Copper Deposits Obtained at an Overpotential of 1,000 mV

The copper deposits obtained at an overpotential of 1,000 mV from 0.30 M CUSO4 in O.5OMH2SO4 with quantities of electricity of 2.5 and 5.0mAh cm-2 are shown in Fig. 27, from which it can be clearly seen that the structures of the deposits obtained from O.3OMQ1SO4 in O.5OMH2SO4 were completely different from those obtained from 0.075 M Q1SO4 in 0.50 M H2SO4 (Fig. 26). 

On the basis of the presented analysis of the electrodeposition processes at an overpotential of 1,000 mV (Figs. 26-28), it is obvious that increasing the concentration of Cu(II) ions leads to a change in the shape of the holes from those forming a honeycomb-like structure to dish-like holes. 

Naturally, both the formation holes and channels through the interior of the deposit occur simultaneously, and these processes can not be observed separately. As already stated, in the initial stage of the electrodeposition process, both nuclei of copper and nuclei  

Meanwhile, some of the freshly formed hydrogen bubbles will not find a way to coalesce with the large hydrogen bubbles because they are situated among copper nuclei which initiate a barrier for their development into large hydrogen bubbles. This effect, with already discussed current density distribution will lead to the formation of a porous channel structure through the interior of the copper deposit (Fig. 29a). 

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Figure 14. (a) Copper deposit obtained at an overpotential of 1,000 mV Time of electrolysis 10 s, (b) the positions of formation of hydrogen bubbles and agglomerates of copper grains, and (c, d) the details from Fig. 14a and b. (Reprinted from Ref.18 with permission from Springer). 

Figure 15. Copper deposit obtained at an overpotential of 1,000 mV Time of electrolysis 30 s. (Reprinted from Ref.18 with permission from Springer).

Figure 21 shows copper deposits obtained at an overpotential of 1,000 mV with different quantities of the electricity, onto stationary vertical copper wire electrodes previously covered by thin copper films. The dependences of average diameters of craters or holes, D formed due to the attachment of hydrogen bubbles and number of craters or holes formed due to the attachment of hydrogen bubbles... 

Figure 27. Copper deposits obtained at an overpotential of 1,000 mV from 0.30 M CuS04 in 0.50 M H2S04. (a) Quantity of the electricity 2.5 mAh cm 2, (b, c) quantity of the electricity 5.0 mAh cm 2. (Reprinted from Ref.58 with permission from Elsevier).

Morphologies of copper deposits obtained at an overpotential of 1,000 mV from these copper solutions are shown in Figs. 35-37. The honeycomb-like structure was formed by the electrodeposition from 0.15 MCUSO4 in 1.0MH2SC>4(Fig.35). From Fig. 35 it can be seen that holes were lined up in parallel rows. The average diameter of formed holes was 50 pm, while the number of formed holes was 71/mm2 surface area of the copper electrode. 

Meanwhile, the macrostructure of the silver deposit produced at an overpotential of 1,000 mV was completely different than that of the copper electrodeposited at the same overpotential. As already mentioned, holes formed by attached hydrogen bubbles surrounded by cauliflower-like agglomerates of copper grains (the honeycomblike structure see other chapters) were formed by copper electrodeposition at an overpotential of 1,000 mV [7, 8, 10-13]. The copper powder obtained by tapping the powdered deposit consists of an aggregate of small cauliflower-like particles [14]. Similar copper structures were also observed by electrodeposition at periodically changing rate [15-20]. 

The powder particles belonging to the second type are shown in Fig. 46a. They are obtained by tapping the copper deposit electrodeposited from 0.15M CuSC>4 in 0.50M H2SO4 at an overpotential of 1,000 mV at which the electrodeposition of copper was accompanied by vigorous hydrogen evolution, corresponding to... 

A particle obtained by tapping of the copper deposit electro-deposited at an overpotential of 1,000 mV is shown in Fig. 3.10a. Channel stmcture generated through the interior of the particle by the simultaneous copper nucleation and strong hydrogen evolution in situ can easily be seen from Fig. 3.1 Oa. This type of powder consists of an aggregate of small cauliflower-like particles (Fig. 3.10b). Top view of the powder shown in Fig. 3.10a clearly revealed its... 

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