Nanoindentation and Raman spectroscopy studies of boron carbide single crystals

Domnich, Vladislav; Gogotsi, Yury; Trenary, Michael; Tanaka, Takaho

doi:10.1063/1.1521580

Cited by 158 publications

(143 citation statements)

References 15 publications

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“…The H and E values of n-B 4 C are comparable to those of microcrystalline B 4 C at similar loads [17][18][19][20] , but less than those of single-crystal B 4 C (ref. 21). The reduced hardness and elastic modulus can be attributed to the presence of nanoporosity and soft amorphous carbon at GBs in n-B 4 C. The fracture toughness of n-B 4 C was measured by nanoindentation according to the following equation 22 :…”

Section: Resultsmentioning

confidence: 99%

“…At low loading levels, the Raman bands extending from 350 to 1,200 cm − 1 are in good agreement with the unindented spectra, and the characteristic Raman bands are located at 481, 531, 732, 830, 1,004 and 1,086 cm − 1 . At the loading levels above 600 mN, intense Raman bands at 1,325 and 1,360 cm − 1 , followed with short peaks at 1,530 and 1,590 cm − 1 and 1,810 cm − 1 , can be observed 21,26 , indicating partial phase transition from crystalline to amorphous boron carbide (a-B 4 C) along with the presence of amorphous carbon.…”

Section: Mechanical Properties and Raman Spectroscopy Analysismentioning

confidence: 99%

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

et al. 2012

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Ceramics typically have very high hardness, but low toughness and plasticity. Besides intrinsic brittleness associated with rigid covalent or ionic bonds, porosity and interface phases are the foremost characteristics that lead to their failure at low stress levels in a brittle manner. Here we show that, in contrast to the conventional wisdom that these features are adverse factors in mechanical properties of ceramics, the compression strength, plasticity and toughness of nanocrystalline boron carbide can be noticeably improved by introducing nanoporosity and weak amorphous carbon at grain boundaries. Transmission electron microscopy reveals that the unusual nanosize effect arises from the deformation-induced elimination of nanoporosity mediated by grain boundary sliding with the assistance of the soft grain boundary phases. This study has important implications in developing high-performance ceramics with ultrahigh strength and enhanced plasticity and toughness.

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Section: Resultsmentioning

confidence: 99%

Section: Mechanical Properties and Raman Spectroscopy Analysismentioning

confidence: 99%

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

et al. 2012

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“…So far, most of experimental results show that boron carbides undergo a transition to amorphous phase at far lower pressure than the above. Gogotsi's group reports a phase transition of boron carbide to disordered or undefined phases by static indentation technique, and the estimated pressure is about 44-49 GPa [129,130]. Also, in their paper they cite a transition pressure of about 20 GPa measured by Manghnani.…”

Section: Gap Problemmentioning

confidence: 95%

Electronic structures and mechanical properties of boron and boron-rich crystals (Part I)

Shirai

2010

J. Superhard Mater.

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“…Chen et al reported the observation of shock-induced local amorphization bands that might be responsible for the low fracture toughness of B 4 C [6]. In addition, amorphization bands had been observed in nanoindentation and scratch experiments, where the loading rate is much lower than for dynamical shock loading [16][17][18][19]. Particularly, recent nanoindentation experiments revealed amorphous shear bands along the (0111) plane [19].…”

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Atomistic Explanation of Shear-Induced Amorphous Band Formation in Boron Carbide

2014

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Boron carbide (B 4 C) is very hard, but its applications are hindered by stress-induced amorphous band formation. To explain this behavior, we used density function theory (Perdew-Burke-Ernzerhof flavor) to examine the response to shear along 11 plausible slip systems. We found that the ð0111Þ=h1101i slip system has the lowest shear strength (consistent with previous experimental studies) and that this slip leads to a unique plastic deformation before failure in which a boron-carbon bond between neighboring icosahedral clusters breaks to form a carbon lone pair (Lewis base) on the C within the icosahedron. Further shear then leads this Lewis base C to form a new bond with the Lewis acidic B in the middle of a CBC chain. This then initiates destruction of this icosahedron. The result is the amorphous structure observed experimentally. We suggest how this insight could be used to strengthen B 4 C. DOI: 10.1103/PhysRevLett.113.095501 PACS numbers: 61.50.Ks, 62.20.M-, 64.70.-p, 82.40.Fp Boron carbide (B 4 C) exhibits such novel properties as high melting temperature, high thermal stability, high hardness, low density, and high abrasion resistance [1][2][3][4][5][6][7][8][9][10][11]. The combination of these properties makes it widely useful in refractory applications, as abrasive powders, in body armor, and as a neutron radiation absorbent [1][2][3][4]. However, the brittle failure under impact exhibited by B 4 C prevents the wide insertion of boron carbide into extended engineering applications. Although B 4 C has a high Hugoniot elastic limit (HEL) of 17-20 GPa, approximately twice that of normal ceramics, it fractures easily just above the HEL at high impact velocities and pressures [12][13][14][15]. Chen et al. reported the observation of shock-induced local amorphization bands that might be responsible for the low fracture toughness of B 4 C [6]. In addition, amorphization bands had been observed in nanoindentation and scratch experiments, where the loading rate is much lower than for dynamical shock loading [16][17][18][19]. Particularly, recent nanoindentation experiments revealed amorphous shear bands along the (0111) plane [19]. Indeed, the same amorphous shear band has been observed experimentally in boron suboxide (B 6 O) [20]. An attempt to understand this through Gibbs free-energy calculations based on density functional theory suggested that the ðB 12 ÞCCC structure provides a possible source of failure of boron carbide just above the HEL [7]. However, despite these extensive experimental and theoretical efforts, the atomistic mechanism underlying pressure-induced amorphization and phase transitions of boron carbide is still not known [3].Stressed materials normally dissipate the accumulating elastic energy through plastic deformation that is mediated by dislocation slip and deformation twinning in metallic systems. Unlike these general deformation mechanisms in conventional metallic materials, we find that boron carbide deforms by atomic scale amorphous band formation, a particular mode of deforma...

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Nanoindentation and Raman spectroscopy studies of boron carbide single crystals

Cited by 158 publications

References 15 publications

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

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

Electronic structures and mechanical properties of boron and boron-rich crystals (Part I)

Atomistic Explanation of Shear-Induced Amorphous Band Formation in Boron Carbide

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