Enhanced Thermal Conductivity of Polyimide Composites with Boron Nitride Nanosheets

1D and 2D Boron Nitride Nano Structures: A Critical Analysis for Emerging Applications in the Field of Nanocomposites

Boron nitride (BN) with its 1D and 2D nano derivatives have gained immense popularity in both the field of research and applications. These nano derivatives have proved to be one of the most promising fillers which can be incorporated in polymers to form nanocomposites with excellent properties. These materials have been around for 25 years whereas significant research has been done in this field for only the past decade. There are many interesting properties which are imparted to the nanocomposites wherein thermal stability, large energy band gap, resistance to oxidation, excellent thermal conductivity, chemical inertness, and exceptional mechanical properties are just a few worthy of mention. Hexagonal boron nitride (h-BN) was selected as the parent material by most researchers reviewed in this paper through which 2D derivative Boron nitride nanosheets (BNNS) and 1D derivative Boron nitride nanotubes (BNNTs) are synthesized. This review will focus on the in-depth properties of h-BN and further will concisely focus on BNNS and BNNTs for their various properties. A detailed discussion of the addition of BNNS and BNNTs into polymers to form nanocomposites, their synthesis, properties, and applications is followed by a summary determining the most suitable synthesizing processes and the materials, keeping in mind the current challenges.

Mott neurons with dual thermal dynamics for spatiotemporal computing

Heat dissipation is a natural consequence of operating any electronic system. In nearly all computing systems, such heat is usually minimized by design and cooling. Here, we show that the temporal dynamics of internally produced heat in electronic devices can be engineered to both encode information within a single device and process information across multiple devices. In our demonstration, electronic NbOx Mott neurons, integrated on a flexible organic substrate, exhibit 18 biomimetic neuronal behaviours and frequency-based nociception within a single component by exploiting both the thermal dynamics of the Mott transition and the dynamical thermal interactions with the organic substrate. Further, multiple interconnected Mott neurons spatiotemporally communicate purely via heat, which we use for graph optimization by consuming over 106 times less energy when compared with the best digital processors. Thus, exploiting natural thermal processes in computing can lead to functionally dense, energy-efficient and radically novel mixed-physics computing primitives.

Emerging 2D Nanomaterials-Integrated Hydrogels: Advancements in Designing Theragenerative Materials for Bone Regeneration and Disease Therapy

This review highlights recent advancements in the synthesis, processing, properties, and applications of 2D-material integrated hydrogels, with a focus on their performance in bone-related applications. Various synthesis methods and types of 2D nanomaterials, including graphene, graphene oxide, transition metal dichalcogenides, black phosphorus, and MXene are discussed, along with strategies for their incorporation into hydrogel matrices. These composite hydrogels exhibit tunable mechanical properties, high surface area, strong near-infrared (NIR) photon absorption and controlled release capabilities, making them suitable for a range of regeneration and therapeutic applications. In cancer therapy, 2D-material-based hydrogels show promise for photothermal and photodynamic therapies, and drug delivery (chemotherapy). The photothermal properties of these materials enable selective tumor ablation upon NIR irradiation, while their high drug-loading capacity facilitates targeted and controlled release of chemotherapeutic agents. Additionally, 2D-materials -infused hydrogels exhibit potent antibacterial activity, making them effective against multidrug-resistant infections and disruption of biofilm generated on implant surface. Moreover, their synergistic therapy approach combines multiple treatment modalities such as photothermal, chemo, and immunotherapy to enhance therapeutic outcomes. In bio-imaging, these materials serve as versatile contrast agents and imaging probes, enabling their real-time monitoring during tumor imaging. Furthermore, in bone regeneration, most 2D-materials incorporated hydrogels promote osteogenesis and tissue regeneration, offering potential solutions for bone defects repair. Overall, the integration of 2D materials into hydrogels presents a promising platform for developing multifunctional theragenerative biomaterials.

