Nanocrystalline TiO2 preparation by microwave route and nature of anatase–rutile phase transition in nano TiO2 (original) (raw)
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Synthesis of nanocrystalline TiO 2 at 100 °C
Materials Letters, 2004
A simple gel to crystal conversion route has been followed for the preparation of TiO 2 at 80 -100 jC under refluxing conditions. Freshly prepared titanium hydroxide gel is allowed to crystallize under refluxing and stirring conditions for 6 -12 h. Formation of nanocrystallites of anatase is confirmed by X-ray diffraction (XRD) study. The anatase phase converts into rutile when calcined at 700 jC for 12 h. Raman scattering experiments were also performed to confirm both anatase and rutile phases. Transmission electron microscope (TEM) investigations revealed that the average particle size is 10 nm for the anatase phase whereas it is 35 nm for the rutile polymorph. D
CrystEngComm, 2015
Amongst nanomaterials, metal oxides play an increasingly dominant role, with titanium dioxide (titania, TiO 2 ) being widely used for various applications, such as light-to-energy conversion and storage, and photocatalysis. In this work, TiO 2 has been synthesised via an aqueous sol-gel method, using three different mineral acids (HNO 3 , HCl and HBr) to peptise the sol, and hence provide counter-ions. Dried sols were thermally treated at three different temperatures (450, 600 and 800°C), using three different dwell times (2, 4, and 8 h). Advanced X-ray methods were used to monitor the effect that the counter-ions had on the anatase-to-rutile phase transformation (ART). Quantitative phase analysis (QPA) using the Rietveld method was applied to assess the true amount of crystalline phases in the systems, and the amount of amorphous phase. Furthermore, the average crystalline domain diameter was also investigated, using whole powder pattern modelling (WPPM). With the advanced XRPD data (actual crystalline phase weight fraction in the samples and their average domain diameter and size distribution), it was possible to carry out a semiquantitative study of the ART transformation kinetics. At a low temperature of 75°C, the Cl − counter-ion was the most favourable to obtain anatase as the major crystalline phase, delaying the onset of the ART. Conversely, the Br − ions, maintained more anatase at 450°C, with a lower ART rate. In general, halides were more effective in delaying the ART than NO 3 − counterions. Moreover, we observed an inverse linear relationship between the lattice volume expansion of rutile and the increase of its crystalline domain size at 450 and 600°C isotherms. As the domain sizes increased with temperature, this effect reversed and became a direct linear dependence at the 800°C isotherm, suggesting a critical size limit <90 nm for this effect.
Synthesis and characterization of pure anatase TiO 2 nanoparticles
Journal of Materials Science-materials in Electronics, 2011
Pure anatase TiO2 nanoparticles were synthesized by microwave assisted sol–gel method and further characterized by powder X-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Visible spectrophotometer, SEM images showed that TiO2 nanoparticles were porous structure. The XRD patterns indicated that TiO2 after annealed at 300 °C for 3 h was mainly pure anatase phase. The crystallite size was in the range of 20–25 nm, which is consistent with the results obtained from TEM images. Microwave heating offers several potential advantages over conventional heating for inducing or enhancing chemical reactions.
Thermal Analysis of Nanocrystallization of Anatase TiO2
2010
In the present paper, nanosized titanium dioxide (TiO2) is synthesized by wet-chemical technique, and characterized by x-ray diffraction (XRD), Fourier transform infrared reflectance (FTIR) and differential scanning calorimeter (DSC) thermograms. DSC thermogram shows a definite exothermic peak indicating the transformation from amorphous to crystalline phase. The FTIR spectra shows main peak around 1384 cm-1, which is attributed to the Ti-O bond in both the i.e. amorphous and crystalline samples.
Controlled structure of anatase TiO2 nanoparticles by using organic additives in a microwave process
Applied Catalysis A: General, 2011
Synthesis of anatase nanoparticles was carried out in a microwave system. Crystal morphology was controlled by organic additives including PAAc (polyacrylic acid) and PVP (polyvinylpyrrolidone). Modified TiO 2 particles were compared to the bare TiO 2 anatase structure. The synthesis of materials via the microwave system has great advantages due to the short reaction period and low energy requirement and is therefore an environmentally friendly process compared to the hydrothermal process. The decomposition of acetaldehyde was studied to determine the photocatalytic activity of the modified anatase TiO 2 material.
