2016-Sustainable Industrial Processing Summit
SIPS 2016 Volume 9: Molten Salts and Ionic Liquids, Energy Production
| Editors: | Kongoli F, Gaune-Escard M, Turna T, Mauntz M, Dodds H.L. |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2016 |
| Pages: | 390 pages |
| ISBN: | 978-1-987820-24-9 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Some news about speciation in molten fluorides... or… a successful connection between experiments and modeling
Catherine Bessada1; Kelly Machado1; Didier Zanghi1; Sylvian Cadars2; Vincent Sarou-Kanian1; Mathieu Salanne3;1CNRS CEMHTI, Orleans, France; 2CNRS-IMN, Nantes, France; 3CNRS PHENIX, Paris, France;
Type of Paper: Regular
Id Paper: 400
Topic: 13
Abstract:
Because of severe experimental hindrances, the knowledge on molten fluoride salts chemistry has long remained limited to few experimental approaches. Molten fluorides mixtures can be strongly organized at unusually long distances due to the predominance of coulombic interactions and described by the formation of an intermediate range ordering. The description of free fluorine content evolution is also of primary importance for a better understanding of their properties. NMR spectroscopy is one of the techniques able to provide such information. Nevertheless, these systems cumulate high temperatures (from 500 K to 1800 K), corrosive properties towards most of the materials and sensitivity to moisture and oxygen making the NMR experiment a real challenge. We have already shown that thanks to the specific design of the sample container and of the heating system it was possible to obtain NMR spectra in the melt and to follow the evolution of the local structure with temperature and composition up to 1500°C. The signal position, or the isotropic chemical shift, is the weighted averaged chemical shift of the different components in the melt. Knowing the chemical shift of the individual species, it is possible to define their proportions depending on the composition, except when the number of individual species becomes too high compare with the equilibrium equations. We are now able to calculate directly the chemical shifts corresponding to the system, thanks to the coupling between molecular dynamic calculations and theoretical approach of the NMR chemical shifts DFT calculations.
This new step towards a better description of the speciation in such molten salts will provide a new capability to determine the physical and chemical properties of molten fluorides.