The preparation of superhydrophilic surface of TiO2 coating without ultraviolet irradiation through annealing treatment

The superhydrophilic surface without ultraviolet light irradiation is obtained only through the modulation of annealing process on surface morphology of TiO₂ coating. Meantime, the influence of annealing temperature on the structural, optical and wetting properties of the TiO₂ coating is investigated. As the increase of annealing temperature, the root mean square roughness of the TiO₂ coating surface increases from 8.6 to 30.7 nm and the nanoparticle surface is formed. Meanwhile, the refractive index increases linearly from 2.02 to 2.22, the thickness decreases from 120 to 82 nm, the transmittance varies from 90 to 62 %, and it is more important the WCA is reduced from 68° to 0°. Furthermore, through analyzing the thickness variation, it is illustrated that the structure variation of TiO₂ coating includes the removal process of solvent and the crystallization process with the increase of annealing temperature, and the 400 °C is a critical temperature. When the annealing temperature is above 400 °C, the TiO₂ coating starts to be crystallized and exhibits excellent antifogging property.