Phase formation of nano-TiO2 particles during flame spraying with liquid feedstock

摘要

The nanostructured TiO2 photocatalytic coatings were synthesized through flame spraying with liquid feedstock under different conditions. The nanostructured TiO2 deposit of substantial anatase phase was annealed at different temperatures. X-ray diffraction analysis showed that significant transformation from anatase to rutile occurred at a temperature above 600 °C. However, thermal analysis suggested that the phase transformation from anatase to rutile started at a temperature from 400 to 500°C. It was found that the grain size of rutile phase was larger than that of anatase. The deposits annealed at temperatures lower than 450°C were photocatalytically active. However, the deposit annealed at 500°C, which contained 95% anatase crystalline, became photocatalytically inactive. Based on the experimental findings, a model is proposed to explain the phase transformation of the nano-TiO2 particles and the phase formation in flame-spraying of nanostructured TiO2 deposit with liquid feedstock.