High-Throughput and Scalable Exfoliation of Large-Sized Ultrathin 2D Materials by Ball-Milling in Supercritical Carbon Dioxide

The 2D materials exhibit numerous technological applications, but their scalable production is a core challenge. Herein, ball milling exfoliation in supercritical carbon dioxide (scCO2) and polystyrene (PS) is demonstrated to completely exfoliate hexagonal boron nitride nanosheets (BNNSs), graphene, molybdenum disulfide (MoS2), and tungsten disulfide (WS2). The exfoliation yield of 91%, 93%, 92%, and 92% and average aspect ratios of 743, 565, 564, and 502 for BNNSs, graphene, MoS2, and WS2, respectively, are achieved. Integrating exfoliated BNNSS in the polystyrene matrix, 3768 % thermal conductivity in the axial direction and 316% in the cross-plane direction at 12 wt.% loading is increased. Also, the in-plane and cross-plane electrical conductivity of 6.3 × 10-4 S m-1 and 6.6 × 10-3 S m-1, respectively, and the electromagnetic interference (EMI) of 63.3 dB is achieved by exfoliated graphene nanosheets based composite. High thermal and electrical conductivities and EMI shielding are attributed to the high aspect ratio and ultrathin morphology of the exfoliated nanosheets, which exert high charge mobility and form better the percolation network in the composite films due to their high surface area. The process demonstrate herein can produce substantial quantities of diverse 2D nanosheets for widespread commercial utilization.

Thermal Conductivity Enhancement of Polymeric Composites Using Hexagonal Boron Nitride: Design Strategies and Challenges

With the integration and miniaturization of chips, there is an increasing demand for improved heat dissipation. However, the low thermal conductivity (TC) of polymers, which are commonly used in chip packaging, has seriously limited the development of chips. To address this limitation, researchers have recently shown considerable interest in incorporating high-TC fillers into polymers to fabricate thermally conductive composites. Hexagonal boron nitride (h-BN) has emerged as a promising filler candidate due to its high-TC and excellent electrical insulation. This review comprehensively outlines the design strategies for using h-BN as a high-TC filler and covers intrinsic TC and morphology effects, functionalization methods, and the construction of three-dimensional (3D) thermal conduction networks. Additionally, it introduces some experimental TC measurement techniques of composites and theoretical computational simulations for composite design. Finally, the review summarizes some effective strategies and possible challenges for the design of h-BN fillers. This review provides researchers in the field of thermally conductive polymeric composites with a comprehensive understanding of thermal conduction and constructive guidance on h-BN design.

Preparation of boron nitride nanosheets by glucose-assisted ultrasonic cavitation exfoliation

Boron nitride nanosheets (BNNSs) have been widely used in many fields due to their excellent properties. However, low preparation rates and difficulty in functionalization hinder their further development. This study proposes a novel glucose-assisted ultrasonic cavitation exfoliation (GAUCE) method with glucose as an auxiliary solution to prepare BNNSs. Results show that the method has a high preparation yield of 55.58%, which is higher than the average preparation yield of 33.86%. The mechanism of preparing BNNSs by GAUCE was also investigated. The exfoliation of BNNSs was achieved using the energy of ultrasonic cavitation bubble collapse, which will break the interlayer forces in h-BN. The grafting of hydroxyl groups decomposed by glucose on the edge and surface of BNNSs during cavitation prevented the re-aggregation of the nanosheets, thereby increasing the exfoliation yield of BNNSs. In addition, the contact angle of BNNSs prepared by GAUCE was reduced, and the hydrophilicity was greatly improved.

