期刊
SCIENTIFIC REPORTS
卷 4, 期 -, 页码 -出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/srep05063
关键词
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资金
- National Natural Science Foundation of China [51072213, 11234012, 51121064]
- State Oceanic Administration [SHME2013JS01]
- Local Colleges Faculty Construction [11160501000]
- Basic Research Field for Science and Technology Commission of Shanghai Municipality [11JC1404700, 13JC1402900, 14XD1424300]
- US Department of Energy [DE-FC26-04NT42278]
- GM
- National Science Foundation [1235535]
- Kyocera Corporation
- Directorate For Engineering
- Div Of Civil, Mechanical, & Manufact Inn [1235535] Funding Source: National Science Foundation
The quest of novel compounds with special structures and unusual functionalities continues to be a central challenge to modern materials science. Even though their exact structures have puzzled scientists for decades, superhard transition-metal borides (TMBs) have long been believed to exist only in simple crystal structures. Here, we report on a polytypic phenomenon in superhard WB3 and MoB3 with a series of energetically degenerate structures due to the random stacking of metal layers amongst the interlocking boron layers. Such polytypism can create a multiphase solid-solution compound with a large number of interfaces amongst different polytypes, and these interfaces will strongly hinder the interlayer sliding movement within each polytype, thereby further increase the hardness of this particular material. Furthermore, in contrast to the conventional knowledge that intrinsically strong chemical bonds in superhard materials should lead to high lattice thermal conductivity, the polytypic TMB3 manifest anomalously low lattice thermal conductivity due to structural disorders and phonon folding. These findings promise to open a new avenue to searching for novel superhard materials with additional functionalities.
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