Boron Nitride Hybrid Research Articles

Waterproof Perovskite-Hexagonal Boron Nitride Hybrid Nanolasers with Low Lasing Thresholds and High Operating Temperature

Solid-state perovskites have recently emerged as promising coherent light sources, due to their efficient gain. While the continuous-wave (CW) optically pumped perovskite laser has been achieved at low temperatures, the final frontier of an electrical perovskite-based laser diode remains challenging due to the heat management and intrinsic instability of perovskite materials. Here, we demonstrate waterproof perovskite-hexagonal boron nitride (hBN) hybrid nanolasers with low lasing thresholds and high operating temperature. After capping with the hBN flake, which possesses superb and anisotropic thermal conductivity, heat dissipation of the perovskite nanolaser is accelerated and an overheated hot spot is avoided. This results in the significant reduction of lasing thresholds (17.05% to 60.15%) in 16 measured samples and clear lasing behavior under a temperature as high as 75.6 °C. Moreover, hBN with high environmental stability can effectively protect the perovskite from the polar solvents. The hBN encapsulated CsPbI3 nanolaser can incessantly lase in water for an hour, and the lasing behavior can be retained even after 24 h of immersion in water. The reduction of lasing threshold, improved heat removal, and higher temperature tolerance of the hybrid structure nanolaser marks a major step toward a CW-pumped perovskite laser at room temperature, while also allowing perovskites to be integrated into high power density optoelectronic devices and future electrically driven lasers. In addition, as the sandwiching of perovskites with hBN can withstand polar solvents, this method may serve as a reliable method for both the future fabrication of perovskite-based devices and sensor-based applications in solvent systems.

Physico-chemical characterization of hybridized graphene and boron-nitride layers

New materials can be created by modifying matter. In this work, we characterize graphene and boronnitride (BN) layers after doping them with BN and carbon dimers, respectively, in different amounts and with different spatial distributions. We provide the energetic description, electron density features, molecular electrostatic potential maps, net charge populations, and the speeds of propagating waves on the hybridized layers. We show the possibility of designing molecular electrostatic potentials from a spatially controlled doping. A strategy is illustrated on a BN hybrid layer with the adsorption of DNA nucleic acid bases.

A topologically substituted boron nitride hybrid aerogel for highly selective CO2 uptake

A topologically mediated synthesis of porous boron nitride aerogel has been experimentally and theoretically investigated for carbon dioxide (CO2) uptake. Replacement of the carbon atoms in a precursor aerogel of graphene oxide and carbon nanotubes was achieved using an elemental substitution reaction, to obtain a boron and nitrogen framework. The newly prepared BN aerogel possessed a specific surface area of 716.56 m2/g and exhibited an unprecedented twentyfold increase in CO2 uptake over N2, adsorbing 100 cc/g at 273 K and 80 cc/g in ambient conditions, as verified by adsorption isotherms via the multipoint Brunauer-Emmett-Teller (BET) method. Density functional theory calculations were performed to give hints on the mechanism of such high selectivity of CO2 over N2 adsorption in BN aerogel, which may be due to the interaction between the intrinsic polar nature of B–N bonds and the high quadrupole moment of CO2 over N2.

