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Abstract: Supersaturated nanocrystalline (16–19nm) Cu50Ag50 and Cu70Ag30 solid solutions are synthesized by high-energy ball milling. Varying the milling time fcc solid solutions with different lattice parameters are obtained. Thus an increase of the lattice constant that levels off after 20h of milling is registered for the Cu50Ag50 solid solution. At the same time broad overlapped exothermic effects in the temperature range of 170–370°C are detected by DTA. These can be associated mainly with solid solution decomposition and a grain growth process. Electrochemical selective dissolution reveals a quasi-critical potential of Cu dissolution in Cu70Ag30 that is shifted 40mV positively, compared to the dissolution potential of pure Cu, thus ascertaining the Cu (Ag) solid solution formation. The linear area development with the in-depth progress of the Cu dissolution front confirms the dealloying applicability for fabrication of nanoporous Ag structures in this case. [Copyright &y& Elsevier]

Abstract: Nanocrystalline Mg powder without and with 2mol% Nb2O5 catalyst was studied in a 6M KOH electrolyte as electrode material for electrochemical hydrogen charging processes. Since the hydrogen overpotential of Mg, which is a measure of the hydrogen evolution at the electrode surface, was observed to be reduced by the addition of Nb2O5, it is assumed that the catalyst influences the electrode reactions. Considering this assumption hydrogenation was studied at different current densities. The storage capacity as well as the kinetic of Mg/Nb2O5 electrodes increased significantly up to 1wt.% H2 at a charging time of 30min with decreasing current density. The storage capacity of nanocrystalline Mg powder showed only minor changes to lower hydrogen contents with decreasing current density. [Copyright &y& Elsevier]

Abstract: Nanocrystalline Mg powder without and with 2mol% Nb2O5 catalyst was studied as an electrode material for electrochemical hydrogen charging in a 6M KOH electrolyte. A strong influence of the compaction parameters, the current density and the catalyst on the hydrogenation behavior was observed. The addition of graphite and PTFE to the Mg/Nb2O5 electrodes improves the charging kinetics as well as the hydrogen content. The hydrogen contents achieved in Mg with Nb2O5, however, show a broad scatter. It was concluded that the catalyst distribution influences the upper limit of the storage capacity as well as the oxidation process at the surface during preparation. Since the addition of Nb2O5 was observed to reduce the hydrogen overpotential of Mg depending on the catalyst distribution, it is assumed that the catalyst influences the electrode reactions. Therefore, hydrogenation was investigated for different Nb2O5 distributions at different current densities in detail. [Copyright &y& Elsevier]

This review presents existing results on the formation of porous metal structures by selective dissolution of metallic glasses. The compositions of the initial amorphous alloys, the conditions of chemical and electrochemical selective dissolution, the morphology and microstructure of the resulting porous structures, and their main applications are included and discussed. The examined results have allowed to make some generalizations concerning the influence of the precursor alloy composition, the type and concentration of electrolytes, temperature, and time of selective dissolution on the phase composition, shape and size of pores and ligaments of the final porous material. Certain conclusions are also formulated to guide potential researchers in the search for suitable amorphous alloys and de-alloying conditions to achieve porous structures with predefined properties and hence sought applications. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline Mg powders of different particle size were obtained by inert gas evaporation and studied during electrochemical and gas-phase hydrogen cycling processes. The samples were compared to dehydrided samples obtained by mechanical milling of MgH2 with and without 2mol% Nb2O5 as catalyst. The hydrogen overpotential of the pure Mg, which is a measure of the hydrogen evolution at the electrode surface, was observed to be reduced with smaller particle sizes reaching values comparable to samples with Nb2O5 additive. On the other hand gas-phase charging experiments showed the capacity loss with smaller particle sizes due to oxidation effects. These oxidation effects are different depending on the synthesis method used and showed a major influence on the hydrogen sorption kinetics. [Copyright &y& Elsevier]