Thermal Transformations in the System NaF-CaF 2 -AlF 3 and X-Ray Diffraction Control of Ca-Containing Electrolytes for Aluminum Production
Thermal Transformations in the System NaF-CaF 2 -AlF 3 and X-Ray Diffraction Control of Ca-Containing Electrolytes for Aluminum Production
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DOI：
10.4236/ojmetal.2013.34013
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发表时间：
2013-12
期刊：
影响因子：
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通讯作者：
Yulia N. Zaitseva;I. Yakimov;S. Kirik
中科院分区：
文献类型：
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作者：
Yulia N. Zaitseva;I. Yakimov;S. Kirik
The details of ternary fluoride crystallization in the system NaF-CaF2-AlF3 have been specified. The phases NaCaAlF6, Na2Ca3Al2F14 and NaAlF4 have been obtained by high-temperature synthesis. Their thermal transformations have been studied using high-temperature X-ray diffraction. The occurring transformations can be considered in a quasibinary system CaF2-NaAlF4, where at T = 745°C - 750°C invariant equilibrium is established with the phases CaF2-NaCaAlF6-Na2Ca3Al2F14-(NaAlF4). The compounds NaCaAlF6 and Na2Ca3Al2F14 are stable in different temperature ranges. The phase NaCaAlF6 was fixed by rapid quenching from the melt. It decomposes at heating before 640°C yielding Na2Ca3Al2F14 and NaAlF4. Direct and inverse transformations between NaCaAlF6 and Na2Ca3Al2F14 occur in the bulk samples of the electrolyte. A thermal treatment procedure was proposed for the solid electrolyte sample to get a sample corresponding to the composition of the melt and providing high phase crystallinity for the purposes of quantitative X-ray phase diffraction analysis.
