Few-layer Boron Nitride Nanosheets Research Articles

BN nanosheets reinforced zirconia composites: An in-depth microstructural and mechanical study

This paper deals with the effect of hydroxylated boron nitride nanosheets (BNNS) incorporation on the microstructural and mechanical features of zirconia ceramics. Few-layered BNNS were synthesized via a simple hydroxide-assisted planetary ball milling exfoliation technique. 3 mol% yttria tetragonal zirconia polycrystal (3Y-TZP) with 2.5 vol% BNNS powders were prepared by an environmentally friendly process in water, and spark-plasma sintered at three temperatures to explore the in-situ reduction of the functionalized BNNS. An exhaustive study by (S)TEM techniques was performed to elucidate the influence of the sintering temperature on the matrix and the 3Y-TZP/BNNS interfaces, revealing that BNNS were homogeneously distributed throughout the matrix with an abrupt transition at 3Y-TZP/BNNS interfaces. BNNS effectively hindered slow crack growth, thus increasing the composite’s crack growth resistance by about 30 %. A 1 MPa·m1/2 rising R-curve was also induced by crack bridging.

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.

Amino Acid-Assisted Sand-Milling Exfoliation of Boron Nitride Nanosheets for High Thermally Conductive Thermoplastic Polyurethane Composites.

Boron nitride nanosheets (BNNSs) show excellent thermal, electrical, optical, and mechanical properties. They are often used as fillers in polymers to prepare thermally conductive composites, which are used in the production of materials for thermal management, such as electronic packaging. Aside from the van der Waals force, there are some ionic bond forces between hexagonal boron nitride (h-BN) layers that result in high energy consumption and make BNNSs easily agglomerate. To overcome this issue, L-lysine (Lys) was first employed as a stripping assistant for preparing graft-functionalized BNNSs via mechanical sand-milling technology, and the obtained Lys@BNNSs can be added into thermoplastic polyurethane (TPU) by solution mixing and hot-pressing methods to prepare thermally conductive composites. This green and scalable method of amino acid-assisted sand-milling can not only exfoliate the bulk h-BN successfully into few-layer BNNSs but also graft Lys onto the surface or edges of BNNSs through Lewis acid-base interaction. Furthermore, benefiting from Lys's highly reactive groups and biocompatibility, the compatibility between functionalized BNNSs and the TPU matrix is significantly enhanced, and the thermal conductivity and mechanical properties of the composite are remarkably increased. When the load of Lys@BNNSs is 3 wt%, the thermal conductivity and tensile strength of the obtained composites are 90% and 16% higher than those of the pure TPU, respectively. With better thermal and mechanical properties, Lys@BNNS/TPU composites can be used as a kind of heat dissipation material and have potential applications in the field of thermal management materials.

BaTiO3-assisted exfoliation of boron nitride nanosheets for high-temperature energy storage dielectrics and thermal management

Currently, massive preparation of boron nitride nanosheets (BNNSs) towards large-size and good structural integrity via ball milling remains a key challenge, limiting its extensive applications in thermal management and energy storage. Low-cost and recyclable BaTiO3 nanoparticles with good piezoelectric effect can concurrently act as collision buffers and strong reductants to suppress the in-plane crystal structure damage and surface oxidation triggered by high-energy mechanical impact. Herein, an environmentally friendly, simple to operate and easy to realize industrial production method, referred to as BaTiO3-assisted ball milling (BTABM), is demonstrated to prepare high quality few-layered BNNSs with an average lateral size of 0.56 μm and a high yield of 91.2%. This milling process involves the synergetic effects of mechanical shear and mechanochemical peeling provided by deformed BaTiO3. The incorporation of the prepared BNNSs into the P(VDF-CTFE) matrix by BTABM effectively improved simultaneously the dielectric properties and breakdown strength of the ternary P(VDF-CTFE)/BaTiO3/BNNS nanocomposites as well as their thermal management capability, due to the formation of 3D BNNS networks. This novel method provides a guidance for not only scalable exfoliation of other layered 2D materials but also massive fabrication of polymeric nanocomposites applied in high-temperature energy storage devices.