PVDF/h-BN hybrid membranes and their application in desalination through AGMD

A new procedure to produce poly(vinylidene fluoride)/boron nitride hybrid membrane is presented for application in membrane distillation (MD) process. The influence of hexagonal boron nitride (h-BN) incorporation on the performance of the polymeric membranes is studied through the present investigation. For this aim, h-BN nanopowders were successfully synthesized using the simple chemical vapor deposition (CVD) route and subsequent solvent treatments. The resulting h-BN nanosheets were blended with poly(vinylidene fluoride) (PVDF) solution. Then, the prepared composite solution was subjected to phase inversion process to obtain PVDF/h-BN hybrid membranes. Various examinations such as scanning electron microscopy (SEM), wettability, permeation flux, mechanical strength and liquid entry pressure (LEP) measurements are performed to evaluate the prepared membrane. Moreover, Air gap membrane distillation (AGMD) experiments were carried out to investigate the salt rejection performance and the durability of membranes. The results show that our hybrid PVDF/h-BN membrane presents higher water permeation flux (~18 kg/m2 h) compared to pristine PVDF membrane. In addition, the experimental data confirms that the prepared nanocomposite membrane is hydrophobic (water contact angle: ~103 degree),has a porous skin layer (>85%), as well competitive fouling resistance and operational durability. Furthermore, the total salt rejection efficiency was obtained for PVDF/h-BN membrane. The results prove that the novel PVDF/h-BN membrane can be easily synthesized and applied in MD process for salt rejection purposes.

Photodriven Shape-Stabilized Phase Change Materials with Optimized Thermal Conductivity by Tailoring the Microstructure of Hierarchically Ordered Hybrid Porous Scaffolds

Graphene oxide (GO)/boron nitride (BN) hybrid porous scaffolds (HPSs) with the optimally three-dimensional (3D) aligned network structure are fabricated using an unidirectional ice-templated strategy. A variety of HPSs with multilayer structure are obtained due to the various temperature gradients generated by tuning freezing temperature, in which GO and BN are expelled from the ice growth front to assemble between the oriented ice crystals. We demonstrate that the obtained HPSs have a significant influence on the properties of the resulting composite phase change materials (PCMs), including thermal conductivity and shape-stability. Various thermally conductive pathways are formed by tuning freezing temperature, which contributes to further understanding the relationship between thermal conductivity of composites and their internal network structure. Upon increasing the freezing temperature from −120 to −30 °C, the thermal conductivity of the composite PCMs increases and reaches a maximum value at −50 °C ...

Merger of Energetic Affinity and Optimal Geometry Provides New Class of Boron Nitride Based Sorbents with Unprecedented Hydrogen Storage Capacity.

Hydrogen is an ideal synthetic fuel because it is lightweight, abundant and its oxidation product (water) is environmentally benign. However, its utilization is impeded by the lack of an efficient storage device. A new building block approach is proposed for an exhaustive search of optimal hydrogen uptakes in a series of low density boron nitride (BN) nanoarchitectures via extensive 3868 ab initio-based multiscale simulations. By probing various geometries, temperatures, pressures, and doping ratios, these results demonstrate a maximum uptake of 8.65 wt% at 300 K, the highest hydrogen uptake on sorbents at room temperature without doping. Li+ doping of the nanoarchitectures offers a set of optimal combinations of gravimetric and volumetric uptakes, surpassing the US Department of Energy targets. These findings suggest that the merger of energetic affinity and optimal geometry in BN building blocks overcomes the intrinsic limitations of sorbent materials, putting hybrid BN nanoarchitectures on equal footing with hydrides while demonstrating a superior capacity-kinetics-thermodynamics relationship.

N-Doped Hybrid Graphene and Boron Nitride Armchair Nanoribbons As Nonmagnetic Semiconductors with Widely Tunable Electronic Properties

The electronic and chemical properties of N-doped hybrid graphene and boron nitride armchair nanoribbons (N-doped a-GBNNRs) in comparison with graphene armchair nanoribbon (pristine a-GNR) and hybrid graphene and boron nitride armchair nanoribbon (C-3BN) are investigated using the density functional theory method. The results show that all the mentioned nanoribbons are nonmagnetic direct semiconductors and all the graphitic N-doped a-GBNNRs are n-type semiconductors while the rest are p-type semiconductors. The N-doped graphitic 2 and N-doped graphitic 3 structures have the lowest work function and the highest number of valence electrons (Lowdin charges) which confirms that they are effective for use in electronic device applications.

