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Abstract: In this work, the deposition of gold on copper substrates from solutions of HAuCl4.3H2O in 1-butyl-1-methylpyrrolidinium dicyanamide was studied. Deposition was carried out in open-circuit and under potentiostatic control at temperatures from 293 to 353K, in normal atmosphere, with deposition conditions allowing water from atmospheric absorption up to 0.8wt.%. Films of gold were obtained by both methods. Deposition at open-circuit occurs by galvanic displacement mechanism. Involvement of Cu+ species in the electrodeposition process was suggested by cyclic voltammetry. Furthermore, copper incorporation in the gold films was confirmed by X-ray diffraction. SEM observation and XRD analysis show that films are nanocrystalline with a globular morphology except for the films formed under potentiostatic control at 353K, which show a dendritic structure. The size of the crystallites determined by Scherrer's equation varies in the range from 6 to 25nm. [Copyright &y& Elsevier]

Abstract: The electrodeposition of gold from a HAuCl4.3H2O solution in 1-butyl-1-methyl-pyrrolidinium dicyanamide is reported in the present paper. A cyclic voltammetry study of the electrochemical behaviour of the plating solution showed that the reduction of gold occurs by a two-step process. Gold thin films were obtained by electrodeposition on nickel substrates under potentiostatic control at a constant potential of −1V, for temperatures from 293 to 353K and deposition times of 1500 and 4500s. The films prepared at 293 and 333K consist of 9–15nm diameter polyhedral particles aggregated in clusters 50–250nm in diameter. The films deposited at 353K consist of a quasi-continuous film of nanoparticles covered by nanosized dendrites. This morphology evolves towards a globular structure with increasing deposition time. [Copyright &y& Elsevier]

Abstract: The electrochemical behaviour of trivalent chromium (Cr3+) in 1-butyl-3-methylimidazolium tetrafluoroborate [BMIm][BF4] ionic liquid solutions was studied by cyclic voltammetry and chronoamperometry. The reduction of Cr3+ occurs in two steps, Cr3+ to Cr2+ and Cr2+ to Cr0, respectively. The first step is quasi-reversible with a diffusion coefficient of Cr3+ in solution of 3.13×10−8 cm2 s−1 at 303K and 25.8×10−8 cm2 s−1 at 358K, estimated from cyclic voltammetry data. Black chromium films were electrodeposited on copper, stainless steel and carbon steel substrates at a constant potential of −1.5V vs Pt quasi-reference electrode. The films consist of aggregates of nanosized particles. The coatings in the as-deposited condition present an amorphous structure but after annealing for 4h, a nanocrystalline Cr2O3 phase is formed, with an average crystallite size of 17nm. [Copyright &y& Elsevier]