Thermal behaviour of the TiO2-based gels obtained by microwave-assisted sol–gel method
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In order to establish the influence of the preparation method on thermal behaviour of gels obtained by the sol–gel and microwave-assisted sol–gel methods, a comparative thermal analysis study was conducted by the thermogravimetric and differential thermal analysis (TG/DTG/DTA) and evolved gas analysis (EGA) on TiO2 and V2O5-doped TiO2 gels, where TiO2:V2O5 molar ratio was set to 99.95:0.05 and 98.0:2.0. In contrast to TiO2 gels, for which the thermal behaviour was not significantly influenced by the preparation method, the microwave-irradiated binary samples showed a more complex and prolonged decomposition compared to their non-irradiated counterparts. This observation was correlated with influence of microwaves in enhancing the reaction rate between the Ti and V reagents leading to formation of more complex compositions of gels. Based on TG/DTG/DTA results, the temperatures of 300 and 450 °C were chosen for the processing of powders in air. All samples thermally treated at 300 and 450 °C crystallized in a single anatase phase except the TiO2:V2O5 with a molar ratio 99.95:0.05, obtained by microwave-assisted sol–gel method that contains also small amount of rutile phase. At 550 °C all samples contain mixture of anatase and rutile phases.
KeywordsMicrowave-assisted sol–gel method TiO2-based gels Thermal behaviour
This work was supported by the research programme “Materials Science and Advanced Methods for Characterization” of “Ilie Murgulescu” Institute of Physical Chemistry, financed by the Roumanian Academy and project—PN-IIPT-PCCA-2013-4(0864)-(94/2014)—“Cleanphotocoat”. Support of the EU (ERDF) and Roumanian Government, which allowed for acquisition of the research infrastructure under POS-CCE O 2.2.1 project INFRANANOCHEM—Nr.19/01.03.2009, is gratefully acknowledged. Barbara Malič and Katarina Vojisavljević acknowledge the support of Slovenian Research Agency (Programme P2-0105).
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