Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Ultrahard nanotwinned cubic boron nitride


Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall–Petch effect—the tendency for hardness to increase with decreasing grain size1,2. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers3. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as 14 nm (refs 1, 2, 4, 5). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness 3.8 nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100 GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (1,294 °C) and a large fracture toughness (>12 MPa m1/2, well beyond the toughness of commercial cemented tungsten carbide, 10 MPa m1/2). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall–Petch effect below a critical grain size or the twin thickness of 10–15 nm found in metals and alloys.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Starting oBN nanoparticles and nt-cBN bulk synthesized at 15 GPa and 1,800 °C.
Figure 2: Microstructure of synthetic nt-cBN.
Figure 3: The HV of an nt-cBN bulk sample as a function of applied load ( F).
Figure 4: HV as a function of average grain size ( d ) or twin thickness ( λ ) for polycrystalline cBN bulk materials.

Similar content being viewed by others


  1. Dubrovinskaia, N. et al. Superhard nanocomposite of dense polymorphs of boron nitride: noncarbon material has reached diamond hardness. Appl. Phys. Lett. 90, 101912 (2007)

    Article  ADS  Google Scholar 

  2. Solozhenko, V. L., Kurakevych, O. O. & Le Godec, Y. Creation of nanostuctures by extreme conditions: high-pressure synthesis of ultrahard nanocrystalline cubic boron nitride. Adv. Mater. 24, 1540–1544 (2012)

    Article  CAS  Google Scholar 

  3. Britun, V. F. & Kurdyumov, A. V. Mechanisms of martensitic transformations in boron nitride and conditions of their development. High Press. Res. 17, 101–111 (2000)

    Article  ADS  Google Scholar 

  4. Sumiya, H., Uesaka, S. & Satoh, S. Mechanical properties of high purity polycrystalline cBN synthesized by direct conversion sintering method. J. Mater. Sci. 35, 1181–1186 (2000)

    Article  ADS  CAS  Google Scholar 

  5. Dub, S. N. & Petrusha, I. A. Mechanical properties of polycrystalline cBN obtained from pyrolytic gBN by direct transformation technique. High Press. Res. 26, 71–77 (2006)

    Article  ADS  CAS  Google Scholar 

  6. Wentorf, R. H., DeVries, R. C. & Bundy, F. P. Sintered superhard materials. Science 208, 873–880 (1980)

    Article  ADS  CAS  Google Scholar 

  7. Liew, W. Y. H., Yuan, S. & Ngoi, B. K. A. Evaluation of machining performance of STAVAX with PCBN tools. Int. J. Adv. Manuf. Technol. 23, 11–19 (2004)

    Article  Google Scholar 

  8. Krauss, A. R. et al. Ultrananocrystalline diamond thin films for MEMS and moving mechanical assembly devices. Diamond Related Materials 10, 1952–1961 (2001)

    Article  ADS  CAS  Google Scholar 

  9. Hall, E. O. The deformation and ageing of mild steel: III. Discussion of results. Proc. Phys. Soc. B 64, 747–753 (1951)

    Article  ADS  Google Scholar 

  10. Petch, N. J. The cleavage strength of polycrystals. J. Iron Steel Inst. 174, 25–28 (1953)

    CAS  Google Scholar 

  11. Irifune, T., Kurio, A., Sakamoto, S., Inoue, T. & Sumiya, H. Ultrahard polycrystalline diamond from graphite. Nature 421, 599–600 (2003)

    Article  ADS  CAS  Google Scholar 

  12. Sumiya, H. & Irifune, T. Hardness and deformation microstructures of nano-polycrystalline diamonds synthesized from various carbons under high pressure and high temperature. J. Mater. Res. 22, 2345–2351 (2007)

    Article  ADS  CAS  Google Scholar 

  13. Schiøtz, J., Di Tolla, F. D. & Jacobsen, K. W. Softening of nanocrystalline metals at very small grain sizes. Nature 391, 561–563 (1998)

    Article  ADS  Google Scholar 

  14. Schiøtz, J. & Jacobsen, K. W. A maximum in the strength of nanocrystalline copper. Science 301, 1357–1359 (2003)

    Article  ADS  Google Scholar 

  15. Lu, L., Chen, X., Huang, X. & Lu, K. Revealing the maximum strength in nanotwinned copper. Science 323, 607–610 (2009)

    Article  ADS  CAS  Google Scholar 

  16. Pande, C. S. & Cooper, K. P. Nanomechanics of Hall–Petch relationship in nanocrystalline materials. Prog. Mater. Sci. 54, 689–706 (2009)

    Article  CAS  Google Scholar 

  17. He, L. L., Akaishi, M. & Horiuchi, S. Structural evolution in boron nitrides during the hexagonal–cubic phase transition under high pressure at high temperature. Microsc. Res. Tech. 40, 243–250 (1998)

