2D Boron Nitride Nanosheets Research Articles

Highly thermally conductive and flexible nanocomposites prepared by integrating 1D/2D polyethyleneimine-modified boron nitride

Thermally conductive composites rely on efficient heat transfer networks. Here, we employ polyethyleneimine to modify 1D boron nitride nanotubes (BNNTs) and 2D boron nitride nanosheets (BNNSs) to improve their dispersion while enhancing the interfacial interaction between them and the matrix through amide bonds, hydrogen bonds, and Lewis acid-base interactions, thereby reducing interfacial thermal resistance. Moreover, the introduction of 1D BNNTs bridges 2D BNNSs, boosting the thermal conductivity network. This resulted in an enhanced thermal conductivity of the composite film by 17.8 %, reaching 28.71 W/(m·K) at a 30 wt% filler content. Coupled with satisfactory mechanical strength and thermal stability, this heat dissipation capability is highly valuable for applications.

Designing Nanofluidic Channels of Boron Nitride Nanosheets/Aramid Nanofibers/Covalent Organic Frameworks Nanofiltration Membrane for Ultrafast Mass Transport.

2D lamellar nanofiltration membrane is considered to be a promising approach for desalinating seawater/brackish water and recycling sewage. However, its practical feasibility is severely constrained by the lack of durability and stability. Herein, a ternary nanofiltration membrane via a mixed-dimensional assembly of 2D boron nitride nanosheets (BNNS) is fabricated, 1D aramid nanofibers (ANF), and 2D covalent organic frameworks (COF). The abundant 2D and 1D nanofluid channels endow the BNNS/ANF/COF membrane with a high flux of 194 L·m‒2·h‒1. By the synergies of the size sieving and Donnan effect, the BNNS/ANF/COF membrane demonstrates high rejection (among 98%) for those dyes whose size exceeds 1.0nm. Moreover, the BNNS/ANF/COF membrane also exhibits remarkable durability and mechanical stability, which are attributed to the strong adhesion and interactions between BNNS, ANF, and COF, as well as the superior mechanical robustness of ANF. This work provides a novel strategy to develop robust and durable 2D lamellar nanofiltration membranes with high permeance and selectivity simultaneously.

Synergistic Improvement in the Thermal Conductivity of Hybrid Boron Nitride Nanotube/Nanosheet Epoxy Composites.

Epoxy composites with excellent thermal properties are highly promising for thermal management applications in modern electronic devices. In this work, we report the enhancement of the thermal conductivity of two different nanocomposites, using epoxy resins LY564 (epoxy 1) and LY5052 (epoxy 2), by incorporating multiwalled boron nitride nanotubes (BNNT) and boron nitride nanosheets (BNNS) as fillers. The synergistic interaction between the 1D BNNT and 2D BNNS allows for improved thermal conductivity via several different mechanisms. The highest thermal conductivity was measured at a loading of 1/30 wt % of BNNT/BNNS, resulting in values of 2.6 and 3.4 Wm-1 K-1, respectively, for each epoxy matrix. This improvement is attributed to the formation of a three-dimensional heat flow path formed through intercalation of the nanotubes between the BNNS. The thermal conductivity of the epoxy 1 and 2 nanocomposites improved by 940 and 1500%, respectively, making them suitable as thermal interface materials in electronic applications requiring electrical resistivity.

Excellent high-temperature energy storage capacity for polyetherimide nanocomposites with hierarchically structured nanofillers

High-temperature electronic power systems need reliable dielectric energy storage materials, but conductive losses in extreme conditions impair their performance. Hierarchically-structured fillers are promising to not only integrate the benefits of diverse components but also effectively utilize interface engineering and electron scattering effects to optimize dielectric and breakdown properties, thereby modulating energy storage performance in polymer-based composites. In this work, we successfully fabricated hierarchical nanofillers comprising 2D boron nitride nanosheets (BNNS) and 0D ultrafine strontium titanate (ST) nanoparticles. The paraelectric ceramic ultrafine ST possesses a high dielectric constant and low residual polarization, which enhances the energy storage density of composite materials while ensuring high conversion efficiency. The PEI-based nanocomposites loaded with hierarchical BNNS@ST nanofillers attain remarkable discharged energy density (4.29 J cm−3) and charging and discharging efficiency (η > 80%) at 150 °C. This approach utilizing hierarchically-structured nanofillers offers a feasible strategy to explore high-energy–density polymer dielectrics applied in extreme environments.

