion of mover device, which is a platinum coated La-Ni alloy film deposited on a polyimide sheet, has been successfully developed. Influence of the operating temperature on the motion strain has been evaluated. When the operating temperature is 373 K, the maximum value of bending strain (Δe) is 408 ppm, which is 1.4 times larger than that (300 ppm) of an unheated film operated at 323 K.

THERMODYNAMICS AND AMORPHIZATION OF THE NICKEL–LANTHANUM ALLOYS

The thermodynamic properties of liquid and crystalline Ni–La alloys were studied over the whole range of compositions and a wide temperature range, 685–1854 K, by Knudsen mass spectrometry and an integral variant of the effusion method realized under ultrahigh oilless vacuum. Complete and reliable thermodynamic description of all intermediate phases in the Ni–La system was obtained. The thermodynamic functions of the melts were described by the associated solution model. The existence of the complexes NiLa and Ni2La in the melts was found. The contributions of various intercomponent chemical interaction types (covalent and metallic) to thermodynamic functions were estimated. The present results were applied to computation of the phase diagram. Obtained thermodynamic description of the Ni–La alloys allowed the analysis of their transformation into amorphous state. It was determined that the magnitude of the associate formation entropy should be used for quantitative concept development of the propensity of metallic melts to amorphization.

Hydrogen storage properties and structure of La 1− xMg x(Ni 1− yMn y) 3 intermetallics and their hydrides

‘Hybrid’ RNi 3 (R = rare earth metal) crystal structures are built of the slabs of simpler types, CaCu 5 and MgZn 2. Different affinities of these slabs to hydrogen result in unusual “anisotropic” expansion of the RNi 3 and R 2Ni 7 (R = La, Ce) structures upon hydrogenation. This work focuses on studies of the hydrogenation behaviour of LaNi 3 and on the properties of the hydrides of the modified by Mg and Mn La–Ni alloys. The crystal structure of LaNi 3D 2.8 and the crystal structure and hydrogen storage behaviours of the La 1.5Mg 0.5Ni 7 and La(Ni 1− x Mn x ) 3 ( x = 0; 0.067; 0.133; 0.2; 0.267; 0.3; 0.333; 0.4) alloys were in focus. The deuteration of LaNi 3 with PuNi 3 type of structure leads to the formation of LaNi 3D 2.8 and is accompanied by a deformation of the metal matrix causing a change of the initial rhombohedral symmetry (space group R 3 ¯ m ) to a monoclinic one (space group C2/ m; a = 8.6408(7) Å, b = 4.9281(4) Å, c = 32.774(3) Å; β = 90.850(8)°; V = 1395.5(2) Å 3). Similar to the earlier studied CeNi 3D 2.8, preferential occupation by deuterium atoms of the AB 2 layers takes place, leading to the “anisotropic” expansion of the unit cell along [0 0 1] (Δ c/ c = 30.6%). 14 occupied D crystallographic sites have 4 chemically different types of metal-atom surroundings, including Ni 4 (2), La 2Ni 2 (2), La 3Ni (6), and La 3Ni 3 (4). Modification of the La–Ni alloys by magnesium and manganese leads to the formation of intermetallic compounds crystallising with the PuNi 3, CeNi 3, and Ce 2Ni 7-type structures. An ordered substitution of La by Mg in the MgZn 2-type slabs was observed, causing a complete alteration of the hydrogenation behaviour of the original LaNi 3 alloy. La 1.5Mg 0.5Ni 7D 9 isotropically expands upon its formation and leads to a substantial increase of the stability against hydrogenation-induced amorphisation. On the other hand, replacement of Ni by Mn leads to the change in crystal-structure type from PuNi 3 to CeNi 3 in the LaNi 3− x Mn x alloys ( x > 0.1). An ordered substitution of Ni by Mn proceeds inside the RNi 5 slabs only. This decreases the stability of the initial alloy against amorphisation on hydrogenation.

