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Locating Si atoms in Si-Doped Boron Carbide: a Route to Understand Amorphization Mitigation Mechanism

Khan, Atta U. and Etzold, Anthony M. and Yang, Xiaokun and Domnich, Vladislav and Xie, Kelvin Y. and Hwang, Chawon and Behler, Kristopher D. and Chen, Mingwei and An, Qi and Lasalvia, Jerry and Hemker, Kevin J. and Goddard, William A., III and Haber, Richard A. (2018) Locating Si atoms in Si-Doped Boron Carbide: a Route to Understand Amorphization Mitigation Mechanism. Acta Materialia, 157 . pp. 106-113. ISSN 1359-6454. https://resolver.caltech.edu/CaltechAUTHORS:20180711-164757330

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Abstract

The well-documented formation of amorphous bands in boron carbide (B4C) under contact loading has been identified in the literature as one of the possible mechanisms for its catastrophic failure. To mitigate amorphization, Si-doping was suggested by an earlier computational work, which was further substantiated by an experimental study. However, there have been discrepancies between theoretical and experimental studies, about Si replacing atom/s in B_(12) icosahedra or the C-B-C chain. Dense single phase Si-doped boron carbide was produced through a conventional scalable route. A powder mixture of SiB_6, B_4C, and amorphous boron was reactively sintered, yielding a dense single phase Si-doped boron carbide material. A combined analysis of Rietveld refinement on XRD pattern coupled with electron density difference Fourier maps and DFT simulations were performed in order to investigate the location of Si atoms in the boron carbide lattice. Si atoms occupy an interstitial position, between the icosahedra and the chain. These Si atoms are bonded to the chain end C atoms, which result in a kinked chain. Additionally, these Si atoms are also bonded to the neighboring equatorial B atom of the icosahedra, which is already bonded to the C atom of the chain, forming a bridge like structure. Owing to this bonding, Si is anticipated to stabilize the icosahedra through electron donation, which is expected to help in mitigating stress-induced amorphization. Possible supercell structures are suggested along with the most plausible structure for Si-doped boron carbide.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.actamat.2018.07.021DOIArticle
ORCID:
AuthorORCID
An, Qi0000-0003-4838-6232
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2018 Acta Materialia Inc. Published by Elsevier. Received 15 March 2018, Revised 6 June 2018, Accepted 7 July 2018, Available online 11 July 2018. This research was sponsored by the Army Research Laboratory under Cooperative Agreement No. W911NF-12-2-0022, the Defense Advanced Research Projects Agency under Grant No. W31P4Q-13-1-0001, and the National Science Foundation I/UCRC Directorate under Award No. 1540027 and NSF-DMREF-DMR-1436985.
Funders:
Funding AgencyGrant Number
Army Research LaboratoryW911NF-12-2-0022
Defense Advanced Research Projects Agency (DARPA)W31P4Q-13-1-0001
NSFIIP-1540027
NSFDMR-1436985
Subject Keywords:Crystal structure; Ceramics; Si-doped boron carbide; Density Functional Theory simulations; Scanning Transmission Electron Microscopy
Other Numbering System:
Other Numbering System NameOther Numbering System ID
WAG1297
Record Number:CaltechAUTHORS:20180711-164757330
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180711-164757330
Official Citation:Atta U. Khan, Anthony M. Etzold, Xiaokun Yang, Vladislav Domnich, Kelvin Y. Xie, Chawon Hwang, Kristopher D. Behler, Mingwei Chen, Qi An, Jerry C. LaSalvia, Kevin J. Hemker, William A. Goddard, Richard A. Haber, Locating Si atoms in Si-doped boron carbide: A route to understand amorphization mitigation mechanism, Acta Materialia, Volume 157, 2018, Pages 106-113, ISSN 1359-6454, https://doi.org/10.1016/j.actamat.2018.07.021. (http://www.sciencedirect.com/science/article/pii/S1359645418305494)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87788
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:12 Jul 2018 14:43
Last Modified:03 Oct 2019 19:59

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