Aerosol production and crystallization of titanium dioxide from metal alkoxide droplets

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Doctoral thesis (article-based)
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55, [62]
VTT publications, 439
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.
aerosols, particles, synthesis, pyrolysis, hydrolysis, alkoxides, titanium dioxide, anatase, rutile, crystal morphology
Other note
  • P. P. Ahonen, E. I. Kauppinen, J.-C. Joubert, J.-L. Deschanvres and G. Van Tendeloo. 1999. Preparation of nanocrystalline titania powder via aerosol pyrolysis of titanium tetrabutoxide. Journal of Materials Research, Vol. 14, pp. 3938-3948.
  • P. P. Ahonen, U. Tapper, E. I. Kauppinen, J.-C. Joubert and J.-L. Deschanvres. 2001. Aerosol synthesis of Ti-O powders via in-droplet hydrolysis of titanium alkoxide. Materials Science and Engineering: A, Vol. 315, pp. 113-121.
  • P. P. Ahonen, O. Richard and E. I. Kauppinen. 2001. Particle production and anatase formation in amorphous particles at in-droplet hydrolysis of titanium alkoxide. Materials Research Bulletin, Vol. 36, pp. 2017-2025.
  • P. P. Ahonen, J. Joutsensaari, O. Richard, U. Tapper, D. P. Brown, J. K. Jokiniemi and E. I. Kauppinen. 2001. Mobility Size Development and the Crystallization Path during Aerosol Decomposition Synthesis of TiO2 Particles. Journal of Aerosol Science, Vol. 32, pp. 615-630.
  • P. P. Ahonen, A. Moisala, U. Tapper, D. P. Brown, J. K. Jokiniemi and E. I. Kauppinen. 2001. Gas-phase crystallization of titanium dioxide nanoparticles. Journal of Nanoparticle Research, submitted for publication.
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