Understanding of homogeneous spontaneous precipitation for monodispersed TiO2 ultrafine powders with rutile phase around room temperature

Citation
Sd. Park et al., Understanding of homogeneous spontaneous precipitation for monodispersed TiO2 ultrafine powders with rutile phase around room temperature, J SOL ST CH, 146(1), 1999, pp. 230-238
Citations number
21
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Inorganic & Nuclear Chemistry
Journal title
JOURNAL OF SOLID STATE CHEMISTRY
ISSN journal
0022-4596 → ACNP
Volume
146
Issue
1
Year of publication
1999
Pages
230 - 238
Database
ISI
SICI code
0022-4596(199908)146:1<230:UOHSPF>2.0.ZU;2-N
Abstract
Monodispersed TiO2 ultrafine particles were obtained from aqueous TiOCl2 so lution with a 0.67 M Ti4+ concentration prepared by diluting TiCl4 with the homogeneous precipitation process in the range 17-230 degrees C. With the spontaneous hydrolysis of TiOCl2, which means the natural decrease of the p H value in the aqueous solution, all monodispersed precipitates were crysta llized with the anatase or rutile TiO2 phase during the reactions. The TiO2 precipitate with the pure rutile phase was fully formed at temperatures be low 65 degrees C, which did not involve the evaporation of H2O, and above 1 55 degrees C, which mere available by suppressing it. The TiO2 precipitate with the rutile phase, including a small amount of the anatase phase, start ed to be formed at intermediate temperatures above 70 degrees C, showing th e full formation of the anatase phase above 95 degrees C under the free eva poration of H2O. However, in the case of completely suppressing H2O evapora tion at temperatures above 70 degrees C, the TiO2 precipitate with the anat ase phase that had already been formed by rapid reaction was fully transfor med with the reaction time into the precipitate with the rutile phase by th e vapor pressure of H2O. Therefore, the formation of TiO2 precipitates with the rutile phase around room temperature would be caused by the existence of capillary pressure between the agglomerated needle-shaped particles or t he ultrafine clusters, together with the slow reaction rate. (C) 1999 Acade mic Press.