Fabrication of Ultra-Fine Micro-Vias in Non-Photosensitive Polyimide for High-Density Vertical Interconnects

With the growing demands for transferring large amounts of data between components in a package, it is required for advanced packaging technologies to form smaller vertical vias in the insulators. Plasma etching is one of the most widely used micro-vias formation processes. This paper has developed a fabrication process for 5-10 µm residue-free micro-vias with 70° tapered angle in polyimide film based on O₂/CHF₃ inductively coupled plasma (ICP). The etch rate would monotonically increase with the ICP power, RF power, and gas flow rate. As for the gas ratio, there is an optimum range of CHF₃ ratio, which could obtain the highest etch rate. The results have clearly shown that the enhancement of ion bombardment and prolongation of etching time would be beneficial to grass-like residue removal. In addition, during the etching of partially cured polyimide, the lateral etch rate would significantly increase in the region near the metal hard mask.

Enhanced thermal transportation across an electrostatic self-assembly of black phosphorene and boron nitride nanosheets in flexible composite films

For effective heat dissipation in portable electronics, there is a great demand for lightweight and flexible films with superior thermal transport properties. Despite extensive efforts, enhancing the intrinsic low thermal conductivity of polymers while simultaneously maintaining their flexibility is difficult to achieve due to the dilemma of quarrying appropriate filler loading. Herein, a cellulose nanofiber-based film with high in-plane thermal conductivity up to 72.53 W m^-1 K^-1 was obtained by harnessing the advantage of functionalized boron nitride nanosheets (f-BNNS) and black phosphorene (BP) via the vacuum filtration process. Besides, our unique design based on the electrostatic coupling of black phosphorene and functionalized boron nitride nanosheets significantly reduced the interfacial thermal resistance of the composite films. This work offers new insights into establishing a facile, yet efficient approach to preparing high thermal conductive heat spreaders.

Microscopic Pyrolytic and Electric Decomposition Mechanism of Insulating Polyimide/Boron Nitride Nanosheet Composites based on ReaxFF

High thermal conductivity insulating materials with excellent comprehensive properties can be obtained by doping boron nitride nanosheets (BNNSs) into polyimide (PI). To study the microscopic mechanism of composite material decomposition in an actual working environment and the inhibitory effect of BNNS doping on the decomposition process, molecular dynamics simulations were carried out at high temperatures, in intense electric fields, and with various reactive species in plasma based on the reactive force field (ReaxFF). The results showed that the decomposition was mainly caused by hydrogen capture and adsorption, which broke the benzene ring and C-N bond on the PI chains and led to serious damage to the PI structure. The BNNS filling was shown to inhibit the decomposition of the PI matrix at high temperatures and in intense electric fields. Moreover, the BNNS filling also inhibited the material decomposition caused by ·OH and ·NO. The erosive effect of the positive corona on the PI composites was more obvious than that of the negative corona. In this paper, the microscopic dynamic reaction paths of material pyrolysis in various environments were revealed at the atomic level, and it was concluded that BNNS doping could effectively inhibit the decomposition of PI in various environments.

Polyhedral oligosilsesquioxane-modified boron nitride enhances the mechanical properties of polyimide nanocomposites

A novel high-strength polyimide (PI) nanocomposite film was designed and constructed by the copolymerization of epoxidized polyhedral oligomeric silsesquioxane-modified hexagonal boron nitride and polyamic acid (PAA). The composite filler (EPPOSS@Gh-BN) was composed of silane coupling agent KH550 modified hexagonal boron nitride (Gh-BN) and epoxidized polyhedral oligomeric silsesquioxanes (EPPOSS), which improved not only the dispersion of the h-BN but also the effective interfacial stress transfer, leading to an enhanced mechanical strength of the resultant PI nanocomposite film of 114 MPa even with a slight EPPOSS@Gh-BN loading of 0.30 wt%, and the storage modulus was increased by more than 30% to 4 GPa compared to pure PI. Meanwhile, the PI/EPPOSS@Gh-BN nanocomposite has better heat transfer performance, higher hydrophobicity, lower dielectric properties, and higher heat stability than pure PI, and is therefore expected to provide an ideal platform for the development of highly flexible electronics in the future.

