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Title: Integral structural and chemical analysis of TiO2 in relation to photoactivity
Author: Mahdjoub, Noredine Loeid
ISNI:       0000 0004 2690 178X
Awarding Body: The Manchester Metropolitan University
Current Institution: Manchester Metropolitan University
Date of Award: 2009
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Ti02 referred to as "titania" exists in a number of crystalline forms. The most widespread are anatase and rutile. By far it is mainly used as a pigment, where it is applied in powder form and used in films for coatings on plastics. Titania nano-powders used in the present study and synthesised by "Millenium Chemicals", were provided for investigation and characterisation. In this first part of the study, the nano-powders were annealed in air at temperatures up to 1022 K for 30 mins. Micro-Raman analysis and crystallite size measurements were made by X-Ray Diffraction (XRD), these measurements were supported by Low Energy Scanning Electron Microscopy (SEM) analysis. Typical anatase, rutile and brookite phase structures were observed at different temperature treatments, and from the SEM images changes in morphology were noticeable. Subsequently, the samples were photocatalytically assessed by monitoring the degradation of a methyl orange dye by the TiO2 nano-powders irradiated under UV radiation and revealed a high activity of the TiO2; anatase, anatase-rutile, anatase-brookite and anatase-brookite-rutile mixed phases. The TiO2 rutile phase on its own did not show any photocatalytic activity. In the second part of this investigation, titania thin films were created by reactive ion sputter-deposition from titanium targets at various partial pressures and deposition parameters. The films were deposited onto substrates with temperatures ranging from 350 K to 620 K. Micro-Raman spectra and X-Ray Diffraction data were acquired from as-deposited and in-air annealed films at temperatures up to 1022 K for 10 min. The film stoichiometries were determined by Energy Dispersive X-Ray analysis. As-deposited the films were formed to have predominantly anatase-rutile mixed structures. Films deposited at low temperature and without energy assistance from the plasma tend to be amorphous, while films deposited on a hot substrate and/or with high ion energy assistance tend to have a mixed crystalline phase. On subsequent annealing the films changed to a pure anatase structure at temperatures above 670K, while mixed anatase-rutile films change to predominantly rutile structure at temperatures above 870K. In order to determine the relation between growth conditions, phase transitions and photoactivity, photacatalytic investigations were undertaken utilising the photodegradation of a stearic acid by TiO2 thin films under UV irradiation. This II photacatalytic investigation revealed a high photo-activity for the samples made under high oxidising atmosphere and having a mixed rutile-anatase phase.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available