Vittorio Violante

Temperature coefficient of resistivity at compositions approaching PdH

Abstract Measurements have been made of the temperature coefficient of resistivity, λ , versus hydrogen concentration, H/Pd, at very high concentrations in the Pd–H system. Unusually high hydrogen compositions were achieved using an electrochemical loading procedure which allowed stable Pd–H systems to be obtained. It is well known that increasing the H/Pd concentrations leads to three different phases ( α , α + β , β ), respectively, in the Pd–H system; the β phase is thought to end in an asymptotic limit. Possible evidence that a new phase ( γ ) exists, bordering the β phase at compositions H/Pd > 0.9 is reported and discussed.

Light scattering from a rough metal surface: theory and experiment

There is still great interest in the determination of microtopographic properties of rough metallic surfaces from light scattering measurements. According to Beckmann-Kirchhoff theory a clear relationship is established between the in-plane angular scattered light intensity and the statistical properties of the surface. We discuss one way to invert this relationship, and we introduce a new iterative procedure to retrieve the height autocorrelation function even for a very rough metallic surface (rms surface roughness of the same order of the optical wavelength). The procedure is eventually applied to the experimental data of a known metallic surface for validation.

Deformations induced by high loading ratios in palladium–deuterium compounds

Abstract The strong concentration gradients produced during the loading process in palladium hydride are responsible for the well known difficulty in obtaining high loading ratios (H(D)/Pd≈1). Experiments on electrolytic loading of palladium with deuterium have been carried out in which the loading ratio was monitored through a four wire resistance technique. Preliminary results show that dynamic loading strongly affects the maximum ratio achievable.

Steady-state concentration profiles of hydrogen in tubular metallic membranes

Abstract This article analyzes the stress-induced diffusion (SID) model for hydrogen transport in thin cylindrical membranes when the planar approximation, usually adopted in the literature, is relaxed. The SID model, explicitly formulated for a cylindrical membrane predicts a non-linear steady-state concentration profile, characterized by a concentration gradient at the inner surface which can be significantly lower than the macroscopic concentration gradient imposed, depending on the initial hydrogen content of the membrane. We provide analytical arguments to show that this effect is due to the fact that concentration-induced stresses do not relax at steady state, and this is a peculiar feature of thin hollow cylinders, not occurring in thin plates.

Electromagnetic Field Enhancement at Electrochemical Interface Due to Surface Defects on a Metallic Electrode

Strong electromagnetic field localization can be obtained at the electrode/electrolyte interface of dielectric inclusions in a metal foil. The enhancement is driven by the strong electrostatic field present close to the metal surface .