| Ultrahard nanotwinned cubic boron nitride. | |
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MedLine Citation:
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PMID: 23325219 Owner: NLM Status: In-Process |
Abstract/OtherAbstract:
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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 size. 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 layers. 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 m(1/2), well beyond the toughness of commercial cemented tungsten carbide, ∼10 MPa m(1/2)). 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. |
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Authors:
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Yongjun Tian; Bo Xu; Dongli Yu; Yanming Ma; Yanbin Wang; Yingbing Jiang; Wentao Hu; Chengchun Tang; Yufei Gao; Kun Luo; Zhisheng Zhao; Li-Min Wang; Bin Wen; Julong He; Zhongyuan Liu |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Nature Volume: 493 ISSN: 1476-4687 ISO Abbreviation: Nature Publication Date: 2013 Jan |
Date Detail:
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Created Date: 2013-01-17 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0410462 Medline TA: Nature Country: England |
Other Details:
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Languages: eng Pagination: 385-8 Citation Subset: IM |
Affiliation:
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State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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