Synthesis and characterization of TiO2 thin film on fly ash cenospheres
Paulina Szołdra, Waldemar Pichór, Katarzyna Cholewa-Kowalska, Anna Adamczyk, Wojciech Szudek
Quarterly No. 2, 2019 pages 71-75
DOI:
keywords: TiO2 thin film, titanium(IV) butoxide, sol-gel method, fly ash cenospheres
abstract Titanium dioxide (TiO2) thin films obtained on quartz glass and fly ash cenospheres were studied. Titanium(IV) butoxide (Ti(OBu)4), diethanoloamine (DEA), ethanol and deionized water were used as the starting materials. A layer of TiO2 nanoparticles was coated on the surface of the substrates using the sol-gel method. The thickness of the TiO2 coatings and the influence of the annealing temperature on the formation of TiO2 crystallites were studied. The dried gels were treated for 90 min in the temperature range of 400÷640°C to obtain crystallized anatase and rutile. Additional nanopowder TiO2 samples were prepared and their crystallinity was determined using X-ray diffraction (XRD). It was successfully shown that the anatase crystalline phase is formed when the TiO2 gel is heated to 480°C, while the rutile phase is obtained at 640°C. Changes in film thickness were studied using an atomic force microscope (AFM). The profound effect of gel viscosity on the thickness of the film was noticed. UV-Vis absorption spectroscopy, performed on the sample treated at 480°C (containing anatase phase only), showed strong ultraviolet light absorption below 400 nm. The estimated band-gap value was 3.2 eV. Transmission scanning microscopy (TEM) examination of the powders revealed agglomerated nanoparticles. A uniform, continuous layer on the surface of the treated microspheres was observed under a scanning electron microscope (SEM). The study shows that the annealing temperature has a profound effect on the phase composition and crystallite size of the sol-gel synthesized TiO2 nanopowders.