Three-dimensional Boron Nitride Research Articles

High thermal conductivity and low dielectric loss of three-dimensional boron nitride nanosheets/epoxy composites

Electronic power devices are moving towards high frequency, high integration, and high power, which urgently needs to develop high thermal conductive encapsulating insulation materials to improve the heat dissipation of electronic devices. Herein, we propose to modify the commercialized encapsulating materials of epoxy resin (EP) by incorporating three-dimensional hydroxylated boron nitride nanosheets (3D-BNNSs). The cryogel and vacuum freeze-drying techniques are employed to prepare the 3D-BNNSs using agarose. The results show that the constructed high thermal conductive structure of 3D-BNNSs can effectively enhance the thermal conductivity of EP and reduce the interfacial thermal resistance between BNNSs fillers. The thermal conductivity of 3D-BNNSs/EP composites with 33.03 wt% BNNSs reach 2.54 W/(m·K), which is 13.11 times higher than that of EP (0.18 W/(m·K)). Meanwhile, the resultant composites remain outstanding electrical insulation and dielectric properties. Because agarose contains numerous hydroxyl groups that can form hydrogen bonds with the hydroxyl groups on the surface-functionalized BNNSs, hydrogen bonding can lead to strong intermolecular interactions, which is conductive to accelarate phonon transport. Additionally, agarose can cross-link with the molecular chains of epoxy, impeding the movement of molecular chain segments and resulting in composites with low dielectric loss at high frequencies. This study demonstrates that the 3D-BNNSs/EP composites have great potential for application in thermal management of electronic components.

Preparation of three dimensional boron nitride-aluminum oxide dual thermal network resin-based composite materials and their performance study

With the gradual miniaturization and integration of electronic devices, the design and development of new high thermal conductivity polymer-based composite materials are crucial for enhancing the performance of modern electronic devices. In this study, three-dimensional boron nitride (3D-BN) aerogels with vertically aligned structures were prepared using the ice templating method, serving as the primary thermal conductive network. Subsequently, aluminum oxide (Al2O3)/epoxy resin (EP) nanofluids were infiltrated into the aerogel’s air pores using vacuum impregnation. The Al2O3 particles in contact with each other formed the secondary thermal conductive network. Thus, a 3D BN-Al2O3/EP composite material with a dual thermal conductive network structure was successfully fabricated. The composite material exhibited a high thermal conductivity coefficient of 1.077 Wm−1K−1 when loaded with 17.67 wt% BN and 26.23 wt% Al2O3, representing a 496 % increase compared to pure EP and a 211 % increase compared to 3D-BN/EP composite materials. Furthermore, this composite material demonstrated excellent thermal stability and mechanical properties. This work provides a new direction for designing novel polymer-based composite materials with low filler loading and high thermal conductivity performance.

Enhanced thermal conductivity of epoxy resin by incorporating three-dimensional boron nitride thermally conductive network.

Packaging insulation materials with high thermal conductivity and excellent dielectric properties are favorable to meet the high demand and rapid development of third generation power semiconductors. In this study, we propose to improve the thermal conductivity of epoxy resin (EP) by incorporating a three-dimensional boron nitride thermally conductive network. Detailedly, polyurethane foam (PU) was used as a supporter, and boron nitride nanosheets (BNNSs) were loaded onto the PU supporter through chemical bonding (BNNS@PU). After immersing BNNS@PU into the EP resin, EP-based thermally conductive composites were prepared by vacuum-assisted impregnation. Fourier transform infrared spectrometer and scanning electron microscope were used to characterize the chemical bonding and morphological structure of BNNS@PU, respectively. The content of BNNS in BNNS@PU/EP composites was quantitatively analyzed by TGA. The results show that the thermal conductivity of the BNNS@PU/EP composites reaches 0.521 W/m K with an enhancement rate η of 30.89 at an ultra-low BNNS filler content (5.93 wt. %). Additionally, the BNNS@PU/EP composites have excellent dielectric properties with the frequency range from 101 to 106Hz. This paper provides an interesting idea for developing high thermal conductivity insulating materials used for power semiconductor packaging.

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.

