Damping of convection in liquid diffusion experiments

The knowledge of diffusion coefficients in the liquid state is necessary to get a better understanding of the structure and the transport phenomena in metallic and semiconducting melts. In liquid diffusion measurements, one o f the main problems is the additional transport by convection. The measured diffusion coefficients are often too high due to the additional mass trans port of the natural convection, especially at high temperatures. In microgr avity on space vehicles, self diffusion experiments were performed successf ully but interdiffusion experiments with major density differences failed b ecause of residual accelerations. The influence of convection is analysed q uantitatively and different methods of convection damping are investigated. With the finite element method the convection suppression by stabilising c oncentration gradients is proofed. The Monte Carlo method is used to calcul ate the influence of convection caused by oscillatory acceleration. Taylor' s expression for effective diffusity can be enhanced with a frequency depen dent proportionality constant. Magnetohydrodynamic damping is discussed.