Water adsorption on plasma sprayed transition metal oxides

The aim of this study was to characterize water adsorption on plasma sprayed chromia and titania coatings. Both materials are widely used in industry as wear and corrosion resistant coatings. During plasma spraying both materials become oxygen deficient so that high concentrations of oxygen vacancies are formed. Vapor adsorption experiments were performed using microcalorimetry and isothermal gas adsorption experiments. Studies were performed to samples of two or three different degree of surface hydroxylation. The surface hydroxide content was controlled using heat treatments at 100, 200 or 400 8C. All experiments were repeated to plasma sprayed coating samples, which were pre-heat-treated (12 h at 1000 8C). It was found that behavior of water adsorption is sensitive to both temperature of dehydroxylation and initial concentration of surface defects especially for TiO2 samples