Boron Nitride Network Research Articles

Topological and site disorder in boron nitride networks.

Amorphous boron nitride (a-BN) is modelled over a wide range of densities using a relatively simple potential model augmented with site charges. The local topology (defined, for example, through the total nearest-neighbour coordination number), appears near-constant across a wide range of densities and site charges. Furthermore, total scattering and total pair distribution functions also show few changes as a function of either density or site charge. Variation of the site charges directly controls the level of site (rather than topological) disorder meaning that although total pair functions may be near-constant, the underlying partial contributions may be very different. Direct contact is made with both experiment and (more recent) density-functional theory-based modelling work.&#xD.

Construction of tree-ring mimetic 3D networks in polyvinyl alcohol/boron nitride composites for enhanced thermal management and mechanical properties

Constructing a three-dimensional (3D) filler network in polymer thermal interface materials (TIMs) is crucial for enhancing thermal conductivity and mechanical properties. However, the discontinuous and loose network of fillers are one of the main reasons hindering the joint improvement of thermal conductivity and mechanical properties. The construction of a regular and dense 3D continuous filler network remains a significant challenge. In this study, an innovative bidirectional freezing technique was designed to create a polyvinyl alcohol (PVA)/boron nitride (BN) composite with a tree-ring-like 3D network. This technique promotes the formation of 3D network consisting of long-range lamellar BN layers with a tree-ring-like structure by controlling the nucleation and growth of ice crystals along the bidirectional temperature gradient induced by a polytetrafluoroethylene (PTFE) cone. The resulting PVA/BN composite exhibits high thermal conductivity (6.25 W/m·K) due to the lower interfacial thermal resistance between fillers (1.271 × 10−7 K m2/W), and an enhanced tensile strength of 41.71 MPa, which is attributed to the regular and dense BN network. This study presents a feasible strategy for constructing a 3D continuous network structure in polymer-based TIMs, paving the way for advancements in thermal management solutions.

Constructing highly thermally conductive polystyrene-based composites by introducing multi-walled carbon nanotubes into melamine foam-supported boron nitride network

High-density 3D thermally conductive nanofiller network plays a vital role in the fabrication of polymer-based composites with high thermal conductivity (TC) for thermal management systems. In this work, highly thermally conductive polystyrene (PS)-based composites were prepared by introducing boron nitride nanosheets-coated melamine foam (MF@BNNSs) and carboxylated multi-walled carbon nanotubes (MWCNT–COOH). In this unique structure, MF@BNNSs can provide a 3D thermally conductive network, while MWCNT–COOH is embedded into the MF@BNNSs skeleton to improve the network-density. Specifically, the TC of PS/MWCNT/MF@BNNSs composite with 0.6 wt% MWCNT–COOH loading reaches 5.33 W /m· K, about 4.4-fold as high as that of the PS/MF@BNNSs. Moreover, the PS/MWCNT/MF@BNNSs composite exhibits effective heat dissipation capacity after assembling the power LED chip. Due to the isolation effect of MF@BNNSs skeleton, the PS/MWCNT/MF@BNNSs maintain electrical insulation properties. Consequently, the design of the thermal conductive network based on MF@BNNSs and MWCNT–COOH offered a substantial potential avenue for the preparation of polymer-based composites with high TC and insulating properties.

Vitrimeric phase change material facilitating 3D-structured boron nitride network for reliable thermal conductive interface materials