Design of B/N Co-doped micro/meso porous carbon electrodes from CNF/BNNS/ZIF-8 nanocomposites for advanced supercapacitors

Boron (B) and nitrogen (N) co-doped 3D hierarchical micro/meso porous carbon (BNPC) were successfully fabricated from cellulose nanofiber (CNF)/ boron nitride nanosheets (BNNS)/ zinc-methylimidazolate framework-8 (ZIF-8) nanocomposites prepared by 2D BNNS, ZIF-8 nanoparticles, and wheat straw based CNFs. Herein, CNF/ZIF-8 acts as versatile skeleton and imparts partial N dopant into porous carbon structure, while the introduced BNNS can help strengthen the hierarchical porous superstructure and endow abundant B/N co-dopants within BNPC matrix. The obtained BNPC electrode possesses a high specific surface area of 505.4 m2/g, high B/N co-doping content, and desirable hydrophilicity. Supercapacitors assembled with BNPC-2 (B/N co-doped porous carbon with a CNF/BNNS mass ratio of 1꞉2) electrodes exhibited exceptional electrochemical performance, demonstrating high capacitance stability even after 5 000 charge-discharge cycles. The devices exhibited outstanding energy density and power density, as well as the highest specific capacitance of 433.4 F/g at 1.0 A/g, when compared with other similar reports. This study proposes a facile and sustainable strategy for efficiently fabrication of rich B/N co-doped hierarchical micro/meso porous carbon electrodes from agricultural waste biomass for advanced supercapacitor performance.

Reticulated Polyamide Thin-Film Nanocomposite Membranes Incorporated with 2D Boron Nitride Nanosheets for High-Performance Nanofiltration.

Nanofiltration (NF) technology has been widely used in saline wastewater treatment due to its unique separation mechanism. However, the NF membrane, as the core of the nanofiltration technology, is restricted by the trade-off between permeability and selectivity, which greatly restricts the development of NF membranes. The interlamellar arrangement of 2D boron nitride nanosheets (BNNSs) can provide additional transport channels and selectivity, as well as strong adsorption capacity due to its high specific surface area, exhibiting significant potential for advanced membranes. In this work, BNNSs prepared by tannic acid (TA)-assisted exfoliation (TA@BNNSs) were successfully adopted to fabricate thin-film nanocomposite (TFN) membranes via interfacial polymerization (IP). The resultant TFN membranes' structure and properties were systematically characterized via various methods. The results demonstrated that the surface morphology of polyamide membranes evolved gradually from a nodular structure to a reticular topography, accompanied by the decrease of the thickness of the polyamide selective layer when incorporating TA@BNNSs into the membranes. This phenomenon can be mainly ascribed to that the uptake density and diffusion of piperazine (PIP) monomer were effectively regulated by BNNSs. This is validated by molecular dynamics and revealed by the adsorption of PIP in BN models, the diffusion coefficients, and interaction energies, respectively. In addition, the TFN membranes demonstrated improved permeance and stable solute rejection for the inorganic salts. Specifically, the water flux of PA-TA@BNNSs-10%/PMIA membrane could reach up to 109.1 ± 2.49 L·m-2·h-1 while keeping a high rejection of 97.5 ± 0.38% to Na2SO4, which was superior to most of the reported membranes in the literature. Besides, the PA-TA@BNNSs-10%/PMIA membrane exhibited an excellent stability in the long-term filtration process. The finding in this work provides a potential strategy for developing the next-generation 2D material-based membranes with high-performance for separation applications.

