Microstructures of undercooled Germanium droplets |
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| Affiliation: | 1. School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China;2. National-Local Joint Research Center of Non-ferrous Metal Materials and Processing Technology, Hefei 230009, China;1. School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907-2017, USA;2. Tokai Works, Nuclear Fuel Industries Ltd., 3135-41 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1196, Japan;1. Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan;2. International Exchange Center, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan;3. Department of Oral Health Care Sciences, Clinical Oral Science of Tokyo Medical and Dental University, 5-45 Yushima 1-chome, Bunkyo-ku, Tokyo 113-8549, Japan |
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| Abstract: | Small liquid Ge droplets (0.3–0.5 mm diameter) have been undercooled 150–415 ± 20°C below Tm in B2O3 flux before solidifying to the diamond cubic phase. A correlation was found between initial undercooling and final grain size. Droplets undercooled <300°C exhibited a coarse grain structure. At greater undercoolings, the grain size became progressively finer. This correlation may be subsidiary to the dependence of grain size on interfacial undercooling. Ge droplets lightly doped with Sn solidified dendritically for undercoolings greater than 250°C. Twinned dendrites have been observed at small undercoolings (~ 10°C) in other experiments. It appears that larger interfacial undercoolings are necessary to grow the twin-free dendrites which we have observed. The correlation between grain size and the presence of dendrites suggests that the grain refinement observed in Ge samples undercooled > 300°C stems from dendritic break-up during solidification. |
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