INSITU RAMAN-SPECTRA OF ANODICALLY FORMED TITANIUM-DIOXIDE LAYERS IN SOLUTIONS OF H2SO4, KOH, AND HNO3

The electrochemical oxidation of Ti electrodes in H2SO4, KOH, and HNO3 electrolytes has been followed by in situ Raman spectroscopy. The transformation of amorphous Ti-oxide films to the anatase, brookite, and rutile mineral forms is described in terms of the nature and concentration of the electrolyte, the applied anodizing voltage and current, and the anodization time. Under certain conditions, the crystallization of anatase is found to occur from a film of amorphous Ti-oxide without any changes in film thickness. Crystallization occurs after the film breakdown. Evidence for the formation of brookite has been obtained after controlled oxidation of a Ti electrode in KOH electrolyte.