Modify The Self-cleaning Nano-TiO₂Films By N-ion Doping And SiO₂Compositing

TiO2nanocrystalline sols were synthesized by colloidal chemical method using cheaper raw material (TiO2). Its properties were improved by N-ion doping and SiO2compositing. The sols possessed a good performance without heat treatment. Then TiO2thin films coated on glass were prepared from TiO2sols via the dip-coating method.The XRD, XPS, SEM and some other methods were used to characterize the microstructure of TiO2sols and films. The results showed:The optimum content of N-ion was5%, while the optimum content of SiO2was0.3. The TiO2sols were anatase with high crystallinity, which was the same as TiO2thin films. The crystal size of TiO2decreased when doping N-ion or compositing SiO2. When heated to1000℃, the powder lost16%of its weight and the SiO2composited sample had a better thermal stability. In the SiO2composited sample, the Si element existed in two forms:SiO2and Ti-O-Si, while most N atoms were incorporated into the lattice of TiO2in N-ion doping sample. The film surface was piled by the irregular spherical secondary particles of TiO2, the three-dimensional morphology was some steeple-like protrusions. The modified nano-TiO2films were more densification Films of three layers had the best photocatalytic, and its thickness was about150nm.The transmittance and chemical stability of the films were good enough to meet the demands. The absorption band of the modified nano-TiO2had a red shift obviously. The photocatalytic activity of the modified samples towards methylene blue reached95%under UV-light irradiation, and the effect was apparently better than pure TiO2under visible light. The water contact angel of modified samples decreased to0°, which indicated a better hydrophilicity than pure TiO2. What’s more, the degradation of Oleic showed that the films of modified samples had a better self-cleaning performance than pure TiO2.