Nucleation and growth process during the heat treatment of TiO2 nanoparticles prepared from different pH solution

Control of the size, shape, and structure of the colloidal precursor is an important factor in determining the properties of the final material. It has been demonstrated that the nanostructure of titania precursors prepared by hydrolyzing titanium alkoxide greatly affects the crystallization behavior and characteristics of the final powder [1]. The peptization process has the same advantage of flexibility as the sol-gel method, in which the reaction can be carried out at molecular level by the aim of heating of the solution or using peptization agent [1]. The most important factors affecting the final properties of the powder are the alkoxy groups of alkoxides, the concentration of reactants, the pH of the solution and the hydrolysis temperature [2]. The pH value of the sol- gel system for the preparation of primary TiO2 nanoparticles from titanium hydroxide (Ti(OH)4) is a decisive factor for controlling the hydrolysis rate and so final particle size and shape of product [3]. Li et.al. have been investigated that the particle growth is successfully prevented at either the acidic or neutral solution. However the basic solution accelerates the particle growth at the same condition [4]. It has also been shown that in HCl acidic solution the more is HCl concentration the smaller is the resultant particle size [5]. In the present work, not only the effect of pH on the as prepared particle size is quantified but also the effect of nucleation and growth process during the heat treatment at elevated temperatures on the product powder size is examined