Scalable production of boron nitride nanosheets in ionic liquids by shear-assisted thermal treatment

Due to their intriguing properties, boron nitride nanosheets (BNNSs) with large lateral size and high crystallinity have great promise for many applications. However, the quantitative exfoliation of hexagonal boron nitride (h-BN) into good quality BNNSs still remains a key challenge. Herein, we report a scalable method to exfoliate BNNSs in ionic liquids (ILs) via shear-assisted thermal treatment. Few-layer BNNSs with well-preserved structural integrity are successfully prepared by this method. The synergistic effects of strong physical adsorption and intercalation of IL molecules, chemical interactions between hydrogen fluoride (HF) and h-BN, activation energy provided by heat treatment, and shear forces generated by repetitive stirring effect contribute to the exfoliation of BNNSs.

Incorporation of elaborately Synthesized BNNSs by a mild mechanical stirring process for the concurrent enhancement of thermal conductivity and dielectric breakdown strength of PVDF

Due to the growing energy demands, it is highly desirable to concurrently improve the thermal conductivity and dielectric breakdown strength of dielectric film capacitors. Polyvinylidene fluoride (PVDF) is hitherto regarded as a most satisfactory alternative for dielectric capacitors but with relatively low thermal conductivity and dielectric breakdown strength. Herein, a major contribution is made to the concurrent enhancement of PVDF-based thermal conductivity and dielectric properties. It can be readily achieved through the incorporation of as-prepared high-quality few-layered boron nitride nanosheets (BNNSs) with a minimized loading (defined as PVDF-BNNSs). BNNSs dispersion with intact structure and a large aspect ratio is prepared by a unique mild mechanical stirring process assisted by dimethyformamide/1-butanol (DMF/1-butanol) solvent and a low power ultrasonic. Encouragingly, the characteristic breakdown strength with a maximum value of 334 MV/m reaches for PVDF-BNNSs composite only with 3 vol% BNNS loading, to be 1.6 times of pure PVDF. It also presents a high discharged energy density up to 9.9 J cm-3, along with an efficiency of 68.3%. Synchronously, the thermal conductivity accomplishes a high value of 1.12 W/m·K with only 8 vol% BNNS loading. A further theoretical analysis reveals that high-quality appropriate BNNSs loading could be preferentially arranged in parallel with PVDF surface. It indicates that BNNSs have good interface compatibility with PVDF, thus to improve its associated performances concurrently.

Novel synthesis of boron nitride nanosheets from hexagonal boron nitride by modified aqueous phase bi-thermal exfoliation method

The hexagonal Boron Nitride Nanosheets (BNNSs) were derived from commercially available hexagonal Boron Nitride (h-BN) by the pressure assisted aqueous bi-thermal method. The few-layered BNNS could be identified from PXRD measurements that showed lower peak intensity for (002) plane when compared to that of bulk h-BN. The characteristics of h-BN and BNNSs were further evaluated by using different analytical methods and instruments like PXRD, UV–Visible DRS, FTIR, FESEM and HRTEM etc. The Boron Nitride nanosheets synthesized using this green exfoliation protocol provided nanosheets with improved band gap. The assessment from UV–Vis DRS spectra of Boron Nitride nanosheets supported this opinion. The band gap energy deduced from UV–Vis DRS measurement showed rise in the band gap energy from 5.4 for h-BN to 5.8 eV for BNNSs implying improved insulating properties of BNNSs. The Boron Nitride Nanosheets were thus found to act as better insulators than the parent material h-BN. This work described a green, low cost, facile and scalable technique for exfoliation of commercially available hexagonal Boron Nitride.

Co-Solvent Exfoliation of Hexagonal Boron Nitride: Effect of Raw Bulk Boron Nitride Size and Co-Solvent Composition.

