BN Compounds Research Articles

Designing two sp3 hybridization polymorphs of BN: A comprehensive study

Two BN compounds Amm 2 BN and P 321 BN are predicted in this work by random strategy combined with group and graph theory, and the physical properties of Amm 2 BN and P 321 BN are systematically investigated by density functional theory. Each of the proposed BN compounds is dynamically, thermally and mechanically stable. The anisotropy properties of Amm 2 BN and P 321 BN are investigated by the three-dimensional surface plotting's of Poisson's ratio, Young's modulus, and shear modulus. Moreover, the electronic band structures of Amm 2 BN and P 321 BN are study by the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional, and it is found that Amm 2 BN and P 321 BN are indirect gap semiconductor materials, while the P 321 BN can be considered as a quasi-direct band gap of semiconductors with the band gap of 3.775 eV. • Two novel BN polymorphs are proposed. • P 321 BN is a semiconductor with quasi-direct band gap. • Amm 2 BN is a superhard material.

Ambient-pressure high- Tc superconductivity in doped boron-nitrogen clathrates La(BN)5 and Y(BN)5

${\mathrm{LaH}}_{10}$ exhibits the near-room-temperature superconductivity, but the high fabrication pressure exceeding 200 GPa limits the possibility of its experimental research and application. To examine the feasibility of high-temperature superconductivity at ambient pressure in light-element compounds, we study the crystal structure, metallization, and electron-phonon interaction of $M{(\mathrm{BN})}_{5}$ ($M$ = La and Y) with ${\mathrm{LaH}}_{10}$-like clathrate configuration, based on the first-principles calculations. The result shows that adopting B and N to substitute H, the strong $s{p}^{3}$ hybridization between B and N greatly reduces the pressure to keep the dynamical stability. We predict that the strong electron-phonon coupling exists in $M{(\mathrm{BN})}_{5}$ and the ${T}_{c}$ values of $\mathrm{La}{(\mathrm{BN})}_{5}$ and $\mathrm{Y}{(\mathrm{BN})}_{5}$ reach 69 and 59 K at ambient pressure, respectively. As a result, the high-temperature superconductivity at ambient pressure in clathrate BN compounds has been proved theoretically, which provides a way to lower the work pressure of hydride superconductors.

Fabrication and properties of SiCnw‐reinforced SiC composites by reactive melt infiltration with BN and PyC interface

AbstractTo tailor the fiber–matrix interface of SiC nanowires‐reinforced SiC (SiCnw/SiC) ceramic matrix composites (CMCs) for improved mechanical properties, SiC nanowires were coated with BN and pyrolytic carbon (PyC) compound coatings prepared by the dip‐coating process in boric acid and urea solution and the pyrolysis of phenolic resin. SiCnw/SiC CMC with PyC/BN interfaces were fabricated by reactive melt infiltration (RMI) at 1680°C for 1 h. The influences of phenolic resin content on the microstructure and mechanical properties of the CMC were investigated. The results showed that the flexural strength and fracture toughness reach the maximum values of 294 MPa and 4.74 MPa m1/2 as the phenolic resin content was 16 and 12 wt%, respectively. The displacement–load curve of the sample exhibited a gradient drop with increasing phenolic resin content up to 12 wt%. The results demonstrated that the PyC/BN compound coatings could play the role of protecting the SiCnw from degradation as well as improving the more moderate interfacial bonding strengths during the RMI.

Substitution pattern controlled charge transport in BN-embedded aromatics-based single molecule junctions.

The understanding of charge transport at a single molecule level is a prerequisite for the fabrication of molecular devices. Here, the relationship between molecular conductance, substitution pattern and stimuli response in BN-embedded aromatics was systematically investigated using the break junction technique. It was found that the para-phenylthioether-anchored BN molecule (p-BN-p) shows the highest conductance of 10-4.86G0, and the meta-phenylthioether-anchored BN molecule (m-BN-m) exhibits the lowest conductance which is lower than the instrument detection limit (<10-6.0G0). The m-BN-p and p-BN-m molecules, with both para- and meta-substituted anchor groups on two termini, show moderate conductances of 10-5.50G0 and 10-5.45G0, respectively. The conductance difference is interpreted as a distinct quantum interference effect caused by the substitution pattern of the anchoring groups. Notably, their conductance changes slightly upon coordination with a fluoride ion, in spite of the distinct change of their frontier orbital energy levels. These results demonstrate that, in addition to the frontier orbital energy levels, the anchors play an important role in the design of stimuli-responsive molecular electronic devices with a high on/off current ratio.