Improved thermal conductivity of epoxy composites filled with three-dimensional boron nitride ceramics-carbon hybrids

Epoxy (EP) is the preferred packaging materials used as a crucial component in power semiconductor devices. However, its low thermal conductivity (TC) always has negative impact in the heat dissipation of electronic devices. In this paper, we use hole-making method to prepare three-dimensional boron nitride ceramics-carbon (3D-BN-C) hybrids which are filled in EP matrix to improve the TC of the 3D-BN-C/EP composites. The results show that TC values of 3D-BN-C/EP composites are much superior to the BN/EP composite with random distribution of BN and 3D-BN/EP composite without carbon. The improved TC is mainly attributed to the high TC-3D skeleton structure and the low interface thermal resistance (R) due to the carbon connected with BN fillers. Infrared thermal images and Comsol simulation demonstrate that high TC 3D-BN-C/EP composite offers excellent heat dissipation capability of EP composites used as packing insulation materials. In addition, the dielectric loss of 3D-BN-C/EP composite still remains at a relative low level in a wide frequency range, exhibiting good insulation property and great potential to be used as high-performance packing insulation materials in electronic device applications.

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.

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.

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.

High thermal conductivity of epoxy-based composites utilizing 3D porous boron nitride framework

With the rapid development of the third generation of wide bandgap semiconductor devices, there is an urgent need for highly thermally conductive and electrically insulating packaging materials to solve the heat dissipation problem in the microelectronic devices. In this work, the three-dimensional boron nitride (3D-BN) is successfully constructed by using a facile method, where the healthy and non-toxic food-grade material, curdlan, is used to provide a stable skeletons for growing 3D-BN using an aqueous foaming technique combined with a freeze-drying process. The thermally conductive network of 3D-BN is beneficial to improve the thermal conductivity of the epoxy resin (EP). The thermal conductivity of 1.63 W/(m·K) is obtained in the 3D-BN/EP composites at a BN content of 29.67 wt%, which is 9.1 times higher than that of pure EP. More importantly, the prepared composites also maintain excellent electrical insulation and dielectric properties, exhibiting a good potential to be used as the thermal interface material in the electronic devices.

Ice-templated graphene in-situ loaded boron nitride aerogels for polymer nanocomposites with high thermal management capability

Efficient heat dissipation is essential for further improving the integration of high-power electronic packaging equipment. Through-plane direction aligned three-dimensional boron nitride nanosheets/graphene(3D-BNNS/Gr) aerogels are designed as heat transferring skeletons for epoxy nanocomposites. Graphene was in-situ synthesized on BNNS by a combustion synthesis method to ensure good contact, and subsequent aligning of BNNS/Gr nanofillers by a self-assembly ice-templating strategy to reduce contact resistance between individual BNNS. At a relatively low 3D-BNNS/Gr loading of 11.2 vol%, the composites exhibit superior through-plane thermal conductivities of 2.23 and 1.09 W m−1 K−1, demonstrating a 1073% and 1069% thermal conductivity enhancement at room temperature (RT) and liquid nitrogen temperature (77 K) compared with pure epoxy resin. Meanwhile, the mechanical properties of the composites at RT and 77 K were synchronously enhanced. Furthermore, the 3D-BNNS/Gr-epoxy nanocomposite film then acts as a heat spreader for heat dissipation of high-power LED modules and exhibits superior cooling efficiency.

Finite Element Simulation of Graphene Thermal Conductivity Framework

With the rapid development of electronic devices towards miniaturization and high integration, the problem of overheating and heat dissipation forces people to find thermal conductive materials with good comprehensive properties to meet the needs of development. Inspired by the three-dimensional boron nitride network, this paper creatively proposed the construction of a composite thermal conductive material with 3D graphene network structure and PDMS as filling matrix, and carried out finite element analysis and simulation with COMSOL. The results show that the thermal conductivity of the composite thermal conductive material with graphene 3D network structure is significantly better than that of the single thermal conductive material without graphene and the thermal conductive material with random distribution of graphene, and most of the heat flow forms a connected thermal conductive path along the heat transfer direction in the graphene of 3D network composite. It can be seen that the prepared composites with 3D thermal conduction network structure have excellent thermal conductivity, and will have broad market prospects in the fields of heat dissipation materials, computers, smart phones, laser weapons and so on.

