Hydrogen diffusion in palladium by galvanostatic charging

Early, J G

doi:10.1016/0001-6160(78)90005-6

Cited by 57 publications

(20 citation statements)

References 16 publications

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“…(4) depend on the initial and surface conditions, leading to a series of diffusion models. Concentration of H 2 or D 2 in our samples during UV-irradiation (i.e., when a constant flux F i is established at the irradiated surface (x = 0) of a sample of thickness l, the initial H 2 or D 2 concentration is zero throughout the sample, and concentration at x = l is C(l, t) = 0 at all times) is modeled by the following equation (Early 1978):…”

Section: Theoretical Modelsmentioning

confidence: 99%

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Martín-Doménech

Dartois

Caro

2016

A&A

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Context. Hydrogenated amorphous carbon (a-C:H) has been proposed as one of the carbonaceous solids detected in the interstellar medium. Energetic processing of the a-C:H particles leads to the dissociation of the C-H bonds and the formation of hydrogen molecules and small hydrocarbons. Photo-produced H 2 molecules in the bulk of the dust particles can diffuse out to the gas phase and contribute to the total H 2 abundance. Aims. We have simulated this process in the laboratory with plasma-produced a-C:H and a-C:D analogs under astrophysically relevant conditions to investigate the dependence of the diffusion as a function of temperature. Methods. Experimental simulations were performed in a high-vacuum chamber, with complementary experiments carried out in an ultra-high-vacuum chamber. Plasma-produced a-C:H and a-C:D analogs were UV-irradiated using a microwave-discharged hydrogen flow lamp. Molecules diffusing to the gas-phase were detected by a quadrupole mass spectrometer, providing a measurement of the outgoing H 2 or D 2 flux. By comparing the experimental measurements with the expected flux from a one-dimensional diffusion model, a diffusion coefficient D could be derived for experiments carried out at different temperatures. −0.0023 cm 2 s −1 ). Conclusions. The strong decrease of the diffusion coefficient at low dust particle temperatures exponentially increases the diffusion times in astrophysical environments. Therefore, transient dust heating by cosmic rays needs to be invoked for the release of the photoproduced H 2 molecules in cold photon-dominated regions, where destruction of the aliphatic component in hydrogenated amorphous carbons most probably takes place.

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Section: Theoretical Modelsmentioning

confidence: 99%

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Martín-Doménech

Dartois

Caro

2016

A&A

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“…i~ = toe ~2~ [4] DF J~ = L-Co [5] where j| is the steady-state permeation current density, ~q is the overpotential, a = F/RT, Co is the hydrogen concentration directly beneath the cathode surface, C, is the saturation value of Co, ~ is the transfer coefficient of reaction 1, ~2 is the transfer coefficient of reaction 2, ic is the cathodic current density, D is the hydrogen diffusion coefficient, and L is the membrane thickness. Bockris et aI.…”

Section: J~=f[kl(1-~)e ~-K 1coe (1-~l)an] [3]mentioning

confidence: 99%

Hydrogen‐Atom Direct‐Entry Mechanism into Metal Membranes

Zheng

Popov

White

1995

J. Electrochem. Soc.

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“…14,15 The first variation, referred to as the potentiostatic charging, is based on the assumption that a constant potential at the entry surface would immediately establish a constant hydrogen concentration in the meta) fust below the entry side. In the second variation, galvanostatic charging, It is assumed that a constant cathodic current on the entry side produces a constant hydrogen flux.…”

Section: Hydrogen Diffusivitymentioning

confidence: 99%

“…In this case, suitable linear relationships similar to equation (2) are [17][18][19] : log(ip1 " -i P )t' 12 vs 1/t for decay and log(i p -i pl s)t vs 1/t for build up, where i p ,¢ is the initial steady-state permeation rate at a chosen cathodic current density before its change, and i, is the actual permeation rate at a chosen time after applying a new cathodic current density. The stopes of these relationships, expressed as in Equation (2) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] .from these transients are given in Figure 9. The obtained relationships are linear and close to one another.…”

Section: Hydrogen Diffusivitymentioning

confidence: 99%

Diffusion and Absorption of Hydrogen in Liquid-Quenched and Annealed Ni₈₁P₉₁Alloy

Zakroczymski¹,

Flis²

1989

CORROSION

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Transport and absorption of hydrogen were studied in the Nia1 P79 alloy in the as-quenched amorphous state and after annealing for 1 h at temperatures up to 873°K. The diffusivity and the amount of diffusible and trapped hydrogen were determined from electrochemical permeation measurements performed at 298°K. After annealing below the crystallization temperature (Tc = 560°K), the hydrogen diffusivity and absorption rose by up to about twice, whereas at higher temperatures (formation of the Ni and N13P phases) they drastically decreased, with a drop in diffusivity being almost three orders of magnitude. Below Tom, the ratio of trapped hydrogen to total absorbed hydrogen almost did not change with the annealing temperature, being about 0.75. The rise in the hydrogen diffusivity and absorption below T c may result from local ordering of atoms; it demonstrates that the behavior of hydrogen may be a sensitive measure of structural relaxation in the amorphous alloy.KEY WORDS: amorphous and annealed Ni81 P79 alloy, hydrogen absorption and diffusion.

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Hydrogen diffusion in palladium by galvanostatic charging

Cited by 57 publications

References 16 publications

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Hydrogen‐Atom Direct‐Entry Mechanism into Metal Membranes

Diffusion and Absorption of Hydrogen in Liquid-Quenched and Annealed Ni₈₁P₉₁Alloy

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Hydrogen diffusion in palladium by galvanostatic charging

Cited by 57 publications

References 16 publications

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Hydrogen‐Atom Direct‐Entry Mechanism into Metal Membranes

Diffusion and Absorption of Hydrogen in Liquid-Quenched and Annealed Ni81P91Alloy

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Diffusion and Absorption of Hydrogen in Liquid-Quenched and Annealed Ni₈₁P₉₁Alloy