An Air‐ and Water‐Stable B4N4‐Heteropentalene Serving as a Host Material for a Phosphorescent OLED

AbstractReplacement of the carbon–carbon bonds of antiaromatic compounds with polar boron–nitrogen bonds often provides isoelectronic BN compounds with excellent thermodynamic stability and interesting photophysical properties. By this element‐substitution strategy, we synthesized a new B4N4‐heteropentalene derivative, 1, which is fully substituted with mesityl groups. Owing to kinetic protection by the sterically bulky substituents, 1 is remarkably stable toward air and even water. Single‐crystal X‐ray analysis of 1 revealed the bonding characteristics of the B4N4‐heteropentalene structure. In a glassy matrix, 1 emitted short‐wavelength phosphorescence with an onset at 350 nm, indicating that the triplet energy is substantially high. DFT calculations reasonably explained the ground‐ and excited‐state electronic structures of 1 as well as its emission properties. Motivated by the high‐energy triplet state of 1, we used it as a host material to fabricate a phosphorescent organic light‐emitting diode with an external quantum efficiency of 15 %.

An Air- and Water-Stable B4 N4 -Heteropentalene Serving as a Host Material for a Phosphorescent OLED.

Replacement of the carbon-carbon bonds of antiaromatic compounds with polar boron-nitrogen bonds often provides isoelectronic BN compounds with excellent thermodynamic stability and interesting photophysical properties. By this element-substitution strategy, we synthesized a new B4 N4 -heteropentalene derivative, 1, which is fully substituted with mesityl groups. Owing to kinetic protection by the sterically bulky substituents, 1 is remarkably stable toward air and even water. Single-crystal X-ray analysis of 1 revealed the bonding characteristics of the B4 N4 -heteropentalene structure. In a glassy matrix, 1 emitted short-wavelength phosphorescence with an onset at 350 nm, indicating that the triplet energy is substantially high. DFT calculations reasonably explained the ground- and excited-state electronic structures of 1 as well as its emission properties. Motivated by the high-energy triplet state of 1, we used it as a host material to fabricate a phosphorescent organic light-emitting diode with an external quantum efficiency of 15 %.

Boron nitride nanotube precursor formation during high-temperature synthesis: kinetic and thermodynamic modelling

We performed integrated modelling of the chemical pathways of formation for boron nitride nanotube (BNNT) precursors during high-temperature synthesis in a B/N2 mixture. Integrated modelling includes quantum chemistry, Quantum–classical molecular dynamics, thermodynamic modelling, and kinetic approaches. We demonstrate that BN compounds are formed via the interaction of molecular nitrogen with small boron clusters, rather than through interactions with less reactive liquid boron. (This process can also be described as N2 molecule fixation.) Liquid boron evaporates to produce these boron clusters (B m with m ≤ 5), which are subsequently converted into B m N n chains. The production of such chains is crucial to the growth of BNNTs because these chains form the building blocks of bigger and longer BN chains and rings, which are in turn the building blocks of fullborenes and BNNTs. Additionally, kinetic modelling revealed that B4N4 and B5N4 species in particular play a major role in the N2 molecule fixation process. The formation of these species via reactions with B4 and B5 clusters is not adequately described under the assumption of thermodynamic equilibrium, as is demonstrated in our kinetic modelling. Thus, the accumulation of both B4N4 and B5N4 depends on the background gas pressure and the gas cooling rate. Long BN chains and rings, which are precursors of the fullborene and BNNT growth, form via self-assembly of components B4N4 and B5N4. Our modelling results—particularly the increased densities of B4N4 and B5N4 species at higher gas pressures—explain the experimentally observed effect of gas pressure on the yield of high-quality BNNTs. The catalytic role of hydrogen was also studied; it is shown that HBNH molecules can be the main precursor of BNNT synthesis in the presence of hydrogen.

