Evolved gas analysis of amorphous precursors for S-doped TiO2 by TG-FTIR and TG/DTA-MS Part 3. Candidate from thiourea and Ti(IV)-ethoxide

• Published in: Journal of thermal analysis and calorimetry Vol. 97; no. 1; pp. 265 - 271
• Main Authors: Madarász, János, Brăileanu, Ana, Crişan, Maria, Răileanu, Malina, Pokol, György
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Dordrecht Springer Netherlands 01-07-2009; Springer
• Subjects: Analytical Chemistry; Chemistry; Chemistry and Materials Science; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Inorganic Chemistry; Materials science; Measurement Science and Instrumentation; Other topics in materials science; Physical Chemistry; Physics; Polymer Sciences; Simultaneous thermogravimetry and differential thermal analysis; Anatase; Titanium(IV)-ethoxide; Thiourea; Titania precursor; FTIR-spectroscopic gas cell; Evolved gas analysis; Mass spectrometry; Titanium IV Oxides; Infrared spectroscopy; Fourier transformation; Coupled method; Gas release; Thermogravimetry; Doped materials; Mass spectroscopy; Differential thermal analysis; Gas analysis; Amorphous state; Precursor; Titanium Oxides; Thermal analysis; Sulfur
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-009-0235-9

Thermal decomposition of an amorphous precursor for S-doped titania (TiO
2
) 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:TiO
2
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 (NH
3
) from 170 to 350 °C in three steps, and organic mater (probably ether and ethylene) between 140 and 230 °C. The evolution of CO
2
, H
2
O and SO
2
, 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 CO
2
and SO
2
. 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 CO
2
evolution and small exothermic effects.