Exfoliation of two-dimensional boron nitride nanosheets (BNNSs) from parent bulk material has been receiving intensive attention because of its fascinating physical properties. Liquid exfoliation is a simple, scalable approach to produce single-layer or few-layer BNNS. In this paper, water/propanol co-solvent exfoliation of bulk boron nitride under the assistance of sonication was investigated in detail. Special attention was paid on the effect of raw bulk boron nitride size and co-solvent composition. The results show that sonication of small-size hexagonal boron nitride tends to generate large nanosheets, due to a predominant solvent wedge effect. In addition, it is found that the composition of water/propanol co-solvent has an important effect on exfoliation efficiency. Interestingly, although two isomers of 1-propanol (NPA) and 2-propanol (IPA) have the same molecular weight and similar surface tension, their aqueous solutions allow the formation of boron nitride nanosheets dispersion with markedly different concentrations. It is proposed that due to their spatial configuration difference, NPA with its longer molecular chain and fewer hydrophobic methyl group tends to form dynamic water-NPA clusters with larger size than water-IPA clusters. The hydrodynamic radius of the co-solvent “clusters” was calculated to be 0.72 nm for water/NPA system and 0.44 nm for water/IPA system at their maximum, respectively. Their size changes, represented by two curves, indicate a strong “cluster size” effect on exfoliation efficiency. Our work provides an insight into co-solvent exfoliation of hexagonal boron nitride and emphasizes the importance of co-solvent cluster size in exfoliation efficiency.

Enhanced interfacial polarization in poly(vinylidene fluoride-chlorotrifluoroethylene) nanocomposite with parallel boron nitride nanosheets

The miniaturization of electronics provides an opportunity for the polymer film capacitor due to its lightweight and flexibility. In order to improve energy density and charge–discharge efficiency of the film capacitor, the development of a polymer nanocomposite is one of the effective strategies, in which the distribution of the fillers plays a key role in the enhancement of the electrical energy capability. In this work, the few-layer boron nitride nanosheets (BNNSs) was exfoliated with assistance of the fluoro hyperbranched polyethylene-graft-poly(trifluoroethyl methacrylate) (HBPE-g-PTFEMA) copolymer as stabilizer, which was adsorbed on the surface of the nanosheets via a CH-π non-covalent interaction. The morphological results confirm the lateral size of ∼0.4 μm for resultant nanosheets with the intact crystal structure. The loading of 0.5 vol% BNNSs was embedded into poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)) matrix by solution casting method, and then the nanocomposite film was uniaxial stretched to achieve the orientation of nanosheets in polymer host. The dielectric constant of stretching nanocomposite with ratio of 4 at 50 mm min−1 reaches 51.1 at 100 Hz with low loss as 0.016, while the energy density of 7.0 J cm−3 at 250 MV m−1 with charge–discharge efficiency of 56% is obtained in current nanocomposite film, which is attributed to the interfacial polarization as well as parallel nanosheets blocking the growth of electrical treeing branches. This strategy of the aligned nanosheets/polymer nanocomposite establishes a simple route to construct heterogeneity in polymer films with enhanced electrical energy capability for flexible capacitors.

Scalable exfoliation for few-layered hexagonal boron nitride nanosheets (BNNSs) by microwave-assisted expansion and liquid nitrogen intercalation

The low cost and facile scalable exfoliation route for two-dimensional hexagonal boron nitride (h-BN) was still indispensable for potential applications. In this work, we presented a convenient and scalable exfoliation for few-layer BNNSs. Taking advantage of the advantages of swift heating of microwave and ultra low temperature vaporization of liquid nitrogen, bulk h-BN was high-efficiently exfoliated into few-layer BNNSs. The as-exfoliated BNNSs had a 2−6 nm thickness and approximately 7.91% yield, exhibiting scalable, facile and environment-friendly features. Furthermore, the as-exfoliated BNNSs were applied as additive in oil for reducing friction of oil. The COF of the BNNSs-based grease reduced by 20.10% compared to grease, and the antiwear performance decreased by 55.8% and 45.1% relative to grease and h-BN-based grease.

Few-layer boron nitride nanosheets exfoliated with assistance of fluoro hyperbranched copolymer for poly(vinylidene fluoride-trifluoroethylene) nanocomposite film capacitor