Cooling Photoluminescent Phosphors in Laser-Excited White Lighting with Three-Dimensional Boron Nitride Networks

Cooling Photoluminescent Phosphors in Laser-Excited White Lighting with Three-Dimensional Boron Nitride Networks

Prediction of three-dimensional stretchable boron nitride nanoribbons

In this paper, a series of fully sp2-hybrid three-dimensional boron nitride nanoribbons (3D-BNNRs) polymorphs entirely composed of hexagonal rings is described herein. The 3D-BNNRs can be considered as connected BNNRs with different widths. All the predicted structures are thermodynamically metastable with 0.111–0.281 eV per BN unit higher than hBN. The elastic constants and phonon dispersion calculations show the 3D-BNNRs are mechanically and dynamically stable. The 3D-BNNRs are semiconductors, which are independent of the width of BNNRs. Tensile strength calculations show the 3D-BNNRs are very strong in the BNNRs-like plane, comparable to graphene and BNNRs. Moreover, under uniaxial strains, the 3D-BNNRs are very stretchable, and can hold more deformation along the direction perpendicular to BNNRs motif than in other directions, although the ideal strengths are lower than those in-plane direction.

Bi-directional high thermal conductive epoxy composites with radially aligned boron nitride nanosheets lamellae

Hexagonal boron nitride (h-BN), as a high thermal conductive filler, has been widely used to construct thermal transport network in polymers. However, anisotropic thermal property of BN and its conventional thermal conductive network usually lead to high thermal conductivity in one direction that limits the overall heat dissipation effect. Herein, we report a novel radially aligned three-dimensional boron nitride nanosheets/epoxy composite for thermal interface materials via radial freeze-casting method. The as-prepared composite with radially aligned boron nitride nanosheets lamellae exhibits bidirectional high thermal conductivity, with 4.02 W m−1 K−1 in the through-plane direction and 3.87 W m−1 K−1 in the in-plane direction even at low BNNS loading (e.g., 15 vol%), respectively. Besides, excellent electronic insulation property and shape stability can also meet the requirements of isotropic TIM in thermal management.

Thermal conductivity of polycaprolactone/three-dimensional hexagonal boron nitride composites and multi-orientation model investigation

Three-dimensional boron nitride (3D-BN) scaffolds were fabricated by the ice-templating method, and polycaprolactone/3D-BN (PCL/3D-BN) composites were prepared by vacuum impregnation of caprolactone monomers into 3D-BN scaffolds and then polymerization via the microwave-assisted technique. The results reveal that hexagonal boron nitrides (hBNs) in the PCL/3D-BN composites present three orientation patterns, that is, parallel (z-direction) and vertical (x-direction) alignment in the direction of ice-crystal and random orientation. Moreover, the orientation of hBNs plays an essential role in improving the thermal conductivity of the composite. The maximum thermal conductivities of the PCL/3D-BN composite are 1.42 and 1.01 W m−1 K−1 in the z-direction and x-direction, which are 7.10 and 5.05 times higher than that of the pure PCL, respectively. However, the existing models cannot be used to analyze the orientation of hBNs in the composites quantitatively. In this work, based on two-phase models, a multi-orientation model was developed to explore the volume fractions of hBNs oriented in each pattern. The results indicate that the hBN ratio of random orientation (fr/f) enhances with the increase of hBN content in the PCL/3D-BN composites, and especially while increasing the hBN content from 13.41 vol% to 15.48 vol%, the value of fr/f has soared from 33.0% to 63.7%, leading to the decrease of thermal conductivities. The predictions from the multi-orientation model are in good agreement with the experimental data for the other composites, implying that the model could be used to analyze the orientation of fillers quantitatively and guide the design of thermally conductive scaffolds.

3D boron nitride foam filled epoxy composites with significantly enhanced thermal conductivity by a facial and scalable approach

Polymer composites with excellent thermal conductivity, low dielectric constant and low dielectric loss are urgently required for microelectronics and wireless communication systems. However, traditional thermal conductive polymer composites realized by simply adding inorganic fillers, cannot have high thermal conductivity and good electrical insulation concurrently, which greatly hinders the practical application. In this work, a facile and scalable assembly technique to construct a three-dimensional boron nitride foam (3D-BN) for the formation of 3D-BN/epoxy composites has been proposed to address this long-standing challenge. Herein we built a self-support and pressure reinforced 3D-BN foam composed of only bulk-BN microplates to serve as the thermal pathway. The obtained composite with greatly enhanced thermal conductivity enhancement (TCE) exhibits the highest through-plane thermal conductivity of 6.11 W m−1 K−1 ever reported for bulk-BN polymer composites. Further analysis by finite element simulation revealed that the high thermal conductivity is attributed to the polymer-free, pressure reinforced 3D-BN foam which serves as a more effective pathway for the phonons transmission. This work offers an easy approach and provides a new paradigm for the fabrication and design of thermal management polymers.

