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An in situ energy-dispersive X-ray diffraction experiment was undertaken on operational titanium electrowinning cells to observe the formation of rutile (TiO2) passivation layers on Magnéli-phase (Ti nO2 n−1; n = 4-6) anodes and thus determine the relationship between passivation layer formation and electrolysis time. Quantitative phase analysis of the energy-dispersive data was undertaken using a crystal-structure-based Rietveld refinement. Layer formation was successfully observed and it was found that the rate of increase in layer thickness decreased with time, rather than remaining constant as observed in previous studies. The limiting step in rutile formation is thought to be the rate of solid-state diffusion of oxygen within the anode structure. [ABSTRACT FROM AUTHOR]

The article discusses a study of the characterization of rutile passivation layers on Magnéli-phase titanium oxide inert anodes. Atraverda Ltd. of Great Britain has provided the Ebonex inert anodes. The Bruker General Area Detector Diffraction System (GADDS) and the Power Diffraction beamline were utilized to collect the diffraction data. Rutile and the Magnéli phases titanium oxide were the only phases detected by diffraction.

A tomographic study of electrochemical cells to observe scales formed on inert anodes has been conducted using energy-dispersive synchrotron X-ray diffraction. This study is preparatory to an investigation that will observe this formation in situ during the cells' operation. The purpose of the current work was to determine whether this technique would be appropriate for such a study in terms of its sensitivity and whether the results could be quantified satisfactorily. A method has been developed for the quantitative phase analysis of energy-dispersive data using crystal-structure-based Rietveld refinement. This has been tested with standard materials and found to be comparable in accuracy to results obtained from traditional angular-dispersive diffraction. The lower limits of detection of the method have not been established quantitatively but qualitative differences can be seen between Cells that have been cycled at different times. These differences indicate a linear relationship between scale formation and electrolysis time. [ABSTRACT FROM AUTHOR]