Session V25: High Pressure: Experiment

8:00 AM–11:00 AM, Thursday, March 1, 2012
Room: 257A

Sponsoring Units: DCOMP DCMP
Chair: Anatoly Belonoshko, Royal Institute of Technology

Abstract ID: BAPS.2012.MAR.V25.6

Abstract: V25.00006 : Amorphous diamond -- A high-pressure superhard carbon allotrope

9:00 AM–9:12 AM

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Authors:

  Yu Lin
    (Geological and Environmental Sciences, Stanford University)

  Li Zhang
    (Geophysical Laboratory, Carnegie Institution of Washington)

  Ho-kwang Mao
    (Geophysical Laboratory, Carnegie Institution of Washington)

  Paul Chow
    (High Pressure Collaborative Access Team, Geophysical Laboratory)

  Yuming Xiao
    (High Pressure Collaborative Access Team, Geophysical Laboratory)

  Maria Baldini
    (High Pressure Synergetic Consortium, Geophysical Laboratory)

  Jinfu Shu
    (Geophysical Laboratory, Carnegie Institution of Washington)

  Wendy Mao
    (Geological and Environmental Sciences, Stanford University)

Compressing glassy carbon above 40 GPa, we have observed a new carbon allotrope with a fully \textit{sp}$^{3}$-bonded amorphous structure and diamond-like strength. Synchrotron x-ray Raman spectroscopy revealed a continuous pressure-induced \textit{sp}$^{2}$-to-\textit{sp}$^{3}$ bonding change, while x-ray diffraction confirmed the perseverance of non-crystallinity. The transition was reversible upon releasing pressure. Used as an indenter, the glassy carbon ball demonstrated exceptional strength by reaching 130 GPa with a confining pressure of 60 GPa. Such an extremely large stress difference of $>$70 GPa has never been observed in any material besides diamond, indicating the high hardness of this high-pressure carbon allotrope. The nanoscale transmission x-ray microscopy is being utilized for accurate pressure-volume determination of glassy carbon and its high-pressure phase.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.V25.6