Pedro Pablo Trigueros

Pattern morphologies in zinc electrodeposition

Abstract A systematic experimental study of quasi two-dimensional zinc electrodeposition in an electrochemical cell with parallel electrodes is reported. The well-known different growth regimes, from anisotropically dendritic to irregularly disordered fractal, described previously in radial cells, are shown together with a novel mixed texture composed of dendritic backbones with ramified open branches. Experiments conducted by varying the cell thickness and electrode separation show significant effects by the current on the pattern morphology. Finally, the self-similarity of the electrodeposits is examined for two different growth regimes.

Some effects of cell dimensions on zinc electrodeposits

Abstract Some specific effects of cell dimensions on the morphology of zinc electrodeposits in a parallel cell are reported. At high concentration values, a transition from mixed to string-like structures is observed as cell thickness is increased. Homogeneous patterns which are observed at low concentration values seem to be the most stable against modification of cell parameters.

Monte Carlo simulation of diffusion-controlled response functions at 2D experimental rough electrodes

The theoretical models proposed for the study of electrode processes under diffusion control on rough surfaces are tested using quasi-two-dimensional experimental electrodes obtained by zinc electrodeposition. Exponents of a generalized scaling law similar to the classical Cottrell equation, which depend on the fractal dimension of the mass distribution measure of the electrode, are calculated using Monte Carlo simulation. The validity of the algorithms of the simulation has been tested previously on flat electrodes.

Quasi-twodimensional electrodeposition: a summarized review on morphology and growth mechanisms

Abstract A short review on the morphologies developped in quasi-twodimensional electrodeposition, is presented in relation to the different transport regimes participating in the whole reaction. The ohmic model for homogeneous (dense parallel) patterns and some convection effects are also reviewed.

A computer simulation model for the diffusion controlled nucleation and growth processes on electrode surfaces—a two-dimensional study

A computer simulation model is presented to study the monolayer formation under conditions of diffusion controlled nucleation and growth in a linear electrode in contact with a bidimensional solution. The diffusion of the electroactive particles in the solution and on the electrode surface is described explicitly. This fact allows the study of the nucleation and growth phenomena without the need to impose analytical laws that would condition the behaviour of the system. The model is focused on the role of the diffusion process in the kinetics of the electrode surface coverage and in the spatial distribution of nuclei. Thus, no restrictions are imposed on the position where a nucleus may appear and on the overlap among growing nuclei. The temporal evolution of the number of nuclei and the rate of nuclear growth is analysed. The electrode surface coverage values yielded by the computer simulations differ by 5–20% from the Avrami theorem predictions due to a non-random distribution of nuclei on the electrode surface as the g(r) internuclear pair correlation functions indicate. The electrode coverage follows a non-poissonian probability distribution which has been characterized. The correlation found among the g(r) curves, the rate of nuclear growth and the nucleation probability values permit the non-Avrami behaviour to be interpreted in terms of the depletion of electroactive particles and the appearance of zones of reduced nucleation around every growing nucleus. A nuclear deficiency parameter is defined to quantify the reduced nucleation zones. Finally, the influence of the surface diffusion on the coverage properties is also studied.

A MNDO and AM1 quantum chemical study of the reaction mechanism of the McLafferty type rearrangement in the butanal radical cation

Abstract The stepwise and concerted reaction mechanisms of the McLafferty type rearrangement in the butanal radical cation have been studied by both MNDO and AM1 (Dewars semi-empirical methods). The calculations indicate a favored concerted reaction mechanism. Results obtained from the study of this reaction at semiempirical level were consistent with both ab initio and experimental data.

FRACTAL ELECTRODEPOSITS: MORPHOLOGY, GROWTH DYNAMICS AND DIFFUSION-LIMITED RESPONSE FUNCTIONS

Fractal characterization of zinc electrodeposits obtained in a quasi two-dimensional film cell under suitable applied potential and zinc sulphate concentrations is reported. Our results show that these deposits are formed according to a Laplacian growth mode, and moreover, their self-similar fractal nature allows the generalization of the Cottrell law for diffusion-limited electrochemical processes occurring on these surfaces.

Growth Patterns in Zinc Electrodeposition

Non-equilibrium growth processes are conspicuous in nature. Electrodeposition constitutes a particularly fascinating example belonging to such general class of phenomena1. By slightly changing the experimental conditions under which electrodeposits are formed, they may become shaped either in a anisotropic dendritic form or without any apparent regularity as typical fractal aggregates2–4. A full understanding of the actual mechanism involved in electrodeposition is still lacking, and it is well recognized that this goal can only be achieved by working complementary from the theory, simulation and experimental practice of electrodeposition.

Mechanism of deoxygenation of butyraldehyde by atomic carbon

Abstract The reaction mechanism of the deoxygenation of butyraldehyde by atomic carbon has been studied using the AM1 method. The “end-on” mechanism is favoured over the “sideways” one. However, an alternative mechanism which is a mixing of the “end-on” and “sideways” mechanisms is preferred from an energetic point of view. This new mechanism is consistent with the experimental evidence reported in the literature.