The polymer film capacitor has been widely applied in electronics and stationary power system due to the large power density and graceful dielectric reliability. The current requirements for flexible film capacitor are mainly on the development of polymer nanocomposite with high energy density and charge-discharge efficiency during applied electric field. Here we employed the fluoro hyperbranched polyethylene-graft-poly(trifluoroethyl methacrylate) (HBPE-g-PTFEMA) copolymer to exfoliate the boron nitride nanosheets (BNNSs) in low-boiling-point solvent, and then, the flexible poly(vinylidene fluoride-trifluoroethylene) (P(VDF-CTFE)) nanocomposite film incorporated with BNNSs was prepared by the simple solution casting. The stable BNNSs dispersion was obtained with assistance of fluoro hyperbranched copolymer as the stabilizer, which was adsorbed on the nanosheets via the noncovalent CH-π interaction against aggregation. The presence of fluoro segments improves the compatibility of BNNSs/P(VDF-CTFE) nanocomposite, which contributes to the large interfacial polarization. The energy density in 0.4 wt% nanocomposite achieves 6.8 J/cm3 with charge-discharge efficiency of 66% at 300 MV/m, which is ascribed to the large content of electroactive phase and the enhanced interfacial polarization. The fluoro hyperbranched copolymer functionalized BNNSs/P(VDF-CTFE) nanocomposite film exhibits high electric storage capability as well as lightweight feature and flexibility, which is benefit to potential applications for portable and implantable electrical devices where both the weight and size are primary concerns.

Flexible, thermally conductive layered composite films from massively exfoliated boron nitride nanosheets

Flexible, electrically insulating and highly thermally conductive materials are desired in the thermal management application of next-generation electronic devices. In this work, bulk boron nitride are exfoliated in N-methyl-2-pyrrolidone solvent through a unique combination of large and small ball milling, generating large-volume dispersion with plane defect-free, few-layered boron nitride nanosheets. The exfoliated dispersion is concentrated through centrifugation and further processed into large-area, layered composite films with poly(vinylidene fluoride) through a scalable doctor-blading technique. The high quality of boron nitride nanosheets and their well-ordered layered arrangement imparts the composite film with high in-plane thermal conductivity and low through-plane thermal conductivity. With incorporation of 60 wt% boron nitride nanosheets, the in-plane thermal conductivity is as high as 11.88 W/m K, two orders of magnitude larger than neat poly(vinylidene fluoride). The through-plane thermal conductivity is only 0.41 W/m K, about the same as neat poly(vinylidene fluoride). Besides, the composite film is highly flexible and can be folded without fracture.

Novel thin film nanocomposite membranes decorated with few-layered boron nitride nanosheets for simultaneously enhanced water flux and organic fouling resistance

Abstract Operational longevity of conventional thin film composite (TFC) nanofiltration (NF) membranes is significantly challenged by natural organic matter (NOM) fouling. Besides, surface modification of TFC membranes with nanomaterials results in their partial to complete confinement within the thin film, hampering the exploitation of nanomaterials full potential in improving NF performance. Incompatibility of nanomaterials with the polymeric matrix, and the resultant defect formation in the thin film can also lead to detachment of nanomaterial from the membrane surface. Herein, a modified interfacial polymerization (IP) reaction is developed to fabricate fouling-resistant thin film nanocomposite (TFN) NF membranes decorated with few-layered amine functionalized-boron nitride BN(NH2) nanosheets. The reactive edges of nanosheets are the geneses of fantastic properties; amine functionalities and electron deficient B atoms available at the edge regions render the nanosheets highly hydrophilic and negatively charged, respectively, favouring fouling mitigation. Compared with control counterparts, membranes decorated with BN(NH2) nanosheets revealed 59% enhancement in flux and 50% improvement in total fouling resistance, while maintaining NOM separation above 92%. BN(NH2)-decorated membranes showed long-term operational stability and enhanced recoverability, and nanosheet detachment tests eliminated the possibility of BN(NH2) leaching out during filtration.

Enhancing thermal properties of few-layer boron nitride by high-k Al2O3 capping layer

Atomically thin boron nitride (BN) film has attracted increasing attention among two-dimensional materials for the potential application in electronics devices. The thermal properties of few-layer BN nanosheets (∼2.27 nm) on SiO2/Si substrates have been investigated without and with high-k Al2O3 capping layer, using the temperature-dependent and polarized-laser power-dependent Raman spectroscopy measurements. Due to the effect of Al2O3 capping layer, Raman spectrum illustrates the blue-shift of frequency from 1364.9 cm−1 to 1367.9 cm−1, and the first order temperature coefficient for E2g mode of BN layers increases from −0.02243 cm−1/K to −0.06544 cm−1/K. Furthermore, the room-temperature thermal conductivity of BN with Al2O3 capping layer is found to be 332.57 W/mK, which is much larger than that of BN without Al2O3 capping layer (∼94.51 W/mK). The enhancement is attributed to the interface charges and compressive stress at the interface between BN and Al2O3 capping layer, which has been clarified by the first principle calculations. This work is aimed at expanding the applications of BN materials and improving the performances of BN-based devices in thermal properties.

