Sol–gel preparation of thick titania coatings aided by organic binder materials

Nanostructured titania has been reported to be used in many applications in areas ranging from optics via solar energy to gas sensors. We report in this paper a low-cost method of producing nanostructured titania coatings. TiO2 films were spin-coated on silicon substrates via methylcellulose (MC) aided aqueous sol–gel route using Ti(Obut)4–HAC–EtOH as starting materials. SEM, TGA, FTIR and XRD techniques were used to characterize the microstructure and properties of the composite films. It is shown that, relative dense, crack-free and transparent TiO2 composite films (∼0.9 μm in thickness) were achieved via the MC assisted sol–gel and single-step deposition process at room temperature. TGA results showed the rapid decomposition of organic compounds in the composites at the range of 200–450 °C. Remarkable changes in microstructure of the composite film were observed after being heated at 600 °C for 15 min, including formation of a nodular morphology of TiO2 particles (∼40 nm in diameter) within the films, appearance of crevice in nanoscale on the surface of the coating, and shrinkage of the films in thickness. It is worthy to note that the film uniformity was retained upon the heating; no cracks and flaking off from the substrates were observed. The structural evaluation and crystallization behavior with thermal treatment up to 900 °C are followed by FTIR and XRD.