S.V. Mitrokhin

Structure and hydrogen sorption properties of (Ti,Zr)-Mn-V alloys

The present investigation is a part of the series of works on the development of new materials as highly efficient hydrogen accumulating media. Earlier we reported on the investigation of Ti–Mn–V alloys of Laves phase type. This work is the continuation of these studies. The work was aimed on the determination of concentration boundaries of Laves phase and investigation of hydrogen sorption properties of alloys. Using X-ray, EDXA and electron microscopy methods the phase compositions of over 50 alloys were studied. The Laves phase concentration boundaries were determined to extend up to 26 at.% of vanadium. Compared to ternary Ti–Mn–V system the region of λ1-phase is about 2 at.% wider for Ti–Mn side of concentration triangle. Depending on metal concentrations lattice parameters were determined to increase proportionally with increasing titanium or vanadium concentration according to Vegard rule. The interaction of alloys with hydrogen was studied by PC-isotherm method. The isotherms were measured at three different temperatures and thermodynamic parameters of reaction were calculated using the vant Hoff equation. The hydrogen sorption properties were analysed in view of overall alloy composition. The enthalpy of desorption was found to depend proportionally on unit cell volume of alloy.

Metal hydrides: properties and practical applications. review of the works in cis-countries

Abstract A short review of RandD in the field of hydrogen hydride technologies in Russia and CIS countries is presented. As a result of basic research of physical and chemical features of intermetallic alloys and their hydrides, their structural peculiarities, absorption kinetics, thermal processes, etc., methods have been developed for creation high efficient alloys for different applications in metal hydride technology. Original devices such as hydrogen accumulators, thermal compressors, heat transformation systems and other experimental devices with unique characteristics have been created. The results of reviewed RandD demonstrate high efficiency of metal hydride technologies. These investigations and developments give reliable scientific and technical background for the development of the new research projects in the framework of the new Russian program of RandD in hydrogen energy and technology and for international cooperation.

Structure of (Ti,Zr)–Mn–V nonstoichiometric Laves phases and (Ti0.9Zr0.1)(Mn0.75V0.15Ti0.1)2D2.8 deuteride

Abstract The structure of several Laves phase alloys and deuteride was studied using methods of X-ray analysis and time-of-flight neutron diffraction. The refinement of diffraction profiles was performed using the Rietveld method. Introduction of hydrogen does not change the metal matrix structure and the hydriding is accompanied by isotropic increase of cell volume by 20%. The minimisation of the R -factor showed that the best fit is achieved for the model of deuterium location in three sites, 24(l) , 12(k) 1 and 6(h) 1 . However, at low temperature approximately 0.11 deuterium atoms relocate from the 24(l) to the 12(k) 1 position. The analysis of alloy and deuteride structure performed in this work as well as the reference data allow to draw a conclusion, that the set of sites in hexagonal Laves phase structure which are occupied by deuterium is a stable one and does not depend on temperature or alloy composition.

Hydrogen sorption peculiarities in FeTi-type TiFeVMn alloys

Abstract The interaction of hydrogen with FeTi-based alloys of the TiFeVMn system was investigated using P-C isotherms, energy dispersive X-ray analysis (EDXA) and Auger electron spectroscopy (AES). In narrow concentration ranges of both vanadium and manganese, the β- and γ-hydride decomposition pressure values approach each other and the corresponding plateaux transform into one sloping plateau on the desorption isotherm. We call this phenomenon the “pressure smoothing effect”. The alloying of FeTi with vanadium and manganese does not lead to considerable changes in the resistance of the alloys to contamination. The presence of vanadium and especially manganese changes the surface properties and influences the activation mechanism of hydrogen absorption.

Synthesis and properties of multicomponent hydrides with high density

Abstract The results of research of interaction of hydrogen with alloys of Ti–V–M (M=Fe, Co, Ni), Ti–Ta; Zr–Ta; Ti–W; Ti–Ta–W; Zr–Sc; Hf–Sc systems are presented. The study of these materials was carried out in two directions aimed at an increase of hydride density preserving a high content of hydrogen in them and a decrease of synthesis parameters preserving high thermal stability of hydrides. The phase diagrams of the studied systems were obtained.

