High temperature reaction calorimetry applied to metastable and nanophase materials

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21 Scopus citations

Abstract

Materials with high surface areas and small particle size (nanophases), metastable polymorphs, and hydrated oxides are increasingly important in both materials and environmental science. Using modifications of oxide melt solution calorimetry, we have developed techniques to study the energetics of such oxides and oxyhydroxides, and to separate the effects of polymorphism, chemical variation, high surface area, and hydration. Several generalizations begin to emerge from these studies. The energy differences among different polymorphs (e.g., various zeolite frameworks, the α- and γ-alumina polymorphs, manganese and iron oxides and oxyhydroxides) tend to be small, often barely more than thermal energy under conditions of synthesis. Much larger contributions to the energetics come from oxidation reduction reactions and charge-coupled substitutions involving the ions of basic oxides (e.g., K and Ba). The thermodynamics of hydration involve closely balanced negative enthalpies and negative entropies and are very dependent on the particular framework and cage or tunnel geometry.

Original languageEnglish (US)
Pages (from-to)653-658
Number of pages6
JournalJournal of Thermal Analysis and Calorimetry
Volume57
Issue number3
StatePublished - 1999
Externally publishedYes
EventProceedings of the 1998 International Symposium on New Frontier of Thermal Studies of Materials - Yokohama, Jpn
Duration: Oct 26 1998Oct 27 1998

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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