For hydrogen absorption

The Pd H system. Quoting from the detailed and comprehensive review by Manchester and Pitre (1994) it can be said that this system is the paradigm of metal hydrogen systems, the longest studied, the easiest to activate for hydrogen absorption and probably the richest in the number of physically interesting phenomena observed. A Tlx projection from the P-T-x surface is shown in Fig. 3.37. 

Our data indicate that ammonia acts as a mild inhibitor for hydrogen absorption in Ni-containing AB5 alloys. The measured heat of adsorption of NH3 on Ni is about -11 kcal/mol NH3, suggesting weak, physical adsorption. Since Ni is viewed to be a catalyst for the hydriding reaction, weak physical adsorption of NH3 at these Ni sites would retard the reaction and promote a broadening of the reaction front as shown in Figures 12 and 13. 

Palladium shows a great capacity for hydrogen absorption. This takes place with changes in the crystalline structure of the metal with the formation of Pd2H or Pd4H2 hydrides. 

Deuterium absorption isotherms were determined similarly for TiMo. The temperature range examined was the same as that for hydrogen absorption, but the range of deuterium contents was significantly smaller, extending only to D/M zz 0.01. The data are presented in Figure 6. It is evident that Sieverts Law is... 

Fukada, S., et al. (2004b), Profiles of Hydrogen Molar Fraction and Temperature in ZrV19Fe01 Alloy Bed for Hydrogen Absorption , Journal of Alloys and Compounds, 381, 258-265. 

Shoemaker D.P., Shoemaker C.B. (1979) Concerning atomic sites and capacities for hydrogen absorption in the AB2 ffiauf-laves phases. Les-Common Met. 668, 43-58. 

Figure 15. Enhancement factor for hydrogen absorption in an aqueous hydroxylamine solution as a function of the reciprocal Sauter mean diameter of Pd/activated carbon catalyst particles esPs = 1.5 kgm-3, flat interface stirred cell (from Wimmers et al. [123]).

Fig. 6.15 Pressure composition isotherms for hydrogen absorption in a typical intermetallic compound on the left-hand side. The solid solution (a-phase), the hydride phase (/J-phase) and the region of the coexistence of the two phases. The coexistence region is characterized by the flat plateau...

Evaluation of rate constants for hydrogen absorption and diffusivity into metals 341... 

Model descriptions for hydrogen absorption in amorphous alloys have been given by Kirchheim et al. (1982), Kirchheim (1982) and Griessen (1983). Griessen notes that the absence of a plateau pressure in these materials may not always be primarily due to disorder. In his model he describes the hydrogen-hydrogen interaction by means of a mean field approximation and shows that the critical temperature (below which the pressure composition isotherms may exhibit a plateau) is positive if a Stoner-like criterion is satisfied ... 

Let us consider now diffusion inside a sphere neglecting the diffusion gradient outside the sphere. Such a case might be observed for hydrogen absorption or Li intercalation into spherical particles. Diffusion inside the sphere can go only to the sphere center and is called finite-length internal spherical diffusion. In the steady state in which the impedance measurements are carried out, dc concentration inside the sphere is uniform, and no dc current is flowing. Ac perturbation causes oscillations of concentration at the sphere surface, which diffuse inside the sphere. In such a case, two boundary conditions in Eq. (4.94) are changed ... 

Zirconium has a high affinity for hydrogen. Absorption of hydrogen leads to hydrogen embrittlement, which can lead to failure of the zirconium tubing used as cladding for... 

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