A novel high-strength polyimide nanocomposite film was obtained by the copolymerization of epoxidized polyhedral oligomeric silsesquioxane-modified hexagonal boron nitride and polyamic acid.

Scalable Polyimide-Poly(Amic Acid) Copolymer Based Nanocomposites for High-Temperature Capacitive Energy Storage

The developments of next-generation electric power systems and electronics demand for high temperature (≈150 °C), high energy density, high efficiency, scalable, and low-cost polymer-based dielectric capacitors are still scarce. Here, the nanocomposites based on polyimide-poly(amic acid) copolymers with a very low amount of boron nitride nanosheets are designed and synthesized. Under the actual working condition in hybrid electric vehicles of 200 MV m^-1 and 150 °C, a high energy density of 1.38 J cm^-3 with an efficiency higher than 96% is achieved. This is about 2.5 times higher than the room temperature energy density (≈0.39 J cm^-3 under 200 MV m^-1 ) of the commercially used biaxially oriented polypropylene, the benchmark of dielectric polymer. Especially, the energy density and efficiency at 150 °C show no sign of degradation after 20 000 cycles of charge-discharge test and 35 days' high-temperature endurance test. This research provides an effective and low-cost strategy to develop high-temperature polymer-based capacitors.

Enhanced catalysis through structurally modified hybrid 2-D boron nitride nanosheets comprising of complexed 2-hydroxy-4-methoxybenzophenone motif

Tuning the structural architecture of the pristine two dimensional hexagonal boron nitride (h-BN) nanosheets through rational surface engineering have proven advantageous in the fabrication of competent catalytic materials. Inspired by the performance of h-BN based nanomaterials in expediting key organic transformations, we channelized our research efforts towards engineering the inherent surface properties of the exclusively stacked h-BN nanosheets through the incorporation of a novel competent copper complex of a bidentate chelating ligand 2-hydroxy-4-methoxybenzophenone (BP). Delightfully, this hybrid nanomaterial worked exceptionally well in boosting the [3 + 2] cycloaddition reaction of azide and nitriles, providing a facile access to a diverse variety of highly bioactive tetrazole motifs. A deep insight into the morphology of the covalently crafted h-BN signified the structural integrity of the exfoliated h-BN@OH nanosheets that exhibited lamellar like structures possessing smooth edges and flat surface. This interesting morphology could also be envisioned to augment the catalysis by allowing the desired surface area for the reactants and thus tailoring their activity. The work paves the way towards rational design of h-BN based nanomaterials and adjusting their catalytic potential by the use of suitable complexes for promoting sustainable catalysis, especially in view of the fact that till date only a very few h-BN nanosheets based catalysts have been devised.

Recent Advances on Thermally Conductive Adhesive in Electronic Packaging: A Review

The application of epoxy adhesive is widespread in electronic packaging. Epoxy adhesives can be integrated with various types of nanoparticles for enhancing thermal conductivity. The joints with thermally conductive adhesive (TCA) are preferred for research and advances in thermal management. Many studies have been conducted to increase the thermal conductivity of epoxy-based TCAs by conductive fillers. This paper reviews and summarizes recent advances of these available fillers in TCAs that contribute to electronic packaging. It also covers the challenges of using the filler as a nano-composite. Moreover, the review reveals a broad scope for future research, particularly on thermal management by nanoparticles and improving bonding strength in electronic packaging.

