Liquid forming amorphous alloy belongs to a simple atomic system. In recent years, there are many reports about the liquid-liquid phase transition of this system, but there are few studies on the glassy state of metal glaciers, the product of liquid-liquid phase transition. Some experiments think it is "ultra-stable", while others think it is nanocrystalline effect. Molecular dynamics simulation shows that silver liquid will transform into a new "G" phase after isothermal annealing near its glass transition temperature, which is amorphous in the radial distribution function. At the same time, there is an obvious "endothermic peak" in the "G" phase during the heating process. These are the characteristics of glassy state of glaciers.
Recently, under the guidance of Academician Wang Weihua, Bai Haiyang, and Sun Yonghao, a special researcher, Shen Jie, a Ph.D. student from the Institute of Physics of Chinese Academy of Sciences and the Key Laboratory of Extreme Condition Physics of Beijing National Research Center for Condensed Matter Physics, successfully prepared metallic glacier glass with La-Ce-based amorphous alloy as the precursor (figure 1 shows the icosahedral structure sequence of glacial facies). First, they prepared an amorphous alloy with the composition of La 32.5 Ce 32.5 Co 25 Al 10 (atomic percentage), and found that the sample had an obvious exothermic peak in differential thermal analysis (Figure 2a). Subsequently, they characterized the heating process in situ and found that the hardness and structure of the new sample changed obviously (Figure 2b-d), but the transformation product was still amorphous (Figure 3). By rapidly cooling the sample after the exothermic peak, they found that the sample had a new glass transition temperature. This proves that the new sample may be a potential metal glacier state. In this work, the research team studied the phase transformation path of La 32.5 Ce 32.5 Co 25 Al 10 amorphous alloy at a series of heating rates by using a flash differential scanning calorimeter (FDSC) (Figure 4), and found that when the heating rate reaches 400-2,000 K/s, an endothermic peak with a similar area will appear after the exothermic peak; The reversible transition from glassy state to initial glassy state can be achieved by adjusting the cooling after absorption/release peak, which excludes the nanocrystalline effect.
Structure, order parameters, thermodynamics and dynamics characterization of glassy state of metal glaciers
The discovery of glassy state of glacier strongly supports the view that liquid-liquid phase transition exists in amorphous alloys, which provides an ideal system for studying liquid-liquid phase transition of metallic liquids and an ideal carrier for subsequent research.
This work has been awarded by the Strategic Pilot Science and Technology Project of Chinese Academy of Sciences (XDB30000000), the State Key R&D Plan (20 18YFA0703603) and the National Natural Science Foundation (17902916/KLOC-0). 5 197 1239) and Guangdong Natural Science Foundation (20 19B03020 10).
Related research results were published in the journal Physical Chemistry Express and included as cover articles. Patent acceptance: 2020 10636902. X
Paper link:
https://doi . org/ 10. 102 1/ACS . jpclett . 0c 0 1789