Diffusion of hydrogen in metals

Birnbaum, H.K.; Wert, Charles

doi:10.1002/bbpc.19720760835

Ber Bunsenges Phys Chem

1972

DOI: 10.1002/bbpc.19720760835

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Diffusion of hydrogen in metals

H.K. Birnbaum

Charles Wert

Abstract: Published measurements of the diffusion of hydrogen in fcc metals are summarized with particular emphasis on the isotope effect. The observations are generally consistent with the usual rate theory model but with the energy levels in both the equilibrium site and the saddle point quantized according to an Einstein oscillator. Not all data fit this scheme, however, diffusion in Pd being a notable exception. Published work for the bcc metals shows much less consistency; surface effects and internal trapping at d… Show more

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Cited by 110 publications

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Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu₃ with a Critical Temperature of 42 K under Atmospheric Pressure

Tian,

He,

Zhu

et al. 2023

Adv Funct Materials

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Since the prediction of multi‐hydrogen high‐temperature superconductor by Ashcroft in 2004, many possible candidates have been proposed, e.g., LaH10 showing the highest superconducting transition temperature (Tc) around 250–260 K at 170‐200 GPa hitherto. However, this pressure is too large to be taken into practical use. To address this challenge, it proposes a few‐hydrogen metal‐bonded perovskite superconductor, MgHCu3, by combining a novel design idea with first‐principles calculations. Different from multi‐hydrogen hydrides, whose high Tc relies on extreme pressure, the metallic bond in few‐hydrogen superconductor MgHCu3 improves the structural stability and ductility at atmospheric pressure. Here, the small amount of hydrogen is found to be vital for Tc. After the incorporation of hydrogen, the electron–phonon coupling constant of MgHCu3 is increased to 0.83, which is larger than that of the well‐known MgB2. Moreover, the anisotropy of MgHCu3 also plays an important role in enhancing Tc. Based on the Migdal‐Eliashberg theory, it predicts that the phonon‐mediated metal‐bonded perovskite MgHCu3 is a superconductor with Tc of 42 K. The first predicted ternary metal‐bonded perovskite, MgHCu3, enriches the family of perovskite and will promote further investigation on few‐hydrogen superconductors under atmospheric pressure.

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Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu₃ with a Critical Temperature of 42 K under Atmospheric Pressure

Tian,

He,

Zhu

et al. 2023

Adv Funct Materials

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The Kinetics of Hydrogen Absorption in Palladium (α‐ and β‐phase) and Palladium‐Silver‐Alloys

Auer

Grabke

1974

Ber Bunsenges Phys Chem

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The reaction H2 → 2 H (dissolved) on thin Pd and Pd‐Ag foils (2.5–5 μm) was studied, with the aid of resistance measurements, in a flow apparatus at temperatures in the range 20–150°C. The rate determining step is the dissociation of the H2‐molecule on the metal surface. It is assumed that in the formation of the activated complex one atom (proton) already enters an interstitial site in the lattice. For very low hydrogen concentrations xH in α‐phase Pd and in Pd‐Ag alloys, where Sieverts law applies, the following rate law is valid equation image The rate law shows that there is a segregation equilibrium between dissolved atoms and atoms in the interstitial reaction sites. For α‐phase Pd the enthalpy of this segregation is ‐1.9 kcal/mol H, the activation energy of the forward reaction is 6.8 kcal and of the backward reaction 11.5 kcal, which yields the reaction enthalpy ‐4.7 kcal/mol H.In a range of higher hydrogen concentrations the forward reaction rate is accelerated by a factor exp(gxH). This leads to the decreased slope of the isotherm p1/2 vs. xH, that is known from thermodynamic studies. The acceleration is ascribed to the lattice expansion caused by the dissolved atoms. After the d‐band of the metal phase is filled by electrons from hydrogen (and silver), the forward reaction rate decreases with increasing xH and the backward reaction rate increases exponentially. This leads to the known steep rise of the isotherm p1/2 vs. xH in the ß‐phase region or in the Pd – Ag alloys after d‐band filling.

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Elektronische Einflüsse bei der Diffusion von Wasserstoff in Legierungsreihen des Palladiums

Buchold¹,

Sicking²,

Wicke³

1976

Ber Bunsenges Phys Chem

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Die Beweglichkeit von Tritium in Palladiumlegierungen rnit Ag, V und Ni als Legierungspartner wurde rnit einem time-lag-Verfahren untersucht, wobei die P-Strahlung des Tritium-Zerfalls als MeBsignal benutzt wurde; diese Methode gestattet die Messung innerer Konzentrationsverschiebungen ohne den EinfluR storender Grenzflachenhemmungen. Es wurde gefunden, daB geringe Legierungszusatze die Aktivierungsenergie der Tritium-Diffusion nicht beeinflussen; hohere Legierungsanteile an Ag und V fuhren dagegen zu einem starken Anwachsen der Aktivierungsenergie, wahrend der isoelektronische Legierungspartner Ni die Aktivierungsenergie innerhalb der MeBfehlergrenzen nicht verandert. Zur Deutung der Ergebnisse wird die Aktivierungsenergie der Diffusion in einen Grundanteil des Pd-Wirtsgitters und einen elektronischen Zusatzterm aufgespalten. Dieser steht in engem Zusammenhang rnit der VEK und kann aus dem Abschirmpotential der zulegierten Storatome annahernd berechnet werden. Der Grundanteil der Aktivierungsenergie kann in erster Naherung mit der Energie der elastischen Verzerrung des Pd-Wirtsgitters beim Diffusionssprung identifiziert werden.The mobility of tritium in Pd-alloys with Ag, V and Ni has been investigated by time-lag measurements, where the P-radiation of the tritium decay was taken as measuring signal; this method allows the determination of internal concentration shifts without disturbance by inhibiting effects of interface transfer. It has been found, that small additions of the alloying components do not change the activation energy of tritium diffusion; higher concentrations of Ag and V, however, lead to steep rises of the activation energy, whereas the isoelectronic Ni as alloying partner does not influence the activation energy within the limits of experimental error. For interpretation of the results the activation energy of diffusion is divided into a basic contribution of the Pd host lattice and an additional electronic term. This term is closely connected with the VEC, and can be calculated from the screening potential of the impurity atoms. The basic part of the activation energy can approximately be identified with the energy of elastic strain of the Pd lattice brought about by the diffusion jump.

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Diffusion of hydrogen in metals

Cited by 110 publications

References 43 publications

Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu₃ with a Critical Temperature of 42 K under Atmospheric Pressure

Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu₃ with a Critical Temperature of 42 K under Atmospheric Pressure

The Kinetics of Hydrogen Absorption in Palladium (α‐ and β‐phase) and Palladium‐Silver‐Alloys

Elektronische Einflüsse bei der Diffusion von Wasserstoff in Legierungsreihen des Palladiums

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Diffusion of hydrogen in metals

Cited by 110 publications

References 43 publications

Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu3 with a Critical Temperature of 42 K under Atmospheric Pressure

Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu3 with a Critical Temperature of 42 K under Atmospheric Pressure

The Kinetics of Hydrogen Absorption in Palladium (α‐ and β‐phase) and Palladium‐Silver‐Alloys

Elektronische Einflüsse bei der Diffusion von Wasserstoff in Legierungsreihen des Palladiums

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Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu₃ with a Critical Temperature of 42 K under Atmospheric Pressure

Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu₃ with a Critical Temperature of 42 K under Atmospheric Pressure