Ultra-Robust Thermoconductive Films Made from Aramid Nanofiber and Boron Nitride Nanosheet for Thermal Management Application

The development of highly thermally conductive composites with excellent electrical insulation has attracted extensive attention, which is of great significance to solve the increasingly severe heat concentration issue of electronic equipment. Herein, we report a new strategy to prepare boron nitride nanosheets (BNNSs) via an ion-assisted liquid-phase exfoliation method. Then, silver nanoparticle (AgNP) modified BNNS (BNNS@Ag) was obtained by in situ reduction properties. The exfoliation yield of BNNS was approximately 50% via the ion-assisted liquid-phase exfoliation method. Subsequently, aramid nanofiber (ANF)/BNNS@Ag composites were prepared by vacuum filtration. Owing to the "brick-and-mortar" structure formed inside the composite and the adhesion of AgNP, the interfacial thermal resistance was effectively reduced. Therefore, the in-plane thermal conductivity of ANF/BNNS@Ag composites was as high as 11.51 W m-1 K-1, which was 233.27% higher than that of pure ANF (3.45 W m-1 K-1). The addition of BNNS@Ag maintained tensile properties (tensile strength of 129.14 MPa). Moreover, the ANF/BNNS@Ag films also had good dielectric properties and the dielectric constant was below 2.5 (103 Hz). Hence, the ANF/BNNS@Ag composite shows excellent thermal management performance, and the electrical insulation and mechanical properties of the matrix are retained, indicating its potential application prospects in high pressure and high temperature application environments.

Ultrahigh-Aspect-Ratio Boron Nitride Nanosheets Leading to Superhigh In-Plane Thermal Conductivity of Foldable Heat Spreader

The rapid development of integrated circuits and electronic devices creates a strong demand for highly thermally conductive yet electrically insulating composites to efficiently solve "hot spot" problems during device operation. On the basis of these considerations, hexagonal boron nitride nanosheets (BNNS) have been regarded as promising fillers to fabricate polymer matrix composites. However, so far an efficient approach to prepare ultrahigh-aspect-ratio BNNS with large lateral size while maintaining an atomically thin nature is still lacking, seriously restricting further improvement of the thermal conductivity for BNNS/polymer composites. Here, a rapid and high-yield method based on a microfluidization technique is developed to obtain exfoliated BNNS with a record high aspect ratio of ≈1500 and a low degree of defects. A foldable and electrically insulating film made of such a BNNS and poly(vinyl alcohol) (PVA) matrix through filtration exhibits an in-plane thermal conductivity of 67.6 W m^-1 K^-1 at a BNNS loading of 83 wt %, leading to a record high value of thermal conductivity enhancement (≈35 500). The composite film then acts as a heat spreader for heat dissipation of high-power LED modules and shows superior cooling efficiency compared to commercial flexible copper clad laminate. Our findings provide a practical route to produce electrically insulating polymer composites with high thermal conductivity for thermal management applications in modern electronic devices.

Anisotropic heat transfer properties of two-dimensional materials

The anisotropic heat transfer properties of two-dimensional materials play an important role in controlled heat transfer and intelligent heat management. At present, there are many references on anisotropic heat transfer of two-dimensional materials, but less systematic review of their development status, problems, and future directions. In this paper, intrinsic anisotropic heat transfer of two-dimensional materials, influencing factors and control means are introduced. The preparation methods of thin film with two-dimensional material and the influence factors of macroscopic anisotropic thermal properties are summarized. The technology of two-dimensional material oriented arrangement in matrix and the influence factors of macroscopic anisotropic thermal properties of the composite are outlined.

Thermal interface materials with graphene fillers: review of the state of the art and outlook for future applications

We review the current state-of-the-art graphene-enhanced thermal interface materials for the management of heat in the next generation of electronics. Increased integration densities, speed and power of electronic and optoelectronic devices require thermal interface materials with substantially higher thermal conductivity, improved reliability, and lower cost. Graphene has emerged as a promising filler material that can meet the demands of future high-speed and high-powered electronics. This review describes the use of graphene as a filler in curing and non-curing polymer matrices. Special attention is given to strategies for achieving the thermal percolation threshold with its corresponding characteristic increase in the overall thermal conductivity. Many applications require high thermal conductivity of composites, while simultaneously preserving electrical insulation. A hybrid filler approach, using graphene and boron nitride, is presented as a possible technology providing for the independent control of electrical and thermal conduction. The reliability and lifespan performance of thermal interface materials is an important consideration towards the determination of appropriate practical applications. The present review addresses these issues in detail, demonstrating the promise of graphene-enhanced thermal interface materials compared to alternative technologies.

