Determination of the Solute Diffusion Coefficient by the Droplet Migration Method

Further analysis of droplet migration in a temperature gradient field indicates that different terms can be used to evaluate the solute diffusion coefficient in liquid (D _L ) and that there exists a characteristic curve that can describe the motion of all the droplets for a given composition and temperature gradient. Critical experiments are subsequently conducted in succinonitrile (SCN)-salol and SCN-camphor transparent alloys in order to observe dynamic migration processes of a number of droplets. The derived diffusion coefficients from different terms are the same within experimental error. For SCN-salol alloys, D _L = (0.69 ± 0.05) × 10⁻³ mm²/s, and for SCN-camphor alloys, D _L = (0.24 ± 0.02) × 10⁻³ mm²/s. This article is based on a presentation made in the symposium entitled “Solidification Modeling and Microstructure Formation: In Honor of Professor John Hunt,” which occurred March 13-15, 2006, during the TMS Spring Meeting in San Antonio, Texas, under the auspices of the TMS Materials Processing and Manufacturing Division, Solidification Committee.