Molecular dynamics study of pristine and defective hexagonal BN, SiC and SiGe monolayers

The structural and thermodynamical properties of 2D honeycomb hybrids are investigated over a wide temperatures range by carrying out atomistic simulations using Tersoff-type interatomic empirical potential. The variance of the radial distribution as well as the height correlation functions in terms of temperature and buckling parameter are discussed for the SiC, SiGe and BN compounds. A non-monotonic growth of mean square displacement is observed when increasing the defect concentration. The energetic of Stone–Wales defects and vacancies as well as the magnitude of thermally excited ripples for both pristine and defective monolayers increase significantly at higher temperatures, which is caused by the increase in bond lengths and atom’s velocities, resulting in higher kinetic energy. It follows that thermal rippling is intricately related to thermal expansion.

Rapid Construction of Fold-Line-Shaped BN-Embedded Polycyclic Aromatic Compounds through Diels-Alder Reaction.

The Diels-Alder reaction strategy that can rapidly extend the conjugated backbone was applied to facilely synthesize fold-line, coplanar BN-embedded polycyclic aromatic hydrocarbons from simple small BN compounds. The molecular structures and packing modes of these BN-embedded acenes were confirmed by single-crystal X-ray diffraction. Their electronic and photophysical properties were studied by using UV-vis, fluorescence spectroscopy, electrochemical cyclic voltammetry, and density functional theory calculations. These results demonstrate the efficiency and feasibility of this synthetic strategy.

Nitridated Ru/B4C multilayer mirrors with improved interface structure, zero stress, and enhanced hard X-ray reflectance.

Ru/B4C multilayer mirrors are used for hard X-ray monochromators with moderate spectral resolution and high integral flux. To overcome the problem of large compressive stress inherent in Ru/B4C multilayers, a reactive sputtering technique using a mixture working gas of argon and nitrogen with different partial pressures was tested, and the fabricated multilayers had a period of 3 nm. The intrinsic stress was essentially reduced after nitridation and relaxed to zero value at approximately 15% partial pressure of nitrogen in the working gas. Interface roughness was slightly increased which can be caused by the polycrystalline structure inside the nitridated samples. More importantly, the nitridated multilayers showed an enhanced reflectance (67% at 8.04 keV photon energy) as compared with the one fabricated with pure Ar (54%). The structure analysis with transmission electron microscopy and X-ray photoelectron spectroscopy demonstrated that nitrogen incorporated into a multilayer structure was mostly located in the B4C layers forming BN compounds, which suppressed the diffusion of boron, stabilized the interfaces and enhanced the reflectance.

Pressure effect on the structural, electronic and optical properties of the cubic triangular quaternary BNxAsyP1−x−y alloys: First principle study

Predicted results of the structural, electronic and optical properties of the cubic zinc-blende phase of BN, BAs and BP binary compounds and their related ternary and quaternary alloys are presented. The density functional theory (DFT) within full potential linearized augmented plan wave (FP-LAPW) is employed. Different exchange correlation approximations were used to calculate the structural properties as well as the total energies, lattice parameters, bulk modulus and its first pressure derivative. The electronic band structures were treated with the local density approach and Tran Blaha modified Beck-Johnson (TB-mBJ) approximation. A quadratic fit of the lattice parameter, bulk modulus and band gap was performed, where a nonlinear variation with the composition x and y is found. Moreover, the optical properties have been investigated, where the dielectric behavior, the refractive index variations and the loss energy were studied. Furthermore, the electronic and optical properties were computed under hydrostatic pressure. Our results showed great agreement with the previous available experimental and theoretical data found in the literature.

Ferromagnetism induced by Cr, V single and double impurities doped BN from Ab-initio and Monte Carlo study

Using the Ab initio calculations and Monte Carlo (MC) simulations, we investigate the electronic and magnetic properties of cubic BN compound doped and co-doped with Chromium (Cr) and Vanadium (V) atoms. The calculated electronic band structure and density of states (DOS) of doped BN with single and double impurities can induce localized edge states around Fermi level, leading from semiconductor to half-metal transition. Thereafter, the stability of ferromagnetic (FM) ordering and disordered local magnetic moment (DLM) configurations has been explored. The interesting Curie temperature (Tc), magnetization and susceptibility results for the various concentrations of Chromium (Cr) and Vanadium (V) co-doped (doped) BN suggest a vast exploitation attention in spintronic applications.

