Hardness and deformation microstructures of nano-polycrystalline diamonds synthesized from various carbons under high pressure and high temperature


Mechanical properties of high-purity nano-polycrystalline diamonds synthesized by direct conversion from graphite and various non-graphitic carbons under static high pressures and high temperatures were investigated by microindentation testing with a Knoop indenter and observation of microstructures around the indentations. Results of indentation hardness tests using a superhard synthetic diamond Knoop indenter showed that the polycrystalline diamond synthesized from graphite at ⩾15 GPa and 2300–2500 °C (consisting of fine grains 10–30 nm in size and layered crystals) has very high Knoop hardness (Hk ⩾ 110 GPa), whereas the hardness of polycrystalline diamonds synthesized from non-graphitic carbons at ⩾15 GPa and below 2000 °C (consisting only of single-nano grains 5–10 nm in size) are significantly lower (Hk = 70 to 90 GPa). Microstructure observations beneath the indentations of these nano-polycrystalline diamonds suggest that the existence of a lamellar structure and the bonding strength of the grain boundary play important roles in controlling the hardness of the polycrystalline diamond.

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  1. 1

    T. Irifune, A. Kurio, S. Sakamoto, T. Inoue H. Sumiya: Ultrahard polycrystalline diamond from graphite. Nature 421, 599 2003

    CAS  Article  Google Scholar 

  2. 2

    H. Sumiya, T. Irifune, A. Kurio, S. Sakamoto T. Inoue: Microstructure features of polycrystalline diamond synthesized directly from graphite under static high pressure. J. Mater. Sci. 39, 445 2004

    CAS  Article  Google Scholar 

  3. 3

    H. Sumiya T. Irifune: Indentation hardness of nano-polycrystalline diamond prepared from graphite by direct conversion. Diamond Relat. Mater. 13, 1771 2004

    CAS  Article  Google Scholar 

  4. 4

    S. Naka, K. Horii, Y. Takeda T. Hanawa: Direct conversion of graphite to diamond under static pressure. Nature 259, 38 1976

    CAS  Article  Google Scholar 

  5. 5

    A. Onodera, K. Higashi Y. Irie: Crystallization of amorphous carbon at high static pressure and high temperature. J. Mater. Sci. 23, 422 1988

    CAS  Article  Google Scholar 

  6. 6

    H. Yusa, K. Takemura, Y. Matsui, H. Morishima, K. Watanabe, H. Yamawaki K. Aoki: Direct transformation of graphite to cubic diamond observed in a laser-heated diamond anvil cell. Appl. Phys. Lett. 72, 1843 1998

    CAS  Article  Google Scholar 

  7. 7

    H. Yusa: Nanocrystalline diamond directly transformed from carbon nanotubes under high pressure. Diamond Relat. Mater. 11, 87 2002

    CAS  Article  Google Scholar 

  8. 8

    N. Dubrovinskaia, L. Dubrovinsky, F. Langenhorst, S. Jacobsen C. Liebske: Nanocrystalline diamond synthesized from C60. Diamond Relat. Mater. 14, 16 2005

    CAS  Article  Google Scholar 

  9. 9

    H. Sumiya, H. Yusa, T. Inoue, H. Ofuji T. Irifune: Conditions and mechanism of formation nano-polycrystalline diamonds directly from graphite and non-graphitic carbon at high-pressure and high-temperature. J. High Press. Res. 26, 63 2006

    CAS  Article  Google Scholar 

  10. 10

    N. Kawai S. Endo: The generation of ultra hydrostatic pressure by a split sphere apparatus. Rev. Sci. Instrum. 41, 1178 1970

    CAS  Article  Google Scholar 

  11. 11

    T. Irifune H. Sumiya: Nature of polycrystalline diamond synthesized by direct conversion of graphite using Kawai-type multianvil apparatus. New Diamond Frontier Carbon Technol. 14, 313 2004

    CAS  Google Scholar 

  12. 12

    H. Sumiya: Super-hard diamond indenter prepared from high-purity synthetic diamond crystal. Rev. Sci. Instrum. 76, 026112 2005

    Article  Google Scholar 

  13. 13

    H. Sumiya, N. Toda S. Satoh: Mechanical properties of synthetic type IIa diamond crystal. Diamond Relat. Mater. 6, 1841 1997

    CAS  Article  Google Scholar 

  14. 14

    H. Sumiya, K. Yamaguch S. Ogata: Deformation microstructure of high-quality synthetic diamond crystal subjected to Knoop indentation. Appl. Phys. Lett. 88, 161904 2006

    Article  Google Scholar 

  15. 15

    N. Dubrovinskaia, L. Dubrovinsky, W. Crichton, F. Langenhorst A. Richter: Aggregated diamond nanorods, the densest and least compressible form of carbon. Appl. Phys. Lett. 87, 083106 2005

    Article  Google Scholar 

  16. 16

    N. Dubrovinskaia, S. Dub L. Dubrovinsky: Super wear resistance of aggregated diamond nanorods. Nano Lett. 6, 824 2006

    CAS  Article  Google Scholar 

  17. 17

    S. Veprek: Nanostructured superhard materials in Handbook of Ceramic Hard Materials edited by R. Riedel, Wiley-VCH Vch Verlagsgesellschaft Mbh 2000 104

    Google Scholar 

  18. 18

    S. Yip: The strongest size. Nature 391, 532 1998

    CAS  Article  Google Scholar 

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The authors thank H. Yusa, T. Inoue, H. Ofuji, and K. Harano for their help with this study. This work was partially supported by a grant from the New Energy and Industrial Technology Development Organization, Japan (NEDO).

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Sumiya, H., Irifune, T. Hardness and deformation microstructures of nano-polycrystalline diamonds synthesized from various carbons under high pressure and high temperature. Journal of Materials Research 22, 2345–2351 (2007). https://doi.org/10.1557/jmr.2007.0295

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