Non-isothermal crystallization kinetics of nano-sized amorphous TiO2 prepared by facile sonochemical hydrolysis route

Abstract

The synthesized nano-sized amorphous TiO2 was successfully obtained by sonochemical hydrolysis of titanium tetraisopropoxide (TTIP). The microstructure and amorphous feature of TiO2 were examined by X-ray diffraction (XRD) as well as high-resolution transmission electron microscope (HRTEM). Moreover, the selected area electron diffraction (SAED) pattern confirmed the amorphous nature of the obtained titania (TiO2) powder. The thermal behavior of the obtained titania powder was studied using differential scanning calorimetry (DSC) measurements and thermogravimetry (TG) analysis. The transformation characterization of amorphous to anatase titania phase was carried out using the obtained exothermic peaks for anatase crystallization under the investigated non-isothermal conditions of the DSC measurements at constant heating rates (5, 10, 15 and 20 °C/min). The investigated transformation of amorphous to anatase titania was introduced using model-free isoconversional approach. The crystallization kinetics together with its dimensionality were studied to identify the growth of the anatase phase. The obtained results showed the independency of the activation energy of crystallization on the crystallized fraction and it has been found around 202.4 ± 7.5 KJ/mol. Moreover, the dimensionality of crystal growth found to be in one direction that is identifying the crystallization process by dominated nucleation is the surface nucleation. The growth mechanism was discussed in view of the expected homogeneous formation of a large number of seed nuclei during sonochemical reaction.