A Review on van der Waals Boron Nitride Quantum Dots

Boron nitride quantum dots (BNQDs) have gained increasing attention for their versatile fluorescent, optoelectronic, chemical, and biochemical properties. During the past few years, significant progress has been demonstrated, started from theoretical modeling to actual application. Many interesting properties and applications have been reported, such as excitation-dependent emission (and, in some cases, non-excitation dependent), chemical functionalization, bioimaging, phototherapy, photocatalysis, chemical, and biological sensing. An overview of this early-stage research development of BNQDs is presented in this article. We have prepared un-bias assessments on various synthesis methods, property analysis, and applications of BNQDs here, and provided our perspective on the development of these emerging nanomaterials for years to come.

Hypergravity-Induced Accumulation: A New, Efficient, and Simple Strategy to Improve the Thermal Conductivity of Boron Nitride Filled Polymer Composites

Thermal conductive polymer composites (filled type) consisting of thermal conductive fillers and a polymer matrix have been widely used in a range of areas. More than 10 strategies have been developed to improve the thermal conductivity of polymer composites. Here we report a new "hypergravity accumulation" strategy. Raw material mixtures of boron nitride/silicone rubber composites were treated in hypergravity fields (800-20,000 g, relative gravity acceleration) before heat-curing. A series of comparison studies were made. It was found that hypergravity treatments could efficiently improve the microstructures and thermal conductivity of the composites. When the hypergravity was about 20,000 g (relative gravity acceleration), the obtained spherical boron nitride/silicone rubber composites had highly compacted microstructures and high and isotropic thermal conductivity. The highest thermal conductivity reached 4.0 W/mK. Thermal interface application study showed that the composites could help to decrease the temperature on a light-emitting diode (LED) chip by 5 °C. The mechanism of the improved microstructure increased thermal conductivity, and the high viscosity problem in the preparation of boron nitride/silicone rubber composites, and the advantages and disadvantages of the hypergravity accumulation strategy, were discussed. Overall, this work has provided a new, efficient, and simple strategy to improve the thermal conductivity of boron nitride/silicone rubber and other polymer composites (filled type).

Functionalized Boron Nitride-Based Modification Layer as Ion Regulator Toward Stable Lithium Anode at High Current Densities

It is difficult to achieve higher energy density with the existing system of lithium (Li)-ion batteries. As a powerful candidate, Li metal batteries are in the renaissance. Unfortunately, the uncontrolled growth process of Li dendrites has limited their actual application. Hence, inhibiting the formation and spread of Li dendrites has become an enormous challenge. Herein, a novel composite separator is developed with functionalized boron nitride nanosheet modification layer as a Li-ion regulator to regulate Li-ion fluxes. The composite separator contains abundant polar groups and nanoscale channels and could achieve uniform electrochemical deposition via the lithiophilic effect and shunting action. Under the synergy influence of the lithiophilic effect and shunting action, Li dendrites are effectively suppressed. As proof, the Li||Li symmetrical cells with composite separators can circulate steadily for a long time under high current densities (10 mA cm^-2, 800 h). Moreover, the LiFePO₄||Li full cells display excellent long cycling performance (82% retention after 800 cycles).