Compression-Induced Modification of Boron Nitride Layers: A Conductive Two-Dimensional BN Compound.

The ability to create materials with improved properties upon transformation processes applied to conventional materials is the keystone of materials science. Here, hexagonal boron nitride (h-BN), a large-band-gap insulator, is transformed into a conductive two-dimensional (2D) material- bonitrol-that is stable at ambient conditions. The process, which requires compression of at least two h-BN layers and hydroxyl ions, is characterized via scanning probe microscopy experiments and ab initio calculations. This material and its creation mechanism represent an additional strategy for the transformation of known 2D materials into artificial advanced materials with exceptional properties.

Microstructure and strength of high nitrogen steel joints brazed with Ni-Cr-B-Si filler

ABSTRACTBrazing of high nitrogen austenitic stainless steels was carried out by using Ni-Cr-B-Si filler metal. The effects of brazing temperature (1020–1100°C) on the microstructure and shear strength of the joints were investigated. The results show that BN compounds with hexagonal structure are formed at the interface by the reaction of N from substrate and B from filler. The brittle Cr5B3 compounds with high microhardness are observed in the centre of brazing seam. The BN content increases and the Cr5B3 content decreases with the increase in brazing temperature. However, the content of BN compounds played a determinable role on the joint strength. The optimal shear strength of joints was 176.7 MPa when the joining temperature was 1020°C.

Influence of the Lewis Acidity of Gallium Atoms on the Reactivity of a Frustrated Lewis Pair: Experimental and Theoretical Studies

The reactivity of the Ga/P-based frustrated Lewis pair (FLP) Mes2P–C[═C(H)–Ph]–GatBu2 (3) is influenced by the relatively weak Lewis acidity of its Ga atom and differs significantly from that of the analogous Al compound 1. The adduct of 3 with CO2 was only detectable at low temperature by NMR spectroscopy. Benzaldehyde was coordinated only via a Ga–O bond; the P atom was not involved. In contrast, a relatively persistent adduct was formed with soft CS2 to yield a five-membered GaCPCS heterocycle. Dehydrocoupling with H3B←NHMe2 afforded the dimeric amidoborane (H2B–NMe2)2, while an adduct with a GaCPBN heterocycle was isolated with the sterically less shielded ammonia–borane H3B←NH3. The latter product was unstable in solution and decomposed by H2 elimination and formation of oligomeric BN compounds. Small quantities of 3 catalyzed hydrogen transfer from H3B←NH3 to an imine. The Lewis acidities of the Al/P- and Ga/P-based FLPs were examined by experiments (Gutmann–Beckett method) and by calculation of the...

Thermal stability of B-based multilayer mirrors for next generation lithography

The evolution of microstructure and reflective properties in a La/B4C and LaN/B4C multilayer was studied at elevated temperatures up to 800°C. It was shown, that the observed opposite period thickness changes in La/B4C and LaN/B4C multilayers during annealing are based on structural modifications and chemical reactions at the interfaces. For T>400°C the period thickness of the La/B4C multilayer decreased, while it increased drastically in the LaN/B4C multilayer, which is explained by the formation of LaB6 crystallites and amorphous BN compounds, respectively. These thermally induced processes also lead to reflectivity drops at the wavelength of ~6.7nm for both investigated systems. Even after annealing at 800°C for 10h the LaN/B4C multilayer showed an EUV reflectance of 12.6%, with is significantly higher than the La/B4C multilayer (2.3%), pointing up their higher thermal resistance.

The Effect of Proximal Functionality on the Allylic Azide Equilibrium

This report describes an investigation into the effect that proximal functionality has on the allylic azide equilibrium. We report 16 allylic azides with varied functionality from three subclasses. We observe a correlation of % branched azide to the pKa of the OR group. We also observe that RN–H azides have a higher % branched azide relative the corresponding RN–Bn compound. These two effects combine to describe the observed equilibrium for the known compound hydroxy‐crotyl azide. DFT calculations support several stereoelectronic effects that contribute to the relative energetics.

