Kinetics study on phase transformation from titania polymorph brookite to rutile
- Department of Geology and Geophysics, Materials Science Program, University of Wisconsin-Madison, 1215 West Dayton Street, Madison, WI 53706 (United States)
TiO{sub 2} is a polymorphic material of great scientific interest due to its semiconductor properties and uses in heterogeneous photocatalysis. Understanding the stability of the polymorphs is important for designing TiO{sub 2}-based photocatalysts and solar cells. Although the phase transformation of anatase{yields}rutile has been well studied, there is only one published work on brookite{yields}rutile to date. The brookite{yields}rutile transformation has been studied in this work using natural material from the Magnet Cove igneous complex mechanically processed to several micrometers in size. The pure phase brookite is annealed from 800 to 900 deg. C without detection of the anatase polymorph. The transformation kinetics are described by both the standard first-order model, with an activation energy of E{sub a}=411.91 kJ/mol, and the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, with an activation energy of E{sub a}=492.13 kJ/mol. The rate parameter of the first-order model for the phase transformation is expressed as k=6.85x10{sup 14} exp(-49,451/T) s{sup -1} for the first-order model and k=4.19x10{sup 18} exp(-59,189/T) s{sup -1} using the JMAK model. The obtained activation energy is higher than that of brookite nano-crystals. Our results show that the JMAK model fits the kinetics data better than other models. - Graphical abstract: The transformation kinetics from titania brookite to rutile can be described by both the standard first-order model and the JMAK model. The obtained activation energy for micron-sized brookite crystals is much higher than that for brookite nano-crystals.
- OSTI ID:
- 21043918
- Journal Information:
- Journal of Solid State Chemistry, Vol. 181, Issue 3; Other Information: DOI: 10.1016/j.jssc.2007.12.015; PII: S0022-4596(07)00533-6; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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