Phase change materials (PCMs) shows great promise as thermal interface materials (TIMs) due to their compliance and thermal management properties from solid-liquid phase transition characteristics. However, the significantly reduced thermal conductivity resulting from that randomly dispersed thermal conductive fillers susceptible to localized volume change by solid-liquid phase transition deteriorates the reliable heat transfer of TIM but is often overlooked. In this work, 3D-structured network of boron nitride (BN) fillers is created in vitrimeric PCM (vPCM) consisting of dynamic covalent crosslinked polyolefin elastomer (POE)/paraffin wax (PW) blends. The resulted composites with interconnected BN network show a through-plane thermal conductivity (κ⊥) of 3.08 W m−1 K−1 at 29.8 vol% BN. Significantly, the composites can keep the BN network continuous when heated, and remain κ⊥ of about 1.4 W m−1 K−1 after the solid-liquid phase transition of PW, which ensures reliable heat transfer when achieving thermal management by melting endotherm of PW. Moreover, the composites conform to the surface topography of sandwiching surfaces through solid plasticity under low stress when the crosslinked network rearranges via the exchange of dynamic covalent bonds activated by the melting of POE, reducing the thermal contact resistance. When the composites are used as TIM through thermally triggered reconfigurable package procedures at 80 °C and 50 kPa, the heat dissipation is better than a commercial thermal pad with κ⊥ of 3.86 W m−1 K−1. Vitrimeric PCM facilitates reliable 3D-structured BN network and thermally triggered conformability, paving a promising way for high-performance TIM with excellent heat dissipation.

Dressing Paraffin Wax/Boron Nitride Phase Change Composite with a Polyethylene "Underwear" for the Reliable Battery Safety Management.

Phase change material (PCM) can provide a battery system with a buffer platform to respond to thermal failure problems. However, current PCMs through compositing inorganics still suffer from insufficient thermal-transport behavior and safety reliability against external force. Herein, a best-of-both-worlds method is reported to allow the PCM out of this predicament. It is conducted by combining a traditional PCM (i.e., paraffin wax/boron nitride) with a spirally weaved polyethylene fiber fabric, just like the traditional PCM is wearing functional underwear. On the one hand, the spirally continuous thermal pathways of polyethylene fibers in the fabric collaborate with the boron nitride network in the PCM, enhancing the through-plane and in-plane thermal conductivity to 10.05 and 7.92Wm-1 K, respectively. On the other, strong polyethylene fibers allow the PCM to withstand a high puncture strength of 47.13 N and tensile strength of 18.45MPa although above the phase transition temperature. After this typical PCM packs a triple Li-ion battery system, the battery can be promised reliable safety management against both thermal and mechanical abuse. An obvious temperature drop of >10°C is observed in the battery electrode during the cycling charging and discharging process.

Hexaphenoxy cyclotriphosphazene/boron nitride high-efficiency charring system enhancing the flame retardancy and thermal conductivity of polycarbonate

Polycarbonate (PC), as an engineering plastic, has excellent mechanical properties and electrical insulation properties. Nevertheless, with the rapid spread of 5 G applications, there is an increasing demand for functional PC materials with both thermal conductivity and flame retardant properties. In this study, the flame retardant thermal conductivity composite system of boron nitride (BN) and hexaphenoxy cyclotriphosphazene (HPCP) was constructed to study the simultaneous improvement of the flame retardant and thermal conductivity of PC. The results reveal that the inclusion of HPCP and BN in PC can significantly enhance its flame retardancy. This enhancement is evidenced by prolonged ignition time, reduced heat release rate and decreased total smoke production. In particular, 20BN/3HPCP/PC composite shows the best flame retardant effect. Through the investigation of flame retardant mechanisms, it has been found that the network structure formed by the BN sheets with phosphorus-containing products of HPCP decomposition can effectively filter and adsorb pyrolysis debris and increase the residence time of burning fragments in the pyrolysis zone promoting the pyrolysis products further fully burned to reduce the smoke caused by incomplete combustion. The phosphoric acid substances after the decomposing of HPCP can promote PC matrix to dehydration and carbonization to form the phosphorus-containing residues, which adheres on the BN network structure to form hardness char layers in the condensed phase to play an excellent role in blocking heat and combustible flue gas, which has a positive effect on reducing heat release rate and improving flame suppression. In terms of improving thermal conductivity, the infrared thermal imaging experiment further confirmed that BN sheets can increase the thermal conductivity of PC composites by more than 4 times, and the layer and layer stacks structure of BN sheets can endow an efficient thermal conductivity path for PC matrix to improve the thermal conductivity. Therefore, this study is meaningful practical exploration for developing the PC composites with excellent thermal conductivity and flame retardancy.

