Correlation of Plasma Process Conditions, Phase Content, and Photocatalytic Performance of Induction Plasma-Sprayed Titania Coatings

Systematic variation of the induction plasma spray (IPS) conditions, i.e. (i) plasma power, (ii) carrier gas flow rate, and (iii) powder feed rate was performed to deposit TiO₂ coatings using statistical design of experiments (SDE) methodology. The microstructure, surface morphology, and anatase-rutile ratio of the coatings were studied by grazing-incidence X-ray diffraction (GIXD) and surface mapping with micro-probe Raman spectroscopy to determine the spatial phase distribution of anatase and rutile. The photocatalytic activity of the TiO₂ coatings was tested by decomposition of 4-chlorophenol in aqueous solution in the dark and under UV irradiation. The rates of pH changes measured were compared with those of standard Degussa P-25 coatings. The photocatalytic activity of the samples shows a reasonable correlation with the phase content and the plasma processing conditions prevailing during coating deposition.