morphology study of zinc electrodeposits from alkaline zincate solutions.
Published: 2006
Language: eng
Number of pages: 163
ISBN-13: 9780494217818
Description: The morphology of zinc deposited from alkaline zincate solutions was systematically investigated over a wide range of deposition conditions using  in situ microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effects of the deposition conditions were studied using an innovatively modified Hull Cell, and a functional morphology diagram was constructed. Preferred orientations of the specific morphologies, dendrites and single zinc filaments, were determined using powder X-ray diffraction (XRD) and selected area electron diffraction (SAD).The study revealed that zinc morphology is determined by the electrochemical ratecontrolling mechanisms of mass transfer and charge transfer which depend on deposition conditions, and by adatom attachment modes determined by the specific crystal lattice configuration. The work provides a frame work for morphology control in zinc deposits.The zinc deposition morphologies were categorized as heavy spongy, dendritic, boulder, layer-like, and filamentous mossy. The study showed that heavy spongy morphology is a result of non-equilibrium nucleation and is promoted by stirring. The initiation and growth of dendrites are under diffusion control. The growth of boulder morphology is under mixed activation and diffusion control. The formation of layer-like and filamentous mossy morphologies is under activation control.For the first time, the morphology, the initiation and growth mechanisms of filamentous mossy have been explained. It is proposed that zinc filaments initiate due to the fast growth on new clusters grown from surface inhomogeneities. The size of zinc filaments is found to be inversely proportional to the crystallization overpotential. The change of growth direction from &lt;0001> to [11 20] (or [1010]) and the random growth in six symmetrical [1120] (or [1010]) directions were demonstrated to be the cause for the entanglement of mossy zinc.Individual dendrites were found to grow on the {1010} planes in the [1120] direction, while single zinc filaments were determined to grow on the (0001) plane in the &lt;0001> and [11 20] (or [1010]) directions. Adatom attachment mode for the dendrites was found to be direct attachment, while for the filaments attachment was by surface diffusion.
Notes: Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0465.

Thesis (Ph.D.)--University of Toronto, 2006.

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