The structure and mechanical properties of thick rutile–TiO2 films using different coating treatments

The hardness and Youngʹs modulus of thick rutile–TiO2 films were determined using a continuous stiffness measurement (CSM) technique in this study. Pure rutile–TiO2 nanopowders (image, image and image) were prepared using a modified homogeneous-precipitation process at low temperature (MHPPLT) method. The TiO2 films were prepared from sols using 3% (w/w) of the prepared-TiO2 suspension solution coated onto silicon wafers. After dip-coating was completed, the coatings were further treated by natural air-drying, water-vapor exposure, and calcination, respectively. An ellipsometry with a monochromator was used to measure the thickness and refractive index of the TiO2 films, and a scanning electron microscopy (SEM) to determine their morphology. Three coatings of image, image and image demonstrated their refractive indexes of around 1.60 under three treatments. Volumetric expansion and thickness of the coatings should influence their refractive index. Furthermore, the continuous stiffness measurement (CSM) technique was used to perform nanoindentation testing on the hardness and Youngʹs modulus of prepared rutile–TiO2 coatings. The mean hardness and Youngʹs modulus of three coatings increased with preparation temperature. In addition, the image coatings demonstrated greater hardness and modulus than those of image and image coatings in the natural air-drying condition. Surface cracking observed on the calcinated image should be the reason why an obvious decrease of the mean hardness and Youngʹs modulus appeared. Finally, two mechanical properties and related nanoindentation depth of the coatings were discussed in detail.