In order to determine the effect of gravity on the results from earlier liquid diffusion experiments in low earth orbit, comparative experiments involving Au, Ag, and Sb diffusing in liquid lead were carried out using a liquid diffusion ground-based unit under terrestrial conditions. It was found that buoyancy-driven convection still persists in the liquid even when conditions were arranged for a continuously decreasing density gradient up the long axis of a melted long capillary diffusion couple. It was suggested that radial temperature gradients in the diffusion samples cause such buoyancy-driven convection, and so enhance the solute transport and increase the measured diffusion coefficient values; however, it was noted that if the density of the solute was considerably less than that of the solvent, then the convective flow and the corresponding solute transport were much reduced.

The Effects of Buoyancy Convection on the Measured Solute Diffusion Coefficients in Dilute Metallic Liquids. W.D.Huang, B.J.Yang, R.W.Smith: Journal of Applied Physics, 2004, 96[11], 6213-9