Cauliflower-like deposits

A cauliflower-like deposit is formed under such conditions, as is shown in Fig. 1.4. It can be seen from Fig. 1.4a that the distance between the cauliflower-like grains is sufficiently large to permit the formation of spherical diffusion zones around each of them. Simultaneously, second-generation protrusions grow in all directions, as shown in Fig. 1.4b, c. This confirms the assumption that the deposition takes place in a spherically symmetric fashion. 

In the case of copper, electrodeposition at low overpotentials produces large grains with relatively well-defined crystal shapes. Further increasing the overpotential leads to the formation of cauliflower-like and carrot-like protrusions, and finally, dendritic deposits are formed in the absence of strong hydrogen co-deposition.13... 

Figure 5. Copper deposit obtained at an overpotential of 550 mV (a) cauliflower-like structure, and (b) the detail from Fig. 5a. Quantity of electricity 10 mAh cm-2. (Reprinted from Ref.10 with permission from Elsevier).

This concept can be also applied for the case of the electrodeposition of copper. As mentioned earlier, the morphology of the copper deposit obtained at cathodic potential of -500 mV/SCE under the parallel field was of cauliflower-like structure (Fig. 12b), while the morphology of the copper deposit obtained without the applied magnetic field had very dendritic structure (Fig. 12a). It is known that dendritic structures are main characteristic of electrodeposition in conditions of full diffusion control, while cauliflower-like structures are a characteristic of a dominant diffusion in mixed control of electrodeposition process.13... 

The copper deposit electrodeposited from 0.075 M C11SO4 in 0.50 M H2SO4 at an overpotential of 550 mV with a quantity of the electricity of 10 mAh cm-2 was cauliflower-like structure. Copper... 

The morphologies of the copper deposits electrodeposited at an overpotential of 550 mV are cauliflower-like and dendritic ones.68 The size of the cauliflower-like particles did not change with increasing temperature, but the size of sub-particles constituting the cauliflower-like forms which decreased with increasing temperature of electrodeposition. The decrease of the size of sub-particles with increasing temperature can be explained by the well-known dependence of the nucleation rate on temperature,69 which was derived by Volmer and Weber.70... 

The morphologies of the copper deposits electrodeposited at an overpotential of 800 mV are shown in Fig. 40, from which the strong effect of evolved hydrogen on the morphologies of copper deposits is visible. Very porous structures, holes formed due to the attachment of hydrogen bubbles, cauliflower-like forms, and the absence... 

The B4C surface morphologies of field A and field B were shown in Fig.2. It can be seen that the temperature fields have important effects on the surface morphologies of deposits. Under the role of field A, the surface morphology was crystal-like and coarse. The edges of surface particles were very obvious. However, the surface morphology was cauliflower-like under the role of field B. The cauliflower-like particles consisted of small particles. 

The above results showed that the morphology, composition and microstructure were different under two different temperature fields. Under field A, the deposits were crystal B13C2 with high boron concentration and crystalline-like morphologies. Under field B, the deposits were amorphous boron carbide with low boron concentration and cauliflower-like morphologies. The characteristics of deposits depended on deposition mechanism. It was apparent that there were different deposition mechanisms for boron carbide since the characteristics of deposits were very great different under... 

Under field B, the deposition mechanism can be hypothesized as follows. According to cauliflower-like morphology and amorphous phase, BCI3 and CH4 might be reacted before deposition. Therefore, the following reaction might have occurred during deposition process expect for reaction (1) and (2). 

We have demonstrated the effects of temperature fields on deposit characteristics. The temperature distribution of field B is more uniform than that of field A. The temperature fields have important effect on the morphologies, phases, microstructute and compositions of deposits. Under the temperature field A, the morphologies were crystalline-like, the boron concentration was 87.11 at.%, the phase of deposit was B13C2 according to XRD and TEM examinations. Under the temperature field B, the morphologies were cauliflower-like, the boron concentration was 75.34 at.%, the phase of deposit was amorphous... 

Dendrites were also formed with a deposition pulse of 5 ms (Fig. 5.10e), but they were more branchy than those obtained with a depositimi pulse of 3 ms. Very disperse cauMower-like agglomerates of Cu grains were formed with a deposition pulse of 20 ms (Fig. 5. lOf). The numerous micro- and nanopores are formed around small Cu agglomerates of grains inside large cauliflower-like agglomerates. 

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