BN Graphene Research Articles

Improved hot workability of TiAl composite with core-shell structure via in-situ synthesized multi-phases ceramic particles

TiAl composite with core-shell structure was in-situ synthesized incorporating BN nanosheets and graphene oxide into TiAl alloy using SPS, and the hot deformation behaviors were subsequently investigated on a Gleeble-1500D thermal simulation machine. The microstructural evolution and the influence of ceramic particles on hot deformation were revealed using OM, SEM, TEM, and EBSD. The results demonstrated a refined microstructure of TiAl composite induced by ceramic particles providing extra nucleation sites for DRX, contributing to lower flow stress, with peak stresses of 387 and 360 MPa for TiAl alloy and TiAl composite deformed at 1200 °C/1s−1, respectively. Moreover, dislocation slip was inhibited by ceramic particles leading to dislocation pile-up, facilitating the nucleation and growth of DRX at lamellar colony boundaries and α2/γ interfaces. Notably, the “shell” composed of TiB2 and Ti2AlN nanoparticles coordinated the deformation of lamellar colonies with different orientations, improving the hot workability of TiAl composite.

Adsorption Characteristics of the Anticancer Drug Hydroxyurea with Armchair BN Graphene Nanoribbons Containing and Lacking Vacancy Defects: Insight via DFT Calculations

Adsorption Characteristics of the Anticancer Drug Hydroxyurea with Armchair BN Graphene Nanoribbons Containing and Lacking Vacancy Defects: Insight via DFT Calculations

Comparative DFT study on the H2 adsorption and the sensing properties of BN-, BP-, AlN-, and AlP-decorated graphene nanoflakes

In this research, the application of BN, BP, AlN, and AlP edge-doped graphene nanoflakes as sensor for sensing of H 2 molecule was studied by DFT approach. The M06-2X/6-311G++(d,p) level of theory have been used in the calculations. The results showed that the adsorption of H 2 molecule on the BN, BP, and AlN was very weak (−0.97, −0.16, and −1.14 kcal.mol −1 , respectively). By considering the acceptable adsorption of H 2 molecule on the AlP-doped graphene with −5.03 kcal.mol −1 , further calculations were performed on this sheet. Upon adsorption of H 2 molecule, the HOMO–LUMO gap ( E g ) of the AlP-doped graphene nanoflake decreased slightly from 2.01 to 1.92 eV. Therefore, the electrical conductivity of AlP-doped graphene sheet increased. Moreover, Δ H ad = −3.38 kcal.mol −1 and Δ G ad = −1.38 kcal.mol −1 show that the adsorption of H 2 molecule on the AlP-doped graphene is an exothermic and spontaneous phenomenon at room temperature. The NCI-RDG analyses verifies the presence of vdW interactions between H 2 molecule and the AlP-doped graphene. Finally, according to the very low recovery time as 4.65 ns, AlP-doped graphene might be utilized as an effective and fast sensor for H 2 molecule at room temperature. • The effect of BN, BP, AlN, and AlP edge doping of graphene on the H 2 sensing is studied. • Adsorption of H 2 molecule on the AlP-edge doped graphene occurs thermodynamically effective. • NCI-RDG analysis shows that the H 2 adsorption on the AlP-edge doped graphene occurs via vdW interactions. • AlP-edge doped graphene can be considered as an ultrafast H 2 sensor with 4.65 ns recovery time.

Silicon-doped boron nitride graphyne-like sheet for catalytic N2O reduction: A DFT study

In this work, spin-polarized density functional theory calculations are conducted to evaluate the possible applicability of a single Si atom doped boron nitride graphyne-like nansoheet (Si@BN-yne) for reduction of nitrous oxide (N2O). The calculations show that Si-doping in BN graphene is energetically favorable, and the resulting Si@BN-yne is both dynamically and thermodynamically stable. According to our findings, N2O spontaneously dissociates when it interacts with the Si@BN-yne from its O site without the need for an energy barrier, releasing 2.89 eV of energy. The adsorption energy of CO molecule on the Si@BN-yne is less negative than that of N2O, implying that N2O will predominately occupy the catalyst surface. The CO + Oad reaction is used to remove the remaining oxygen atom (Oad) from the Si@BN-yne surface. The calculations show that the reaction proceeds through a low energy barrier of 0.05 eV, which is much lower than the previously reported catalysts. This demonstrates the high catalytic activity of Si@BN-yne nanosheet. Furthermore, the adsorption of H2O and O2 species on the Si@BN-yne nanosheet is investigated. The results show that the presence of these species has no effect on the catalytic activity of the Si@BN-yne for N2O reduction. These results show that the proposed novel Si@BN-yne catalyst can be regarded as an efficient material in the development of promising active catalysts for N2O elimination from the environment.