Enhancing thermal conductivity of polyimide composite film by electrostatic self-assembly and two-step synergism of Al2O3 microspheres and BN nanosheets

To improve the perfection of a three-dimensional thermally conductive network in polyimide (PI) composite film and with respect to the economy and simplicity of processing, a strategy of the two-step synergism of Al2O3 microspheres and hexagonal boron nitride (BN) nanosheets was proposed. First, BN nanosheet-coated Al2O3 microspheres (Al2O3@BN) were prepared by electrostatic self-assembly method for the first step of the synergism. Then, the Al2O3@BN&BN/PI composite film containing Al2O3@BN and BN was fabricated by a two-step method for the second step of the synergism, and was systematically characterized. With an optimized mass ratio of 2 : 1 of Al2O3@BN to BN, the thermal conductivity of the 35 wt% Al2O3@BN&BN/PI composite film reached 3.35 W m-1 K-1, and was increased by 1664% compared to that of pure PI. The synergism of the Al2O3 and BN was the most significant in the Al2O3@BN&BN/PI composite film with the thermal conductivity, which was 36.6%, 23% and 22% higher than that of the Al2O3/PI, BN/PI and Al2O3@BN/PI composite films, respectively. The enhancement mechanism of heat conduction was clearly demonstrated. The BN coated on the surface of Al2O3 mainly played a bridging role between the Al2O3 and the BN network, which improved the perfection of the thermally conductive network. The Al2O3@BN segregated the PI matrix to construct the BN network with the typical segregated structure in the composite film, resulting in an efficient thermally conductive network. This work provided a novel strategy for the preparation of conductive polymer composites.

Thermal Conductive 2D Boron Nitride for High-Performance All-Solid-State Lithium-Sulfur Batteries

Polymer-based solid-state electrolytes are shown to be highly promising for realizing low-cost, high-capacity, and safe Li batteries. One major challenge for polymer solid-state batteries is the relatively high operating temperature (60-80 °C), which means operating such batteries will require significant ramp up time due to heating. On the other hand, as polymer electrolytes are poor thermal conductors, thermal variation across the polymer electrolyte can lead to nonuniformity in ionic conductivity. This can be highly detrimental to lithium deposition and may result in dendrite formation. Here, a polyethylene oxide-based electrolyte with improved thermal responses is developed by incorporating 2D boron nitride (BN) nanoflakes. The results show that the BN additive also enhances ionic and mechanical properties of the electrolyte. More uniform Li stripping/deposition and reversible cathode reactions are achieved, which in turn enable all-solid-state lithium-sulfur cells with superior performances.

Poly(l-lactic acid)/Boron Nitride Nanocomposites: Influence of Boron Nitride Functionalization on the Properties of Poly(l-lactic acid)

Differently functionalized boron nitride nanosheets (BNNSs) [hydroxyl (OH_BNNSs), amine (NH₂_BNNSs), and poly(ethylene glycol) (PEG) (PEG_BNNSs)] were synthesized, and their effects on the structure and thermal properties of poly(l-lactic acid) (PLLA) along with those of the pristine BNNSs were studied. Highly dispersed nanocomposites were prepared using PLLA and 0.5 wt % of pristine/functionalized BNNSs via a solvent blending method. Homogeneous dispersion of BNNSs in the polymer matrix was confirmed using X-ray diffraction and scanning electron microscopy. Pristine BNNSs and OH_BNNSs accelerated the crystallization of PLLA as effective nucleating agents and favored the formation of the α form in melt-crystallized samples. On the other hand, NH₂_BNNSs and PEG_BNNSs incorporated samples result in the moderate crystallization rate of PLLA and lead to the formation of a mixture of α and α' forms similar to the PLLA. It is also found that thermal stability and thermal conductivity of PLLA nanocomposites significantly depend on the type of functionalization of BNNSs. At 0.5 wt % loading, the thermal conductivity enhancement is maximum for PEG_BNNSs incorporated PLLA (∼62%), and that is only 9% for pristine BNNSs incorporated PLLA. The thermal stability of PLLA nanocomposites was significantly improved by 32-41 °C depending on the type of functionalized BNNSs compared to PLLA. It is proposed that the strong interaction between functionalized BNNSs and PLLA matrix is responsible for the improved thermal management properties.

