Thermal transformation of quaternary compounds in NaF-CaF2-AlF3 system

Описание

Тип публикации: статья из журнала

Год издания: 2009

Идентификатор DOI: 10.1016/j.jssc.2009.05.043

Ключевые слова: Phase equilibrium diagram of the system, NaF-AlF3-CaF2, Calcium-sodium-aluminum fluorides, High-temperature XRD, Aluminum production, Industrial electrolytes, Phase equilibrium diagram of the system NaF-AlF3-CaF2, Bulk samples, Equilibrium temperatures, Experimental conditions, High temperature, High temperature X-ray diffraction, In-vacuum, Invariant equilibria, Liquid melt, Metastability, Normal pressure, Phase equilibrium diagram of the system NaF-AlF<sub>3</sub>-CaF<sub>2</sub>, Quasi-binary, Quaternary compound, Quaternary phasis, Reverse Transformation, Solid phase synthesis, Thermal analysis, Thermal behaviors, Thermal transformations, Alumina, Aluminum metallography, Calcium, Calcium alloys, Diffraction, Electrolytes, Fluorine compounds, Liquids, Phase equilibria, Quenching, Sodium, Strontium compounds, Sulfur compounds, Superconducting films, Thermoanalysis, X ray diffraction, X ray diffraction analysis, Aluminum

Аннотация: Details of quaternary compounds formation in the system NaF-CaF2-AlF3 are specified. To achieve this aim, the samples of phases NaCaAlF6 and Na2Ca3Al2F14 have been obtained by high-temperature solid-phase synthesis. Their thermal behavior when heated up to 800 degrees C has been studied using the methods of high-temperature X-ray dПоказать полностьюiffraction (XRD) and thermal analysis (TA). The system under consideration can be regarded as a quasibinary section CaF2-NaAlF4, where at T = 745-750 degrees C invariant equilibrium is implemented with the phases CaF2-NaCaAlF6-Na2Ca3Al2F14-(liquid melt)-(NaAlF4). The peculiarity of the equilibrium is NaAlF4 metastability at normal pressure. Below the equilibrium temperature the quaternary phase Na2Ca3Al2F14 is stable and NaCaAlF6 above this temperature. The phase NaCaAlF6 fixed by rapid quenching from high temperatures and when heated up to 640 degrees C decomposes, yielding Na2Ca3Al2F14. Further heating in vacuum at temperature up to 740 degrees C results in decomposition of Na2Ca3Al2F14 into CaF2 and Na3AlF6. The expected reverse transformation of Na2Ca3Al2F14 into NaCaAlF6 has not been observed under experimental conditions. Transformations in bulk samples reveal direct and reverse transformation of quaternary phases. Synopsis: Thermal transformation of the quaternary compounds in system (NaF-CaF2-AlF3) was investigated using high-temperature X-ray diffraction (XRD) and thermal analysis (TA). In the system the invariant equilibrium is implemented with the phases CaF2-NaCaAlF6-Na2Ca3Al2F14-(liquid melt)-(NaAlF4) at T = 745-750 degrees C. (C) 2009 Elsevier Inc. All rights reserved.

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Издание

Журнал: JOURNAL OF SOLID STATE CHEMISTRY

Выпуск журнала: Vol. 182, Is. 8

Номера страниц: 2246-2251

ISSN журнала: 00224596

Место издания: SAN DIEGO

Издатель: ACADEMIC PRESS INC ELSEVIER SCIENCE

Авторы

  • Zaitseva J.N. (Institute of Chemistry,Chemical Technology SB RAS)
  • Kirik S.D. (Siberian Federal University)
  • Yakimov I.S. (Siberian Federal University)

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