Correlation between sintering conditions and water contact angles for Ti–O thick films screen printed on an alumina substrate

TiO2, TiO2−x and Ti3O5 thick-film structures on corundum Al2O3 substrates were prepared using screen-printing technology. The screen-printed deposits were sintered up to 1500 °C in oxidising and reducing atmospheres to vary the Ti4+/Ti3+ ratio and consequently water contact angle. The structure of the thick films was studied with an X-ray powder diffractometer (XRD). The microstructural characteristics and the chemical composition were checked with a scanning electron microscope, equipped with an energy-dispersive spectrometer (EDS). The Ti–O films, up to 55 μm thick, exhibited excellent adhesion to the substrate and had uniform grain- and pore-size distributions. Ti3O5 and Al2O3 were found to be compatible phases up to 1500 °C in a reducing atmosphere. However, rutile-type TiO2 and Al2O3 are not compatible compounds at temperatures up to 1400 °C, in either oxidising or reducing atmospheres. TiO2 and TiO2−x form two types of reaction products with Al2O3. These reaction products were found to have various Ti/Al ratios.