Authors:
János Madarász Budapest University of Technology and Economics Department of Inorganic and Analytical Chemistry Szt. Gellért tér 4 Budapest 1521 Hungary

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Ana Brăileanu Institute of Physical Chemistry Ilie Murgulescu Roumanian Academy 202 Splaiul Independenţei Bucharest 060021 Romania

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Maria Crişan Institute of Physical Chemistry Ilie Murgulescu Roumanian Academy 202 Splaiul Independenţei Bucharest 060021 Romania

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Malina Răileanu Institute of Physical Chemistry Ilie Murgulescu Roumanian Academy 202 Splaiul Independenţei Bucharest 060021 Romania

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György Pokol Budapest University of Technology and Economics Department of Inorganic and Analytical Chemistry Szt. Gellért tér 4 Budapest 1521 Hungary

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Abstract  

Thermal decomposition of an amorphous precursor for S-doped titania (TiO2) nanopowders, prepared by controlled sol–gel hydrolysis–condensation of titanium(IV) tetraethoxide and thiourea in aqueous ethanol, has been studied up to 800 °C in flowing air. Simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR) have been applied for analysis of released gases (EGA) and their evolution dynamics in order to explore and simulate thermal annealing processes of fabrication techniques of the aimed S:TiO2 photocatalysts with photocatalytic activities under visible light. The precursor sample prepared with thiourea, released first water endothermically from room temperature to 190 °C, carbonyl sulfide (COS) from 120 to 240 °C in two stages, ammonia (NH3) from 170 to 350 °C in three steps, and organic mater (probably ether and ethylene) between 140 and 230 °C. The evolution of CO2, H2O and SO2, as oxidation products, occurs between 180 and 240 °C, accompanied by exothermic DTA peaks at 190 and 235 °C. Some small mass gain occurs before the following exothermic heat effect at 500 °C, which is probably due to the simultaneous burning out of residual carbonaceous and sulphureous species, and transformation of amorphous titania into anatase. The oxidative process is accompanied by evolution of CO2 and SO2. Anatase, which formed also in the exothermic peak at 500 °C, mainly keeps its structure, since only 10% of rutile formation is detected below or at 800 °C by XRD. Meanwhile, from 500 °C, a final burning off organics is also indicated by continuous CO2 evolution and small exothermic effects.

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Journal of Thermal Analysis and Calorimetry
Language English
Size A4
Year of
Foundation
1969
Volumes
per Year
1
Issues
per Year
24
Founder Akadémiai Kiadó
Founder's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher
Chief Executive Officer, Akadémiai Kiadó
ISSN 1388-6150 (Print)
ISSN 1588-2926 (Online)

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