Hydrogenation Induced Bending Motion of Composite Device of La-Ni Alloy Film Deposited on Copper Foil

In order to obtain a large movement with high power and responsiveness, a hydrogenation operated bimetal device made of La-Ni alloy film deposited on a thin copper (Cu) substrate foil, has been successfully developed. The sample of La-Ni film deposited on the Cu thin foil exhibits about 50% larger bending displacement than that on a thick sheet of polyimide substrate within 50 s. The influence of load on bending motion has also been investigated. The moving yield of the La-Ni film deposited on the Cu thin foil is larger than that on a polyimide thick sheet.

Crystal structure and electrochemical characteristics of non-AB5 type La–Ni system alloys

Abstract The La–Ni system compounds have been prepared by arc-melting method under Ar atmosphere. X-ray diffraction analysis reveals that the as-prepared alloys consist of different phases. The electrochemical properties, including activation, maximum discharge capacity, high rate chargeability (HRC), and high rate dischargeability (HRD) of these alloy electrodes have been studied through the charge–discharge recycle testing at different temperatures and charge (or discharge) currents. Among the La–Ni alloy electrodes studied, LaNi 2.28 alloy has the most excellent high rate charging performance, and La 2 Ni 7 alloy exhibit the highest high rate dischargeability, while La 7 Ni 3 alloy is capable of discharging at low temperature.

Hydride stability and hydrogen desorption characteristics in melt-spun and nanocrystallized Mg–Ni–La alloy

The hydrogen desorption properties of Mg-rich alloys are significantly improved by nanostructure formation. This effect is examined for a melt-spun and nanocrystallized Mg–Ni–La alloy by pressure–composition isotherm (PCT) and thermal desorption spectrum (TDS) measurements. This alloy exhibits fast desorption kinetics and favorable PCT characteristics with an H-capacity of ∼4.6 wt%. TDS measurements reveal a definite peak ascribable to release of hydrogen from nanoboundaries, in addition to those associated with decompositions of hydrides such as MgH 2, Mg 2NiH 4 and LaH 3. Hydrogen transport along the nanoboundaries appears to facilitate the desorption kinetics in this alloy.

Electrochemical hydrogen storage in Li-doped pentacene

Porous metal-incorporated nanostructured organic compounds represent an innovative concept in hydrogen storage. This work reports in detail the first practical realization of electrochemical hydrogen storage in such a material, Li-doped pentacene. Although lithium doping is at a very low level the conductivity of pentacene increases considerably after the doping of lithium, which makes ordered layer-stacked Li-doped pentacene very promising as electrode material for electrochemical hydrogen storage. A discharge capacity of ca. 238 mA h g(-1) has been achieved in 6M KOH for the Li-doped pentacene electrode, which is comparable to that obtained from commonly used electrode material, LaNi5 alloy for electrochemical hydrogen storage. Furthermore, a great improvement in the hydrogen storage capacity can be expected from the Li-doped pentacene by simply raising the lithium doping level.

Study on the surface reaction of LaNi5 alloy during discharge process in KOH solution

A new method for studying surface reaction of LaNi5 absorbing alloy in KOH solution (pH 12) was established. It is based on tip–substrate voltammetry of scanning electrochemical microscopy (SECM) where the tip faradic current is recorded while scanning the substrate potential. The Pt electrode is selected as tip electrode, and the Pt oxide formation–reduction is used as a pH-dependent reaction while the tip potential is held at a constant value. As substrate surface reactions proceed, the pH of solution can be changed, and then the tip faradic current is recorded. The mechanism of discharge process of LaNi5 alloy was analyzed by comparing the tip current (Itip) versus substrate potential (Esub) curve, which reflects the exchange of H+ or OH− between the alloy surface and the solution, with the substrate current (Isub) versus substrate potential (Esub) curve, which reflects the exchange of electron on the LaNi5 alloy surface. The results showed that the OH− adsorption process is occurred before the electron transfer process during discharge process, and the adsorptive OH− helps the oxidation of adsorbed hydrogen atom on the alloy surface. A quantitative assessment for the maximum changes of pH during discharge process is also proposed, and the variation as large as 2.65 pH unit was detected.