High thermal conductive polyurethane composite films with a three-dimensional boron nitride network in-situ constructed by multi-folding and multi-laminating

Based on the chemical modifications of the few-layer boron nitride nanosheets (BNNSs) prepared by ball milling, several BNNS/polyurethane (PU) composite films (non-laminated films) were prepared by solution blending. It showed that the modified BNNSs (M-BNNSs) in PU matrices assembled into boron nitride (BN) micro-flakes and mildly orientated along the film planes. Then, an approach of multi-folding and multi-laminating further promoted the orientation, stacking and connection of BN micro-flakes, by which a three-dimensional (3D) BN network composed of lamellar BN skeleton and a small number of BN linkers was in-situ constructed in the PU composite films (laminated films). For the existence of a continuous heat conductive channel based on the 3D BN network, the thermal conductivities (TCs) of the laminated films were obviously enhanced compared to the corresponding non-laminated films. The incorporation of M-BNNSs further improved the electrical insulation of the laminated films. When the M-BNNS content was 50 wt%, the in-plane TC of the laminated film reached 23.80 W/m·K. The laminated film with M-BNNS content of 30 wt% showed high TC, good flexibility, and outstanding electrical insulation, who is a promising candidate for the flexible thermal management materials.

Thermally Conductive, Electrically Insulating Epoxy Pads with Three-Dimensional Polydopamine-Modified and Silver Nanoparticle-Functionalized Hexagonal Boron Nitride Networks

Thermally Conductive, Electrically Insulating Epoxy Pads with Three-Dimensional Polydopamine-Modified and Silver Nanoparticle-Functionalized Hexagonal Boron Nitride Networks

Heat-conducting elastic ultrafine fiber sponges with boron nitride networks for noise reduction

Industrial and traffic noise has become increasingly serious with the progress of industrialization. Most existing noise-absorbing materials suffer from poor heat dissipation and insufficient low-frequency (<1000 Hz) noise absorption, which not only reduces working efficiency but also leads to safety risks. Herein, heat-conducting elastic ultrafine fiber sponges with boron nitride (BN) networks were prepared by integrating direct electrospinning and impregnation method. The large acoustic contact area of ultrafine fibers and the vibration effect of BN nanosheets in a three-dimensional direction endow fiber sponges with good noise reduction, which can reduce white noise by 28.3 dB with a high noise reduction coefficient of 0.64. Moreover, thanks to good heat-conducting networks composed of BN nanosheets and porous structures, the obtained sponges exhibit superior heat dissipation with thermal conductivity of 0.159 W m−1 K−1. Besides, the introduction of elastic polyurethane and following crosslinking endow the sponges with good mechanical properties, which have almost no plastic deformation after 1000 compressions, and the tensile strength and strain are as high as 0.28 MPa and 75%. The successful synthesis of heat-conducting elastic ultrafine fiber sponges overcomes poor heat dissipation and low-frequency noise reduction of noise absorbers.

Sustainable Synthesis of Highly Biocompatible 2D Boron Nitride Nanosheets.

2D ultrafine nanomaterials today represent an emerging class of materials with very promising properties for a wide variety of applications. Biomedical fields have experienced important new achievements with technological breakthroughs obtained from 2D materials with singular properties. Boron nitride nanosheets are a novel 2D layered material comprised of a hexagonal boron nitride network (BN) with interesting intrinsic properties, including resistance to oxidation, extreme mechanical hardness, good thermal conductivity, photoluminescence, and chemical inertness. Here, we investigated different methodologies for the exfoliation of BN nanosheets (BNNs), using ball milling and ultrasound processing, the latter using both an ultrasound bath and tip sonication. The best results are obtained using tip sonication, which leads to the formation of few-layered nanosheets with a narrow size distribution. Importantly, it was observed that with the addition of pluronic acid F127 to the medium, there was a significant improvement in the BN nanosheets (BNNs) production yield. Moreover, the resultant BNNs present improved stability in an aqueous solution. Cytotoxicity studies performed with HeLa cells showed the importance of taking into account the possible interferences of the nanomaterial with the selected assay. The prepared BNNs coated with pluronic presented improved cytotoxicity at concentrations up to 200 μg mL-1 with more than 90% viability after 24 h of incubation. Confocal microscopy also showed high cell internalization of the nanomaterials and their preferential biodistribution in the cell cytoplasm.