Phân lập và tuyển chọn một số dòng nấm từ gỗ mục có khả năng loại màu thuốc nhuộm ở Đồng bằng sông Cửu Long

The main objective of this study was to isolate and identify indigenous white rot fungi for bioremediation of dye textile compounds. Fungal fruit body samples were collected from decaying woods in the Mekong Delta for isolation. The dye textile compound decolourisation capacity of isolated fungi was tested on MT3 (Jonathan and Fasidi, 2001) containing 500 mgL-1Brilliant Black BN or Bromophenol blue. The results showed that 54 fungal isolates were isolated from decaying wood. Twelve out of fifty four fungal isolates showed their capacity in decolourisation of Bromophenol blue. The HG1 strain was able to degrade 493 mg.L-1 Bromophenol blue, corresponding to 92% within 8 days of incubation, while fifteen out of fifty four fungal isolates showed their capacity in decolourisation of 1Brilliant Black BN. The maximum decolourisation of this compound was 99% (493 mg.L-1) within 7 days of incubation by TV13 strain . HG1 and TV13 were identified as the best candidates for decolourisation of Brilliant Black BN and Bromophenol blue compounds, respectively. Based on the results of 18S-rRNA sequences, these two candidates were genetically and relatively identified as genus of Marasmiellus. Thus, these two fungal isolates were relatively identified as Marasmiellus sp. HG1 and Marasmiellus sp. TV13.

Preparation of borate ester and evaluation of its tribological properties as an additive in different base oils

N-containing borate ester (MEBE) with five-member ring structure as a lubricant additive was synthesised. The tribological properties in liquid paraffin (LP), poly-alpha-olefin (PAO) and dioctyl sebacate (DOS) were evaluated, and the action mechanisms in different base oils were also explored. It was found that as-synthesised borate ester possesses excellent antiwear performance in LP and PAO. XPS analysis suggests that the additive forms a protective film on the rubbing surfaces which is composed of BN, Fe2O3, polyoxyethylene ether and N-containing organic compounds. The inorganic and organic protective films in the metal surface effectively improve the antiwear ability of the base stock. However, when the additive MEBE was introducted into DOS base oil which is prone to adsorbing to the metal surface because of the high polarity of DOS, it influences the compactness of the film formed by the DOS, resulting in weak antiwear property. Copyright © 2016 John Wiley & Sons, Ltd.

From Saturated BN Compounds to Isoelectronic BN/CC Counterparts: An Insight from Computational Perspective.

In the present study, the inorganic analogues of alkanes as well as their isoelectronic BN/CC counterparts that bridge the gap between organic and inorganic chemistry are comparatively studied on the grounds of static DFT and Car-Parrinello molecular dynamics simulations. The BN/CC butanes CH3 CH2 BH2 NH3 , BH3 CH2 NH2 CH3 , and NH3 CH2 BH2 CH3 were considered and compared with their isoelectronic counterparts NH3 BH2 NH2 BH3 and CH3 CH2 CH2 CH3 . In addition, systematical replacement of the NH2 BH2 fragment by the isoelectronic CH2 CH2 moiety is studied in the molecules H3 N(NH2 BH2 )3-m (CH2 CH2 )m BH3 (for m=0, 1, 2, or 3) and H3 N(NH2 BH2 )2-m (CH2 CH2 )m BH3 (for m=0, 1, or 2). The DFT and Car-Parrinello simulations show that the isosteres of the BN/CC butanes CH3 CH2 BH2 NH3 , BH3 CH2 NH2 CH3 , and NH3 CH2 BH2 CH3 and of larger oligomers of the type (BN)k (CC)l where k≥l are stable compounds. The BN/CC butane H3 NCH2 CH2 BH3 spontaneously produces molecular hydrogen at room temperature. The reaction, prompted by very strong dihydrogen bonding NH⋅⋅⋅HB, undergoes through the neutral, hypervalent, pentacoordinated boron dihydrogen complex RBH2 (H2 ) [R=(CH2 CH2 )n NH2 ]. The calculations suggest that such intermediate and the other BN/CC butanes CH3 CH2 BH2 NH3 , BH3 CH2 NH2 CH3 , and NH3 CH2 BH2 CH3 as well as larger BN/CC oligomers are viable experimentally. A simple recipe for the synthesis of CH3 CH2 BH2 NH3 is proposed. The strength of the dihydrogen bonding appeared to be crucial for the overall stability of the saturated BN/CC derivatives.