Tunable thermal rectification in graphene/hexagonal boron nitride hybrid structures

Using non-equilibrium molecular dynamics simulations, we investigate thermal rectification (TR) in graphene/hexagonal boron nitride (h-BN) hybrid structures. Two different structural models, partially substituting graphene into h-BN (CBN) and partially substituting h-BN into graphene (BNC), are considered. It is found that CBN has a significant TR effect while that of BNC is very weak. The observed TR phenomenon can be attributed to the resonance effect between out-of-plane phonons of graphene and h-BN domains in the low-frequency region under negative temperature bias. In addition, the influences of ambient temperature, system size, defect number and substrate interaction are also studied to obtain the optimum conditions for TR. More importantly, the TR ratio could be effectively tuned through chemical and structural diversity. A moderate C/BN ratio and parallel arrangement are found to enhance the TR ratio. Detailed phonon spectra analyses are conducted to understand the thermal transport behavior. This work extends hybrid engineering to 2D materials for achieving TR.

Buckling behavior of boron nitride nanotubes under combined axial compression and torsion via molecular dynamics simulations

Buckling behavior of boron nitride nanotubes under combined axial compression and torsion is presented by using molecular dynamics simulation. In order to study the effect of helicity and nanotube size, three groups of nanotubes are considered. The first group is a pair of boron nitride nanotubes with a similar geometry but different helicities, the second group includes three armchair naotubes having equal length but different radii, and three armchair (8, 8)-nanotubes with different lengths form the third group. The simulation is conducted by applying Nose-Hoover thermostat in a temperature range from 50 K to 1200 K. Based on the interatomic interactions given by Tersoff-type potentials, the molecular dynamics method is used to study variations of atomic interaction in initial linear deformation and postbuckling stages with various load-proportional parameters, and to determine the interactive buckling loads relationship. By comparing typical buckling modes under different loads, it is found that the boron nitride nanotube experiences complex micro-deformation processes, resulting in different variations of atomic interaction and strain energies. When the axial compressive load is relatively large, the change of atomic interaction for boron nitride nanotubes under combined loads is similar to that found under the pure axial compression. The onset of buckling leads to the abrupt releasing of strain energy. As the torsional load is relatively large, the nanotube shows torsion-like buckling behavior, no obvious reduction of strain energy is observed after the critical point. The present simulation results show that both the armchair and zigzag nanotubes exhibit nonlinear interactive buckling load relationships. Rise in temperature results in the decrease of interactive buckling load, and the effect of temperature varies with the value of load-proportional parameter. That is, the axial compressive load is relatively large, and the effect of temperature is more significant. It is found that the buckling behavior in the case of combined loading is strongly size dependent. The interactive critical axial and shear stress decrease as nanotube radius or length increases. The studies also reveal that under both simple loading and combined load condition, carbon nanotubes possess higher buckling loads than those of boron nitride nanotubes with a similar geometry, which provides valuable guidance for forming carbon and boron nitride hybrid nanotubes as well as coaxial nanotubes with superior mechanical properties.

Scratch behavior of boron nitride nanotube/boron nitride nanoplatelet hybrid reinforced ZrB2-SiC composites

Spherical instrumented scratch behavior of ZrB2-SiC composites with and without hybrid boron nitride nanotubes (BNNTs) and boron nitride nanoplatelets (BNNPs) was investigated in this research. Typical brittle fracture such as microcracks both in and beyond the residual groove and grain dislodgement was observed in ZrB2-SiC composite, while hybrid BN nanofiller reinforced ZrB2-SiC composite exhibited predominantly ductile deformation. The peculiar three-dimensional hybrid structure in which BNNPs retain their high specific surface area and de-bundled BNNTs extend as tentacles contributes to the improved tolerance to brittle damage. Additionally, easier grain sliding due to BN hybrid nanofillers located at grain boundaries and these BN hybrid nanofillers attached on the scratch surface would provide significant self-lubricating effect to reduce lateral force during scratch and to alleviate contact damage.

