INVESTIGADORES
SARACCO Gustavo Pablo
artículos
Título:
Pinning effects and Growth Kinetics of electrochemically formed quasi 2D Silver pattens in non newtonian media
Autor/es:
PASQUALE, M. A.; SARACCO, G. P.; MARCHIANO, S. L.; ARVÍA, A. J.
Revista:
JOURNAL OF PHYSICAL CHEMISTRY B
Referencias:
Año: 2005 vol. 109 p. 20256 - 20265
ISSN:
1089-5647
Resumen:
The formation of silver patterns via electrolysis from aqueous silver sulfate + x%
w/v agarose sol and gel media, with and without supporting electrolyte,
in a quasi-two-dimensional (2D) cylindrical cell at room temperature,
is utilized as a reference system to investigate the complexity of
pinning effects. From pattern morphology and electrochemical data, both
delocalized and localized pinning in the bulk dominate the drift of the
growth front, depending on the concentration of agarose in the
heterogeneous media. Delocalized pinning results from mobile, small
agarose aggregates at the growth front and from their accumulation by
the front drift. For gels, localized pinning comes from their own
percolated structure. A depinning/pinning transition is observed in
going from sols to gels. The relative contribution of diffusion and
advection in mass-transport-controlled silver electrodeposition depends
on the plating bath composition. On the other hand, silver ion
attachment to the cathode appears to be interfered with by some
screening caused by weakly adsorbed, mobile agarose aggregates at the
metal surface without slowing down the rate of the electron-transfer
step at the cathode. Their relative contribution of a delocalized,
localized pinning and screening effect to a great extent determines the
morphology and transition in the growth mode of silver patterns in both
media. The analysis of charge and current transients and the
corresponding silver pattern morphologies for open and dense radial
patterns is made. Results are qualitatively simulated with a novel,
rather simple cellular automaton algorithm.