Energetics of nanocrystalline TiO2
- M. R. Ranade*,
- A. Navrotsky*,†,
- H. Z. Zhang‡,
- J. F. Banfield‡,
- S. H. Elder§,
- A. Zaban¶,
- P. H. Borse∥,
- S. K. Kulkarni∥,
- G. S. Doran**, and
- H. J. Whitfield††
- *University of California, Department of Chemical Engineering and Materials Science, Thermochemistry Facility, Davis, CA 95616;‡ University of Wisconsin, Department of Geology and Geophysics, Madison, WI 53706; §Intel Corporation, Hillsboro, OR 97124; ¶Bar-Ilan University, Department of Chemistry, Ramat-Gan 52900, Israel; ∥University of Pune, Department of Physics, Pune 411007, India; **CSIRO Manufacturing Science and Technology Clayton, Victoria 3169, Australia; and†† Department of Applied Physics, Royal Melbourne Institute of Technology University, GPO Box 2476V, Melbourne, Victoria 3001, Australia
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Contributed by A. Navrotsky
Abstract
The energetics of the TiO2 polymorphs (rutile, anatase, and brookite) were studied by high temperature oxide melt drop solution calorimetry. Relative to bulk rutile, bulk brookite is 0.71 ± 0.38 kJ/mol (6) and bulk anatase is 2.61 ± 0.41 kJ/mol higher in enthalpy. The surface enthalpies of rutile, brookite, and anatase are 2.2 ± 0.2 J/m2, 1.0 ± 0.2 J/m2, and 0.4 ± 0.1 J/m2, respectively. The closely balanced energetics directly confirm the crossover in stability of nanophase polymorphs inferred by Zhang and Banfield (7). An amorphous sample with surface area of 34,600 m2/mol is 24.25 ± 0.88 kJ/mol higher in enthalpy than bulk rutile.
Footnotes
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↵ † To whom reprint requests should be addressed at: 4440 Chemistry Annex, Thermochemistry Facility, Department of Chemical Engineering and Materials Science, University of California, One Shields Avenue, Davis, CA 95616. E-mail: anavrotsky{at}ucdavis.edu.
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This paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “Nanoscience: Underlying Physical Concepts and Phenomena,” held May 18–20, 2001, at the National Academy of Sciences in Washington, DC.
- Abbreviations:
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XRD, x-ray diffraction patterns
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- Copyright © 2002, The National Academy of Sciences