Mechanical behaviour of 2D hybrid structure fabricated by doping graphene with triangular h-BN cells

A two dimensional (2D) hybrid structure has been fabricated by doping graphene with hexagonal boron nitride (h-BN) cells. Substantial changes are expected as carbon-carbon (C) bonds are substituted by B–N bonds and C–B and C–N bonds are formed between the BN cells and graphene. In this paper, molecular dynamics simulations are performed to explore the tensile behaviour and fracture mechanisms of the 2D HS, and reveal how and to what extent the BN cells impact its overall tensile properties. A comprehensive study of free boundary effects is also conducted for the first time for 2D materials. Herein, the 2D nonlinear elastic constitutive relation has been formulated in terms of the equivalent elastic modulus Ye that decreases almost linearly with BN content α due to the distinct elastic properties between B–N bonds and C–C bonds. The downward trend of the fracture stress with growing α is also achieved due to the α− dependence of Ye and the limit on the fracture strain imposed by the newly formed C–B bonds. In addition, evidence has been accumulated showing that the free boundaries can significantly decrease the elastic moduli and fracture stress but largely enhance the fracture toughness of the 2D nanosheets.

A quantum mechanical study on the application of inorganic BC2N nanotubes in the Na-ion batteries

We scrutinized the potential application of a BC2N nanotube as an anode material for the Na-ion batteries (NIBs) using B3LYP-gCP-D3/6-31G* model chemistry. Two kinds of hexagonal rings (B2C2N2 (α) and BC4N (β)) are identified, being nonaromatic based on the NMR calculations. The Na cation adsorbs on the α and β rings with adsorption energies of −46.7 and −38.1 kcal/mol via different mechanisms, namely, cation-lone-pair and cation-π interactions, respectively. The predicted adsorption energy for Na atom is −12.0 kcal/mol, including a large dispersion term of −5.7 kcal/mol. The BC2N nanotube preserves its initial structure during the Na/Na+ adsorption because of a small calculated deformation energy. The maximum energy barrier for an Na cation migration on the tube surface is 13.7 kcal/mol which yields a diffusion coefficient of 3.70 × 10−10 cm2/s. Thus, the BC2N nanotube provides a great ion mobility leading to a faster charge/discharge rate. The predicted cell voltage for BC2N nanotube is 1.58 V, being larger than that of different BN and AlN nanostructures and graphene. All of above offer the BC2N nanotube as a plausible anode material for application in the NIBs.

Transport and photoelectric properties of vertical black phosphorus heterojunctions

The photoelectric response of heterostructures formed by BP with insulator BN, semiconductor MoS2, and conductor graphene.

Hydrogen Release from NH3 in the Presence of BN Graphene: DFT Studies

<p>Using density functional theory, we investigated the interaction<br />of an NH3 molecule with a pristine and antisite defected BN sheet<br />(g-BN) in terms of energetic, geometric, and electronic properties.<br />The adsorption energy of NH3 on defected g-BN was calculated to be<br />in the range of −0.70 to −2.46 eV, which is considerably more negative<br />than that on the pristine sheet. It was found that the adsorption<br />of NH3 adsorption on the defected sheet may cause the release of an<br />H2 molecule. The electronic properties of the defected BN sheet were<br />significantly changed after the adsorption process so that its HOMO/<br />LUMO energy gap was changed from 3.31 to 3.60-4.97 eV. Moreover,<br />the Fermi level of the defected sheet shifts to higher energies after the<br />interaction, which results in reduced potential barrier of the electron<br />emission for the sheet surface, enhancing the field emission because<br />of the decreased work function.</p>

Catalytic Directional Cutting of Hexagonal Boron Nitride: The Roles of Interface and Etching Agents

