Electrodeposition alloys formed during

It is interesting to consider the metal deposition process from a microscopic point of view. A rate of 20 mA cm , corresponds to the deposition ofabout 50 atomic layers of metal atoms per cm s- This may be too fast for the adatoms to reach their equilibrium positions. It is indeed observed that the alloys formed during electrodeposition are not necessarily those corresponding to the phase diagram of the alloys involved at room temperature. 

A qualitatively different type of precipitation patterns concerns structures formed during the electrodeposition of alloys. In 1938, Raub and Schall observed the formation of propagating wave patterns during the electrodeposition of silver-indium alloy [9, 10]. However, their observation was widely ignored, because no systematic theory was available that could classify these patterns as typical features of systems far from thermodynamic equilibrium. In 1986, the phenomenon was studied by Krastev and Nikolova in the possibly related electrodeposition of a silver-antimony alloy (Figure 11.1) [11]. Furthermore, very similar patterns were observed by Saltykova et al. during the electrodeposition of iridium-ruthenium alloy from molten salts [12]. 

Electrochemical oscillation during the Cu-Sn alloy electrodeposition reaction was first reported by Survila et al. [33]. They found the oscillation in the course of studies of the electrochemical formation of Cu-Sn alloy from an acidic solution containing a hydrosoluble polymer (Laprol 2402C) as a brightening agent, though the mechanism of the oscillatory instability was not studied. We also studied the oscillation system and revealed that a layered nanostructure is formed in synchronization with the oscillation in a self-organizational manner [25, 26]. 

Another mechanism for induced codeposition of Mo was suggested by Chassaing et al for electrodeposition of Mo-Ni alloys from citrate-ammonia electrolytes. Electrochemical impedance spectroscopy (EIS) measurements were carried out in order to better understand the different reactions occurring on the electrode surface during deposition. The proposed mechanism is based on a multi-step reduction of molybdate species. A M0O2 layer is formed via reduction of molybdate ion as in Eq. (42). Then, if free Ni is present in solution, this oxide can first combine at low polarization with Ni, following the reduction reaction ... 

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