Differences in thermal and mechanochemical polymorphism. Effects of impurity on the system aragonite-calcite

Tetsuhiko Isobe, Mamoru Senna

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16 Citations (Scopus)

Abstract

The effects of incorporated Pb2+ and Sr2+ on the thermal and mechanochemical transformations of aragonite into calcite have been studied. The rate of thermal transformation is remarkably retarded on doping. The rate of mechanochemical transformation, in contrast, increases slightly on doping with Pb2+, whereas it decreases slightly on doping with Sr2+. The difference between the two processes is interpreted by assuming that the reduction in the dislocation movement on doping retards the thermal transformation, whereas the retardation effect is overcome by the applied shear stress. In addition, the local decomposition of PbCO3 during grinding in air might have enhanced the mechanochemical transformation of aragonite doped with Pb2+. After the mechanical treatment, the apparent enthalpy of the transformation was reduced, presumably because of the partial cancellation of the endothermic heat of transformation by the liberation of excess enthalpy, as revealed by differential scanning calorimetry.

Original languageEnglish
Pages (from-to)1199-1209
Number of pages11
JournalJournal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
Volume84
Issue number4
DOIs
Publication statusPublished - 1988

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aragonite
Calcium Carbonate
polymorphism
calcite
Polymorphism
Doping (additives)
Impurities
impurities
Enthalpy
Shear stress
enthalpy
Differential scanning calorimetry
Decomposition
grinding
Hot Temperature
cancellation
shear stress
Air
heat measurement
decomposition

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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abstract = "The effects of incorporated Pb2+ and Sr2+ on the thermal and mechanochemical transformations of aragonite into calcite have been studied. The rate of thermal transformation is remarkably retarded on doping. The rate of mechanochemical transformation, in contrast, increases slightly on doping with Pb2+, whereas it decreases slightly on doping with Sr2+. The difference between the two processes is interpreted by assuming that the reduction in the dislocation movement on doping retards the thermal transformation, whereas the retardation effect is overcome by the applied shear stress. In addition, the local decomposition of PbCO3 during grinding in air might have enhanced the mechanochemical transformation of aragonite doped with Pb2+. After the mechanical treatment, the apparent enthalpy of the transformation was reduced, presumably because of the partial cancellation of the endothermic heat of transformation by the liberation of excess enthalpy, as revealed by differential scanning calorimetry.",
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AB - The effects of incorporated Pb2+ and Sr2+ on the thermal and mechanochemical transformations of aragonite into calcite have been studied. The rate of thermal transformation is remarkably retarded on doping. The rate of mechanochemical transformation, in contrast, increases slightly on doping with Pb2+, whereas it decreases slightly on doping with Sr2+. The difference between the two processes is interpreted by assuming that the reduction in the dislocation movement on doping retards the thermal transformation, whereas the retardation effect is overcome by the applied shear stress. In addition, the local decomposition of PbCO3 during grinding in air might have enhanced the mechanochemical transformation of aragonite doped with Pb2+. After the mechanical treatment, the apparent enthalpy of the transformation was reduced, presumably because of the partial cancellation of the endothermic heat of transformation by the liberation of excess enthalpy, as revealed by differential scanning calorimetry.

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