Matter and Radiation at Extremes, Volume. 6, Issue 3, 038402(2021)

Structural transitions of 4:1 methanol–ethanol mixture and silicone oil under high pressure

Xiehang Chen1, Hongbo Lou1, Zhidan Zeng1, Benyuan Cheng1,2, Xin Zhang1, Ye Liu1, Dazhe Xu1, Ke Yang3, and Qiaoshi Zeng1,4、a)
Author Affiliations
  • 1Center for High Pressure Science and Technology Advanced Research, Pudong, Shanghai 201203, People’s Republic of China
  • 2Shanghai Institute of Laser Plasma, Shanghai 201800, People’s Republic of China
  • 3Shanghai Synchrotron Radiation Facility, Shanghai 201800, People’s Republic of China
  • 4Jiangsu Key Laboratory of Advanced Metallic Materials, School of Materials Science and Engineering, Southeast University, Nanjing 211189, People’s Republic of China
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    A 4:1 (volume ratio) methanol–ethanol (ME) mixture and silicone oil are two of the most widely used liquid pressure-transmitting media (PTM) in high-pressure studies. Their hydrostatic limits have been extensively studied using various methods; however, the evolution of the atomic structures associated with their emerging nonhydrostaticity remains unclear. Here, we monitor their structures as functions of pressure up to ~30 GPa at room temperature using in situ high-pressure synchrotron x-ray diffraction (XRD), optical micro-Raman spectroscopy, and ruby fluorescence spectroscopy in a diamond anvil cell. No crystallization is observed for either PTM. The pressure dependence of the principal diffraction peak position and width indicates the existence of a glass transition in the 4:1 ME mixture at ~12 GPa and in the silicone oil at ~3 GPa, beyond which a pressure gradient emerges and grows quickly with pressure. There may be another liquid-to-liquid transition in the 4:1 ME mixture at ~5 GPa and two more glass-to-glass transitions in the silicone oil at ~10 GPa and ~16 GPa. By contrast, Raman signals only show peak weakening and broadening for typical structural disordering, and Raman spectroscopy seems to be less sensitive than XRD in catching these structural transitions related to hydrostaticity variations in both PTM. These results uncover rich pressure-induced transitions in the two PTM and clarify their effects on hydrostaticity with direct structural evidence. The high-pressure XRD and Raman data on the two PTM obtained in this work could also be helpful in distinguishing between signals from samples and those from PTM in future high-pressure experiments.

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    Xiehang Chen, Hongbo Lou, Zhidan Zeng, Benyuan Cheng, Xin Zhang, Ye Liu, Dazhe Xu, Ke Yang, Qiaoshi Zeng. Structural transitions of 4:1 methanol–ethanol mixture and silicone oil under high pressure[J]. Matter and Radiation at Extremes, 2021, 6(3): 038402

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    Paper Information

    Category: High Pressure Physics and Materials Science

    Received: Jan. 20, 2021

    Accepted: Mar. 24, 2021

    Published Online: May. 21, 2021

    The Author Email: Zeng Qiaoshi (zengqs@hpstar.ac.cn)

    DOI:10.1063/5.0044893

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