中国物理B ›› 2003, Vol. 12 ›› Issue (3): 315-321.doi: 10.1088/1009-1963/12/3/312

• CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES • 上一篇    下一篇

Surface behaviour and undercooling in the liquid Ga-Bi binary system detected by optical second harmonic generation

王聪, 王天民   

  1. Centre of Material Physics and Chemistry, School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
  • 收稿日期:2002-05-27 修回日期:2002-12-19 出版日期:2005-03-16 发布日期:2005-03-16
  • 基金资助:
    Project supported by the Alexander von Humboldt (AvH) foundation, Germany.

Surface behaviour and undercooling in the liquid Ga-Bi binary system detected by optical second harmonic generation

Wang Cong (王聪), Wang Tian-Min (王天民)   

  1. Centre of Material Physics and Chemistry, School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
  • Received:2002-05-27 Revised:2002-12-19 Online:2005-03-16 Published:2005-03-16
  • Supported by:
    Project supported by the Alexander von Humboldt (AvH) foundation, Germany.

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摘要： We employ an optical second harmonic generation(SHG) technique to investigate the surface behaviours at the liquid(solid)/vapour interface of the Ga-Bi binary metallic system. In a heating and cooling cycle between 280℃ and room temperature, there is no change of the SH-intensity in the heating process, whereas there exists an abrupt and abnormal change of the SH-intensity in the cooling process. It is interesting to find that a macroscopic Bi-rich solid layer is floating on the surface of the Ga-rich liquid phase just below the monotectic temperature (222℃±2℃) in the cooling process, in spite of the Bi-rich phase being heavier than the Ga-rich phase. On the other hand, different undercooling behaviours are observed at the surface and in the bulk. The behaviours of surface solidification and surface melting are different from those in the bulk.

Abstract: We employ an optical second harmonic generation(SHG) technique to investigate the surface behaviours at the liquid(solid)/vapour interface of the Ga-Bi binary metallic system. In a heating and cooling cycle between 280℃ and room temperature, there is no change of the SH-intensity in the heating process, whereas there exists an abrupt and abnormal change of the SH-intensity in the cooling process. It is interesting to find that a macroscopic Bi-rich solid layer is floating on the surface of the Ga-rich liquid phase just below the monotectic temperature (222℃±2℃) in the cooling process, in spite of the Bi-rich phase being heavier than the Ga-rich phase. On the other hand, different undercooling behaviours are observed at the surface and in the bulk. The behaviours of surface solidification and surface melting are different from those in the bulk.

Key words: surface phase transition, second harmonic generation liquid(solid)/vapour interface, Ga-Bi binary alloy, undercooling

中图分类号:  (Frequency conversion; harmonic generation, including higher-order harmonic generation)

  • 42.65.Ky
68.35.Rh (Phase transitions and critical phenomena)