Enhanced Thermal Conductivity of Epoxy Composites Filled with 2D Transition Metal Carbides (MXenes) with Ultralow Loading

With the development of electronic devices such as integrated circuits toward the continual increase in power density and consumption, the efficient heat dissipation and low thermal expansion of materials become one of the most important issue. However, conventional polymers have the problem of poor thermal dissipation performance, which hinder application for electronic devices. In this work, the two-dimensional material, MXene (Ti₃C₂), is used as the reinforcement additive to optimize the thermal properties of polymers. We reported the preparation of multilayer Ti₃C₂ MXene by HF etching method and obtained few-layer Ti₃C₂ MXene by simple ultrasonication. Meanwhile, Ti₃C₂/epoxy composites were prepared by a solution blending method. The results show that the thermal properties of the composites are improved in comparison with the neat epoxy. Thermal conductivity value (0.587 W/mK) of epoxy composite with only 1.0 wt% Ti₃C₂ MXene fillers, is increased by 141.3% compared with that of neat epoxy. In addition, the composite presents an increased glass transition temperature, high thermal stability and lower coefficient of thermal expansion. This work is of great significance for the research of high-performance composite materials.

Loading of AgNPs onto the surface of boron nitride nanosheets for determination of scopoletin in Atractylodes macrocephala

In this work, silver nanoparticles prepared by a molten salt method were deposited onto the surface of hexagonal boron nitride nanosheet (NS/AgNP) to from a composite. The synthesized nanocomposite was applied for surface modification of screen-printed electrode (SPE). The modified electrode showed a superior performance for electrochemical detection of scopoletin. The electrochemical behaviour of NS/AgNP/SPE was studied in detail. An electrocatalytic oxidation was observed and used for analytical determination of scopoletin concentration. The response of the proposed electrochemical sensing platform was linear over a wide detection range of 2 μM to 0.45 mM with a low limit of detection (LOD) of 0.89 μM. The NS/AgNP/SPE also showed excellent reproducibility and anti-interference property. In addition, the proposed scopoletin sensor was successfully used for the determination of scopoletin in Atractylodes macrocephala herb samples.

Preparation and Properties of Poly(imide-siloxane) Copolymer Composite Films with Micro-Al2O3 Particles

In the current study, poly(imide-siloxane) copolymers (PIs) with different siloxane contents were synthesized and used as a matrix material for PI/Al2O3 composites. The PIs were characterized via their molecular weight, film quality, and thermal stability. Among the PI films, free-standing and flexible PI films were selected and used to prepare PI/Al2O3 composite films, with different Al2O3 loadings. The thermal conductivity, thermal stability, mechanical property, film flexibility, and morphology of the PI/Al2O3 composite films were investigated for their application as heat-dissipating material.

High temperature thermally conductive nanocomposite textile by "green" electrospinning

Recently, thermally regulating textiles have attracted wide interest owing to their ability to realize personal cooling and provide thermal comfort. However, most of the thermally conductive textiles cannot afford higher temperatures (>200 °C), which restricts their further applications in aviation, fire extinguishing or military requiring high temperature heat spreaders. Here, we report a high temperature thermally conductive nanocomposite textile consisting of amino functional boron nitride (FBN) nanosheets and polyimide (PI) nanofibers. Notably, the textile is "green" electrospun from aqueous solution without any toxic organic solvents, which is facile, economical and environmently friendly. Moreover, both FBN and the precursor of PI are modified to be water soluble and exhibit good compatibility in the spinning solution even under high concentrations. The "green" method obtained FBN-PI textile shows high thermal conductivity (13.1 W m-1 K-1) at a high temperature (300 °C), filling in the gap of thermally conductive polymer nanocomposite fibers for high temperature thermal regulation. Furthermore, it also provides efficient cooling capability as a thermal spreader. The good performance is ascribed to the weaving of the aligned FBN filament in a thermally stable PI fiber, which constructs an effective thermally conductive network. In addition, the nanocomposite textile is light weight, soft and hydrophobic, which is promising for electronic packaging or space suits for special high temperature thermal management.