A Novel Anti-Flashover Superhydrophobic Coating with Self-Assembly Characteristic of Surface Energy Differences.

Because of the versatility of superhydrophobic materials, they have attracted a lot of attention even in power electronics, transportation, engineering, and other fields. The volume fraction of fluorinated silicon oxide nanoparticles in superhydrophobic materials is one of the most important factors. Increasing the volume fraction will decrease the stability between the coating and the hydrophobic surface. Especially, the flashover voltage of the coating gradually decreases from 10 to 35vol.%. Meanwhile, the flashover voltage dispersion of the coating increases drastically after 30vol.%. In order to improve the electrical properties of the superhydrophobic coating, self-assembly of surface energy differences strategy is proposed in this work. A binary filling phase of the coating is introduced by 2D boron nitride nanosheets and silicon oxide nanoparticles. Although Hexagonal boron nitride with high surface energy and low roughness, it will be spontaneously assembled and wrapped by silicon oxide nanoparticle based on surface energy differences, which forming a low surface energy filled phase. Experiment results prove that the flashover voltage of the superhydrophobic coating is optimized by the binary filling phase coating. This method offers new ideas for the selection of filling phase and application of superhydrophobic materials.

Improved Energy Density Obtained in Trilayered Poly(vinylidene fluoride)-Based Composites by Introducing Two-Dimensional BN and TiO2 Nanosheets

Dielectric capacitors with an ultrahigh power density have received extensive attention due to their potential applications in advanced electronic devices. However, their inherent low energy density restricts their application for miniaturization and integration of advanced dielectric capacitors. Herein, a novel composite entirely incorporated with two-dimensional (2D) nanosheets with a topological trilayered construction is prepared by a solution casting and hot-pressing method. The 2D boron nitride nanosheets (BNNS) with a wide band gap that are oriented in a poly(vinylidene fluoride) (PVDF) matrix to form the upper and bottom outer layers would efficiently suppress the leakage current in composites, thus significantly improving the overall breakdown strength. Meanwhile, the 2D anatase-type TiO2 nanosheets (TONS) uniformly distributed in the middle layer can enhance their interfacial compatibility and polarization with the PVDF matrix, leading to a synergistic improvement in both the breakdown strength and dielectric constant of the composite. In particular, a significantly improved dielectric constant of ∼11.42, a reduced dielectric loss of 0.03 at 100 Hz, and a maximum discharge energy density (Udis) of 10.17 J cm-3 at an electric field of 370.1 MV m-1 can be obtained from the trilayered composite containing 3 wt % 2D TONS in the middle layer and 2 wt % 2D BNNS on the outer layer. The finding of this research offers an effective strategy for the preparation of advanced polymer-based composites with an outstanding discharge energy density performance.

A facile fabrication of nanocomposites with dual conductive networks based on 3D nickel foam, 1D silver nanowires and 2D boron nitride nanosheets

A facile fabrication of nanocomposites with dual conductive networks based on 3D nickel foam, 1D silver nanowires and 2D boron nitride nanosheets

2D Boron Nitride Nanosheets in Polymer Nanofibers for Triboelectric Nanogenerators with Enhanced Performance and Flexibility

2D Boron Nitride Nanosheets in Polymer Nanofibers for Triboelectric Nanogenerators with Enhanced Performance and Flexibility

Multilayer heterogeneous dielectric films with simultaneously improved dielectric constant and breakdown strength