Thermodynamic properties and phase equilibria in the Nickel-Lanthanum system: Transition of melts into the amorphous state

The vapor composition and thermodynamic properties of liquid and crystalline Ni-La alloys were studied over a wide temperature range, 685–1854 K, and the whole range of compositions. Measurements were performed by the integral variant of the effusion method under superhigh oilless vacuum conditions and Knudsen mass-spectrometry. To extend the range of measurements toward lower temperatures, an approach based on initiating and studying equilibria in reactions with LiF and MgF2 admixtures, which caused the formation of volatile interaction products, was used. A representative array of data was obtained, including more than 1600 component activity values at various compositions and/or temperatures. For the first time, a complete and correct thermodynamic description of all intermediate phases in the Ni-La system was obtained. The accuracy and reliability of the thermodynamic functions found were proved by the coincidence of the results obtained using various calculation methods in studying samples of various compositions under various experimental conditions (various effusion cell and inner cavity coating materials) and agreement with independent experimental data on phase transitions. The thermodynamic functions of Ni-La melts were described with accuracy not inferior to the accuracy of measurements on the assumption of the formation of associates of two types, NiLa and Ni2La. Approaches to determining the contributions of various intercomponent chemical interaction types (covalent and metallic) to thermodynamic functions were developed. The thermodynamic data obtained and the model description of melts suggested were used to calculate phase equilibria in the Ni-La system and construct its phase diagram. The interval of the transition of Ni-La melts into the amorphous state was displaced from the compositions of maximum chemical short-range order close to Ni2La and coincided with the region of the predominance of much less stable NiLa groups characterized by a higher negative entropy of formation. It was this characteristic that determined the dynamics of changes in the structural state of melts, ΔC p and Δfus S, and could therefore be used for creating quantitative criteria of the propensity of liquid metals to form amorphous solids.

Hydrogen storage properties of CNTs treated at different temperature in vacuum

The effect of multi-wall nanotubes (MWNTs) treated at different temperature in vacuum on the electrochemical hydrogen storage properties were investigated. The MWNTs were synthesized by chemical vapor deposition. The CNTs(carbon nanotubes)-LaNi5 electrodes were prepared by mixing MWNTs and LaNi5 alloy in a weight ratio of 1∶10. Three-electrode system was introduced. The CNTs-LaNi5 electrodes were used as the working electrode. Ni(OH)2/NiOOH worked as the counter electrode and Hg/HgO as the reference electrode. 6mol/L KOH solution acted as the electrolyte. Results showed that the CNTs-LaNi5 electrodes with CNTs treated at 850℃ in vacuum has the best electrochemical hydrogen storage capacity with a maximum discharging capacity of 503.6mAh/g and a corresponding discharging plateau voltage of 1.18V under the same testing condition. From 500℃ to 850℃, the higher the temperature of heating, the better the electrochemical hydrogen storage property of WMNTs. However, CNTs-LaNi5 electrodes with CNTs treated at 950℃ in vacuum has lower discharging capacity under the same testing condition. This shows that the temperature of CNTs treatment in vacuum is an important factor that influences its electrochemical hydrogen storage performance.

Investigation of thermal aspects of hydrogen storage in a LaNi5-H2 reactor

In this work, hydrogen absorption in a LaNi5-H2 reactor is investigated experimentally and numerically. Experimental measurements were carried out on a cylindrical metal-hydride reactor filled with LaNi5 alloy. During the experiments hydrogen was charged at a constant pressure. The performance of the reactor during hydriding process was obtained at different fluid temperatures and hydriding process was identified from measured temperature histories. The temperature changes in the reactor were measured at several locations and recorded in a computer. The numerical simulation of the reactor was also performed. A two-dimensional mathematical model has been established and solved numerically by the method of finite volume for the simulation. The numerical results are compared with the measured data to validate the mathematical model. The predicted results are in good agreement with the experimental measurements. Copyright © 2005 John Wiley & Sons, Ltd.

