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Jan Prokleška: Magnetism, magnetic phase transitions and magnetic phase diagrams
Begin: 22.05.2019, 14:10
Location: lecture room F2, first floor Ke Karlovu 5

 
Title: Marie Cerhová: Use of modified supercritical carbon dioxide for direct preparation of crystalline TiO2 aerogels and thin films
Number: 44/19
Status: Closing date exceeded
Begin: Čtvrtek, 16.05. 2019, 14:00
Tutor: Václav Holý and Milan Dopita
Location: Lecture room F2, Facutly of Mathematics and Physics, First floor Ke Karlovu 5, Prague 2

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Nano Seminar

 

Thursday, 16. 5. 2019, 14.00,

Lecture room F2 (1st floor), MFF UK, Ke Karlovu 5

 

Marie Cerhová

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Institute of Chemical Process Fundamentals of the ACS, v.v.i., Prague, The Czech Republic

 

Use of modified supercritical carbon dioxide for direct preparation of crystalline TiO2 aerogels and thin films 

TiO2 is known as an efficient photocatalyst for its good ability to produce the pairs electron-hole under UV light [1]. It has been investigated as photocatalyst promising in water- and air-purification in a form of thin films [2] and as monolithic aerogels with high specific surface area [3]. Properties as phase composition or crystallite-size influence the photocatalytic activity, thus the controlled preparation of nanocrystallites is important for their applications. Commonly used method for the purification and to crystallize TiO2 is calcination [4]. Unfortunately, this thermal treatment is accompanied by excessive sintration, crystallite growth or recrystallization [5]. Use of the combination of several steps with pure and water-modified supercritical carbon dioxide (scCO2) seems to be perspective way to obtain crystalline and pure TiO2 without any subsequent thermal treatment [6-8].
In this work, the extraction by pure and modified supercritical carbon dioxide was tested to prepare a set of crystalline TiO2 thin films and aerogels. The effect of temperature (40-220 °C) and pressure (10-30 MPa) on microstructure and purity of TiO2 thin films were investigated. The structural properties of the prepared monolithic TiO2 and thin films were characterized by Raman spectroscopy. The most promising thin films samples were analyzed by means of X-ray diffraction to determine the crystallite size and the phase composition.
The pure scCO2 caused any crystallization. It was revealed that small amount of water in supercritical CO2 helps titania thin films crystallization. The specific surface areas of mesoporous titania changed between 200-634 m2/g.

References:

[1] Prieto O. et al. Sol. Energy. 2005, 79, 376-383.
[2] Hsien Y.-H. et al. Appl. Catal. B: Environ. 2001, 31, 241–249.
[3] Meng Nan Chong et al. Water res. 2010, 44, 2997-3027.
[4] Zhou M. et al. J. Hazard. Mat. 2008, 154, 1141–1148.
[5] Pourmand M. et al. Current nanoscience. 2008, 4, 151–156.
[6] Shimoyama Y. et al. Chem. Eng. Res. Des. 2010, 88, 1427-1431.
[7] Matejova L. et al. Mater. Res. Bull. 2012, 47, 3573–3579.
[8] Matejova L. et al., EMSF 2014, Marseille, France, p.161.

Acknowledgements.
The financial support of the Grant Agency of the Czech Republic (project no.14-23274S) is gratefully acknowledged.



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