Improved ampacity of buried HVDC cable with high thermal conductivity LDPE/BN insulation

Polyethylene is widely used as insulation in power cables with its excellent electrical properties except its low thermal conductivity. However, insulation-related thermal problems pose a limitation on the ampacity of HVDC cables. Improving the thermal conductivity of insulation may contribute to heat dissipation of cable system and enhance its ampacity. In this work, in order to investigate the effects of improved thermal conductivity of insulation on temperature field and ampacity in a single buried HVDC cable, a numerical simulation model is established by finite element method (FEM) and the cable ampacity is calculated by a modified iteration method. Meanwhile, a range of low-density polyethylene (LDPE) based composites filled with hybrid boron nitride (BN) particles at different loadings are prepared to get reasonable model parameters. Thermal conductivity of various samples is measured and the obtained result shows that the thermal conductivity of BN filled LDPE composite is improved greatly. The simulation results show that the cable core temperature is reduced obviously and the temperature field distribution in insulation becomes more uniform with increasing the thermal conductivity. Besides, the temperature difference between inside and outside of insulation layer shows a decreasing trend at a given load current. Namely, the cable can transmit higher current under the maximum operating temperature due to the improvement of thermal conductivity. All the conclusions imply that the improved thermal conductivity of insulation is of great benefit to the improvement of HVDC cable ampacity.

Influence of Graphite on Tribological Properties of Hexagonal Boron Nitride Hybrid/Polyimide Composites in Wide Temperature Range

Tribological and mechanical properties of aramid fiber (AF), graphite (Gr), and hexagonal boron nitride (h-BN) hybrid polyimide composites were investigated under room and high temperature. Results show that, Gr in composite reinforced with AF and h-BN can reduce coefficient of friction (COF) and improve antiwear property of composites under room temperature. Gr can accelerate the formation of transfer film under high temperature without sacrificing the wear resistant of composites. Transfer film of composites reinforced with Gr and h-BN simultaneously present more smooth and uniform compared with that of composites reinforced with only AF and h-BN. However, under higher temperature, composite reinforced with pure Gr present higher COFs and wear rates (WRs) compared with composites filled with h-BN and Gr simultaneously. Comprehensively, composite filled with 10% AF, 3% h-BN, and 4% Gr is the optimum composition.

Preparation and characterization of Ag2CrO4/few layer boron nitride hybrids for visible-light-driven photocatalysis

Nanosized Ag2CrO4/few layer boron nitride composites were prepared via in situ precipitation method. The crystal structure, morphology, optical properties, and charge carrier behavior were investigated by X-ray diffraction, transmission electrical microscopy, UV-vis diffuse reflectance spectroscopy, and electrochemical impedance spectroscopy, respectively. The photocatalytic activities of the as-prepared hybrids were discussed by degradation of rhodamine B under visible-light irradiation. Experimental results showed that the average size of pure Ag2CrO4 particles was about 20 nm. Moreover, the degradation efficiency of the as-prepared hybrids was first increased and then decreased with increasing the usage amount of few layer boron nitride nanosheets. When it was 10 wt%, in 120 min, the degradation efficiency of the as-prepared hybrids had reached the maximum of 96.7%. It was much higher than 75% of pure Ag2CrO4 nanoparticles. After 3 cycles of the degradation, the efficiency of the as-prepared composites was decreased from 96.7 to 91.8%. Trapping experiment results revealed that holes played a major role during the photocatalysis process. In addition, electrochemical impedance spectroscopy results indicated that few layer boron nitride nanosheets could enhance the separation and transfer of photogenerated electrons and holes.

