التفاصيل البيبلوغرافية
| العنوان: |
Key to Proto-Aragonite Amorphous CaCO3. |
| المؤلفون: |
Farhadi-Khouzani, Masoud, Chevrier, Daniel M., Peng Zhang, Hedin, Niklas, Gebauer, Denis |
| المصدر: |
Angewandte Chemie International Edition; 7/4/2016, Vol. 55 Issue 28, p8117-8120, 4p |
| مصطلحات موضوعية: |
ARAGONITE, CARBONATE minerals, CALCIUM carbonate, VATERITE, CARBONATE synthesis |
| مستخلص: |
Temperature and pH value can affect the short-range order of proto-structured and additive-free amorphous calcium carbonates (ACCs). Whereas a distinct change occurs in proto-vaterite (pv) ACC above 45°C at pH 9.80, proto-calcite (pc) ACC (pH 8.75) is unaffected within the investigated range of temperatures (7-65 °C). IR and NMR spectroscopic studies together with EXAFS analysis showed that the temperatureinduced change is related to the formation of proto-aragonite (pa) ACC. The data strongly suggest that the binding of water molecules induces dipole moments across the carbonate ions in pa-ACC as in aragonite, where the dipole moments are due to the symmetry of the crystal structure. Altogether, a (pseudo-) phase diagram of the CaCO3 polyamorphism in which water plays a key role can be formulated based on variables of state, such as the temperature, and solution parameters, such as the pH value. [ABSTRACT FROM AUTHOR] |
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