Comprehensive modeling of hydrogen transport and accumulation in titanium and zirconium

Kinetic model for hydrogen absorption in tungsten with coverage dependent surface mechanisms

“…Thus, this description does not include the sub-surface layer described by atomistic simulation in [18,32] where the stable positions of H atoms close to the surface are lower in energy than in the far bulk. To include such a layer in the model, one could use what is developed for H absorption in titanium in [33] where another intermediate layer is considered between the surface and the bulk: it means adding 2 new energies (for the sub-surface → surface transition and for the sub-surface → bulk transition) and an additional concentration of H isotopes in this sub-surface layer. However, because the experiment on which the model is based does not have the resolution to dicern the sub-surface from the bulk, the simpleer approach was chosen.…”

Improved kinetic model of hydrogen absorption and desorption in titanium with subsurface transport

“…The fundamental concept of the numerical model of hydrogen absorption is described in Ref. 19 and schematically depicted in Fig. 1.…”

“…6, 8, and 9,  and  ss are defined in the range below unity. In our previous model [19], we did not account for X max , or X max was treated to be unity. Because of the abovementioned definition of N s , the situation  =  ss = 1 corresponded to the one X = 1 in our previous model.…”

“…does not need to be changed because X varies up to X max , but is not defined in the range below unity, unlikely to  and  ss . As another modification of the model, we assumed that T g and T s were always equal to each other, and therefore treated them as a single, common variable in our previous model [19]. In contrast, we distinguish them for generality in the present model.…”

“…Nevertheless, the kinetics of hydrogen transport in metals, particularly around the surface, have not been completely explained yet [18]. Previously, we developed a kinetic model of hydrogen absorption in Ti [19]. However, for hydrogen desorption from Ti, the model did not sufficiently reproduce experimental data, and therefore its applicability was limited to the absorption process.…”