Due to the development of the microelectronics industry, there is a great demand for flexible polymer dielectrics with simultaneously excellent permittivity and dielectric breakdown strength, so as to realize the prominent dielectric energy storage capability. Here, we prepare sandwich-structure films with ferroelectric dielectric Polyvinylidene Fluoride (PVDF) acting as the top layer, 2D Boron Nitride nanosheets (BNNS) as the middle layer and linear dielectric Polyimide (PI) as the bottom layer. In the films the PVDF ferroelectric layer provides high polarization, the PI linear layer enhances the dielectric breakdown strength and decreases dielectric loss, and the 2D sheet BNNS layer further strengthens the dielectric breakdown insulation. The permittivity of the multilayer films is in the range of 5.0–6.3 and dielectric loss are all below 0.03 at 100 Hz. And the sandwich-structure film with 3 mg/mL BNNS can achieve a highest dielectric energy storage of 4.35 J/cm3 at 417.6 kV/mm, surpassing that of the currently commercial BOPP by about 360 % (≈1.2 J/ cm3 under the electric field of 640 kV/mm). In addition, the multilayer films exhibit satisfactory thermal stability and mechanical properties. The multicomponent heterogeneous layered materials with simultaneously enhanced permittivity and dielectric insulating strength demonstrate a wide application prospect in the field of dielectric energy storage.

Flexible boron nitride composite membranes with high thermal conductivity, low dielectric constant and facile mass production

With the ever-increasing development of 5G technology, high signal propagation loss and high heating flux in miniaturizing devices bring about simultaneous and urgent requirement for thermal management materials with insulating, flexible, highly thermal conductive and low dielectric properties. However, these properties are not easy to simultaneous implement due to the phonon scattering and interfacial polarization, bringing a negative impact on working efficiency and service life of high-power electronics and portable devices. Herein, the flexible boron nitride composite membranes with high thermal conductivity, low dielectric constant and facile mass production was successfully prepared by coating directional forming and vacuum pressure technology. The directional arrangement of 2D boron nitride nanosheets (BNNS) in boron nitride-enhanced heat spreaders (BNHS) made the heat diffuse along in-plane direction and effectively improve the TC as high as 81.49 Wm−1K−1. In addition, the BNHS had a series of advantages of good electric insulation (the order of 1013 Ω cm), low dielectric constant (ϵ＜3) and low dielectric loss in the frequency range of 1 MHz–1 GHz. The BNHS also exhibited excellent flexibility (bending 20,000 times), high thermal stability and low water absorption. Distinguishing from electroconductive and heat-conducting graphite or graphene films, such superior BNHS with electric insulation but high TC and low dielectric constant will carve a distinctive path in the application of thermal management materials, such as RF antenna, filter, resonator and wireless charger.

Improved mechanical, thermal properties and ideal dielectric properties of polyimide composite films by incorporation of boron nitride nanosheets and aramid nanofibers

AbstractIn this work, a high‐performance composite film polyimide (PI)/boron nitride nanosheets (BNNS) + aramid nanofibers (ANFs) was prepared by in‐situ polymerization. Modified two‐dimensional (2D) BNNS were prepared by urea‐assisted ball milling to exfoliate and NH2 functionalize hexagonal boron nitride(h‐BN) in one step. One‐dimensional (1D) ANFs prepared by deprotonation method and 2D BNNS were simultaneously incorporated into PI and used as effective reinforcement nanofillers. This novel PI/BNNS + ANFs composite film has excellent thermal stability and mechanical properties. Compared with pure PI, the glass transition temperature (Tg) increased by approximately 18°C, and the coefficient of thermal expansion (CTE) decreased by 11.45%. Remarkably, the tensile strength and elongation at break of PI/BNNS + ANFs‐1 wt% composite film increased by 18.6% and 133.4%, respectively. The improvement of thermal stability and mechanical properties were ascribed to the uniform dispersion of BNNS + ANFs and the interfacial interaction between BNNS + ANFs and PI matrix. Furthermore, the PI/BNNS + ANFs composite films show good dielectric properties and optical transparency. These excellent comprehensive properties of the PI/BNNS + ANFs composite films make it a good candidate for the flexible substrate.

