Measurements of Impurity Diffusion Coefficients in Ionic Melts with High Accuracy under Microgravity

抄録

In order to determine accurately the diffusion coefficient of silver ion in the eutectic LiCl­ KCl melt, a chronopotentiometry has been done under microgravity so as to avoid the natur­ al convection. The experiment was done as a part of MSL-1 mission. The relative importance of the sources of errors have been evaluated to elucidate the accuracy of the measurements, and the accurate diffusion coefficccients of silver ion in the eutectic LiCl-KCl melt have been derived over the temperature range of 640 and 860 K. By the use of the microgravity, the disturbance due to natural convection has been well suppressed and diffusion coefficients have been determined with the accuracy of 9.6%. Temperature dependence of the diffusion coefficient of silver ion was correlated by the Arrhenius type equation and compared with the results of 10 experiment as follows: D/ (m2s- 1 )= 2.794x 10- 1 exp (-28899/(RT)) for µG, D/ (m2s- 1)= 6.91 x 10- 8 exp (-20402/(RT)) for 1 G, where T is in Kand R is the gas constant, 8.3145 J K- 1•