Modification of TiO2 for Enhanced Surface Properties: Finite Ostwald Ripening by a Microwave Hydrothermal Process (original) (raw)
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Journal of Nanoparticle Research, 2018
A simple, rapid, and effective synthesis methodology for the preparation of high-performance TiO 2 nanoparticles and thin films by combining colloidal solgel and microwave-assisted hydrothermal synthesis was developed. The obtained results indicate that the heating with microwaves at 180°C for 20 min was enough to synthesize crystalline TiO 2 nanoparticles, presenting anatase as a major phase with a crystal size of~7 nm and a specific surface area of 220 m 2 g −1. A secondary thermal treatment improved the crystallinity and induced the anatase-to-rutile transformation. The highest photocatalytic activity was found for the as-synthesized powder without any additional thermal treatment. Thin films were also prepared by dip-coating and its high photocatalytic activity showed a kinetic curve comparable to that of a thin film of commercial TiO 2 powder prepared under similar conditions.
Conventional and Microwave-Hydrothermal Synthesis of TiO2 Nanopowders
Journal of The American Ceramic Society, 2005
The objective of this study was to compare the conventional and microwave hydrothermal treatment of TiOCl2 solutions. Colloidal titania suspensions were prepared by forced hydrolysis at 195°C for different times ranging from 1 to 32 h for the conventional synthesis and from 5 min to 1 h for the microwave ones. The effect of the microwave technology on both the synthesis conditions and titania nanoparticles properties has been evaluated. Particles morphology and crystallinity were studied by using transmission electron microscopy and X-ray diffraction. The thermal and chemical stability of the obtained powders were determined by TG/DTA analysis.
A comparison of microwave and conventional heat treatments of nanocrystalline TiO2
Solar Energy Materials and Solar Cells, 2007
TiO 2 thin films are an important component of dye-sensitized solar cells. For these solar cells, the TiO 2 film must be sintered to achieve crystallization and good interparticle connections. Microwave processing may allow a reduction in the required temperature and time for this heat treatment. Therefore, microwave heating of nanocrystalline TiO 2 has been investigated. No significant difference was found between microwave and conventional heating in the sintering of TiO 2 , but microwave heating promotes the phase transformation from anatase to rutile. Microwave heating improved the solar cell performance when a surface treatment of the TiO 2 film with titanium isopropoxide was applied. r
International Journal of Advanced Science and Engineering, 2020
A simple, rapid, and one step microwave assisted synthesis of high-performance TiO2 nanoparticles within 15 min without using any post annealing treatment. The microwave irradiation power is varied from 180-900 W. The effect of microwave power on the structural, surface morphology, optical and photocatalytic activity has been systematically investigated. Powder XRD results suggest that TiO2 tetragonal with anatase phase formed directly during the microwave irradiation process. Spherical shaped morphology with average diameter of around 25-40 nm was observed by TEM images, which is good agreement with the grain size estimated from XRD. A considerable red shift in the absorption edge and decreasing the band gap (3.25-2.97 eV) was observed for TiO2 with the increase of microwave power. The photocatalytic activity of phenol and congo-red (CR) dyes were investigated using the TiO2 catalyst under visible light irradiation. The results demonstrates that 900 W microwave assisted TiO2 showed superior photocatalytic performance towards CR such as high efficiency (83%) and more stability than other samples. The samples were further characterized by photoluminescence and energy dispersive analysis.
Microwave-hydrothermal processing of titanium dioxide
Materials Chemistry and Physics, 1999
Microwave-hydrothermal synthesis of titanium dioxide under various reaction conditions is reported. Crystallization of rutile from TiOCl 2 solutions was found to be extremely rapid. Titanium dioxide particle size, morphology and polymorph can be controlled by changing various parameters such as concentration, pH, pressure (or temperature), time and anionic species. The main advantages of microwave-hydrothermal processing of TiO 2 are (a) rapid heating to temperature and (b) extremely rapid kinetics of crystallization, both are expected to lead to energy savings.
CrystEngComm, 2014
In this paper, a method to synthesize anatase TiO 2 nanorods by hydrolysis of titanium(IV) isopropoxide (TTIP) in the presence of benzyl alcohol and acetic acid at 210°C was tested. The novelty of the present approach relies on the evaluation of the shape-controlled synthesis of anatase TiO 2 nanocrystals via a microwave-solvothermal method in 45 min. The different TiO 2 nanocrystals were obtained by tuning the TTIP/acetic acid ratio under optimized synthetic conditions and were characterized in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), micro Raman (together with microphotoluminescence) and FT-IR spectroscopies. The acetic acid coordinated on the nanocrystal surface was removed by the reduction of its carboxyl group via a "super-hydride reaction", and the photocatalytic activity of bare TiO 2 nanocrystals, under visible light irradiation, was also evaluated: the best performing TiO 2 anatase nanocrystals exhibited a discrete photoactivity, completely degrading Rhodamine B solution in five hours.
Microwave-hydrothermal processing of titanium dioxide 1 Dedicated to Professor Shigeyuki Somiya. 1
Materials Chemistry and Physics, 1999
Microwave-hydrothermal synthesis of titanium dioxide under various reaction conditions is reported. Crystallization of rutile from TiOCl 2 solutions was found to be extremely rapid. Titanium dioxide particle size, morphology and polymorph can be controlled by changing various parameters such as concentration, pH, pressure (or temperature), time and anionic species. The main advantages of microwave-hydrothermal processing of TiO 2 are (a) rapid heating to temperature and (b) extremely rapid kinetics of crystallization, both are expected to lead to energy savings. # 1999 Elsevier Science S.A. All rights reserved. 1 Dedicated to Professor Shigeyuki Somiya. 0254-0584/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved. PII: S 0 2 5 4 -0 5 8 4 ( 9 9 ) 0 0 1 1 3 -3
Journal of Nanomaterials, 2016
Titanium dioxide with high specific surface area in the crystalline anatase phase is a promising material for environmental applications. In this work, TiO2with good applicability for photocatalytic processes has been obtained using the low energy consumption synthesis based on oxidant peroxide method combined with microwave-assisted low temperature hydrothermal treatment. To prepare the material, titanium propoxide, hydrogen peroxide, and isopropyl alcohol were used. The influence of time and temperature during the hydrothermal step on properties like morphology, crystallinity, phase composition, specific surface area, and photocatalytic behavior were investigated. Photoactivity was measured using the methyl orange decomposition method in UV-A light. Increasing temperature during hydrothermal step, photocatalytic properties could be improved. The nanostructured TiO2particles synthesized at 200°C and 30 min with this method showed photocatalytic activity comparable to commercial Aer...
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.
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.