Solid Solutions of Hydrogen in Complex Materials

Abstract

For Abstract see ChemInform Abstract in Full Text.

Diffusion of Hydrogen

“…This simply means that the thermal energy in the various expressions derived by Kirchheim [9] is given by RT rather than k B T.…”

“…5.24 that, for the case of thermally activated hopping, all the sites visited by the H-atoms have the same average jump frequency. In the following we reproduce various derivations given by Kirchheim [9] for the calculation of the tracer diffusion coefficient from atomic models. In these models the density of site energy (DOSE) of interstitial hydrogen atoms at various locations in the lattice is derived using Fermi-Dirac statistics (Kirchheim [9]).…”

“…In the following we reproduce various derivations given by Kirchheim [9] for the calculation of the tracer diffusion coefficient from atomic models. In these models the density of site energy (DOSE) of interstitial hydrogen atoms at various locations in the lattice is derived using Fermi-Dirac statistics (Kirchheim [9]). Unlike in Kirchheim's approach, we assume that the formulation is in terms of molar, not atomic, quantities of thermodynamic parameters, such as the site energies and the Fermi energy (the latter being the equivalent to the hydrogen chemical potential).…”

“…In addition, it is useful to derive expressions that show how the diffusivity is affected by microstructure as a result of, for instance, trapping at various types of defects or the presence of fast diffusion paths. These objectives are developed in the following sections with the theoretical development based, for the most part, on methods provided by Kirchheim [9] using the DOSE approach documented in Chap. 4.…”

Chemical Composition of Advanced Materials as Obtained by the 3-Dimensional Atom Probe

“…Gibbs concept developed for surfaces and grain boundaries was recently extended to other defects and segregation of solute atoms to these defects (Ref. [12]). This way the analysis of a special alloy provided insight to a rather general behaviour of the defect-solute interaction.…”