2006 Volume 92 Issue 9 Pages 551-556
The lightness of Zn surface electrodeposited with different supporting electrolytes was investigated from the viewpoint of crystal structure and surface morphology using EBSP, AFM and GIXD (Grazing Incidence X-ray Diffraction) techniques. In pulsed current electrolysis containing sodium sulfate for supporting electrolyte, the lightness decreased according to crystal growth of Zn. On the other hand, the lightness remained almost constant in electrolysis containing aluminum sulfate. As for this difference, the usual positive correlation between lightness and preferred orientation of Zn crystal basal plane was not recognized. And GIXD analysis suggested that the crystallographic c axes of Zn electrodeposit using sodium sulfate and aluminum sulfate were roughly oriented perpendicular to the substrate surface, but that there was a small angle deviation inclined in the particular direction to the surface of Zn electrodeposit using sodium sulfate. In contrast, the particular directional deviation was not observed in the surface of Zn electrodeposit using aluminum sulfate. Furthermore, polarization curves of Zn electrodeposition suggested that nuclear generation was enhanced by using aluminum sulfate for supporting electrolyte in comparison with sodium sulfate. From these results, it is presumed that the unregulated crystal growth direction and fast nucleation of Zn crystals with aluminum sulfate caused fine crystal grain. And so, Zn surface possessed excellent smoothness due to its fine crystal facet confirmed by AFM analysis. As a result, it is considered that the lightness is mainly dominated surface smoothness, and that the high lightness of Zn electrodeposit was obtained using aluminum sulfate.