Transition-metal (TM) nanoparticle catalyzed cutting has been proven to be an efficient approach to carve out straight channels in graphene to produce high-quality nanoribbons. However, the applicability of such a catalytic approach to hexagonal boron nitride (h-BN) is still an open question due to binary element compositions. Here, our ab initio study indicates that long and straight channels along either the zigzag or the armchair direction of the BN sheet can be carved out, driven by the energetically favored TM-zigzag or TM-armchair BN interface, regardless of roughness of the TM particle surface. Optimal experimental conditions for the catalytic cutting of either BN or BN/graphene hybrid sheet across the domain boundary are proposed via the analysis of the competition between TM-BN (or TM-graphene) interface and H-terminated BN (or graphene) edge. The computation results can serve to guide the experimental design for the production of highly uniform BN (or hybrid BN/graphene) nanoribbons with atomically smooth edges.

DFT study on the chemical sensing properties of B24N24 nanocage toward formaldehyde

It has been previously shown that the toxic formaldehyde gas (H2CO) cannot be detected by pristine BC2N, carbon, and BN nanotubes, BC3 nanosheet and graphene. Herein, density functional theory calculations were employed to investigate the electronic and structural behavior of a pristine B24N24 nanocluster toward H2CO molecules. It was found that [4,6] BN bonds of the nanocluster are the most favorable sites for the H2CO adsorption, compared to the [4,8], and [6,8] ones. When an H2CO molecule is adsorbed on a [4,6] BN bond, an energy of about 16.40kcal/mol is released and the HOMO-LUMO gap of the cluster is decreased from 6.45 to 2.98eV. Thus, the electrical conductivity of the cluster is significantly increased, indicating that it can produce an electronic noise at the presence of H2CO molecules. Increasing the number of adsorbed H2CO molecules, the electrical conductivity more increases. The recovery time for the H2CO from the surface of B24N24 is calculated to be very short (∼1.02s). Also, the UV–vis spectrum shows that the λmax of the B24N24 shows a large redshift upon the adsorption process and transfers from the UV to the visible region.

Aluminum nitride graphene for DMMP nerve agent adsorption and detection

Using ab initio van der Waals density functional (vdW-DF) calculations, we investigate the adsorption of DMMP nerve agent on graphene, BN and AlN graphenes, involving full geometry optimization. Several active sites for both the interacting systems were considered in the adsorption process. The detailed analysis of the structural and electronical properties of energetically favorable configurations is carried out. The results show that adsorption of DMMP molecule on the Al site of the AlN graphene is energetically preferable. The calculated binding energy and equilibrium distance are about −0.74 eV (−72.34 kJ mol−1) and 2.035 Å, respectively, accompanying with charge transfer of 0.23 e. In addition, the P–O bond is rather significantly elongated when DMMP is adsorbed on AlN graphene. Compared to carbon graphene or BN graphene, the AlN graphene has stronger interaction with the DMMP molecule and can provide more sensitive signal for a single DMMP molecule. In particular, the semiconducting AlN graphene would become metallic after adsorption DMMP. Consequently, the AlN graphene is a promising candidate for the DMMP sensing and detection. Our ab initio vdW-DF findings present evidence for a rational benchmark for the applicability of the AlN graphene for DMMP adsorption and detection.

Graphene nanoribbons generate a strong third-order nonlinear optical response upon intercalating hexagonal boron nitride

An artificial hybrid structure (named as BCNNRs) was designed by inserting wide-gap hexagonal boron nitride (h-BN) nanoribbon in between zero-gap graphene nanoribbon. Third-order nonlinear optical properties of this hybrid structure were calculated by employing the time-dependent density functional theory combined with sum-over-states method. Our calculations reveal that, distinct from individual BN nanoribbons or graphene nanoribbons, the hybrid BCNNRs exhibit a much stronger third-order nonlinear optical response. A giant third-order NLO susceptibility χ(3) of 1 × 10−4 esu is predicted, almost three orders of magnitude larger than that recently experimentally measured for graphene. Furthermore, a maximum third-order non-linear optical response of BCNNRs is obtained by adjusting the size of h-BN nanoribbons. The strong third-order non-linear optical response predicted for BCNNRs originates from the charge redistribution in graphene nanoribbon as h-BN ribbon is inserted. The results reported in this work show that insertion of a wide-gap semiconductor h-BN nanoribbon in zero-gap graphene can give rise to a strong three-order nonlinear optical response, which may guide the future development of structural design and exploration of more advanced nonlinear optical materials.

