Post-graduate theses
Current Record: 4897 of 6553
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| Identifier |
000373185 |
| Title |
Φωτοκαταλυτικές ιδιότητες διοξείδιου του τιτανίου : προσδιορισμός φωτοκαταλυτικής δράσης εμπλουτισμού και μη Ti02 με πρόσμιξη, μη χρησιμοποιώντας CH3CHO παρουσία υπεριώδους και ορατής ακτινοβολίας |
| Alternative Title |
Photocatalytic properties of titanium dioxide |
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Author
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Σαμπάνη, Κυριακή
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Thesis advisor
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Κυριακίδης, Γεώργιος
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Reviewer
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Ηλιόπουλος, Ελευθέριος
Ζεκεντές, Κωνσταντίνος
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| Abstract |
Novel TiO2 photocatalytic powder materials doped with various levels of Mn were synthesized to be used as additives to wall painting in combating indoor and outdoor air pollution. A straight forward, simple and inexpensive process has been developed by sol-gel method for the synthesis of Manganese (Mn) doped and undoped TiO2 photocatalysts. The heterogeneous photocatalytic degradation of gaseous CH3CHO on Mn- TiO2 surfaces under UV/Vis irradiation was investigated, by employing the photochemical static reactor coupled with FTIR spectroscopy (PSR/FTIR) technique.
Experiments were performed by exposing acetaldehyde (3 Torr) and synthetic air mixtures (760 Torr total pressure) on pure TiO2 and doped with various levels of Mn (0.1 - 33% mole percentage) under UV and visible irradiation at room temperature. Photoactivation was initiated using either UV or visible light sources with known emission spectra. Initially, the photolability of CH3CHO under the above light sources, and the physical adsorption of CH3CHO on Mn-TiO2 substrates in the absence of light were determined prior to the photocatalytic experiments. The photocatalytic loss of CH3CHO on pure TiO2 and Mn-TiO2 substrates in the absence and presence of UV or visible irradiation was measured over a long period (60 min), to evaluate their relative photocatalytic activity. The gaseous photocatalytic end products were also determined using absorption FTIR spectroscopy, and CO2 was identified as the main photocatalysis product. It was found that 0.1% Mn- TiO2 substrates resulted in the highest photocatalytic loss of CH3CHO under visible irradiation, and this efficiency was drastically diminished at higher levels of Mn doping (1 - 33%). On the opposite, the CO2 yields were the highest for 0.1% Mn- TiO2substrates under UV irradiation, in agreement with the observed highest CH3CHO decomposition rates. Therefore, it was demonstrated that low-level (0.1%) doping of TiO2 with Mn results in significant increase of their photocatalytic activity in the visible range, compared to pure TiO2, and this elevated activity is lost at high doping levels (1-33%). Finally, the photocatalytic degradation mechanism of CH3CHO on 0.1% Mn-TiO2 surfaces under visible irradiation leading to low CO2 yields is different than that under UV irradiation resulting to high CO2 yields.
X-ray powder Diffractometry (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) revealed the presence of structural nanoparticles with an average nanocrystalline size of about 20 nm. The photocatalytic activity of these materials was evaluated by the degradation of a basic Methylene Blue (MB) as organic contaminant. Mn-doped TiO2 powder with molar ratio 0.1:100 was mixed with calcareous filler (5% and 10% respectively) and the photocatalytic activity was also evaluated by the degradation of inorganic pollutants such as NOx under UV and Visible light.
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| Language |
Greek |
| Subject |
Photocatalysis |
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Powder TiO2 |
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Φωτοκατάλυση |
| Issue date |
2012-07-20 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/e/b/b/metadata-dlib-1343030616-510826-9061.tkl
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| Views |
1143 |
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