A novel gold(III) complex with a monodentate 5,5-dimethylhydantoin ligand, [Au(dmh)4]-, is square planar in geometry, inert and highly stable in alkaline solutions because of soft acid-base interactions, and electrochemically reduced near -0.3 V vs Ag/AgCl to give a gold(0) film with a high current efficiency.
Polyphenol compounds were investigated as reducing agents for non-cyanide electroless gold plating for electronics assembly applications. The pH value and temperature were optimized to determine the conditions that lead to a high deposition rate without precipitation. The surface morphology was evaluated by scanning electron microscopy. Catechol, pyrogallol, and gallic acid yielded deposited films with good appearance and solderability under the optimized conditions. Among the tested reducing agents, catechol is the most suitable for use as a stable plating bath with a long life. It has a moderate reducing ability to stabilize the bath and deposit the film. The calculated values of the heat of formation and the highest occupied molecular orbital levels of the reducing agents supported the experimental results.
Pure aluminum and its dilute alloys are deformed by about 10% at 4.2 K with a tensile testing machine. A recovery of the electrical resistivity due to isochronal and isothermal annealings is measured at temperatures ranging from 30 to 170 K. The main recovery peak observed up to 170 K appears around 85 K with associated activation energies of (0.21 ± 0.02) eV for pure aluminum and (0.24 ± 0.01) eV for AlGe alloy. The suppressive effect of impurities on the recovery is ordered as Ge > Si > Cu > Ag > Mg. An interpretation of stage II recovery is proposed on the basis of these results.
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