Physisorption of DNA Nucleobases on h-BN and Graphene: vdW-Corrected DFT Calculations

We present a comparative study of DNA nucleobases [guanine (G), adenine (A), thymine (T), and cytosine (C)] adsorbed on hexagonal boron nitride (\textit{h}-BN) sheet and graphene, using local, semilocal, and van der Waals (vdW) energy-corrected density-functional theory (DFT) calculations. Intriguingly, despite the very different electronic properties of BN sheet and graphene, we find rather similar binding energies for the various nucleobase molecules when adsorbed on the two types of sheets. The calculated binding energies of the four nucleobases using the local, semilocal, and DFT+vdW schemes are in the range of 0.54 ${\sim}$ 0.75 eV, 0.06 ${\sim}$ 0.15 eV, and 0.93 ${\sim}$ 1.18 eV, respectively. In particular, the DFT+vdW scheme predicts not only a binding energy predominantly determined by vdW interactions between the base molecules and their substrates decreasing in the order of G$>$A$>$T$>$C, but also a very weak hybridization between the molecular levels of the nucleobases and the ${\pi}$-states of the BN sheet or graphene. This physisorption of G, A, T, and C on the BN sheet (graphene) induces a small interfacial dipole, giving rise to an energy shift in the work function by 0.11 (0.22), 0.09 (0.15), $-$0.05 (0.01), and 0.06 (0.13) eV, respectively.

Mechanical properties of hybrid graphene and hexagonal boron nitride sheets as revealed by molecular dynamic simulations

Molecular dynamic simulations are performed to investigate the mechanical properties of hybrid graphene and hexagonal boron nitrogen (h-BN) sheet with the concentration of BN ranging from 0% to 100%. We find that Young's modulus of the hybrid sheet decreases with increasing concentration of BN, irrespective of BN shapes and distributions. However, a little mixing of h-BN and graphene can result in a noticeable drop in the yield strength of the hybrid sheet. In addition, the hybrid sheet exhibits strong plasticity behaviour during the tensile loading, which is not observed in pure graphene and BN sheets. We further demonstrate that this behaviour can be interpreted by the fact that the interface between the BN domain and graphene governs the failure mechanism of the hybrid sheet, which can be approximated by the classical Griffith model. Our results suggest that the mechanical properties of the hybrid graphene–BN sheet should be considered carefully when evaluating its whole performance when it is used in bandgap-engineered applications such as electronics and optics.

Divacancy-assisted transition metal adsorption on the BN graphene and its interaction with hydrogen molecules: a theoretical study

We have performed first-principles calculations to study the chemical functionalization of the BN graphene with divacancy (DV) defect by 12 different transition metal (TM) atoms, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pt, and Au. The results indicate that the DV defect can assist the adsorption of TM atoms on BN graphene. Moreover, some impurity bands are induced within the band gap of DV-BN graphene, leading to the modification of its electronic properties in various ways. Interestingly, Ti- and Co-adsorbed DV-BN graphenes are found to possess ferromagnetic characteristic, while antiferromagnetic state is preferred for V-, Mn-, and Fe-functionalized DV-BN graphenes, and the paramagnetic state is the ground state for Sc-, Cr-, Ni-, Cu, Zn-, Pt-, and Au-decorated DV-BN graphenes. Finally, aiming at evaluating the potential of these functionalized BN graphenes in hydrogen storage, we study their interaction with H2 molecules. It is found that the dispersed Sc, V, and Cr on DV-BN graphene are able to adsorb up to three H2 molecules as strongly as 0.25–0.58eV/H2, suggesting that the three nanomaterials may be suitable candidates for hydrogen storage.

Density functional study of structural defects in h-BNC2 sheets

Structure, energetics, electronic and magnetic properties of single and double vacancies and Stone–Wales defects in h-BNC2 sheets have been calculated using the planewave pseudopotential method within density functional theory. The formation energy of a defect strongly depends on its location within the sheet. In some cases, though not all, the energy ordering of various defects can be rationalized in terms of the strengths of various bonds that are broken or created during the defect formation. Single vacancy defects have rather low migration barriers, and the energy cost of double vacancies is smaller than that of two isolated single vacancies. Barriers of formation for Stone–Wales defects at the interfaces are large, but those for healing these defects are quite small. Therefore, they can heal easily even at moderate temperatures. Thus, double vacancies are the most likely defect structures in these sheets. Many of the defects possess finite magnetic moments. Unlike BN sheets and graphene, some of the double vacancies and Stone–Wales defects are also found to possess finite moment.

