Dislocation behaviors in nanotwinned diamond

See allHide authors and affiliations

Science Advances  21 Sep 2018:
Vol. 4, no. 9, eaat8195
DOI: 10.1126/sciadv.aat8195


Experimental results (Huang et al.) indicated that nanotwinned diamond (nt-diamond) has unprecedented hardness, whose physical mechanism has remained elusive. In this report, we categorize interaction modes between dislocations and twin planes in nt-diamond and calculate the associated reaction heat, activation energies, and barrier strength using molecular dynamics. On the basis of the Sachs model, twin thickness dependence of nt-diamond hardness is evaluated, which is in good agreement with the experimental data. We show that two factors contribute to the unusually high hardness of nt-diamond: high lattice frictional stress by the nature of carbon bonding in diamond and high athermal stress due to the Hall-Petch effect. Both factors stem from the low activation volumes and high activation energy for dislocation nucleation and propagation in diamond twin planes. This work provides new insights into hardening mechanisms in nt-diamond and will be helpful for developing new superhard materials in the future.

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

View Full Text

Stay Connected to Science Advances