Enhanced mechanical properties of nanocrystalline boron carbide by nanoporosity and interface phases

Reddy, Kolan Madhav; Guo, Junjie; Shinoda, Yutaka; Fujita, Takeshi; Hirata, Akihiko; Singh, Jogender; McCauley, James W.; Chen, M.W.

doi:10.1038/ncomms2047

Cited by 137 publications

(45 citation statements)

References 34 publications

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“…However, for grain sizes below some critical value, the dominant deformation mechanism becomes GBs sliding and migration so that the material strength decreases for further decreases in grain size 5 6 . These grain size effects have been studied extensively in metals but not in bulk nanocrystalline ceramics 7 8 . Dislocation migration so important in metals is absent in most ceramics, especially at low temperature, so that we can expect quite different roles of GBs and TBs in the deformation mechanisms of ceramics as compared with metals and alloys.…”

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confidence: 99%

Nucleation of amorphous shear bands at nanotwins in boron suboxide

Reddy

Qian

et al. 2016

Nat Commun

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The roles of grain boundaries and twin boundaries in mechanical properties are well understood for metals and alloys. However, for covalent solids, their roles in deformation response to applied stress are not established. Here we characterize the nanotwins in boron suboxide (B6O) with twin boundaries along the planes using both scanning transmission electron microscopy and quantum mechanics. Then, we use quantum mechanics to determine the deformation mechanism for perfect and twinned B6O crystals for both pure shear and biaxial shear deformations. Quantum mechanics suggests that amorphous bands nucleate preferentially at the twin boundaries in B6O because the twinned structure has a lower maximum shear strength by 7.5% compared with perfect structure. These results, which are supported by experimental observations of the coordinated existence of nanotwins and amorphous shear bands in B6O, provide a plausible atomistic explanation for the influence of nanotwins on the deformation behaviour of superhard ceramics.

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confidence: 99%

Nucleation of amorphous shear bands at nanotwins in boron suboxide

Reddy

Qian

et al. 2016

Nat Commun

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“…Although sintering is a common processing method for manufacturing bulk polycrystalline materials, it can often require long time-at-temperature cycles that pose problems for structural stability, for example, grain growth. In fact, although powder processing and sintering have long been studied as a route to achieve bulk nanocrystalline materials 1 2 3 4 5 6 7 8 , it is a challenge to use enough of a thermal cycle to remove all the porosity without also seeing large changes in grain size. So-called ‘accelerated' sintering techniques, such as activated sintering 9 10 11 or liquid phase sintering 12 13 , have been used for decades to lower the sintering temperature and reduce the cycle time for sintering, but these methods do not apply to the synthesis of nanocrystalline materials.…”

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Accelerated sintering in phase-separating nanostructured alloys

Park

Schuh

2015

Nat Commun

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Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W–Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs.

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“…Due to its low density (2.52 g cm −3 ) and fantastic crack resistance on ballistic performance [1,8], B 4 C has a military application as bulletproof armor. Also the outstanding properties such as high hardness [1,[9][10][11], extreme abrasion resistance [1], high melting point (2450°C) and thermal stability [12] make B 4 C play an important role in mechanical processing industry as wear-resistant and cutting tool material.…”

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confidence: 99%

Exploring configurations and properties of boron carbide by first principle

Liu

Kumar

et al. 2020

Mater. Res. Express

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Based on the first principle, the formation energy, phonon vibration, physical property of three common B 4 C models were extensively study. Through the calculation of thermodynamic formation energy, it is confirmed po model has the most stable energy configuration. Combined the simulated x-ray and experimental data, it is found that the experimental boron carbide is actually composed of a variety of configurations, the majority of which is po model. Via the analysis of phonon vibration, the highest phonon frequencies of the different configurations were identified as the result of stretching vibrations from the triatomic chain. The research of electrical properties of three B 4 C models clarify B 4 C is a semiconductor but will transform to conductor at specific high pressure. The calculation of the mechanical property states that B 4 C is hard material while the hardness will gradually decrease with pressure increases. Both the relationship of their electrical properties and mechanical properties with pressure illustrate that the po model has the fastest structural change and ch model has the slowest change.

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Enhanced mechanical properties of nanocrystalline boron carbide by nanoporosity and interface phases

Cited by 137 publications

References 34 publications

Nucleation of amorphous shear bands at nanotwins in boron suboxide

Nucleation of amorphous shear bands at nanotwins in boron suboxide

Accelerated sintering in phase-separating nanostructured alloys

Exploring configurations and properties of boron carbide by first principle

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