Few-layered boron nitride nanosheets as superior adsorbents for the rapid removal of lead ions from water

Newly few-layered boron nitride (BN-550) nanosheets were developed by a low-temperature synthesis method, which was used to rapidly and efficiently adsorb lead ions (Pb2+). The samples were characterized by using XRD, FT-IR, EELS, SEM, TEM, AFM and XPS, revealing that it possessed the large specific surface area (696 m2 g−1), ultrathin sheet structure (1.2 nm thickness), and abundant chemical bonds as multiple adsorption sites. The adsorption properties showed that higher adsorption capacity (845 mg g−1) for lead ions and less equilibrium time (15 min) than many adsorbents reported at present. The adsorption kinetics and isotherms of BN-550 belonged to the pseudo-second-order model and Langmuir model, respectively. The easy recyclability and stability of BN-550 were verified by the experiments regeneration and pH. Interference experiments indicated that the adsorbents were strong affinity for Pb2+ under the interference of other heavy metal ions such as Ni2+, Cu2+, and Cd2+ ions (their adsorbing capacity individually are 201, 402, and 312 mg g−1). The XPS and FT-IR analysis revealed that the excellent adsorption performances for Pb2+ attributed to the chemical binding reactions with the numerous surface functional groups, such as the strong B–O–Pb interactions and –NH2···Pb complex. The threshold value of Pb2+ removal on BN-550 nanosheets was 1080 mL g−1 when Pb2+ concentration was 50 mg L−1 in adsorption column. The unique characteristics render ultrathin nanosheets highly promising as an ideal candidate for the removal of lead ions.

Advanced synthesis of highly crystallized hexagonal boron nitride by coupling polymer-derived ceramics and spark plasma sintering processes—influence of the crystallization promoter and sintering temperature

Hexagonal boron nitride nanosheets (BNNSs) are promising 2D materials due to their exceptional chemical and thermal stabilities together with their electrical insulation properties. A combined synthesis method involving the polymer-derived ceramics (PDCs) route and the spark plasma sintering (SPS) process is proposed, leading to well-crystallized and pure layered h-BN crystals, prone to be exfoliated into large BNNSs. Here we focus more specifically on the influence of two key parameters of the process to be optimized: the Li3N concentration (0–10 wt%) and the SPS temperature (1200 °C–1950 °C). The presence of Li3N, added as crystal promoter in the pre-ceramic powder, significantly improves the crystallinity level of the product, as evidenced by XRD, SEM and Raman spectrometry. SPS temperature strongly modifies the size of the resulting h-BN flakes. The influence of SPS temperature on both purity and crystallinity is studied using cathodoluminescence. h-BN flakes larger than 200 μm2 (average flake area) are obtained. Few-layered BNNSs are successfully isolated, through exfoliation process.

High-yield synthesis of extremely high concentrated and few-layered boron nitride nanosheet dispersions

Due to the strong ‘lip–lip’ interactions between neighboring nanosheets layers, the scalable exfoliated fabrication of few-layer-thick boron nitride nanosheets (BNNSs) from the bulk hexagonal boron nitride (h-BN) is more challenging than these graphene nanosheets. In this work, few-layer (generally less than 10 layers) BNNSs were efficiently synthesized through a simple ball milling technique with the 2-furoic acid (FA) as a modifier. The BNNSs as-prepared with a average thickness of about 2.0 nm and an extremely high production yield (~98%) as well as unprecedentedly high dispersed concentration (~35 mg ml−1) in water. The stable aqueous dispersions of BNNSs can be directly used to fabricate ultralight aerogels with a low density of 2.0 mg cm−3 and thermally conductive film with a highly thermal conductivity of 25.2 W m−1 K−1. This approach provided us with an environmentally friendly agent with high efficiency for few-layer BNNSs synthesis and demonstrated promising applications for ultralight aerogels and heat dissipation in electronic components.

