self diffusion coefficient, liquid Sn, microgravity environment, MSL mission, material science laboratory, temperature dependence, long capillary method, Marangoni convection, Sn isotope, concentration profile, hard sphere model
Hokkaido University Graduate School of Science
Hokkaido University Graduate School of Science
Ishikawajima Jet Service Co Ltd Space Department
Ishikawajima-Harima Heavy Industries Co Ltd Materials Technology Department, Research Institute
Ishikawajima-Harima Heavy Industries Co Ltd Space Experiment System Development Department
Ishikawajima-Harima Heavy Industries Co Ltd Space Experiment System Development Department
Tokyo Institute of Technology Interdisciplinary Graduate School of Science and Engineering
National Space Development Agency of Japan Space Utilization Research Center
National Space Development Agency of Japan Space Utilization Research Center
National Space Development Agency of Japan Space Utilization Research Center
出版者
宇宙開発事業団
出版者（英）
National Space Development Agency of Japan (NASDA)
The self-diffusion of liquid Sn under microgravity was studied in the wide temperature range in the MSL (Material Science Laboratory)-1 mission to confirm the validity of microgravity for the study of diffusion in melts with high melting temperature and to investigate the temperature dependence of diffusion based on the exact diffusion data under microgravity. The self-diffusion coefficient was measured at temperature of 900, 1,191, 1,423 and 1,622 K by the use of the long capillary method. Carbon spring was used to apply the slight pressure to the liquid sample throughout the course of experiments to cope with the considerable volume change and to prevent the Marangoni convection in liquids. The graphite was selected as the material for a sample container because of its non-wetting property to liquid Sn with a wide contact angle. The enriched stable isotope Sn-124 was employed as the tracer and natural Sn of 5 N purity was employed as the counter part. The concentration profile of Sn-124 in the sample was analyzed by SIMS (Secondary Ion Mass Spectroscopy) analysis. The self-diffusion coefficient was determined as a function of temperature using the iteration method. A considerably good agreement between experiments and calculations was obtained. The temperature dependence of self-diffusion coefficient obtained by the long capillary method in MSL-1 mission was investigated. The temperature dependence was summarized by means of the power law of temperature, and 1.81 of the power index was obtained. The experimental data of self-diffusion coefficient did not show such an abrupt increase even in higher temperature range up to 1,622 K as that shown in ground experiment data for temperature over 1,100 K. The self-diffusion coefficient was calculated based on the hard sphere model adopting the packing fraction of 0.464. The power index of 1.77 for the temperature dependence was obtained from the equation.
Diffusion of liquid metals and alloys: The study of self-diffusion under microgravity in liquid Sn in the wide temperature range
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