Thermal conductivity of BN-C nanostructures

Chemical and structural diversity present in hexagonal boron nitride ((h-BN) and graphene hybrid nanostructures provide new avenues for tuning various properties for their technological applications. In this paper we investigate the variation of thermal conductivity ($\kappa$) of hybrid graphene/h-BN nanostructures: stripe superlattices and BN (graphene) dots embedded in graphene (BN) are investigated using equilibrium molecular dynamics. To simulate these systems, we have parameterized a Tersoff type interaction potential to reproduce the ab initio energetics of the B-C and N-C bonds for studying the various interfaces that emerge in these hybrid nanostructures. We demonstrate that both the details of the interface, including energetic stability and shape, as well as the spacing of the interfaces in the material exert strong control on the thermal conductivity of these systems. For stripe superlattices, we find that zigzag configured interfaces produce a higher $\kappa$ in the direction parallel to the interface than the armchair configuration, while the perpendicular conductivity is less prone to the details of the interface and is limited by the $\kappa$ of h-BN. Additionally, the embedded dot structures, having mixed zigzag and armchair interfaces, affects the thermal transport properties more strongly than superlattices. Though dot radius appears to have little effect on the magnitude of reduction, we find that dot concentration (50% yielding the greatest reduction) and composition (embedded graphene dots showing larger reduction that h-BN dot) have a significant effect.

Chemical functionalization of BN graphene with the metal-arene group: a theoretical study

Chemical functionalization of BN graphene allows wider flexibility in engineering its electronic and magnetic properties as well as its chemical reactivity, thus making it have potential applications in many fields. In the present work, the chemical functionalization of BN graphene with six different metal-arenes (MC6H6, M = Ti, V, Cr, Mn, Fe, and Co) has been studied systematically by performing density functional theory (DFT) calculations. Particular attention is paid to searching for the most stable configurations, calculating the corresponding binding energies, and evaluating the effects of MC6H6 functionalization on the electronic and magnetic properties of BN graphene. We find that all of the studied MC6H6 groups can be stably adsorbed on BN graphene, with binding energies ranging from 0.97 eV (for FeC6H6) to 1.40 eV (for MnC6H6), which are weakly dependent on the concentration of adsorbates. Moreover, the adsorption of MC6H6 groups can induce certain impurity states within the band gap of the pristine BN graphene, leading to a reduction of the band gap. Most MC6H6/BN graphenes exhibit nonzero magnetic moments, contributed largely by the transition metal atoms. Interestingly, the adsorption of an O2 molecule on BN graphene is greatly enhanced due to MC6H6 functionalization. The elongation of the O–O bonds of the adsorbed O2 molecules indicates that MC6H6/BN graphenes could be used to fabricate oxidative catalysts.

Graphene-like BN allotropes: Structural and electronic properties from DFTB calculations

Using the density-functional-based tight-binding (DFTB) method a systematic study of comparative stability, structural and electronic properties for six various monolayered allotropes of graphene-like BN (so-called white graphene), which are composed of alternant B-N bonds and include the atoms of different hybridization types (sp2, sp2+sp1, and sp2+sp3) was performed. All these allotropes are found to be less stable, than white BN graphene, though, preserving their integrity during molecular-dynamics simulations. Independing on the hybridization type the BN structures considered here are semiconducting with smaller band gaps, than white BN graphene.

Field-Emission Mechanism of Island-Shaped Graphene–BN Nanocomposite

Recent experiments have shown that gap opening and work function modulating in graphenes have been obtained by substituting C atoms with B or N atoms. Especially, some efforts have been set on the fabrication of semiconducting graphene nanocomposites. Here we propose an island-shaped graphene–BN nanocomposite for potential applications as field-emission electron sources. The field emission mechanism of the graphene–BN has been investigated by using density functional theory calculations. Our results show that graphene has a high level of emission currents with a low external electric field. The combination of BN nanocage and graphene makes use of the curvature effect and the nitrogenation that induce local charge enhancement. The presence of an BN nanocage allows for an important enhancement of the field emission properties. The graphene–BN nanofabrication perhaps leads to a unique hybrid platform consisting of graphene and nonmetal, paving the way in future field-emission electron sources.