Measuring self-diffusion coefficients up to 1500 K: a powerful tool to investigate the dynamics and the local structure of inorganic melts.
Self-diffusion is a fundamental property of liquid dynamics that also provides important structural information. To explore the dynamics in inorganic melts with high liquidus temperature, we propose a new setup based on pulsed field gradient NMR combined with laser heating that makes possible in situ self-diffusion coefficient measurements up to 1500 K. Applied to several corrosive molten fluorides in a wide range of compositions and temperature, we have evidenced the different key parameters of their motion along with their structural characteristics. In alkali fluorides, the self-diffusion coefficient of fluorine depends slightly on the composition compared to the temperature, displaying these systems as an ideal bath of polarizable hard spheres. In contrast, self-diffusion in rare earth and alkali fluorides mixtures presents a complicated balance between temperature and the network-forming process of the ionic long-lived units. These results open wide perspectives in the study of high temperature liquids.
Rollet
Anne-Laure
AL
CNRS, Université d'Orléans, UPR 3079 CEMHTI, 45071 Orléans, France. anne-laure.rollet@upmc.fr
Sarou-Kanian
Vincent
V
Bessada
Catherine
C