| In electrodeposition, as the electrolyte is confined to a thin layer, the electrodeposit becomes quasi-two-dimensional and some extraordinary phenomena, such as fast propagation of the deposit and a rich variety of morphological patterns, are observed.;In the present work, the reasons for the spreading mechanism are investigated and the factors affecting the process of morphology selection are identified. The fast propagation of quasi-two-dimensional deposit originates from the confinement of the electrolyte and the lack of convection before the induction time. Consequently, the space-charge layer and the diffusion layer are sustained ahead of the advancing deposit. Surface diffusion is suppressed and starvation of adatoms on the surface occurs. This induces fluctuations, instability and triggers self-organization and bifurcation. The velocity of the deposit is determined by the drift velocity of the anions away from the deposit, as the system is attempting to maintain electroneutrality and to reduce the electric field in space charge region.;Quasi-two-dimensional electrodeposition of zinc, copper, silver, and lithium has been investigated. For zinc, five different forms of morphological patterns have been observed: (a) ramified or fractal-like structure, (b) dense-branched morphology (DBM), (c) dendritic, (d) stringy, and (e) solid needle-like structure. For copper, only two types of morphological patterns have been found: (a) ramified, fractal-like structure and (b) DBM. For silver, dendritic structure predominates, while a coral-like structure is obtained in low concentration and low current density, and parallel-needle or fan-frame structure and 'ice-on-window' structures are also obtained at higher concentrations and current densities. For lithium, only coral-like, porous structure is obtained.;Furthermore, theoretical and experimental studies of the effects of various operational parameters on the growth speed are performed. The growth speed is proportional to the applied current density and inversely proportional to the electrolyte concentration, in good agreement with the theoretical prediction.;In addition, the effect of various factors, such as the fluid flow, gravity, gravity-induced motion, and the proton, alkali cations, dissolved oxygen and impurities, on the morphological pattern have been investigated. The morphological pattern of the quasi-two-dimensional electrodeposition depends on both the transport mechanism and the chemical content of the electrolyte. |