Elastic, electronic and optical properties of new 2D and 3D boron nitrides

The current work investigates a novel three-dimensional boron nitride called bulk B4N4 and its corresponding two-dimensional monolayer B4N4 based on the first-principles of density functional theory. The phonon spectra prove that bulk B4N4 and monolayer B4N4 are dynamically stable. The molecular dynamics simulations verify that bulk B4N4 and monolayer B4N4 have excellent thermal stability of withstanding temperature up to 1000 K. The calculated elastic constants state that bulk B4N4 and monolayer B4N4 are mechanically stable, and bulk B4N4 has strong anisotropy. The theoretically obtained electronic structures reveal that bulk B4N4 is an indirect band-gap semiconductor with a band gap of 5.4 eV, while monolayer B4N4 has a direct band gap of 6.1 eV. The valence band maximum is mainly contributed from B-2p and N-2p orbits, and the conduction band minimum mainly derives from B-2p orbits. The electron transitions from occupied N-2p states to empty B-2p states play important roles in the dielectric functions of bulk B4N4 and monolayer B4N4. The newly proposed monolayer B4N4 is a potential candidate for designing optoelectronic devices such as transparent electrodes due to its high transmissivity.

Predicting the structural, electronic and mechanical properties of three-dimensional boron nitride foam containing sp, sp2 and sp3 hybridized bonds

A first-principles approach is utilized to systematically investigate the structural, electronic and mechanical properties from a new BN phase (denoted super-(BN)16). Super-(BN)16 contains sp, sp2 and sp3 hybridized bonds. It is mechanically stable, even though it is energetically unfavorable than c-BN, w-BN, yne-BN, and so on. Due to the different hybridization type and the B-N covalent bonds with ionic characteristics, super-(BN)16 has unequal bonds and bond angles in these equal space positions. The calculated electronic structure showed it is a semiconductor with a direct band gap of 1.94 eV. The electronic states in the region near Fermi level mainly come from the 2p orbitals of the sp hybridized B and N atoms. The elastic constants and moduli of this phase exhibit clear anisotropy and super-(BN)16 should have a low hardness and high ductility. Additionally, it can be obtained from nanosheets, nanotubes and nanoribbons of yne-BN family under pressure.

Preparation and Ablation Performance of BN Fiber Fabrics Reinforced Nitrides Composites

High-performance three-dimensional boron nitride fiber reinforced silicon nitride (BNf/Si3N4) composites were prepared by the infiltration and pyrolysis (PIP) process using BN fiber fabrics as the reinforcing body and excellent nitride organic precursor (Perhydropolysilazane, PHPS) as the Impregnated liquid. The ablation resistance of the composite was evaluated by plasma jet ablation test in air. The results show that a uniform and dense interface layer is formed on the fiber surface, with thickness is about 100 nm, and the XRD test shows that it is hexagonal BN (h-BN). The density of the composite reaches more than 1.72 g·cm-3 and the bending strength is more than 80 MPa. Under the condition of plasma jet ablation test at 2000 °C / 200 s, the mass ablation rate is 3.32 × 10-4 g/s, the linear ablation rate is 4.78 × 10-3 mm/s. The prepared materials have excellent resistance to high temperature ablation, and are expected to be used in the field of high temperature microwave transparent such as high mach missile radome, antenna window and so on.

Hydrogen Bond-Regulated Boron Nitride Network Structures for Improved Thermal Conductive Property of Polyamide-imide Composites.

Highly thermal conductive polymer composites with minimized content of fillers are desirable for handling the issue in thermal management in modern electronics. However, the difficulty of filler dispersion restricts the heat dissipation performance of thermoplastic composites and the intermolecular interaction is another crucial factor in this problem. In the present study, the hydrogen bond was used to regulate the formation of the three-dimensional boron nitride (3D BN) interconnected network to act as a high thermal conductive network in thermoplastic polyamide-imide (PAI) materials. The prepared electrical insulated PAI/3D-BN composites have a thermal conductivity (TC) of 1.17 W·m-1·K-1 at a low BN loading of 4 wt %/2 vol % and exhibit a thermal conductivity enhancement of 409%. We attribute the increased TC to the construction of 3D BN interconnected network and the hydrogen bond regulated between hydroxylated BN and polyvinyl alcohol, in which an effective thermal conductive network is constructed. This study provides a guided hydrogen bond strategy for thermally conductive polymer composites with good mechanical and electrical insulation properties in thermal management and other applications.