Journal of Nanoengineering and Nanomanufacturing, 2014
The present investigation reported the synthesis of ultrafine anatase titanium dioxide (TiO 2 ) nanocrystals using titanium isopropoxide (TTIP) as precursor in presence of benzyl alcohol as solvent and glucose as capping agent via a microwave-solvothermal method. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption, micro Raman and Fourier transform infrared spectroscopies (FT-IR). From this preparation method it was demonstrated that the obtainable TiO 2 nanocrystals were less than 10 nm in mean size, mainly in anatase phase, presenting also a mesoporous structure. The use of glucose as capping agent added in the reaction system played a role in the anisotropic growth of the TiO 2 nanocrystals, as evidenced by XRD domain size analysis and promoted an increase of the specific surface area.
Preparation of Mixed Phase (Anatase/Rutile) TiO2 Nanopowder by Simple Sol Gel Method
TiO2 nanopowder having both anatase and rutile phases was prepared by a simple procedure using sol-gel method. Titanium isopropoxide was used as a titania source and mixed with methanol and TiO2 nanopowder was obtained after annealing at 6000C for 1 hour in air. The specimens made from this powder were characterized by X-ray diffraction (XRD), Thermogravimetric analyzer (TGA) and Transmission electron microscopy (TEM). XRD studies revealed the presence of both anatase and rutile phases with an average crystallite size of 35 ± 5 nm. No significant weight loss up to 7000 C was observed by TGA curve which indicates that TiO2 nanopowder is thermally stable. TEM revealed the presence of a number of crystalline grains in a structured matrix and selected electron diffraction pattern showed different arrangement of diffracted rings which confirms a phase evolution of crystalline grains of TiO2 (anatase/rutile) due to thermal annealing. Mixed phase (anatase/rutile) TiO2 nanopowder has been reported [1], [2] to exhibit improved photocatalytic and gas sensing properties. It is proposed to study the gas sensing behavior of these specimens during our research investigations on TiO2 nanopowder.
Journal of Solid State Chemistry, 2009
This study has demonstrated that the synthesis of TiO 2 and V/TiO 2 thin layers may be significantly improved and extended if microwave energy is employed during the drying and/or calcination step. Thin nanoparticulate titania layers were prepared via the sol-gel method using titanium n-butoxide as a precursor. As prepared films were then analyzed by means of various characterization techniques (Raman spectroscopy, UV/Vis, AFM, XPS) in order to determine their functional properties. The photocatalytic activities of prepared layers were quantified by the decoloring rate of Rhodamine B. All thermal treatments in microwave field were done in the same manner, by using an IR pyrometer in the microwave oven and monitoring the temperature of the heating. Nevertheless the microwave and thermally prepared materials were different. This in turn may lead to differences in their functional and also photocatalytic properties.
Asian Journal of Chemistry, 2013
We report the synthesis of TiO2 nanoparticles in anatase and rutile structures in SiO2-TiO2 composite. The SiO2-TiO2 nanostructure was synthesized based on the sol-gel method. The nanoparticles were characterized by X-ray fluorescents, X-ray diffraction, field emission scanning electron microscopy and Fourier transmission infrared absorption (FTIR) techniques. Phase formation was achieved by hydrothermal treatment at elevated temperatures. The anatase nanoparticles were obtained under 300 ºC calcined temperature, while rutile phase were obtained in higher than 300 ºC calcined temperature. The mass fraction of anatase and rutile phases was calculated. It can be fined that as the calcined temperature increases the per cent of rutile phase content grows, as well as when the content of TiO2 in SiO2-TiO2 composite increases, the per cent of rutile phase content grows. The effects of chemical compositions and calcinations temperature on the surface topography and the crystallization of phases were studied.
Structural, Functional and Optical Characters of TiO 2 Nanocrystallites: Anatase and Rutile Phases
The anatase and rutile phases of titania (TiO 2) nanoparticles were synthesized by Sol-gel technique at room temperature with appropriate reactants. The XRD patterns confirmed the tetragonal crystal structure and the structural properties were determined. The relative functional groups and purity of the prepared products were identified by FTIR spectroscopy. DRS measurements indicated that the blue shift in the absorption band edges with respect to bulk titania. The allowed direct and indirect band gap energies, as well as the optical constants were evaluated.