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摘要: 本文研究了常压下液态Bi在落管所提供的高清洁、无容器环境中自由下落和在氦气保护下经循环过热处理后的过冷行为。通过控制液滴的尺寸和冷却速率得到了较大的过冷度。过冷样品具有与常压稳定相Bi-Ⅰ（三角点阵）完全不同的单斜点阵。其点阵参数为a=0.696 8 nm，b=0.628 6 nm，c=0.339 7 nm, =110.33；单胞体积为0.148 8 nm3，它与Brugger等人在2.6 GPa下得到的Bi-Ⅱ高压相（单斜点阵）的单胞体积相比，后者有一个9.34%的体积压缩，这与Bridgman的结果符合得很好。Abstract: This paper studied the undercooling of liquid bismuth and the formation possibility of bismuth-Ⅱ phase at normal pressure by using a high clean and containerless environment provided by a five meters long drop-tube and an alternate approach to heat and cool the molten bismuth in helium atmosphere. The two methods have allowed the ability of undercooling for liquid bismuth to be extended through controlling of the droplet size and cooling rate. The result of X-ray diffraction indicated that the undercooling samples have a monoclinic lattice with the lattice parameters a=0.696 8 nm, b=0.628 6 nm, c=0.339 7 nm and =110.33. To make a comparison between the volume of unite cell and that of the bismuth-Ⅱ (monoclinic lattice) obtained by Brugger at 2.6 GPa, the latter has a compression of 9.34% relative to the former, the result is in good agreement with Bridgman's.
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Key words:
- undercooling /
- containerless /
- nucleation centre /
- high pressure phase
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Brugger R M, et al. Physics Letters, 1967, 24A: 714. Bridgman P W. Proc Am Acad Arts Sci, 1942, 74: 425. Ostwald W. Z Phys Chem, 1897, 22: 289. WADC Technical Report, 59-747, 1960: 37. Jamieson J C, et al. Rev Sci Instru, 1959, 30: 1016. Perepezko J H. Rapid Solidification Processing Principles and Technologies Ⅱ. Edited by M Cohen, B H Kear, R Mehrabian, 1980: 56. Johnson J N, Hayes D B, Asay J R. J Phys Chem Solids, 1974, 35: 501. Klement W, et al. Phys Rev, 1963, 131: 632. -
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