Calorimetric investigation of multicomponent Laves phase interaction with hydrogen and deuterium

Abstract The interaction of multicomponent TiMn1.5-type Laves phases with hydrogen and deuterium was investigated by means of standard pressure-composition isotherms and a calorimetric method. One of the studied alloys was selected using a mathematical approach based on the Bernauer phenomenological model. The thermodynamic parameters of the reaction of hydrogen desorption for the alloy of composition Ti0.98Zr0.02Mn1.5V0.43Cr0.05Fe0.09 were found to be ΔH = 22.8 ± 0.2 kJ mol H2−1 and ΔS = 96.5 ± 0.7 J K−1 mol H2−1. For the alloy Ti0.9Zr0.1Mn1.5V0.25Cr0.1Fe0.05Ni0.05Co0.05 these parameters turned out to be ΔH = 22.4 ± 0.2 kJ mol H2−1 and ΔS = 94.2 ± 0.5 J K−1 mol H2−1. The latter alloy with a d-electron concentration of 3.93 is characterized by a narrower α region, in good accordance with model predictions. The desorption of deuterium from the alloy Ti0.9Zr0.1Mn1.5V0.25Cr0.1Fe0.05Ni0.05Co0.05 is characterized by values of ΔH = 28.7 ± 0.2 kJ mol H2−1 and ΔS = 93.8 ± 0.7 JK−1 mol H2−1.

Ti-based laves phase hydrides with high dissociation pressures

Abstract The interaction of Laves phase multicomponent alloys with hydrogen has been studied by means of P–C isotherms, X-ray, EDX and atomic adsorption analysis. The comparison of experimental and calculated parameters is discussed. The studied alloys can be employed in the thermosorption compressors.

HYDROGEN ABSORPTION PROPERTIES ZrFe2 AND ZrCo2 BASED ALLOYS

In this work Zr1-xTix(Fe1-yAly)2 system and the alloys Zr0.8Ti0.2Co1.6Al0.4 and Zr0.9Gd0.1Co2 were studied with the purpose to investigate the influence of zirconium substitution by titanium or a rare earth metals on hydrogen sorption properties of IMC ZrFe2 and ZrCo2. The hydrogen absorption properties were studied by measuring PCT absorption and desorption isotherms using a high hydrogen pressure apparatus at a hydrogen pressure below 3,000 atm. Hydrogen desorption pressures and hydrogen storage capacity decrease with increasing aluminium content in Zr1-xTix(Fe1-yAly)2alloys. The catalytic effect of gadolinium addition on acceleration of reaction of ZrCo2with hydrogen was established. The thermodynamic parameters of hydrogen desorption reactions were calculated for number alloys.

Electrochemical And Hydrogen Sorption Properties of Ab5—Type Alloys Where A — La, Ce; B — Ni, Co, Mn, Fe, Cu, Cr, Al

Like other accumulator types Ni-MH batteries are unable to keep high characteristics in the temperature range -30°C to +40°C. To solve this problem the negative electrode material - intermetallic compound (IMC) hydride - must have dissociation pressure of 0.1-1.5 atm in this temperature interval. The IMC composition was calculated with mathematic model. The model describes dependence of IMC hydrides properties on IMC composition. Using calculation results series of alloys were prepared and their hydrogen absorption and electrochemical properties were studied. The best alloy is CeMn0.5Co0.25Al0.5Ni3.75. The sample has discharge capacity 275 mAh/g, keeps 95% of this value at 40°C and 40% at -30°C.

Study of Structure and Hydrogen Absorption Properties of Alloys of Ti-Mn-V System

Ti-Mn-V metallic system is practically not described in literature. In present work the investigation of the composition and structure and their influence on alloy hydrogen absorption properties was done. The alloys were prepared by arc melting with consequent annealing at 850°C. The investigation was conducted by means of X-ray, chemical and microscopic analysis and determination of “pressure-composition” isotherms.