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Hydrogen Diffusion in Metals

In Pd and other transition metals, hydrogen has a high solubility and diffuses very fast, possibly because of the high d-electron density in the band structure of these metals. During absorption, the hydrogen molecule is first dissociated in the Pd surface subsequently, the adsorbed hydrogen atoms are ionized, and are incorporated directly into the material as protons and electrons, e, as follows [31,32] [Pg.234]

Therefore, it is possible to consider that a neutral dissociation of hydrogen occurs as follows [32]  [Pg.234]

11 jTbfgas) — H (solid solution) where the equilibrium constant for this reaction is [Pg.234]

CH is the hydrogen concentration in the solid, which is equivalent to the proton concentration and h2 are the pressures of hydrogen in the gas phase [Pg.234]

In this case, it is well known that the process occurs in steady state. To understand this process, one must consider it as a special case of binary diffusion, where the diffusivity of the Pd atoms is zero. Consequently, the frame of reference is the fixed coordinates of the solid Pd thin film. The interdiffusion or chemical diffusion coefficient is the diffusivity of the mobile species [20], that is, hydrogen. Then, the hydrogen flux in the Pd thin film is given by [Pg.234]


Majer, G., Eberle, U., Kimmerle, F., Stanik E. and Orimo, S. (2003) Hydrogen diffusion in metallic and nano structured materials, Physica B 328, 81-89. [Pg.147]

Hydrogen diffusion within metals is also known to be governed by the stress-strain state therein. Roughly, it may be considered that hydrogen diffuses in metals obeying a Fick type diffusion law including additional terms to account for the effect of the stress-strain state. Concerning the role of stress, this is... [Pg.131]

However it turned out that the structural, chemical and dynamical details are essential for complex descriptions of long-range proton transport. These parameters appear to be distinctly different for different families of compounds, preventing proton conduction processes from being described by a single model or concept as is the case for electron transfer reactions in solutions (described within Marcus theory [23]) or hydrogen diffusion in metals (incoherent phonon assisted tunneling [24]). [Pg.714]

In this section we present a brief overview of experimental methods used to study hydrogen motion in metals. The methods giving microscopic information on the hydrogen jump motion are emphasized. We restrict ourselves to a discussion of the basic principles of these methods only. More detailed consideration of the application of different methods to studies of the hydrogen diffusion in metals can be found in the reviews [7-14]. [Pg.788]

VoUd J, Alefeld G (1975) Hydrogen diffusion in metals. In Nowick AS, Burton JJ (eds) Diffusion in solids, recent developments. Academic Press, New York, pp 232-295... [Pg.78]

A residence time Tq and a non-negligible jump time Ti are also introduced to describe the proton translational motion in solids but in contrast with liquids, the jump direction and length are determined by quasi-equilibrium sites which form a periodic interstitial lattice. In this case, as exemplified by studies of hydrogen diffusion in metals it becomes very interesting to look at the anisotropy of the motion by studying selected crystal orientations relative to Q, particularly when the conductivity itself is anisotropic. [Pg.331]

Sholl DS. Using density functional theory to study hydrogen diffusion in metals a brief overview. J AUoy Compd 2007 446 462-8. [Pg.158]

A variety of techniques have been used to monitor hydrogen diffusion in metallic glasses when the hydrogen contents are small (i.e., H/M < 0.1). However, very few studies other than the NMR measurements,... [Pg.247]

This choice and the resulting approximations are best illustrated by two examples. In the first, we consider hydrogen diffusion in metals. This diffusion substantially reduces a metal s ductility, so much so that parts made from the embrittled metal frequently fracture. To study this embrittlement, we might expose the metal to hydrogen under a variety of conditions and measure the degree of embrittlement versus these conditions. Such empiricism would be a reasonable first approximation, but it would quickly flood us with uncorrelated information that would be difficult to use effectively. [Pg.4]


See other pages where Hydrogen Diffusion in Metals is mentioned: [Pg.330]    [Pg.313]    [Pg.88]    [Pg.234]    [Pg.132]    [Pg.787]    [Pg.791]    [Pg.795]    [Pg.797]    [Pg.797]    [Pg.825]    [Pg.732]    [Pg.159]    [Pg.143]    [Pg.57]    [Pg.135]   


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