Nanomechanical Properties of Prepared-TiO2 Films Using Nanoindentation Technique

Nanoindentation was used to measure the hardness and Young's modulus of prepared-TiO2 films. The thickness and refractive index of the TiO2 films were measured using ellipsometry with a monochromator. Scanning electron microscopy was used to determine the micrography of the TiO2 films. Pure TiO2 films were prepared from sols made by 3 % (w/w) of prepared-TiO2 suspension solution coated onto silicon wafers. After the dip-coating was completed, the coatings were further treated by various procedures. natural air-drying, water-vapor exposure, and calcinations. The prepared-TiO2 films were smooth and free of macro cracking. The grain sizes of these films were uniform and in the range of 50-100 rim and the films were of rutile structure. The prepared-TiO2 coatings exhibited more favorable porosity in water-vapor exposure than those under other conditions. The T-(H2SO4) coatings exhibited higher hardness and modulus than those with T-(H2O) and T-(NH4OH) coatings after high temperature calcination. The values of hardness and modulus for T-(H2SO4) coatings were 11.93 GPa and 226.25 GPa, respectively. Curves of hardness and modulus as a function of depth (0-2200 nm) of the coatings under calcination conditions show a peak at shallow contact depth within 100 rim and then demonstrate being rather constant. The hardness and modulus curve obtained from T-(H2SO4) coatings in water-vapor exposure are rather constant.