Synergistic effect of hybrid graphene and boron nitride on the cure kinetics and thermal conductivity of epoxy adhesives

In the present study, the synergistic effect of hybrid boron nitride (BN) with graphene on the thermal conductivity of epoxy adhesives has been reported. Graphene was prepared by chemical reduction of graphite oxide (GO) in a mixture of concentrated H2SO4/H3PO4 acid. The particle size distribution of GO was found to be ~10 μm and a low contact angle of 54° with water indicated a hydrophilic surface. The structure of prepared graphene was characterized by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), Raman spectroscopy and atomic force microscopy (AFM). The thermal conductivity of adhesives was measured using guarded hot plate technique. Test results indicated an improvement in the thermal conductivity up to 1.65 W/mK, which was about ninefold increase over pristine epoxy. Mechanical properties of different epoxy formulations were also measured employing lap shear test. The surface characterization of different epoxy adhesive systems was characterized through XRD, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies. Fourier transform infrared also served to determine the nature of interactions between filler particles and epoxy resin. Non‐isothermal differential scanning calorimetric (DSC) technique was used to investigate the effects of graphene and BN particles on the cure kinetics and cross‐linking reaction of epoxy cured with amine curing agent. The Kissinger equation, the model‐free isoconversional Flynn–Wall–Ozawa method and the Ozawa model were used to analyze the kinetic parameter. Copyright © 2017 John Wiley & Sons, Ltd.

Synergistic improvement of thermal conductivities of polyphenylene sulfide composites filled with boron nitride hybrid fillers

Hybrid fillers of micrometer boron nitride/nanometer boron nitride (mBN/nBN) were employed to fabricate the highly thermally conductive insulating mBN/nBN/polyphenylene sulfide ((mBN/nBN)/PPS) composites via mechanical ball-milling followed by hot-compression method. The thermally conductive coefficient (λ), dielectric constant (ε) & dielectric loss tangent (tanδ) values and thermal stabilities were all enhanced with the increasing addition of mBN/nBN hybrid fillers. The λ value was improved from 0.286W/mK for pristine PPS matrix to 2.638W/mK for the (mBN/nBN)/PPS composite with 60wt% mBN/nBN (mass fraction, 2:1) hybrid fillers. Appropriate addition of the mBN/nBN hybrid fillers played a role of heterogeneous nucleation for PPS matrix. Agari model fitting revealed that the mBN/nBN hybrid fillers could be much easier to form the continuous thermally conductive channels & networks. The corresponding ε and tanδ values still maintained relatively lower level of 3.96 and 0.022, respectively. And the corresponding THeat-resistance index (THRI) value was beyond 277.8°C.

Development of Cu-Al2O3-CBN Hybrid Composite through Powder Metallurgy Process and Analysis of Mechanical Properties

In this study Copper-Aluminum Oxide-Cubic Boron Nitride hybrid composites were developed using Powder Metallurgy method. In copper matrix reinforcements used were aluminum oxide which is 5 % of total weight and Cubic Boron Nitride which is varying in composition as 0, 1, 2 and 3 % of total weight. This combination results in improvement of wear resistance. Wear resistance increases with the increasing weight percent of Cubic Boron Nitride and co-efficient of friction decreases. However mechanical properties of these hybrid composites are degraded. Various tests e.g. wear analysis, density, hardness, compressive strength and indirect tensile strength were performed in this study.

Thermal conductivity and arcing resistance of micro or hybrid BN filled polyethylene under pulse strength

In this work, in order to investigate the effects of thermal conductivity on arcing resistance from the view of thermal accumulation under pulse strength, a range of polyethylene (PE) based composites filled with micro or hybrid boron nitride (BN) particles at different loadings (0, 3, 6 and 9 wt%) were prepared. Thermal conductivity and relative permittivity were measured to characterize the basic properties of various samples. Influences of thermal conductivity on thermal accumulation and arcing resistance were discussed through surface dielectric breakdown test. Obtained results show that the thermal conductivity of BN filled PE composite is obviously improved and the relative permittivity could maintain a relatively low value. At the same pulse frequency, with increasing filler concentration from 0 to 40 wt%, thermal conductivity and the time to surface dielectric breakdown all present increase trend, whereas sample surface maximum temperature and damage degree reflect the opposite tendency. It implies that the increased thermal conductivity contributes to reduce thermal accumulation during arcing discharge, which can help to promote the resistance to arcing discharge. Moreover, PE/hybrid-BN composite presents a higher thermal conductivity, a longer time to surface dielectric breakdown and a lower surface damage degree at the same filler content. It is concluded that adding hybrid-BN filler into PE resin can suppress thermal accumulation and improve arcing resistance more effectively.

