Characteristics and properties of surface coated nano-TiO2

Nano-TiO₂ was coated with Al₂O₃, SiO₂ and silane coupling agent by chemical liquid deposition. The coating was characterized by Raman spectroscopy, XRD, TEM and FT-IR. The coating content and anti-ultraviolet capacity of nano-TiO₂ were measured by XRF and UV-vis spectrometer. The results show that dense coatings containing 5% Al₂O₃ or SiO₂ can be obtained by mixing slurry at pH 10, adding coating reagent and neutralization reagent into the slurry for 60 min at 85–95 °C, and finally aging for 120 min. Noncrystal SiO₂ was coated on the surface of nano-TiO₂ to form silica gel polymer with a Ti—O—Si bond, while aluminum compound exists in the form of AlOOH and part Al(OH)₃. The integrated dense film can shield photocatalysis effectively. The inorganic coating film can increase the wettability for xylene and stability in water. The surface modification of nano-TiO₂ will not impair its ability for anti-ultraviolet radiation, and more short band ultraviolet radiation can be absorbed. In addition, the optimal coating amount of silane coupling agent should be less than 3% and the best wettability for xylene can be reached when the amount is 1.2%.