Titanium and zirconium hard coatings on glass substrates prepared by the sol–gel method

In this work innovative antiscratch sol–gel coating films deposited on a soda–lime glass substrate are examined. Sol–gel coatings of different composition (TiO2, TiO2/B2O3, ZrO2 and ZrO2/B2O3) were prepared starting from Titanium, Zirconium and Boron alkoxides and from boron oxide. Coatings were obtained at room temperature and at atmospheric pressure by dip-coating using common soda lime silicate glass slides as substrates. Densification was carried out at 550 °C for 2 h in air. The morphology of the coatings has been studied by Atomic Force Microscopy, Scanning Electron Microscopy, and with a profilometer. Roughness grows with thickness and with boron addition. The mechanical properties of the films were evaluated by micro scratch at fixed and variable load. The scratch hardness numbers of ZrO2 and ZrO2/B2O3 coatings reach 6 GPa (glass value = 1.9 GPa), whereas the best value for the critical load is 16.7 N (glass value = 9 N).