Jump to ContentJump to Main Navigation
Show Summary Details
More options …

American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2017: 2.645

CiteScore 2017: 2.31

SCImago Journal Rank (SJR) 2017: 1.440
Source Normalized Impact per Paper (SNIP) 2017: 1.059

Online
ISSN
1945-3027
See all formats and pricing
More options …
Volume 82, Issue 7-8

Issues

Particle size effects on transformation kinetics and phase stability in nanocrystalline TiO2

Amy A. Gribb
  • Department of Geology and Geophysics, University of Wisconsin–Madison, 1215 W. Dayton St., Madison, Wisconsin 53706, U.S.A.
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Jillian F. Banfield
  • Department of Geology and Geophysics, University of Wisconsin–Madison, 1215 W. Dayton St., Madison, Wisconsin 53706, U.S.A.
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2015-11-13 | DOI: https://doi.org/10.2138/am-1997-7-809

Abstract

Kinetic studies conducted primarily between 465 and 525 ℃ demonstrate that the rate of the polymorphic anatase to rutile transformation increases dramatically when the reacting anatase is very finely crystalline. Coarsening of the reactant anatase and product rutile crystallites occurs simultaneously with the transformation. Kinetic behavior and quantifi­cation of transformation rate as a function of average crystallite size indicate that the increase in favorable nucleation sites is a likely cause of increase in transformation rate at small crystallite sizes. Additionally, experimental evidence supports the reversal of stabilities of anatase and rutile at small crystallite sizes. It is proposed that the reversal of stabilities is the result of rutile having a higher surface energy than the anatase phase. Data for coarsening kinetics of anatase and rutile supports the prediction that the surface energy of rutile is significantly larger than that of anatase. Thermodynamic data and theoretical estimates are used to show that a 15% greater surface energy for rutile causes the total free energy of rutile to be greater (less negative) than anatase at crystallite diameters in the few nanometer range. Given the fact that anatase and rutile structures have no poly­merized octahedral fragments in common, this may be significant in determining the nature of the nucleated phase.

About the article

Received: 1996-07-29

Accepted: 1997-03-10

Published Online: 2015-11-13

Published in Print: 1997-07-01


Citation Information: American Mineralogist, Volume 82, Issue 7-8, Pages 717–728, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-1997-7-809.

Export Citation

© 2015 by Walter de Gruyter Berlin/Boston.

Comments (0)

Please log in or register to comment.
Log in