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Journal ArticleDOI

Diffusion of hydrogen interstitials in Zr based AB2 and mischmetal based AB5 alloys

12 Aug 2005-Journal of Physics: Condensed Matter (IOP Publishing)-Vol. 17, Iss: 34, pp 5201-5206
TL;DR: In this paper, the diffusion coefficient of the hydrogen interstitials has been determined from hydrogen absorption kinetics experiments using powder x-ray diffractograms, and the dependence of diffusion coefficient on the alloy content has been discussed.
Abstract: The Zr based AB2 alloys ZrMnFe0.5Ni0.5, ZrMnFe0.5Co0.5 and mischmetal (Mm) based AB5 alloy MmNi3.5Al0.5Fe0.5Co0.5 have been prepared and characterized by means of powder x-ray diffractograms. The hydrogen absorption kinetics of these alloys have been studied in the temperature and pressure ranges 450–650 °C and 10–100 mbar respectively with a maximum H to host alloy formula unit ratio of 0.01, using a pressure reduction technique. The diffusion coefficient of the hydrogen interstitials has been determined from hydrogen absorption kinetics experiments. The dependence of the diffusion coefficient on the alloy content has been discussed. For Mm based MmNi3.5Al0.5Fe0.5Co0.5 alloy, the diffusion coefficient is about an order of magnitude higher than that of the Zr based alloys.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the diffusion of hydrogen in the tetrahedral interstitials of bulk spherical Laves phase ZrMn 0.85 Cr 0.1 V 0.05 Fe 0.5 Ni 0.

16 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the time dependence of hydrogen pressure during the hydrogen absorption process, and the diffusion coefficient data were described by an Arrhenius relation, which was used to determine the partial enthalpy and the chemical potential of dissolved hydrogen.

7 citations

Journal ArticleDOI
TL;DR: In this article, the diffusion constants of hydrogen in cubic (C15-type) Laves phase Ho 1 - x Mm x Co 2 (x = 0, 0.2 and 0.4, Mm = mischmetal ) alloys were measured in the α-phase (solid solution) region over the temperature range of 500 − 800 ∘ C using Sieverts-type apparatus.

3 citations

References
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BookDOI
01 Jan 1988
TL;DR: In this article, the most important diagnostics in this phase will undoubtedly be the neutron diagnostics, but other systems which are essential in unravelling the energy balance, such as the bolometers will retain a key iminence as will diagnostics determining impurity and instability behaviour, including the spectroscopic and X-ray systems.
Abstract: (Laboratorium für Festkörperphysik, ETH) stability and disruption behaviour provoked by the a heat source. The most important diagnostics in this phase will undoubtedly be the neutron diagnostics, but other systems which are essential in unravelling the energy balance, such as the bolometers will retain a key im­ portance as will diagnostics determining impurity and instability behaviour, such as the spectroscopic and X-ray systems. The wall diagnostics will be required to give in­ formation on the plasma wall and radiation damage behaviour in this phase. It would also be useful to have direct information on a particle energy transfer and containment but it is not clear at present that suitable diagnostic techniques can be developed to operate in the intense radiation field. Infor­ mation on the effectiveness of the a parti­ cle heating will however be obtained from the neutron measurements. The various systems giving spatially resolved informa­ tion on temperature and density profiles will be essential for detailed energy balance analysis.

509 citations

Journal ArticleDOI
TL;DR: In this paper, the performance of a metal hydride electrode is determined by both the kinetics of the processes occurring at the metal/electrolyte interface and the rate of hydrogen diffusion within the bulk of the metal.
Abstract: Metal hydrides are being used as electrodes in nickel/metal-hydride batteries because of their ability to store large quantities of hydrogen and because of their many advantages over conventional lead-acid and nickel-cadmium batteries. The performance of a metal hydride electrode is determined by both the kinetics of the processes occurring at the metal/electrolyte interface and the rate of hydrogen diffusion within the bulk of the metal. The constant potential and constant current discharge techniques were used to determine the hydrogen diffusion coefficients in an LaNi{sub 4.25}Al{sub 0.75} electrode. The values obtained were 2.97 {times} 10{sup {minus}11} and 3.30 {times} 10{sup {minus}11} cm{sup 2}/s, respectively. The advantages and disadvantages of these two techniques are discussed.

478 citations

Journal ArticleDOI
TL;DR: The solubility and diffusion coefficient of hydrogen were determined in the austenitic (cubic) high-temperature phase of the shape-memory alloy NiTi in this paper.
Abstract: The solubility and the diffusion coefficient of hydrogen were determined in the austenitic (cubic) high-temperature phase of the shape-memory alloy NiTi The measurements were made between 500 and 950 degrees C, with hydrogen gas pressures of up to 13 bar, and with hydrogen-to-NiTi ratios of up to 0027 The hydrogen was in interstitial solid solution The absorption process is exothermic The enthalpy of solution per hydrogen atom is -183+or-40 meV The diffusion coefficient can be described by an Arrhenius relation with an activation energy E=480+or-50 meV and a pre-exponential factor D0=(47-25+39)*10-3 cm2s-1 NiTi hydride was synthesised in experiments with a higher hydrogen gas pressure (p=150 bar, T=500 K) Because of its brittleness, the hydride is readily pulverised by mechanical methods This yields, after extraction of the hydrogen, NiTi powder which is difficult to prepare by other experimental techniques

92 citations

Journal ArticleDOI
TL;DR: In this article, the symmetry factors for bare and copper-coated electrodes were estimated to be 0.53 and 0.52, respectively, and the hydrogen diffusion coefficient in bare and coated LaNi{sub 4.27}Sn{sub 0.24} electrodes was investigated in alkaline solution.
Abstract: Electrochemical properties of bare and copper-coated LaNi{sub 4.27}Sn{sub 0.24} electrodes were investigated in alkaline solution. The exchange current density, polarization resistance, and equilibrium potential were determined as functions of the state of charge in the electrodes. The symmetry factors for bare and copper-coated electrodes were estimated to be 0.53 and 0.52, respectively. By using a constant current discharge technique, the hydrogen diffusion coefficient in bare and coated LaNi{sub 4.27}Sn{sub 0.24} was estimated to be 6.75 {times} 10{sup {minus}11} cm{sup 2}/s.

67 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the hydrogen absorption isotherms for the CaCu5 hexagonal structured alloys MmNi3.4, Mm Ni3.8Al 0.368Mn0.5Fe0.4Co 0.333V0.333Al0.3Fe0,4Fe 0.5Co 0,5Fe 0,6Al 0,7Al 0 0,8Al0 0.4Fe0 0,4Co0.

48 citations