Hydrogen concentration dependence

HYDROGEN CONCENTRATION DEPENDENCE ON THERMAL AND ELECTRICAL CONDUCTIVITIES OF METAL-HYDRIDE COMPOSITE MATERIALS... 

The pressure-composition isotherm (1 bar = 10 Pa), (e) the hydrogen concentration dependence of the optical transmission and (f) the electrical resisitivity of a 300 nm thick yttrium film capped with 15 nm palladium. The optical transmission is measured at a photon energy E=1.95eV, corresponding to a wavelength k = 535 nm. The weak transmission window of the j6-phase around x = 2 and the transition to the transparent state in the j6-phase are clearly visible. The... 

Fig. 7.15 Hydrogen concentration dependence of (a) the complex ( -2) and (b) the real (ei) part of the dielectric function for YH - Similar dependences are observed in Lai-zYzH alloys although the trihydrides Lai-zYzHs with z< 0.67 remain cubic while for z> 0.86 they are hexagonal. (From Van Gogh et al. (2001), Ref [56].)...

Fig. 7.17 Hysteresis in the p-c isotherms (c) and hydrogen concentration dependence of the electrical resistivity (a) and transmission (b) ofYHy during a hydrogen loading (filled circles) - unloading cycle (open circles). The giant hysteresis (factor 10 ) in...

The maj or exceptions to this simplified picture are probably CuH and ZnH2, which are reported to be stoichiometric, nonmetallic solids like the main group metal hydrides, but their crystal stmctures and physical properties are not well characterized. Borderline cases are the rare earth hydrides, which show a hydrogen concentration-dependent semiconductor-metal transition. E11H2 and YbH2 behave like alkaline earth dihydrides because of the special electron configuration of Eu + (4/ ) and Yb + (4/ " ). 

The presence of different end-group types indicates that various chain transfer or isomerization reactions have participated in the polymerization. However, different mechanisms may produce the same end-group types. In these cases, the response to the changes in polymerizatiOTi conditions may be utilized to reveal the reaction paths. The response to the polymerization temperature, monomer, commiomer, cocatalyst, and hydrogen concentration depend largely on the metallocene. 

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