Nanotwinning and amorphization of boron suboxide

Kunka, Cody; An, Qi; Rudawski, Nicholas G.; Subhash, Ghatu; Zheng, James; Halls, Virginia; Singh, Jogender

doi:10.1016/j.actamat.2018.01.048

Cited by 24 publications

(16 citation statements)

References 53 publications

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“…Shear modulus of the B 6 O crystal is projected to be 227 GPa, agreeing with the available results of 207‐218 GPa in the literature. For the amorphous state the modulus is computed to be 86 GPa.…”

Section: Resultssupporting

confidence: 87%

“…Form these three equations, the Vickers hardness is projected to be about 34 GPa (Teter), 43 GPa (Chen), and 41 GPa (Tian) for the crystal structure, comparable with the experimental predictions of 38‐45 GPa . For the amorphous phase, on the other hand, we compute the Vickers hardness to be 13 GPa (Teter), 18 GPa (Chen) and 17 GPa (Tian).…”

Section: Resultssupporting

confidence: 62%

“…In a high‐pressure study, during pressure release, the B 6 O crystal was found to transform to an amorphous state consisting of the amorphous boron trioxide (a‐B 2 O 3 ) and glassy boron (a‐B). Additionally during the nanoindentation process, a shear‐induced local amorphization of B 6 O was perceived in the experimental study and it was inspected in an ab initio simulation …”

Section: Introductionmentioning

confidence: 99%

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Amorphous boron suboxide

Durandurdu

2019

J Am Ceram Soc

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We study the atomic structure and the electronic and mechanical properties of amorphous boron suboxide (B 6 O) using an ab initio molecular dynamic technique. The amorphous network is attained from the rapid solidification of the melt and found to consist of boron and oxygen-rich regions. In the boron-rich regions, boron atoms form mostly perfect or imperfect pentagonal pyramid-like configurations that normally yield the construction of ideal and incomplete B 12 molecules in the model. In addition to the B 12 molecules, we also observe the development of a pentagonal bipyramid (B 7 ) molecule in the noncrystalline structure. In the oxygen-rich regions, on the other hand, boron and oxygen atoms form threefold and twofold coordinated motifs, respectively. The boron-rich and oxygen-rich regions indeed represent structurally the characteristic of amorphous boron and boron trioxide (B 2 O 3 ). The amorphous phase possesses a small band gap energy with respect to the crystal. On the bases of the localization of the tail states, we suggest that the p-type doping might be more convenient than the n-type doping in amorphous B 6 O. Bulk modulus and Vickers hardness of the noncrystalline configuration is estimated are be 106 and 13-18 GPa, respectively, which are noticeably less than those of the crystalline structure. Such a noticeable decrease in the mechanical properties is attributed to the presence of open structured B 2 O 3 glassy domains in the amorphous model. K E Y W O R D Samorphous, boron suboxide, hardness

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Section: Resultssupporting

confidence: 87%

Section: Resultssupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

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Amorphous boron suboxide

Durandurdu

2019

J Am Ceram Soc

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“…Crystal reorientation was observed in all quasi-plastic zones compared to the corresponding pristine zones (Fig. 4, A and B), which can be attributed to the amorphous shear bands and microcracks (4,23,29). Orientation maps viewed in all three principal directions can be found in fig.…”

Section: Resultsmentioning

confidence: 87%

Tuning the deformation mechanisms of boron carbide via silicon doping

Xiang

Yang

et al. 2019

Sci. Adv.

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Boron carbide suffers from a loss of strength and toughness when subjected to high shear stresses due to amorphization. Here, we report that a small amount of Si doping (~1 atomic %) leads to a substantial decrease in stress-induced amorphization due to a noticeable change of the deformation mechanisms in boron carbide. In the undoped boron carbide, the Berkovich indentation–induced quasi-plasticity is dominated by amorphization and microcracking along the amorphous shear bands. This mechanism resulted in long, distinct, and single-variant shear faults. In contrast, substantial fragmentation with limited amorphization was activated in the Si-doped boron carbide, manifested by the short, diffuse, and multivariant shear faults. Microcracking via fragmentation competed with and subsequently mitigated amorphization. This work highlights the important roles that solute atoms play on the structural stability of boron carbide and opens up new avenues to tune deformation mechanisms of ceramics via doping.

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“…Technically, boron suboxide (B 6 O) can be fabricated under ambient pressure without the requirements of extremely high synthesis pressures at high temperatures, unlike other superhard materials such as diamond and cubic boron nitride [2][3][4][5]. B 6 O mainly exist in the form of a stoichiometric compound [2,6], which is different from in covalently bonded superhard materials are usually sessile at room temperature due to high lattice resistance, it has been found that nanotwins can enhance the hardness, toughness and thermal stability of diamond, BN, B 4 C and B 6 O [15][16][17][18]. Similar to twins and GBs, stacking faults also have a planar feature and can lead to strong interactions with dislocations for interface strengthening.…”

Section: Introductionmentioning

confidence: 99%

Atomic structure and mechanical response of coincident stacking faults in boron suboxide

Reddy

Chen

Shen

et al. 2018

Materials Research Letters

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We report the atomic structure of coincident stacking faults (SFs) in superhard boron suboxide (B 6 O) by combining annular bright field scanning transmission electron microscopy and quantum mechanics (QM) simulations. Different from simple SFs, which only lead to the symmetry breaking, the coincident SF junctions in the complex B 6 O result in local chemical configuration changes by forming an abnormal three-oxygen-atoms chain linking boron icosahedra, instead of the regular two-oxygen-atoms chain in a perfect B 6 O crystal. QM studies demonstrate that coincident SFs lead to the decreased shear strength under pure shear and indentation conditions and are responsible to the initial failure and amorphization of B 6 O. IMPACT STATEMENTCombining ABF-STEM and MD simulations, we demonstrated that the coincident SFs lead to the decrease of shear strength and are responsible for the initial failure and amorphization of B 6 O.

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Nanotwinning and amorphization of boron suboxide

Cited by 24 publications

References 53 publications

Amorphous boron suboxide

Amorphous boron suboxide

Tuning the deformation mechanisms of boron carbide via silicon doping

Atomic structure and mechanical response of coincident stacking faults in boron suboxide

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