Preparation of thin layer of TiO2 on glazed tile substrate and changing hydrophilic to hydrophobicity behavior

The aim of this study is to create TiO2 coating on the tile substrate using cell-gel and immersion method. Initially, TiO2 coating was prepared by sol gel method and then, deposition was performed in three stages with different immersion periods of 20, 40 and 60 s and finally, the samples were calcined at 450 °C. The phases and microstructural characteristics of the samples were analyzed using X-ray analysis and scanning electron microscopy. The results of phase analysis showed that in samples with immersion time of 20 and 40 seconds, the dominant phases were sublayer phases include of mulite and corundum, while in samples with immersion time of 60 seconds, the predominant phase was the anatase phase. Microstructural studies using scanning electron microscopy showed that, in the early stages of deposition, the initial nuclei of TiO2 was formed, and as the deposition time increased, a cover of TiO2 nanoparticles about 50 nm was grown on the initial nuclei. AFM results showed that, the surface porosity fraction of the samples and the surface roughness increased with increasing layer thickness of sample with immersion time of 20 s to sample with immersion time of 60 s. Stearic acid has been used to modify the surface and reduce the surface energy of TiO2 coating.  After surface modification of samples, the sample with immersion time of 20 s showed hydrophilic behavior and the samples with immersion time of 40 and 60 s showed hydrophobic behavior. The contact angles of the samples with immersion time of 20, 40 and 60 s were obtained 74.42 °, 91.23 ° and 99.01 °, respectively. At last, the abrasion resistance of the coatings was assessed using Pin on disc method and the average friction coefficient for TiO2 coating for all three samples was 0.2.