Wire-sheet assembly construction of boron nitride/single-walled carbon nanotube shape-stabilized phase change composites for light-thermal energy conversion and storage

As one of the most abundant energy, solar energy has already drawn great attention both from academia and industry, but how to use it to the utmost extent is still a formidable challenge for the development of human. Phase change material (PCM) is proved to be one of the most promising technique for storing thermal energy. Herein, we designed and fabricated a three-dimensional (3D) phase change composite (PCC) with excellent light-to-thermal conversion by constructing one-dimensional (1D) linear single-walled carbon nanotubes (SWNTs), two-dimensional (2D) boron nitride nanosheets (BNNSs) and polyethylene glycol (PEG) into a 3D bulk structure. This structure supplies the prepared PCMs with high thermal conductivity, excellent solar-thermal conversion efficiency, and high energy storage density. Results showed that the PCCs displayed a well-defined 3D interconnected structure, and their melting and crystallization enthalpies were 156.36 J/g and 153.33 J/g, respectively, which changed only slightly after 110 thermal cycles. The thermal conductivity of the composites could reach 0.92 W∙m−1∙K−1, which effectively enhanced the thermal response rate. Beyond that, the PCCs exhibited good leakage-proof performance and excellent thermal regulation performance. And the light-to-thermal conversion efficiency of PCCs reached 97.15%. These results indicate that this strategy can be efficiently used to develop novel PCCs with improved comprehensive thermal performances and high light-to-thermal conversion.

Coupling two-dimensional fillers with polymer chains in solid polymer electrolyte for room-temperature dendrite-free lithium-metal batteries

The urgent demand for high security and high energy density all-solid-state batteries has generated a strong interest in polyethylene oxide (PEO)-based solid polymer electrolyte (SPE). However, devising a SPE with a high ionic conductivity without sacrificing mechanical properties remains a critical challenge. Herein, an interpenetrating polymer network electrolyte is designed by chemical grafting coupling, where 2D boron nitride nanosheets and poly(ethylene glycol)diacrylate were coupled by a silane coupling agent. A considerable intensification of mechanical strength has been achieved for the SPE via the graft-coupling strategy, and the interpenetrating network with BNNs leads to the generation of amorphous regions for fast Li-ion immigration. The electrolyte integrates high mechanical strength with enhanced room-temperature ionic conductivity, enabling a long-cycle stability dendrite-free Li||Li symmetrical cell, and prominent cyclic performance is demonstrated in full cells at room temperature. Our approach provides a broader promise for the practical applications of solid-state batteries.

2D boron nitride nanosheets in PIM-1 membranes for CO2/CH4 separation

Physical aging represents one of the major obstacles towards adoption of polymer of intrinsic microporosity (PIM) membranes for gas separation applications. In this work, mixed matrix membranes (MMMs) of 2D boron nitride nanosheets (BNNS) and PIM-1 were prepared and applied in the separation of a CO2/CH4 (1:1, v:v) binary gas mixture. The membranes were tested over a period of more than one year to evaluate their anti-aging properties as compared to neat PIM-1. The results show that introducing BNNS into PIM-1 leads to a significant reduction in the physical aging of PIM-1, as demonstrated by the values of reduction in CO2 permeability after 414 days (22% for the MMMs as compared to 58% for neat PIM-1). This work paves the way to using PIM-based membranes in industry.

Sulfate ionic liquids impregnated 2D boron nitride nanosheets for trace SO2 capture with high capacity and selectivity

Owing to the abundant ionic sites and good molecular recognition ability of ionic liquids (ILs), the impregnation of ILs on support materials is an attractive strategy for trace SO2 capture with both desired capacity and high selectivity. Herein, we successfully prepared a kind of hexagonal boron nitride (h-BN) nanosheets impregnated sulfate functionalized ILs tetramethylethylenediamine ethylsulfate (x[TMEDA][DES]@BN, x = mass ratio) for capture of low-concentration SO2. It is found that the low-concentration SO2 uptakes of 1.5[TMEDA][DES]@BN were extremely high, with the amount of 2.3 mmol g−1 at 293.2 K and 0.01 bar, and 0.82 mmol g−1 at 293.2 K and 0.002 bar. Meanwhile, 1.5[TMEDA][DES]@BN showed a very fast SO2 adsorption rate and reached an unprecedented SO2/CO2 selectivity (2714) for the mixture of 1% SO2 and 99% CO2. Finally, dynamic column breakthrough tests further confirmed the excellent separation performance and good reversibility of 1.5[TMEDA][DES]@BN in deeply removing 2000 ppm SO2 in the mixture of SO2/CO2/N2.