Three-dimensional boron nitride network/polyvinyl alcohol composite hydrogel with solid-liquid interpenetrating heat conduction network for thermal management

• Solid-liquid interpenetrating heat conduction network. • Heat conduction and storage function. • Efficient thermal management materials. Polyvinyl alcohol hydrogels have been used in wearable devices due to their good flexibility and biocompatibility. However, due to the low thermal conductivity ( κ ) of pure hydrogel, its further application in high power devices is limited. To solve this problem, melamine sponge (MS) was used as the skeleton to wrap boron nitride nanosheets (BNNS) through repeated layering assembly, successfully preparing a three-dimensional (3D) boron nitride network (BNNS@MS), and PVA hydrogels were formed in the pores of the network. Due to the existence of the continuous phonon conduction network, the BNNS@MS/PVA exhibited an improved κ . When the content of BNNS is about 6 wt.%, κ of the hydrogel was increased to 1.12 W m −1 K −1 , about two times higher than that of pure hydrogel. The solid heat conduction network and liquid convection network cooperate to achieve good thermal management ability. Combined with its high specific heat capacity, the composites have an important application prospect in the field of wearable flexible electronic thermal management.

A guanidine phosphate-assisted boron nitride network enabled simultaneous improvements in flame resistance and thermal conductivity of polyvinyl alcohol (PVA)

Polyvinyl alcohol (PVA) plays an important role in many fields, but its flammability in air limits its wider application. In this work, SiO2@BN, a flame-retardant and heat conductive filler, were synthesized by hydrolysis of ethyl orthosilicate, and its structure and morphology were characterized successfully. SiO2@BN and guanidine phosphate (GP) were mixed evenly in the solution and added to PVA to form PVA composites. Based on the data of thermal conductivity, limiting oxygen index (LOI) and cone calorimeter test (CCT), the thermal conductivity and flame retardancy of the composite were studied, and the flame retardancy mechanism was explained. The results showed that the thermal conductivity of the PVA composite added with 2 wt.% SiO2@BN and 8 wt.% GP was 82.4% higher than that of pure PVA, and its LOI value reached 28.4%, which was 38.5% higher than that of pure PVA. The peak heat release rate (pHRR) and total heat release (THR) of the composites was 65.2% and 44.4% lower than those of pure PVA, respectively. The main reasons were the physical barrier effect of BN and SiO2, the dilution of the noncombustible gas generated by the decomposition of GP when heated, and the dehydration and carbonization of PVA promoted by the generated phosphoric acid, metaphosphoric acid and other substances.

Cooling photoluminescent phosphors in laser-excited white lighting with three-dimensional boron nitride networks

Laser-excited white lighting, which is achieved by laser diodes and phosphor converters, has garnered increasing interest in recent years due to their high-power and high-brightness characteristics. Nevertheless, two long-standing thermal issues remain formidable: first, the photoluminescent phosphors also generate heat due to the Stokes loss, which are the second heat source in the packaging but long ignored; second, the phosphors are embedded in low-thermal-conductivity silicone and the generated heat is rather inefficient to dissipate. As a result, the accumulated heat leads to high temperature in phosphor particles and even thermal quenching, which deteriorate the luminescence, chromaticity, and reliability. In this work, these problems are successfully addressed by establishing three-dimensional (3D) boron nitride (BN) networks to cool the silicone-embedded phosphor particles in a facile and scalable method. When lighted under the driven current of 900 mA, the working temperature of phosphor layer is dramatically decreased by 95.2 °C with the 3D-BN network without sacrificing the luminescence and chromaticity. Such strategy with excellent cooling performance, high reliability, and easy scalability may hold great promise for broader optoelectronics applications beyond laser-excited white lighting.

