Thermomechanical properties of a single hexagonal boron nitride sheet (original) (raw)
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Mechanical properties of atomically thin boron nitride and the role of interlayer interactions
Nature communications, 2017
Atomically thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete. Here we report that high-quality single-crystalline mono- and few-layer BN nanosheets are one of the strongest electrically insulating materials. More intriguingly, few-layer BN shows mechanical behaviours quite different from those of few-layer graphene under indentation. In striking contrast to graphene, whose strength decreases by more than 30% when the number of layers increases from 1 to 8, the mechanical strength of BN nanosheets is not sensitive to increasing thickness. We attribute this difference to the distinct interlayer interactions and hence sliding tendencies in these two materials under indentation. The significantly better interlayer integrity of BN nanosheets makes them a more attractive candidate than graphene for several applications, for example...
Modelling heat conduction in polycrystalline hexagonal boron-nitride films
Scientific Reports, 2015
We conducted extensive molecular dynamics simulations to investigate the thermal conductivity of polycrystalline hexagonal boron-nitride (h-BN) films. To this aim, we constructed large atomistic models of polycrystalline h-BN sheets with random and uniform grain configuration. By performing equilibrium molecular dynamics (EMD) simulations, we investigated the influence of the average grain size on the thermal conductivity of polycrystalline h-BN films at various temperatures. Using the EMD results, we constructed finite element models of polycrystalline h-BN sheets to probe the thermal conductivity of samples with larger grain sizes. Our multiscale investigations not only provide a general viewpoint regarding the heat conduction in h-BN films but also propose that polycrystalline h-BN sheets present high thermal conductivity comparable to monocrystalline sheets.
Bending and interlayer shear moduli of ultrathin boron nitride nanosheet
Journal of Physics D: Applied Physics
We investigate the bending rigidity of ultrathin hexagonal boron nitride nanosheet (BNNS) through quantifying its self-folded conformations on flat substrates by using atomic force microscopy and atomistic simulations. The bending stiffness of two to six layers of BNNS is found to follow a power function of its thickness with a power index of ~2.35 and is substantially higher than that of comparable graphene. In contrast, monolayer graphene possesses a higher stiffness than its h-BN counterpart. We attribute the high bending stiffness of multilayer BNNS to its partially ionic B-N bondings and corrugated electronic structures, which result in one order of magnitude stronger interlayer shear interaction in h-BN than in graphene. The higher out-of-plane bending and interlayer shear rigidities suggest that unlike graphene, BNNS is less prone to interlayer delamination-induced structural inhomogeneities (e.g. shearing, rippling and kinks) and thus is suitable as a building block for atomically thin electronics and a reinforcing filler for nanocomposites.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2020
The mechanical response of two-dimensional nanostructures may be significantly affected by their size. In this work, a molecular structural mechanics model is developed and is implemented in order to predict the nanomechanical behavior and calculate the corresponding elastic properties of hexagonal boron nitride sheets and describe their size-dependence. The finite element approach utilizes appropriate spring-like elements for the modeling of interactions between atoms within the hexagonal boron nitride structure, the stiffness constants of which are obtained by the molecular mechanics theory. Adopting conventional finite element techniques, the global stiffness matrix of the structure of a desired sheet size can be assembled. Applying appropriate boundary conditions, the governing equilibrium static equation can be solved and the elastic mechanical properties as Young's modulus, shear modulus, and Poisson's ratio of the structure can be calculated. Fitting the results of the mechanical properties calculated by the finite element analysis, analytical-empirical equations are proposed for their direct prediction for an hexagonal boron nitride sheet having the size parameters of the structure as independent variables.
Mechanical properties of the hexagonal boron nitride monolayer:< i> Ab initio study
2012
Using density functional theory (DFT) calculations we found that hexagonal boron nitride monolayer (h-BN) shows a non-linear elastic deformation up to an ultimate strength followed by a strain softening to the failure. To develop a continuum based model for such non-linear behavior, we proposed a method to study high order elastic constants of the 2D hexagonal structures. The continuum description of the elastic properties of monolayer h-BN is obtained using this method through ab initio density functional theory.
Mechanical properties of the hexagonal boron nitride monolayer: Ab initio study
Computational Materials Science, 2012
Using density functional theory (DFT) calculations we found that hexagonal boron nitride monolayer (h-BN) shows a non-linear elastic deformation up to an ultimate strength followed by a strain softening to the failure. To develop a continuum based model for such non-linear behavior, we proposed a method to study high order elastic constants of the 2D hexagonal structures. The continuum description of the elastic properties of monolayer h-BN is obtained using this method through ab initio density functional theory. This rigorous continuum description of the elastic response is formulated by expanding the elastic strain energy density in a Taylor series in strain truncated after the fifth-order term. we obtained a total of fourteen non-zero independent elastic constants for up to tenth-order tensor.
Journal of materials science, 2002
The second and third order elastic constants and pressure derivatives of second order elastic constants of hexagonal boron nitride have been obtained using the deformation theory. The strain energy derived using the deformation theory is compared with the strain dependent lattice energy obtained from elastic continuum model approximation to get the expressions for second and third order elastic constants. Higher order elastic constants are a measure of anharmonicity of crystal lattice. The six second-order elastic constants and the ten non-vanishing third order elastic constants and six pressure derivatives of hexagonal boron nitride are obtained in the present work and are compared with available experimental values. The second order elastic constant C 11 which corresponds to the elastic stiffness along the basal plane of the crystal is greater than C 33 . Since C 33 being the stiffness tensor component along the c-axis of the crystal, this result is expected from a layer-like material like boron nitride (BN). The third order elastic constants of hexagonal BN are generally one order of magnitude greater than the second-order of elastic constants as expected of a crystalline solid. The pressure derivative dC 33 /dp obtained in the present study is greater than dC 11 /dp which indicates that the compressibility along c-axis is higher than that along ab-plane of hexagonal BN. C 2002 Kluwer Academic Publishers
Strength and toughness anisotropy in hexagonal boron nitride: An atomistic picture
Journal of Applied Physics
Strength and toughness are two crucial mechanical properties of a solid that determine its ability to function reliably without undergoing failure in extreme conditions. While hexagonal boron nitride (hBN) is known to be elastically isotropic in the linear regime of mechanical deformation, its directional response to extreme mechanical loading remains less understood. Here, using a combination of density functional theory calculations and molecular dynamics simulations, we show that strength and crack nucleation toughness of pristine hBN are strongly anisotropic and chirality dependent. They vary nonlinearly with the chirality of the lattice under symmetry breaking deformation, and the anisotropic behavior is retained over a large temperature range with a decreasing trend at higher temperatures. An atomistic analysis reveals that bond deformation and associated distortion of electron density are nonuniform in the nonlinear regime of mechanical deformation, irrespective of the loading direction. This nonuniformity forms the physical basis for the observed anisotropy under static conditions, whereas reduction in nonuniformity and thermal softening reduce anisotropy at higher temperatures. The chirality-dependent anisotropic effects are well predicted by inverse cubic polynomials.