Branchy dendrites

Dendrites formed around hydrogen bubbles are clearly seen from Fig. 5.10g (tc = 3 ms). Analysis of cross section shown in Fig. 5.1 Oh confirmed formation of more branchy dendrites with a deposition pulse of 5 ms than with 3 ms. The increase of a dispersity of the internal structure is observed with the further increase of deposition pulse. The numerous channels formed around relatively small copper particles and degenerate dendrites are easily observed from Fig. 5.10i (tc = 20 ms). 

The change in morphology of electrodeposited copper from very disperse agglomerates of copper grains to branchy dendrites (Fig. 5.12d-f) clearly points out the decrease of effectiveness of solution stirring of evolved hydrogen and the... 

A typical silver deposit obtained from the ammonium solution at an overpotential of 650 mV is shown in Fig. 2.3a. From Fig. 2.3a, it can be seen that very branchy dendrites are produced at this overpotential. Silver particles obtained by tapping the silver deposit (Fig. 2.3a) are shown in Fig. 2.3b. The dendritic character of this particle is made of the comcob-like elements as presented by the images in Fig. 2.3c, d. A further analysis of the comcob-like elements at the microlevel showed that they are composed of small agglomerates of silver grains (Fig. 2.3d). Anyway, morphologies of silver particles electrodeposited from ammonium solution were completely different than those formed during silver electrodeposition from nitrate electrolyte. 

Morphologies of copper deposits obtained with deposition pulses of 1, 2, and 50 ms and a pause duration of 10 ms are shown in Fig. 3.5. Holes formed by attached hydrogen bubbles, very branchy dendrites, and small agglomerates of copper grains are formed when the applied deposition pulse was 1 ms (Fig. 3.5a, b). The mixture of holes and degenerate dendrites was formed with a deposition pulse of 2 ms (Fig. 3.5c, d). Honeycomb-like copper stracture constructed of holes and cauliflower-like agglomerates of copper grains formed around them was obtained with a deposition pulse of 50 ms (Fig. 3.5e, f). 

Very branchy dendrites and cauliflower-like agglomerates of copper grains were formed during electrodeposition at an overpotential of 650 mV (Fig. 3.7a). The amount of hydrogen evolved... 

From Figs. 3.11 and 3.12, it is very clear that macromorphologies of deposits electrodeposited from 0.30 M CUSO4 in 0.50 M H2SO4 at 1,000 mV and by the PO regime with a deposition pulse of 3 ms were very similar to each other in both cases, holes formed by attached hydrogen bubbles surrounded by very branchy dendrites were formed. 

I) The range of the average current efficiencies of hydrogen evolution, 7i,av(H2), between 0 and 10.0%—the dominant presence of branchy dendrites, independently formed cauliflower-like forms, and the possible formation of individual holes of detached hydrogen bubbles (dish-like hole) [30, 31, 38, 41]. 

Also, it is necessary to note that copper dendrites formed at overpotentials of 550 and 700 mV with the quantity of electricity of 20 mAh cm were mutually different. Copper dendrites formed at an overpotential of 550 mV were very rare, and the copper deposit obtained at this overpotential represented the mixture of cauliflowerlike forms and individual dendrites (Fig. 3.18a). On the other hand, the powdered deposit obtained at 700 mV was constructed from very branchy dendrites (Fig. 3.18b). This clear difference in the surface morphology of deposits is confirmed by the very different specific surfaces of these copper deposits. 

Very branchy dendrites, small cauliflower-hke forms, and shallow holes formed from detached hydrogen bubbles are formed when the amplitude of current density of 0.20 A/cm was applied (Fig. 4.19a). On the other hand, dish-Uke holes and small cauliflower-like agglomerates of copper grains were formed with a current density amplimde of 0.44 A/cm (Fig. 4.19b). The formation of these morphological forms was accompanied by the quantity of evolved hydrogen which corresponded to the average current efficiency of hydrogen evolution, r/i av(H2). of 5.5% with the applied current density amplimde, j, of 0.20 AJcvc [45], and 13.7% with /a of 0.44 A/cm [30]. 

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