Silver nanoparticles bridging segregated hexagonal boron nitride networks for enhancing the thermal conductivity of polystyrene composites

The segregated heat conductive networks constructed from two-dimensional (2D) hexagonal boron nitride (hBN) are promising in improve the thermal conductivity of polymer-based thermal management materials (TMMs), however, the high interfacial thermal resistance between adjacent hBN sheets remains challenging. Hence, high-performance polystyrene (PS)-based composites with continuous segregated hBN@AgNP networks were designed and prepared by hot-pressing method. Benefited from the modification and bridge effect of AgNP, the interconnected hBN exhibited significantly reduced contact thermal resistance, which provide the effective pathways for phonon conduction. The as-fabricated PS/hBN@AgNP composite exhibited high thermal conductivity (1.17 and 1.53 W/mK, 30 wt%) corresponding to enhancements of 738.4% and 989.9% compared with neat PS, significantly higher than random PS/hBN and composites without AgNP in the segregated structure. Therefore, this work provides a strategy for the preparation of high-performance polymer-based TMMs by reducing the interfacial thermal resistance in interconnected filler network.

Construction of compressible dual thermally conductive boron nitride network supported by Polyurethane@Polydopamine skeleton for improved thermal management performance

Due to the increasing heat dissipation problem of modern electronic components, polymer-based thermally conductive composites have attracted extensive attention. Whereas, the improvement of thermal conductivity of composites are often accompanied by the loss of mechanical properties. Here, we report the preparation of polymer-based thermally conductive composites containing dual thermally conductive networks consisting of macro and micro-networks by a simple aqueous dip-coating process combined with a layer-by-layer assembly of core–shell structures. The thermal conductivity of polyurethane@polydopamine@boron nitride/polydimethylsiloxane (FPB/PDMS) composite reaches 0.70 W•m−1•K−1 when the filling amount of boron nitride is only 3.80 vol%, the thermal conductive enhancement reaches 367 %, and toughness reaches 80.00 J•m−3, realizing the collaborative improvement of thermal conductive and mechanical properties. At the same time, the LED chip with the composite which serve as thermal interface materials (TIMs) can effectively dissipate heat, which exhibits thermal management application prospect.

Three-dimensional boron nitride reinforced thermal conductive composites with high elasticity

Polymer-based thermally conductive composites have good interfacial contact, processability and stability. However, because of the low thermal conductivity of polymer materials, usually, a larger percentage of filler is required to achieve high thermal conductivity, which leads to a drop in the resilience of the composite. To solve this problem, a melamine-formaldehyde resin sponge (MS) was used as a skeleton to wrap boron nitride nanosheets (BNNS) through repeated layering assembly, successfully preparing a three-dimensional (3D) boron nitride network (BNNS@MS). The mixture of poly(vinylidene fluoride) and BNNS (PVDF/BNNS) was formed in the pores of the 3D network of BNNS@MS. Due to the existence of the continuous phonon conduction network, the BNNS@MS/PVDF exhibits good thermal conductivity and high elastic deformation (rebound at 90% compression). When the content of BNNS is about 5 wt%, the thermal conductivity of the BNNS@MS/PVDF is increased to 1.43 ± 0.2 W/mK, 51.1% higher than that of PVDF/BNNS. The solid heat conduction network and polymer interplay to achieve good thermal management ability, and the composites have an important application prospect in the field of wearable flexible electronic thermal management.

