Effects of low Ag additions on the hydrogen permeability of Pd–Cu–Ag hydrogen separation membranes

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Effects of low Ag additions on the hydrogen permeability of Pd–Cu–Ag hydrogen separation membranes. / Nayebossadri, Shahrouz; Speight, John; Book, David.

In: Journal of Membrane Science, Vol. 451, 01.02.2014, p. 216-225.

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@article{a7a4bcea21fa40c9b02fadbf00fdadb5,
title = "Effects of low Ag additions on the hydrogen permeability of Pd–Cu–Ag hydrogen separation membranes",
abstract = "Pd–Cu alloys are of potential interest for use as hydrogen purification membranes, but have relatively low permeability compared to the commercially used alloys such as Pd–Ag. In this work, the effects of partial Ag substitution on the hydrogen diffusivity, solubility and the permeability of Pd–Cu membranes with a bcc structure have been investigated. With the addition of 2.3 and 3.9 at% Ag to Pd–Cu, lattice expansions of 0.11% and 0.35% were observed. Structural analyses by in-situ XRD showed that the bcc structure of the 2.3 at% Ag alloy is retained upon heating to 600 °C, whereas an fcc phase forms in the 3.9 at% Ag alloy resulting in a mixed (bcc+fcc) structure. Whilst the diffusion coefficients between 350 and 400 °C for both Pd–Cu–Ag ternary samples were shown to be lower than their binary alloys (which had similar structures), higher solubility values were obtained. The lower diffusion coefficients of the ternary alloys are related to an increase in the diffusion activation barrier in the presence of Ag, and the higher solubility values may be attributed to the lattice expansion and high Ag–H chemical interaction. Hydrogen permeation measurements showed that an enhancement in the hydrogen solubility of the bcc phase Pd45.8Cu51.9Ag2.3, does not have a substantial effect on the permeability of the membrane. In contrast, for the Pd45.1Cu51Ag3.9 sample with a mixed (bcc+fcc) phase, higher hydrogen solubility can lead to a remarkable improvement in permeability. Hence, it is suggested that the hydrogen permeability in the bcc phase is mainly controlled by hydrogen diffusion, and the solubility enhancement can only significantly improve the hydrogen permeability when the fcc phase is present.",
keywords = "Hydrogen separation, Metallic membrane, Palladium-based ternary alloys, Pd–Cu, Pd–Cu–Ag",
author = "Shahrouz Nayebossadri and John Speight and David Book",
year = "2014",
month = feb,
day = "1",
doi = "10.1016/j.memsci.2013.10.002",
language = "English",
volume = "451",
pages = "216--225",
journal = "Journal of Membrane Science",
issn = "0376-7388",
publisher = "Elsevier",

}

RIS

TY - JOUR

T1 - Effects of low Ag additions on the hydrogen permeability of Pd–Cu–Ag hydrogen separation membranes

AU - Nayebossadri, Shahrouz

AU - Speight, John

AU - Book, David

PY - 2014/2/1

Y1 - 2014/2/1

N2 - Pd–Cu alloys are of potential interest for use as hydrogen purification membranes, but have relatively low permeability compared to the commercially used alloys such as Pd–Ag. In this work, the effects of partial Ag substitution on the hydrogen diffusivity, solubility and the permeability of Pd–Cu membranes with a bcc structure have been investigated. With the addition of 2.3 and 3.9 at% Ag to Pd–Cu, lattice expansions of 0.11% and 0.35% were observed. Structural analyses by in-situ XRD showed that the bcc structure of the 2.3 at% Ag alloy is retained upon heating to 600 °C, whereas an fcc phase forms in the 3.9 at% Ag alloy resulting in a mixed (bcc+fcc) structure. Whilst the diffusion coefficients between 350 and 400 °C for both Pd–Cu–Ag ternary samples were shown to be lower than their binary alloys (which had similar structures), higher solubility values were obtained. The lower diffusion coefficients of the ternary alloys are related to an increase in the diffusion activation barrier in the presence of Ag, and the higher solubility values may be attributed to the lattice expansion and high Ag–H chemical interaction. Hydrogen permeation measurements showed that an enhancement in the hydrogen solubility of the bcc phase Pd45.8Cu51.9Ag2.3, does not have a substantial effect on the permeability of the membrane. In contrast, for the Pd45.1Cu51Ag3.9 sample with a mixed (bcc+fcc) phase, higher hydrogen solubility can lead to a remarkable improvement in permeability. Hence, it is suggested that the hydrogen permeability in the bcc phase is mainly controlled by hydrogen diffusion, and the solubility enhancement can only significantly improve the hydrogen permeability when the fcc phase is present.

AB - Pd–Cu alloys are of potential interest for use as hydrogen purification membranes, but have relatively low permeability compared to the commercially used alloys such as Pd–Ag. In this work, the effects of partial Ag substitution on the hydrogen diffusivity, solubility and the permeability of Pd–Cu membranes with a bcc structure have been investigated. With the addition of 2.3 and 3.9 at% Ag to Pd–Cu, lattice expansions of 0.11% and 0.35% were observed. Structural analyses by in-situ XRD showed that the bcc structure of the 2.3 at% Ag alloy is retained upon heating to 600 °C, whereas an fcc phase forms in the 3.9 at% Ag alloy resulting in a mixed (bcc+fcc) structure. Whilst the diffusion coefficients between 350 and 400 °C for both Pd–Cu–Ag ternary samples were shown to be lower than their binary alloys (which had similar structures), higher solubility values were obtained. The lower diffusion coefficients of the ternary alloys are related to an increase in the diffusion activation barrier in the presence of Ag, and the higher solubility values may be attributed to the lattice expansion and high Ag–H chemical interaction. Hydrogen permeation measurements showed that an enhancement in the hydrogen solubility of the bcc phase Pd45.8Cu51.9Ag2.3, does not have a substantial effect on the permeability of the membrane. In contrast, for the Pd45.1Cu51Ag3.9 sample with a mixed (bcc+fcc) phase, higher hydrogen solubility can lead to a remarkable improvement in permeability. Hence, it is suggested that the hydrogen permeability in the bcc phase is mainly controlled by hydrogen diffusion, and the solubility enhancement can only significantly improve the hydrogen permeability when the fcc phase is present.

KW - Hydrogen separation

KW - Metallic membrane

KW - Palladium-based ternary alloys

KW - Pd–Cu

KW - Pd–Cu–Ag

U2 - 10.1016/j.memsci.2013.10.002

DO - 10.1016/j.memsci.2013.10.002

M3 - Article

VL - 451

SP - 216

EP - 225

JO - Journal of Membrane Science

JF - Journal of Membrane Science

SN - 0376-7388

ER -