Metal hydrogen system, 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. 

Palladium hydride is not a stoichiometric chemical compound but simply a metal in which hydrogen is dissolved and stored in solid state, in space between Pd atoms of crystal lattice of the host metal. Relatively high solubility and mobility of H in the FCC (face-centered-cubic) Pd lattice made the Pd H system one of the most transparent, and hence most studied from microstructural, thermodynamic, and kinetic points of view. Over the century that followed many metal-hydrogen systems were investigated while those studies were driven mostly by scientific curiosity. Researchers were interested in the interaction of hydrogen molecule with metal surfaces adsorption and diffusion into metals. Many reports on absorption of in Ni, Fe, Ni, Co, Cu, Pd, Pt, Rh, Pd-Pt, Pd-Rh, Mo-Fe, Ag-Cu, Au-Cu, Cu-Ni, Cu-Pt, Cu-Sn, and lack of absorption in Ag, Au, Cd, Pb, Sn, Zn came from Sieverts et al. [30-33]. 

Figure 1. Ideal absorption and desorption isotherm for a metal-hydrogen system (1)...

The essential requirements for hydrogen storage in solids are that it be (a) high H-mass density (b) high H-volume density (c) appropriate pressure, temperature stability (d) reversible absorption/desorption. The results of research in the field of hydrogen solubility in the metal-hydrogen systems and carbon nanostructures are presented in this paper. 

One of the most thoroughly investigated ternary metal-hydrogen systems is Pd-Ag-H. It is experimentally known ) that addition of Ag to Pd favours hydrogen absorption at low hydrogen concentrations and reduces the maximum solubility at higher pressures. These trends are well reproduced by the calculated isotherms shown in Figs.7 a,b for PdQ o... 

Absorption of Hydrogen Chloride. Effective heat stabilizers have the abiHty to bind hydrogen chloride. Most stabilizer systems contain one or more metallic soaps or salts which readily undergo a simple acid—base reaction with the by-product hydrogen chloride as the PVC degrades ... 

Switendick was the first to apply modem electronic band theory to metal hydrides [5]. He compared the measured density of electronic states with theoretical results derived from energy band calculations in binary and pseudo-binary systems. Recently, the band structures of intermetallic hydrides including LaNi5Ht and FeTiH v have been summarized in a review article by Gupta and Schlapbach [6], All exhibit certain common features upon the absorption of hydrogen and formation of a distinct hydride phase. They are ... 

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