X-ray studies of the α/β miscibility gaps of some palladium solid solution-hydrogen systems

Wise, M. L. H.; Farr, J.P.G.; Harris, I.R.

doi:10.1016/0022-5088(75)90099-5

Cited by 78 publications

(13 citation statements)

References 14 publications

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“…Pure Pd has a lattice parameter of 3.89 Å (10 nm¼1 Å). At room temperature, the α-phase exists up to a composition known as α max and can form alongside with the β min up to a H/Pd atomic ratio of $ 0.6 whereby each phase has a lattice parameter of 3.895 and 4.025 Å, respectively [53]. The coexistence of these two phases gives rise to a notable feature of the phase diagram shown in Fig.…”

Section: Palladium Membranesmentioning

confidence: 97%

“…Such phenomenon has been studied using transmission electron microscopy of a Pd-H alloy containing the αþβ phase showing clear evidence of dislocation production which is a precursor to embrittlement [53]. The effects of embrittlement can be avoided through purging the membrane of any hydrogen prior to thermal cycling in order to prevent crossing the miscibility gap.…”

Section: Metal Crystal Structurementioning

confidence: 99%

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Hydrogen selective membranes: A review of palladium-based dense metal membranes

Al-Mufachi

Rees

Steinberger-Wilkens

2015

Renewable and Sustainable Energy Reviews

363

162

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Section: Palladium Membranesmentioning

confidence: 97%

Section: Metal Crystal Structurementioning

confidence: 99%

Hydrogen selective membranes: A review of palladium-based dense metal membranes

Al-Mufachi

Rees

Steinberger-Wilkens

2015

Renewable and Sustainable Energy Reviews

363

162

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“…( 19) using the experimentally determined pressure hysteresis, ρ 0 , and approximate value of [[c e ]]. We assume a characteristic L = 10-35 nm, obtained as the inverse of the reported dislocation densities in cycled Pd-H [35][36][37]. The pinning potentials for bulk Pd-H are 0.1-0.34 and 0.04-0.15 J m −2 at 333 and 435 K, respectively.…”

Section: A Hysteresis and Hysteresis Energiesmentioning

confidence: 99%

Interface pinning causes the hysteresis of the hydride transformation in binary metal hydrides

Weadock

Voorhees

Fultz

2021

Phys. Rev. Materials

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Hydriding and dehydriding transitions in bulk and nanocrystalline binary metal hydrides were studied using the Pd-H model system by measuring pressure-composition isotherms with in situ x-ray diffractometry. Nanocrystalline Pd showed a smaller pressure hysteresis, solvus hysteresis, and hysteresis in lattice parameter, compared to bulk Pd. The time-dependence of pressure equilibration was measured after dosing with aliquots of hydrogen, giving equilibration times that were much faster in the single-phase regions than in the two-phase plateaus. In the broad two-phase plateaus, the pressure relaxations were exponential functions of time. An explanation of hysteresis is developed that is based on a dissipative potential barrier that impedes the motion of the interface due to interactions between lattice defects and the two-phase interface. The exponential pressure relaxations and hysteresis are consistent for this mechanism. For a simple model of the pinning potential, the potential barrier maximum is an order of magnitude less than typical grain boundary energies. These pinning effects are substantially different in the nanocrystalline Pd, suggesting differences in the hydriding mechanism.

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“…Such alloy is reported to form the Pd 0.772 Ag 0.228 H n hydride with n 0.4 in ambient conditions [11] and with reduced embrittlement problems, so as to be employed successfully as hydrogen permeable membrane in industrial processes [6,7]. Indeed, Pd alloys with silver content over 20%e30% are claimed to present a single hydride phase at room temperature [12], but some peculiar aspects of electrical resistivity at higher T would hint at a possible phase transition [13]. So the problem of an accurate phase diagram for the Pd 0.772 Ag 0.228 H n limit composition is still open.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of deuteration of the Pd0.772Ag0.228 alloy with α/β phase transition by in-situ neutron diffraction

Catti

Fabelo

Filabozzi

et al. 2019

Journal of Alloys and Compounds

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The deuteration reaction of a Pd 0.772 Ag 0.228 foil was studied by neutron powder diffraction measurements vs. time in different T and p(D 2 ) conditions (D20 and D2B high-resolution diffractometers at ILL, France). The system has great importance as permeable membrane for hydrogen separation. At p ¼ 1 bar and T < 200 C Bragg peak splitting indicates the presence of two cubic phases, to be identified with the a and b modifications of palladium hydride. Rietveld refinements provided the corresponding a a and a b lattice constants, the n a and n b occupancies of D, and the b phase volume fraction vs. time during deuteration progress. A continuous a / b transformation takes place till reaction end. At T ¼ 200 C or p > 1 bar a single phase was always observed. The phase diagram of Pd 0.772 Ag 0.228 D n is thus shown to present a aþb two-phase domain less extended but similar to that of PdH n , at variance with most thermodynamic measurements suggesting full single-phase behavior. The n(t) kinetic data of deuteration at 80 C/1 bar can be interpreted by a mechanism based on a first-order nucleation step followed by a zero-order step of surface adsorption and dissociation of the D 2 molecule.

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X-ray studies of the α/β miscibility gaps of some palladium solid solution-hydrogen systems

Cited by 78 publications

References 14 publications

Hydrogen selective membranes: A review of palladium-based dense metal membranes

Hydrogen selective membranes: A review of palladium-based dense metal membranes

Interface pinning causes the hysteresis of the hydride transformation in binary metal hydrides

Kinetics of deuteration of the Pd0.772Ag0.228 alloy with α/β phase transition by in-situ neutron diffraction

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