Open AccessEnergetics of nanocrystalline TiO 2
Author(s) -
M. R. Ranade,
Alexandra Navrotsky,
H. Z. Zhang,
Jillian F. Banfield,
S. H. Elder,
Arie Zaban,
Pramod H. Borse,
S.K. Kulkarni,
Gregory Doran,
H. J. Whitfield
Publication year - 2002
Publication title -
proceedings of the national academy of sciences
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.251534898
Subject(s) - brookite , rutile , anatase , enthalpy , nanocrystalline material , calorimetry , materials science , amorphous solid , energetics , crystallography , chemistry , mineralogy , thermodynamics , nanotechnology , organic chemistry , physics , photocatalysis , catalysis
The energetics of the TiO(2) 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/m(2), 1.0 +/- 0.2 J/m(2), and 0.4 +/- 0.1 J/m(2), 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 m(2)/mol is 24.25 +/- 0.88 kJ/mol higher in enthalpy than bulk rutile.
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