Self-diffusion Measurements of Liquid Sn Using the Shear Cell Technique and Stable Density Layering
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in liquid metals are essential to the understanding of metallurgical phenomena such as solute redistribution at solid–liquid interfaces during solidification processes. In particular, the self-diffusion coefficients in liquid metals are required for the modeling of diffusive theories in liquid metals, given that self-diffusion is the simplest diffusion phenomenon. The self-diffusion coefficients in liquid metals are widely used in diffusive theories[1–6]; namely, the Stokes–Einstein formula,[1] hard sphere model,[2] and molecular dynamics simulations.[3] The measurement of diffusion
MASATO SHIINOKI, NAO HASHIMOTO, HIDETO FUKUDA, and YUKI ANDO are with the Department of Applied Mechanics, Faculty of Science and Engineering, Waseda University, Okubo 3-4-1 Shinjuku-ku, Tokyo 169-8555, Japan. Contact e-mail: [email protected] SHINSUKE SUZUKI is with the Department of Applied Mechanics and Aerospace Engineering, Faculty of Science and Engineering, Kagami Memorial Research Institute of Materials Science and Technology, Waseda University, Okubo 3-4-1 Shinjuku-ku, Tokyo 169-8555, Japan. Manuscript submitted March 30, 2018.
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coefficients in liquid metals under microgravity conditions in space is significantly more reliable than that on the ground. However, prior to space experiments, several experiments were performed on the ground.[7,8] Due to the insufficient experimental data of reliable self-diffusion coefficients in liquid metals on the ground, it is unclear whether these diffusive theories can be demonstrated by the experimental results. On the ground, buoyancy causes natural convection in liquid metals, and the experimental results could be influenced by natural convection. Moreover, the methods using quasi-elastic incoherent neutron scattering are effective for the measurement of self-diffusion coefficients in liquid metals on the ground.[9] However, large equipment is required for experiments using quasi-elastic incoherent neutron scattering, and the number of experiments is limited. It is common knowledge that microgravity conditions are effective in suppressing natural convection. Frohberg et al.[10] conducted diffusion experiments under microgravity conditions using a long capillary technique and measured the self-diffusion coefficients of liquid Sn. It was reported that the self-diffusion coefficients of liquid Sn under microgravity conditions were significantly lower than those measured on the ground.
Moreover, the variation in the self-diffusion coefficients of liquid Sn under microgravity conditions was significantly smaller than that on the ground. Furthermore, Frohberg et al.[11] proposed the power law of temperature dependence D = ATn (A and n are fitting parameters; and the value of n is approximately 2). Itami et al.[12] also conducted a self-diffusion experiment on liquid Sn under microgravity conditions, using a long capillary technique. It was reported that the experimental results were in good agreement with those of Frohberg et al.,[11] and were represented as D = ATn with a maximum te
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