A rare earth alloy as a synthetic reagent: contrasting homometallic rare earth and heterobimetallic outcomes

Reaction of LaNi5 with 2,2′-dipyridylamine (HNpy2) at 170 °C under vacuum gave crystals of dimeric [La(Npy2)3]2 as a previously unknown eight-coordinate isomer (1a) (two μ-η2:η2 and two terminal chelating (Namide,Npy) Npy2 ligands), which reverts to the known ten coordinate isomer (1b) on recrystallisation from THF/PhMe, thereby establishing linkage isomerism of a [Ln(Npy2)3]2 complex for the first time. Reaction of 8-hydroxyquinoline (HOQ) with excess LaNi5 alloy at 190 °C resulted in extraction of both metals and the formation of heterobimetallic [Ni2La(OQ)7] (2). The trinuclear complex has two terminal, fac-octahedral nickel(II) sites, each bound to three chelating 8-quinolinolate anions which bridge through the oxygen atoms to the lanthanum(III) centre. The eight-coordinate lanthanum environment is completed by a chelating OQ ligand.

La-Ni水素吸蔵合金とSm-Fe磁歪合金をポリイミド薄板に両面蒸着した三層構造複合素子の運動歪

A three-layered composite mover device constructed with both hydrogen storage La-Ni and compressive magnetostrictive Sm-Fe alloy thin films on each side surface of polyimide substrate has been prepared by using a flash vacuum evaporation and a direct current magnetron sputtering, respectively. When the motion strain is about -750 ppm at ±400 kA/m of magnetic field before hydrogenation, it is about -1150 ppm after hydrogenation. The hydrogenation of the La-Ni alloy film in the three-layered composite mover device enhances the magnetostriction.

Preparation of Carbon Micro-beads via an Ethanol-thermal Route

Abstract Carbon micro-beads (CMB) with regular and perfect shape, high yields, and narrow size distributions were obtained via an ethanol-thermal reduction process in a stainless steel autoclave at 500 °C. In this process, LaNi5 alloy was used as a catalyst. The products were characterized with X-ray powder diffractometer (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. There were two types of carbon micro-beads, spherical and spindle-like, in the sample. The spherical micro-beads have diameters ranging from 2 to 5 μm. The spindle-like micro-beads had diameters ranging from 2 to 4 μm and lengths ranging from 5 to 10 μm.

Property Changes of Some Hydrogen Storage Alloys upon Hydrogen Absorption-Desorption Cycling

Hydrogen absorption-desorption cycling induced by pressure change in a closed system were carried out with LaNi5, La0.7Ce0.3Ni4Cu and TiFe0.9Ni0.1 alloys. PC isotherms measured during the cycling showed some changes in hydrogen storage capacity, plateau pressure and hysteresis of the alloys. . The half capacity life of LaNi5 alloy can be projected as 70,000 cycles for room temperature pressure cycling. When La0.7Ce0.3Ni4Cu alloy was pressure cycled both of the plateau pressures were decreased significantly and continuously. TiFe0.9Ni0.1 alloy showed a good resistance to cyclic degradation. Heat treatments of the degraded alloys under 1 atm of hydrogen gas recovered most of the hydrogen storage properties to the initial level even though they were degraded again more rapidly upon subsequent cycling.

Development of Hydrogenating Powder Alloys for the Electrodes of Alkali Batteries. Part 3. Production Characteristics of Gas-Atomized Powders of Multicomponent Intermetallic Alloys

Alloy powders containing rare earth metals are prepared by the gas atomization method and their structure, surface, technological, and electrochemical properties are studied. Powders of the alloys LaNi4.5Al0.5, LaNi2.5Co2.4Al0.1, and (Mm, La)Ni3.5Co0.7Al0.35Mn0.4Zr0.05 are prepared with different particle sizes. The morphology, oxygen content and crystal structure of powders in relation to particle size are studied by x-ray analysis, electron microscopy, and surface dispersion spectroscopy. The hydrogen capacity and electrochemical properties of different fractions are determined. It is established that all of the fractions have similar morphology and alloy lattice parameters. The surface of gas atomized powders with less particle size is less contaminated with oxygen compared with larger fractions. At the same time fractions with a particle size <50 μm have poor activity during gas and electrochemical hydrogenation. DTA curves for fractions of fine particles have an additional exothermic peak that may be caused by thermally induced transformation of the amorphous component into crystalline. The coarse fraction of gas atomized powder has the same hydrogen and electrochemical capacity as for fuzzed alloys.