Characterization of 2D boron nitride nanosheets with hysteresis effect in the Schottky junctions

Carbon doped two-dimensional (2D) hexagonal boron nitride nanosheets (BNNSs) are obtained through a CO2—pulsed laser deposition (CO2—PLD) technique on silicon dioxide (SiO2) or molybdenum (Mo) substrates, showing - stable hysteresis characteristics over a wide range of temperatures, which makes them a promising candidate for materials based on non-volatile memory devices. This innovative material with electronic properties of n-type characterized in the form of back-to-back Schottky diodes appears to have special features that can enhance the device performance and data retention due to its functional properties, thermal-mechanical stability, and its relation with resistive switching phenomena. It can also be used to eliminate sneak current in resistive random-access memory devices in a crossbar array. In this sense constitutes a good alternative to design two series of resistance-switching Schottky barrier models in the gold/BNNS/gold and gold/BNNS/molybdenum structures; thus, symmetrical and non-symmetrical characteristics are shown at low and high bias voltages as indicated by the electrical current-voltage (I–V) curves. On the one hand, the charge recombination caused by thermionic emission does not significantly change the rectification characteristics of the diode, only its hysteresis properties change due to the increase in external voltage in the Schottky junctions. The addition of carbon to BNNSs creates boron vacancies that exhibit partially ionic character, which also helps to enhance its electrical properties at the metal-BNNS-metal interface.

Scalable preparation of 2D boron nitride nanosheets and enhancement of UV absorption and thermal conductivity of cellulose nanofibers membrane

Hexagonal boron nitride nanosheets (h-BNNSs) are known to exhibit numerous prominent performances. However, scalable synthesis of h-BNNSs with a green, simple method has been difficult to achieve. In this study, xylitol-assisted discontinuous ball milling exfoliation (XADBME) of hexagonal boron nitride (h-BN) was proposed as a novel strategy for scalable synthesis of h-BNNSs. First, the high yield (above 80 wt%) could be achieved smoothly with this green chemistry method. Moreover, the as-synthesized h-BNNSs exhibited large lateral size, ultra-thin, defect-free. Lastly, the as-synthesized BNNSs and cellulose nanofibers (CNFs) were compounded to form a series of membrane materials. The mentioned membranes exhibited high in-plane thermal conductivity and prominent UV absorption characteristics. 70 wt% BNNS membrane [3.4 W(mK)−1] exhibited nearly 400% higher in-plane thermal conductivity than that of membrane without BNNS [0.7 W(mK)−1]. Thus, it shows promising applications in thermal management of electronic display screens, eye protection equipment, as well as portable mobile devices.

Characterization of boron nitride nanosheets synthesized by boron-ammonia reaction

Boron nitride nanosheets (BNNS) with thickness 5–11 nm were successfully produced when pure boron powder (1–2 μm) interacted with ammonia gas in chemical vapour deposition set up. Under the optimized parameters, at 1200 °C and for uninterrupted 1 h of reaction duration, 2D BNNS with thickness of ca.11 nm were synthesized. BNNS were characterized by X-ray diffraction (XRD) for crystal structure, scanning electron microscopy for dimensions and morphology, energy dispersive X-ray analysis for chemical composition and Fourier transform infrared spectroscopy for sp2 BN bond detection. The thickness of BNNS determined from both XRD data (using Scherrer equation) and atomic force microscopic analysis confirmed the stated product thickness. The BNNS obtained at 1200 °C had high crystallinity, purity and yield.