New sol–gel route for SiO2/ZrO2 film preparation

Silica-zirconia films were prepared by the sol–gel process using TEOS and zirconium acetate as precursors, under either magnetic stirring or sonication. Weight loss and FT-IR analysis pointed for a more effective homogenization process of the sol by sonication compared to magnetic stirring. The sol was deposited by dip-coating over AA-2024 substrates and the influence of the viscosity of the sol during its transition to gel phase was evaluated. Film thickness and homogeneity were evaluated by rugosimetry and by scanning electron microscopy, respectively. It was observed that the as prepared sol containing a non-ionic surfactant showed better viscosity for film application afterwards, and the as deposited film is homogeneous, free of cracks and well adhered to the substrate. If the sol is set to react through condensation process before dip-coating, its viscosity increases exponentially with time and the film thickness increases proportionally, as well as superficial tension that results in higher number and size of cracks.