Conditions Extrêmes et Matériaux : Haute Température et Irradiation

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A.L.Rollet, V.Sarou-Kanian, C.Bessada, 'Self-diffusion coefficients measurement at high temperature by PFG NMR', C. R. Chim. 13 399-404 (2010) doi:10.1016/j.crci.2009.11.005

We have developed a new experimental setup for the measurement of self-diffusion coefficients at high temperature (up to 1500K) in corrosive liquids. It is based on pulsed field gradient NMR using a 10mm liquid probe with 2 channels F-H/X modified and coupled with laser heating. The values obtained thanks to this setup are in good agreement with the available data obtained using the reference method, i.e. the capillary method. We present here results on 19F, 7Li, 23Na, 27Al in molten fluorides. In alkali fluorides mixtures, the self-diffusion coefficients depend weakly on the composition (nature and concentration of the different alkali) but mainly on temperature. In cryolite (Na3AlF6) the diffusion evidences the complexation.