Hydrogen solubility and hydrogen diffusion coefficients have been studied in Ti0.1Zr0.9(Mn0.9V0.1)1.1Fe0.5Ni0.5, Ti0.1Zr0.9Mn0.9V0.1Fe0.55Ni0.55 and (Ti0.1Zr0.9)1.1Mn0.9V0.1Fe0.5Co0.5 in the temperature range 450-650 °C with hydrogen gas pressure up to 100 mbar and hydrogen concentration up to 0.03 hydrogen atoms per formula unit. H2 absorption is exothermic, and the values of partial enthalpy of solution per H atom are in the range from -370 ± 10 meV to -466 ± 50 meV. The silica embedded AB2 alloy particles have been prepared by sol-gel technique. P-C isotherms of encapsulated AB2 alloy particles have been obtained in the pressure and temperature ranges 0-30 bar and 30-100 °C, respectively. Diffusion of H interstitials in sol-gel encapsulated Ti0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5, (Ti0.1Zr0.9)1.1Mn0.9V0.1Fe0.5Ni0.5 and (Ti0.1Zr0.9)1.1Mn0.9V0.1Fe0.5Co0.5 alloy particles have been studied between 500 and 650 °C with H2 gas pressure up to 100 mbar and H concentration up to 0.014 H atoms per formula unit. Diffusion coefficient (D) of H interstitials has been determined for all these samples from the kinetics of hydrogen absorption. The activation energies have been calculated from temperature dependence of diffusion coefficient and the values are in the range 416 ± 15-897 ± 50 meV. © 2006 Elsevier Ltd. All rights reserved.

Sundara Ramaprabhu

Department Of Physics

Diffraction

Diffusion in gases

Encapsulation

Exothermic reactions

Hydrogen

Hydrogen storage

Isotherms

Melting

Sol-gel process

solubility

Hydrogen absorption

Hydrogen diffusion

HYDROGEN GAS

Hydrogen solubility

LAVES PHASES

Zirconium alloys

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Intermetallics

Solubility of H2 gas and diffusion of H interstitials were studied in Ti0.1Zr0.9Mn0.9V 0.1Fe0.5Ni0.5, (Ti0.1Zr 0.9)1.1Mn0.9V0.1Fe 0.5Ni0.5 and Ti0.1Zr0.9Mn 0.9V0.1Fe0.5Co0.5 alloys with C14 hexagonal structure. Data were taken between 400 and 600 ° C, for H 2 gas pressures up to 100 mbar and H concentrations up to 0.012 H atoms per host-metal formula unit (solid solution phase). H2 absorption is exothermic, and the partial enthalpy of solution per H atom is -(210±10) and -(248±10) meV for the two alloys Ti 0.1Zr0.9Mn0.9V0.1Fe 0.5Ni0.5 and (Ti0.1Zr0.9) 1.1Mn0.9V0.1Fe0.5Ni0.5, respectively. The diffusion coefficient of the H interstitials was determined for all three samples from the kinetics of H2 gas absorption. At 500 ° C, the diffusion coefficients are ∼5×10-5 cm2s -1, with activation energies between 292 and 423 meV. © 2005 Elsevier B.V. All rights reserved.

Journal of Alloys and Compounds

Solubility and diffusion of hydrogen in AB2-type Laves phase alloys

Stoichiometric Ti0.1Zr0.9Mn0.9V 0.1Fe0.5Co0.5 and non-stoichiometry (Ti 0.1Zr0.9)1.1Mn0.9V 0.1Fe0.5Co0.5, Ti0.1Zr 0.9(Mn0.9V0.1)1.1Fe 0.5Co0.5 and Ti0.1Zr0.9Mn 0.9V0.1Fe0.55Co0.55 alloys have been synthesized and the lattice constants and unit cell volume have been obtained by using powder X-ray diffractograms. Pressure-composition (PC) isotherms have been obtained in the temperature and pressure ranges 30-125°C and 0.1-30bar using pressure reduction method and the effect of non-stoichiometry on the hydrogen absorption properties have been studied. Maximum hydrogen storage capacity is around 3.4 hydrogen atoms per formula unit at 30bar and 30°C in Ti0.1Zr0.9Mn0.9V0.1Fe 0.5Co0.5. The relative partial molar enthalpy (ΔHH) and relative partial molar entropy (ΔSH) of the dissolved hydrogen have been calculated from the PC isotherms and their variation with hydrogen concentration has been plotted to identify the existence of different phases. The powder X-ray diffraction patterns of Ti 0.1Zr0.9Mn0.9V0.1Fe 0.5Co0.5-Hx (x=1.6 and 3.2) have been obtained in order to study the effect of hydrogenation on the crystal structure. The activation energy and diffusion coefficient of dissolved hydrogen in Ti 0.1Zr0.9Mn0.9V0.1Fe 0.5Co0.5 have been calculated from the kinetics of hydrogen absorption measurements at different temperatures and compared with Ti0.1Zr0.9Mn0.9V0.1Fe 0.5Ni0.5. The effect of non-stoichiometry on the kinetics of hydrogen absorption at 50°C has been studied and discussed. © 2004 Elsevier B.V. All rights reserved.

Hydriding properties of Ti-substituted non-stoichiometric AB2 alloys

Pressure-composition isotherms have been obtained for Ti0.1Zr0.9Mn0.9V0.1 Fe0.5Ni0.5, (Ti0.1Zr0.9)1.1Mn0.9V0.1F e0.5Ni0.5, Ti0.1Zr0.9(Mn0.9 V0.1)1.1Fe0.5Ni0.5 and Ti0.1Zr0.9Mn0.9V0.1Fe0.55 Ni0.55 having the C14 type hexagonal structure in the temperature and pressure ranges 30-100°C and 0.1-50 bar using a pressure reduction method in order to find the effect of non-stoichiometry on hydrogen storage properties. The powder x-ray diffractograms of the alloys show the formation of C14 single phase; the lattice constants and unit cell volumes of these alloys have been calculated. Ti0.1Zr0.9(Mn0.9 V0.1)1.1Fe0.5Ni0.5 has a hydrogen storage capacity of 3.5 hydrogen atoms/fu at 20 bar and room temperature. The dependences of the thermodynamics of the dissolved hydrogen in these alloy hydrides in the temperature range 30-100°C on the hydrogen concentration have shown the existence of α, α + β and β phase regions as seen in the isotherms. The effect of non-stoichiometry on the kinetics of hydrogen absorption in these alloys has been studied at 50°C. The powder x-ray diffractograms of the alloy hydrides show that these alloys do not undergo any structural change upon hydrogenation and that there is only a volume expansion of around 25%. The activation energy and diffusion coefficient of dissolved hydrogen in Ti0.1Zr0.9Mn0.9 V0.1Fe0.5Ni0.5 have been calculated from the kinetics of hydrogen absorption measurements at different temperatures. The activation energy is Ea = 0.17 eV in the α + β phase region and Ea = 0.22 eV in the β phase region and the diffusion coefficient D = 2.7 × 10-11 cm2 s-1 in the β phase at 30°C.

Journal of Physics Condensed Matter

The effect of non-stoichiometry on the hydrogen storage properties of Ti-substituted AB2 alloys

Journal of Electroanalytical Chemistry

Study of hydrogen diffusion in α- and β-phase hydrides of Mg2Ni alloy by microelectrode technique

Physica Scripta

PROGRAMME COMMITTEE

Hydrogen solubility and diffusion studies of Zr-based AB2 alloys and sol-gel encapsulated AB2 alloy particles

Journal	Intermetallics
ISSN	09669795
Open Access	No