Adsorption of estrone with few-layered boron nitride nanosheets: Kinetics, thermodynamics and mechanism

Boron nitride Nanosheets (BNNSs) was fabricated with a method of heating the mixture of boric acid and urea in N2 atmosphere and used to remove estrone (E1) from water. The obtained BNNSs exhibited a higher surface area of 896 m2/g, a large pore volume of 0.76 cm3/g, and only few layers (0.398 nm) with the boric acid and urea ratio of 1:80. The layer number of BNNSs decreased from 15 to 4 with the mole ratio of boric acid and urea decreasing from 1:20 to 1:80, which was identified by SEM, TEM, AFM and BET measurements. More importantly, BNNSs presented an outstanding adsorption performance for estrone with the adsorption capacity of 249.15 mg E1/g BNNSs. The adsorption process could be best fitted by pseudo second-order kinetic model and the equilibrium data at different temperatures were well fitted by Langmuir isotherm model. The thermodynamics analysis revealed that E1 adsorption on BNNSs was spontaneous (ΔG = −29.33 kJ mol−1), enthalpy-retarded (ΔH = 29.75 kJ mol−1), entropy-driven (ΔS = 198.26 J mol−1 K−1), and mostly chemical adsorption. The adsorption rates of E1 in water were sharply enhanced with thinner BNNSs as absorbents and removal efficiency by BN-60 regenerated after 6 times was above 95%, it was shown that the surface areas, mesopores and remarkable structure played important roles in the adsorption process. The firmness of E1 onto BNNSs and the stability of adsorption efficiency made BNNSs as a potential absorbent for efficient removal of E1 from wastewater.

Shear-Assisted Production of Few-Layer Boron Nitride Nanosheets by Supercritical CO2 Exfoliation and Its Use for Thermally Conductive Epoxy Composites

Boron nitride nanosheets (BNNS) hold the similar two-dimensional structure as graphene and unique properties complementary to graphene, which makes it attractive in application ranging from electronics to energy storage. The exfoliation of boron nitride (BN) still remains challenge and hinders the applications of BNNS. In this work, the preparation of BNNS has been realized by a shear-assisted supercritical CO2 exfoliation process, during which supercritical CO2 intercalates and diffuses between boron nitride layers, and then the exfoliation of BN layers is obtained in the rapid depressurization process by overcoming the van der Waals forces. Our results indicate that the bulk boron nitride has been successfully exfoliated into thin nanosheets with an average 6 layers. It is found that the produced BNNS is well-dispersed in isopropyl alcohol (IPA) with a higher extinction coefficient compared with the bulk BN. Moreover, the BNNS/epoxy composite used as thermal interface materials has been prepared. The introduction of BNNS results in a 313% enhancement in thermal conductivity. Our results demonstrate that BNNS produced by supercritical CO2 exfoliation show great potential applications for heat dissipation of high efficiency electronics.

Facile fabrication of flexible layered GO/BNNS composite films with high thermal conductivity

It is a great challenge for facile fabrication of thermal materials with both high thermal conductivity and excellent mechanical behaviors. Here, using tannic acid (TA) as a surface modifying agent, few-layer boron nitride nanosheets (BNNS) were effectively obtained by exfoliation of h-BN microplatelets through wet ball-milling. The existence of TA on the surface of BNNS also increased the dispersibility and stability in aqueous solution. By means of vacuum filtration of the dispersion of graphene oxide (GO) and BNNS, layered composite films of GO/BNNS were fabricated easily and at low cost. Because of the orderly orientation of GO and BNNS along the horizontal direction and high inherent thermal conductivity of the nanosheets used, a high in-plane thermal conductivity of 11.9 W/mK was reached with 80 wt% of BNNS. We also found that the thermal conductivity of the film could be further enhanced through adding 1.6 wt% PVA in the system to fill the voids between the nanosheets. The resulting composite film also exhibited excellent tensile strength of 41.0 MPa, flexibility potential for utilization on a curved surface, and electrical insulation up to 6.8 × 109 Ω cm.