Extraction of Rare Earth from La–Ni Alloys by the Glass Slag Method

The use of the glass slag method in the extraction of rare earth from La–Ni alloys was studied. X-ray diffraction and electron probe microanalysis studies revealed that the La–Ni alloys produced by the glass slag method using boron trioxide consisted of Ni and Ni3B phases. No La-containing phase such as the LaNi5 phase and the La oxide phase was found in the resultant alloys. The chemical analyses confirmed that the La content in the alloys produced by the glass slag method was very limited. However, the glass slag materials contained a large amount of lanthanum. The La in the La–Ni alloys was successfully extracted by the glass slag method using boron trioxide.

Relationship between intermetallic compound formation and glass forming ability of Al–Ni–La alloy

This Letter reports the relationship between intermetallic compound formation and glass forming ability of Al–La–Ni alloy. By controlling over cooling rate, the Al 88Ni 6La 6 amorphous alloy could be obtained at a circumferential speed of 22.00 m s −1. The intermetallic compounds, La 3Al 11 and Al 2La, in the partially amorphous Al 88Ni 6La 6 alloy which was formed at circumferential speeds of 8.25 m s −1 and 11.00 m s −1, have been identified by X-ray diffraction (XRD). The crystallization kinetics of Al 88Ni 6La 6 amorphous alloy is studied by differential scanning calorimetry (DSC). Continuous heating XRD patterns of Al 88Ni 6La 6 amorphous alloy shows that the first peak on its DSC curve (around 230 °C) corresponds to the precipitation of the fcc-Al phase and the second peak around 330 °C corresponds to the formation of intermetallic compounds. The DSC results indicate that the first peak is little affected by the cooling rate. It is believed that the formation of La 3Al 11 has more significant effect on glass forming ability of Al–Ni–La alloy than that of fcc-Al.

Hydrogen storage for carbon nanotubes synthesized by the pyrolysis method using lanthanum nickel alloy as catalyst

We have investigated the adsorption of hydrogen of multiwall carbon nanotubes synthesized by the pyrolysis method using a lanthanum nickel hydrogen storage alloy as a catalyst. The mechanism of carbon nanotubes synthesized using a La–Ni alloy catalyst is discussed. In the hydrogen atmosphere and high-temperature process of carbon nanotube preparation, the LaNi5 alloy particle may be changed into an intermetallic compound of Ni and La by the analysis of the x-ray diffraction patterns and energy-dispersive x-ray spectroscopy of the nanotubes samples using a La–Ni alloy as a catalyst. The H2 uptake capacity of the carbon nanotubes using a La–Ni alloy catalyst is about 5 wt % through to the pressure of 10 MPa. Using a La–Ni alloy as a catalyst increases the effect of chemistry adsorption in the H2 adsorption of the La–Ni alloy catalyzed carbon nanotubes. The P–C–T curve has an approximate plateau. The La–Ni alloy catalyzed carbon nanotubes have better activation for H2 uptake and larger hydrogen uptake in comparison to the carbon nanotubes without using a La–Ni alloy catalyst, and the hydrogen uptake increases with increasing hydrogen pressure from 2 MPa to 8 MPa at room temperature. The hydrogen uptake versus time showing a hydrogen uptake rate of carbon nanotubes using the La–Ni alloy catalyst was raised by the heat treatment from 1.0 wt % (heat treatment temperature 100 °C) to 2.3 wt % (heat treatment temperature 700 °C) at the H2 pressure of 5 MPa.