Lattice mismatch induced curved configurations of hybrid boron nitride–carbon nanotubes

A unique curved configuration is observed in freestanding hybrid boron nitride–carbon nanotubes (BN–CNTs) based on molecular dynamics simulations, which, in previous studies, was tacitly assumed as a straight configuration. The physical fundamentals of this phenomenon are explored by using the continuum mechanics theory, where the curved configuration of BN–CNTs is found to be induced by the bending effect due to the lattice mismatch between the C domain and the BN domain. In addition, our results show that the curvature of the curved BN–CNTs is determined by their radius and composition. The curvature of BN–CNTs decreases with growing radius of BN–CNTs and becomes ignorable when their radius is relatively large. A non-monotonic relationship is detected between the curvature and the composition of BN–CNTs. Specifically, the curvature of BN–CNTs increases with growing BN concentration when the molar fraction of BN atoms is smaller than a critical value 0.52, but decreases with growing BN concentration when the molar fraction of BN atoms is larger than this critical value.

Comparative photoelectrochemical studies of regioregular polyhexylthiophene with microdiamond, nanodiamond and hexagonal boron nitride hybrid films

Recently, we have studied photoelectrochemical properties of films of nanodiamond (ND)-regioregular polyhexylthiophene (RRP3HT), ND-poly(3-dodecylthiophene), polyaniline, and other derivatives of polythiophene. The ND-RRP3HT, BN-RRP3HT and microdiamond (MD)-RRPHTH films were characterized using ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction techniques, respectively. The short circuit current, fill factor, and power conversion efficiency (PCE) for MD-RRP3HT, ND-RRP3HT and hexagonal boron nitride (hBN)-RRP3HT films were compared. The ND-RRP3HT nanostructured film revealed 8 to 20 times more photocurrent than most other nanostructured RRP3HT films in a photoelectrochemical cell. The ND-RRP3HT and hBN-RRP3HT films revealed improved efficiency compared to the MD-RRP3HT film. Due to the increased band gap, the hBN-RRP3HT have a higher PCE than ND as well as MD films. ND-RRP3HT and hBN-RRP3HT hybrid films exhibited comparable photoelectrochemical properties.

Synthesis and radiation response of BCON: a graphene oxide and hexagonal boron nitride hybrid

Since graphene, there has been a focus on several two-dimensional material systems (e.g. boron nitride, borocarbon nitride (BCN), transition-metal dichalcogenides) that provide an even wider array of unique chemistries and properties to explore future applications. Specifically, tailoring graphene/boron nitride heterostructures—which can theoretically retain the character of a single-atom thick sheet, withstand large physical strains, are easily functionalized, and have entirely different optical and mechanical properties compared to graphene—can provide the foundation for entirely new research avenues. In recent years, it has been shown that because of the similar crystal structure, carbon, boron, and nitrogen can co-exist as atomic sheets in a layered structure. We have developed a facile method of integrating boron nitride (hBN) and graphene oxide (GO) via chemical exfoliation which we refer to as BCON. The study of the stability of this material at different pH conditions indicates a stable and a uniform solution is achievable at pH 4–8. X-Ray Photoelectron Spectroscopy helped to identify the new bonds which indicated the formation of BCON linkage. Further, an in situ XPS technique was used to understand the chemical changes while exposing it to ionization radiation specially focusing on the C/O ratio. It was observed that even with a very low energy source, this material is highly sensitive to ionizing radiation, such as neutron, alpha and beta particles.