Mixed SiO2–TiO2 (1:1) sol–gel films on mild steel substrates: Sol composition and thermal treatment effects

Mixed SiO2–TiO2 (1:1) sol–gel films have been deposited on mild steel substrates by spin coating. Different sol compositions have been realised and all of them have produced transparent and electrically non conductive films except in the case of high acidic sol. Special attention has been paid on the thermal treatment (in air) of those films. Evolution of the microstructure of the films with thermal treatment have been characterised by scanning electron microscopy (SEM), glancing incidence X-ray diffraction (GIXD), atomic force microscopy (AFM) and X-ray reflectometry (XRR). Electrical insulating behaviour and micro-hardness evolution have been evaluated. In order to avoid the creation and the diffusion of the oxide substrate layer leading to the destruction of the sol–gel films, the main parameter to control is then the couple time/temperature of the thermal treatment.