The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Dissertation for the degree of Doctor of Science in Technology to be presented, with due permission for public examination and debate in Auditorium E at Helsinki University of Technology (Espoo, Finland) on the 14th of September, 2001, at 13 o'clock.
Overview in PDF format (ISBN 951-38-5858-8) [859 KB]
VTT Publications 439, ISSN 1455-0849
Dissertation is also available in print (ISBN 951-38-5857-X)
Copyright © 2001 VTT Technical Research Centre of Finland
VTT Publications 439, ISSN 1235-0621
VTT-PUBS-439
TKK-DISS-1536
In this experimental study, aerosol methods for producing titanium dioxide powders and increasing our knowledge of particle and crystal formation have been developed. Powders and ultrafine particles of titanium oxide were produced by an aerosol droplet decomposition route in tubular laminar flow reactors in air and nitrogen atmospheres. Reactor temperatures up to 1500°C were used with residence times in the range of 1.50 s. Novel methods were introduced for the production of micron sized powders, investigation of crystallization of anatase in the particles, and for studying the formation of crystal phase and morphology on ultrafine particles at different temperatures. High-resolution transmission electron microscopy, scanning electron microscopy, aerosol measurements by differential mobility analyzer and inertial impactor as well as materials characterization by diffraction and spectroscopic methods were performed. In addition, the production conditions in aerosol reactors were evaluated using computational fluid dynamics calculations. The results showed that titanium dioxide powders can be produced from ultrafine up to micron sized particles via droplet decomposition and in-droplet hydrolysis methods starting from a titanium alkoxide precursor. Crystal phase and crystallite size can be controlled by reactor conditions and by thermal post-annealing. Anatase formation in amorphous particles was observed near surfaces. Investigation of ultrafine particles revealed morphology development of rutile and anatase single crystals. The 60 and 120 nm diameter rutile crystal morphologies development was observed in mobility particle size measurements. The 20 nm diameter anatase particle morphology showed the development of crystallographic {011} and {001} surfaces.
This thesis consists of an overview and of the following 5 publications:
Keywords: aerosols, particles, synthesis, pyrolysis, hydrolysis, alkoxides, titanium dioxide, anatase, rutile, crystal morphology
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© 2004 Helsinki University of Technology