Preparation and characterization of nanocrystalline titania powders by sonochemical synthesis

Abstract

Nanocrystalline mesoporous titania powders were synthesized by hydrolyzing titanium isopropoxide in ethanol-water mixtures which were ultrasonically treated without using any templates or chemicals. Titanium isopropoxide-ethanol mixture was added dropwise to a water-ethanol mixture placed in an ultrasonic bath. The properties of the sonochemically synthesized powder were compared with those of the powders prepared without ultrasonic treatment along with Degussa P-25 titania powder. The phase structure, crystallite size, surface area, particle size, powder density were determined and sintering behavior was analyzed in this work. The nanotitania powder prepared during ultrasonic induced hydrolysis (TiO 2 -U) was determined to be formed from a mixture of anatase and brookite phases at 25°C. The brookite phase in nanotitania powder prepared without ultrasonic treatment (TiO 2 -NoU) was detected at 70°C. The anatase-rutile phase transformation was completed in the 500-700°C range for both powders. The average crystallite sizes of the powders at 25°C were determined as 10 and 5 nm for TiO 2 -NoU and TiO 2 -U, respectively. The surface area decreased from 238 to106 m 2 /g for TiO 2 -NoU and from 287 to 82 m 2 /g for TiO 2 -U when the calcination temperature was increased from 200 to 500°C. The evolution of the N 2 adsorption-desorption behavior with calcination temperature and the corresponding pore size distributions/volumes was attributed to the formation of closely packed submicron aggregates during powder synthesis and calcination. The sintering behavior was concluded to be controlled by 7-10 nm crystallites and the submicron aggregates. The determination of the densification behavior of titania powders prepared by different methods with various levels of dopants may prove to be very useful for a better understanding of the phase/pore structure evolution which is crucial for a significant number of applications.

Heterophase Polymorph of TiO2 (Anatase, Rutile, Brookite, TiO2 (B)) for Efficient Photocatalyst: Fabrication and Activity

“…Sonochemistry has been widely used to synthesize nano-sized materials [ 229 , 230 , 231 , 232 , 233 ]. Arami et al [ 234 ] synthesized TiO 2 nanoparticles with an average diameter of about 20 nm via a simple sonochemical method.…”

Polymorphic phase transition among the titania crystal structures using a solution-based approach: from precursor chemistry to nucleation process

“…Note that pure anatase was observed at 500 C in both these cases. 297 Mesoporous anatase TiO 2 with worm-like framework structures was obtained using long-chain organic amines as the structure-directing agent via ultrasonication (6 h). The large surface area and high stability was achieved with an increase in the alkyl chain length of amines without any change in the morphology.…”

Synthesis and Characterization of Pd over Novel TiO2 Mixtures: Insights on Metal–Support Interactions

“…These results were also in line with the increase in SBET values (Table 1) observed in a further analysis. We estimated the catalysts composition using the most intense Bragg reflections of each titania phase and the equations reported by Duvarci et al [13], obtaining the unusual mixtures of titania phases (not commercially available) present in the supports (Table 1).…”