Flexible 3D porous boron nitride interconnected network as a high-performance Li-and Na-ion battery electrodes

To achieve the high-rate efficiency in a electrochemical energy storage technologies, it is vital for the battery anode to be electronically as well as ionically conductive. Such a requirement has boosted the survey of three-dimensional (3D) porous networks made up of light-weight non-metallic elements, like carbon, boron, and nitride. A wide range of 3D porous materials composed of carbon and/or boron for Li/Na-ion batteries have been recently reported, whereas analogous efforts for lightest 3D porous boron nitride are yet to be addressed. In this work, we explore the 3D porous boron nitride network namely sp3-linked zigzag BN nanoribbons (BNNRs) with a width of 1 (lz1-BN) by assembling the 2D zigzag BNNRs and its first ever application as battery anodes for Li and Na ion batteries. Upon a consistent DFT and AIMD computations, It is revealed that the 3D porous lz1-BN material is chemically and thermally stable and yields a high specific capacity of about 539.94 mAh/g with respect to the commercialized graphite (372 mAh/g for LIBs) and recently reported Janus-graphite anode (≈332 mAh/g for SIBs), fast (Li+,Na+)-ionic diffusion, low potential voltage, and slight volume-expansion. Such puzzling electrochemical characteristics, along with the light-weight and high abundance of B and N elements, strongly support the possibility of 3D porous BN as a desirable candidate for Li and Na-ion battery anodes.

Overlapping electron density and the global delocalization of π-aromatic fragments as the reason of conductivity of the biphenylene network.

Recently fabricated 2D biphenylene network is an astonishing solid-state material, which possesses unique metal-like conductive properties. At the same time, two-dimensional boron nitride network (2D-BN)-an isoelectronic and structural analogue of biphenylene network, is an insulator with a wide direct bandgap. This study investigates the relationship between the electronic properties and chemical bonding patterns for these species. It is shown that the insulating 2D-BN network possesses a strong localization of electron density on the nitrogen atoms. In turn, for a carbon-containing sheet, we found a highly delocalized electron density and an appreciable overlap of pz orbitals of neighboring C6 rings, which might be a reason for the conductive properties of the material.

A novel three-dimensional boron phosphide network for thermal management of epoxy composites

Recently, construction of effective three-dimensional (3D) heat transfer networks inside polymer has emerged as a promising design strategy to improve the isotropic thermal conductivity for electronic packaging materials. Hexagonal boron nitride (BN) sheets are popular carriers for constructing 3D networks. But removing overheat capability of BN was greatly sacrificed due to size limitation when constructing 3D network. Herein, a novel 3D heat-transferring network, interconnected boron phosphide (BP) grains in-situ growing on Ni foam, was designed to alternate 3D BN network. An isotropic [email protected] network with high-quality and integrity was successfully fabricated by a simple high temperature treatment. The synthesized [email protected] was incorporated into epoxy resin (ER) by infiltration to fabricate composites. ER/[email protected] composite, with strong interfacial adhesion between epoxy and [email protected], achieved a high thermal conductivity of 2.01 W/(mK), which corresponded to 908.53% and 402.00% enhancement compared to pure epoxy and ER/Ni composite. The coefficient of thermal expansion (CTE) of the composite reached as low as 26.95 × 10−6/°C, much smaller than epoxy of 60.69 × 10−6/°C and ER/Ni composite of 59.42 × 10−6/°C. The designed ER/[email protected] composite has distinguished heat removal and CTE with semiconductors from traditional polymer composites containing 3D BN network. This strategy is promising to promote the development of electrical packaging materials with high isotropic thermal conductivity.

Constructing three‐dimensional boron nitride network for highly thermally conductive epoxy resin composites

AbstractConstruction of heat conduction channels in polymer matrix plays a key role in thermally conductive composite. In this work, three‐dimensional (3D) boron nitride (BN) framework was successfully fabricated by decomposing the sacrificial material. The resultant 3D‐BN framework with honeycomb‐like structure was further infiltrated with liquid epoxy resin. With the aid of thermally conductive pathways formed by the 3D‐BN framework, the maximum thermal conductivity of EP/3D‐BN composites reaches 3.53 W/m·K with 55.85 vol% BN, which is 17.6 times larger than that of pure EP. The EP/3D‐BN composites demonstrate strong capability to dissipate the heat during heating and cooling processes. This work provides a facile method for developing thermal conductive composites applied in thermal management for electronics.