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Superstrength through Nanotwinning

An, Qi and Goddard, William A., III and Xie, Kelvin Y. and Sim, Gi-Dong and Hemker, Kevin J. and Munhollon, Tyler and Toksoy, Muhammet Fatih and Haber, Richard A. (2016) Superstrength through Nanotwinning. Nano Letters, 16 (12). pp. 7573-7579. ISSN 1530-6984.

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The theoretical strength of a material is the minimum stress to deform or fracture the perfect single crystal material that has no defects. This theoretical strength is considered as an upper bound on the attainable strength for a real crystal. In contradiction to this expectation, we use quantum mechanics (QM) simulations to show that for the boron carbide (B4C) hard ceramic, this theoretical shear strength can be exceeded by 11% by imposing nano-scale twins. We also predict from QM that the indentation strength of nano-twinned B4C is 12% higher than that of the perfect crystal. Further we validate this effect experimentally, showing that nano-twinned samples are harder by 2.3% than the twin-free counterpart of B4C. The origin of this strengthening mechanism is suppression of twin boundary (TB) slip within the nano-twins due to the directional nature of covalent bonds at the TB.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
An, Qi0000-0003-4838-6232
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2016 American Chemical Society. Received 13 August 2016. Published online 7 November 2016. Q.A. and W.A.G. received support from the Defense Advanced Research Projects Agency (W31P4Q-13-1-0010, program manager, John Paschkewitz), the Army Research Laboratory (W911NF-12-2-0022), and the National Science Foundation (DMR-1436985). K.X and K.J.H. acknowledge support from the Army Research Laboratory (W911NF-12-2-0022). T.M., F.M.T and R.A.H acknowledge support from the Army Research Laboratory (W911NF-12-2-0022). We thank Tomoko Sano at ARL for providing us the twin-2 sample. The authors declare no competing financial interests.
Funding AgencyGrant Number
Defense Advanced Research Projects Agency (DARPA)W31P4Q-13-1-0010
Army Research LaboratoryW911NF-12-2-0022
Subject Keywords:Superhard ceramics, Hardness, DFT, Nanoindentation, Deformation mechanism
Issue or Number:12
Record Number:CaltechAUTHORS:20161109-103212104
Persistent URL:
Official Citation:Superstrength through Nanotwinning Qi An, William A. Goddard III, Kelvin Y. Xie, Gi-dong Sim, Kevin J. Hemker, Tyler Munhollon, M. Fatih Toksoy, and Richard A. Haber Nano Letters 2016 16 (12), 7573-7579 DOI: 10.1021/acs.nanolett.6b03414
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71877
Deposited By: Ruth Sustaita
Deposited On:09 Nov 2016 18:49
Last Modified:03 Oct 2019 16:12

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