    Article  CAS  Google Scholar 

  18. Oku, T., Hiraga, K., Matsuda, T., Hirai, T. & Hirabayashi, M. Twin structures of rhombohedral and cubic boron nitride prepared by chemical vapor deposition method. Diamond Related Materials 12, 1138–1145 (2003)

    Article  ADS  CAS  Google Scholar 

  19. Brazhkin, V. et al. What does ‘harder than diamond’ mean? Nature Mater. 3, 576–577 (2004)

    Article  ADS  CAS  Google Scholar 

  20. Tian, Y., Xu, B. & Zhao, Z. Microscopic theory of hardness and design of novel superhard crystals. Int. J. Refract. Met. Hard Mater. 33, 93–106 (2012)

    Article  CAS  Google Scholar 

  21. Harris, T. K., Brookes, E. J. & Taylor, C. J. The effect of temperature on the hardness of polycrystalline cubic boron nitride cutting tool materials. Int. J. Refract. Met. Hard Mater. 22, 105–110 (2004)

    Article  CAS  Google Scholar 

  22. Solozhenko, V. L., Dub, S. N. & Novikov, N. V. Mechanical properties of cubic BC2N, a new superhard phase. Diamond Related Materials 10, 2228–2231 (2001)

    Article  ADS  CAS  Google Scholar 

  23. Berger, C., Scheerer, H. & Ellermeier, J. Modern materials for forming and cutting tools—overview. Materialwiss. Werkstofftech. 41, 5–17 (2010)

    Article  CAS  Google Scholar 

  24. Tse, J. S., Klug, D. D. & Gao, F. M. Hardness of nanocrystalline diamonds. Phys. Rev. B 73, 140102 (2006)

    Article  ADS  Google Scholar 

  25. Gao, F. M. et al. Hardness of covalent crystals. Phys. Rev. Lett. 91, 015502 (2003)

    Article  ADS  Google Scholar 

  26. Li, X., Wei, Y., Lu, L., Lu, K. & Gao, H. Dislocation nucleation governed softening and maximum strength in nano-twinned metals. Nature 464, 877–880 (2010)

    Article  ADS  CAS  Google Scholar 

  27. Oleinik, G. S., Petrusha, I. A., Danilenko, N. V., Kotko, A. V. & Shevchenko, S. A. Crystal-oriented mechanism of dynamic recrystallization nucleation in cubic boron nitride. Diamond Related Materials 7, 1684–1692 (1998)

    Article  ADS  CAS  Google Scholar 

  28. Tang, C. C., Bando, Y., Huang, Y., Zhi, C. Y. & Golberg, D. Synthetic routes and formation mechanisms of spherical boron nitride nanoparticles. Adv. Funct. Mater. 18, 3653–3661 (2008)

    Article  CAS  Google Scholar 

  29. Wang, Y. et al. The large-volume high-pressure facility at GSECARS: a ‘Swiss-army-knife’ approach to synchrotron-based experimental studies. Phys. Earth Planet. Inter. 174, 270–281 (2009)

    Article  ADS  CAS  Google Scholar 

  30. Leinenweber, K. D. et al. Cell assemblies for reproducible multi-anvil experiments (the COMPRES assemblies). Am. Mineral. 97, 353–368 (2012)

    Article  ADS  CAS  Google Scholar 

Download references


We thank J. K. Yu for help with the differential scanning calorimetry measurements. Y.J.T. and Z.Y.L. acknowledge financial support from the Ministry of Science and Technology of China (grants 2011CB808205 and 2010CB731605), Y.J.T., D.L.Y., Y.M.M. and J.L.H. are grateful for financial support from the National Natural Science Foundation of China (grants 51121061, 51172197, 11025418 and 91022029), and Y.B.W. acknowledges financial support from the US National Science Foundation (EAR-0968456).

Author information

Authors and Affiliations



Y.J.T. conceived the project. Y.J.T., B.X., D.L.Y. and Y.B.W. designed the experiments. C.C.T. synthesized oBN precursors, Y.J.T., B.X., D.L.Y., Y.B.W., Y.F.G., K.L. and Z.S.Z. performed the HPHT experiments, Y.B.J. and W.T.H. performed TEM observations, and B.W. performed molecular dynamics simulations. Y.J.T., B.X., D.L.Y., Y.M.M., Y.B.W., L.-M.W., J.L.H. and Z.Y.L. analysed the data. Y.J.T., B.X., Y.M.M. and Y.B.W. co-wrote the paper. Y.J.T., B.X. and D.L.Y. contributed equally to the study. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Yongjun Tian.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-4, Supplementary Table 1 and additional references. (PDF 615 kb)

PowerPoint slides

Rights and permissions

Reprints and permissions

About this article

Cite this article

Tian, Y., Xu, B., Yu, D. et al. Ultrahard nanotwinned cubic boron nitride. Nature 493, 385–388 (2013).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing