Nitride Platelets Research Articles

Silicone Composites with Electrically Oriented Boron Nitride Platelets and Carbon Microfibers for Thermal Management of Electronics

This study investigated silicone composites with distributed boron nitride platelets and carbon microfibers that are oriented electrically. The process involved homogenizing and dispersing nano/microparticles in the liquid polymer, aligning the particles with DC and AC electric fields, and curing the composite with IR radiation to trap particles within chains. This innovative concept utilized two fields to align particles, improving the even distribution of carbon microfibers among BN in the chains. Based on SEM images, the chains are uniformly distributed on the surface of the sample, fully formed and mature, but their architecture critically depends on composition. The physical and electrical characteristics of composites were extensively studied with regard to the composition and orientation of particles. The higher the concentration of BN platelets, the greater the enhancement of dielectric permittivity, but the effect decreases gradually after reaching a concentration of 15%. The impact of incorporating carbon microfibers into the dielectric permittivity of composites is clearly beneficial, especially when the BN content surpasses 12%. Thermal conductivity showed a significant improvement in all samples with aligned particles, regardless of their composition. For homogeneous materials, the thermal conductivity is significantly enhanced by the inclusion of carbon microfibers, particularly when the boron nitride content exceeds 12%. The biggest increase happened when carbon microfibers were added at a rate of 2%, while the BN content surpassed 15.5%. The thermal conductivity of composites is greatly improved by adding carbon microfibers when oriented particles are present, even at BN content over 12%. When the BN content surpasses 15.5%, the effect diminishes as the fibers within chains are only partly vertically oriented, with BN platelets prioritizing vertical alignment. The outcomes of this study showed improved results for composites with BN platelets and carbon microfibers compared to prior findings in the literature, all while utilizing a more straightforward approach for processing the polymer matrix and aligning particles. In contrast to current technologies, utilizing homologous materials with uniformly dispersed particles, the presented technology reduces ingredient consumption by 5–10 times due to the arrangement in chains, which enhances heat transfer efficiency in the desired direction. The present technology can be used in a variety of industrial settings, accommodating different ingredients and film thicknesses, and can be customized for various applications in electronics thermal management.

Facile chemical surface modification of boron nitride platelets and improved thermal and mechanical properties of their polymer compounds for 2.5D/3D packaging applications

Thermally conductive yet electrically insulative epoxy composites are sought after as encapsulation materials to tackle the heat dissipation challenges in modern electronics. In this work, we developed a novel one-step and facile solvothermal reflux method using a high-boiling-point solvent to surface-modify hexagonal boron nitride (h-BN) with glycine. By refluxing glycine at high temperature, amino functional groups are grafted onto the BN surface, which can enhance the affinity of fillers for epoxy and reduce the interfacial thermal resistance of the filler/epoxy composites. We investigated the mechanism of glycine-grafted layer formation, optimizing reactant mass ratios for enhanced interfacial thermal transport. The resulting BN@G11/epoxy composites exhibit a remarkable thermal conductivity of 1.04 W/mK at 30 wt% modified-BN loading, representing a 477.8 % increase over neat epoxy and 57.5 % higher than h-BN/epoxy composites at equivalent BN filler loading. Additionally, these composites demonstrate improved thermomechanical properties, confirming the strengthened BN/epoxy interface bonding using modified BN fillers. Compared to other surface treatment methods, this solvothermal reflux approach stands out for its scalability and cost-effectiveness. This scalable and eco-friendly innovation presents a competitive strategy for designing polymer-based composites for thermal management, catering to the demands of future 2.5D/3D semiconductor packaging.

Boron Nitride/Carbon Fiber High-Oriented Thermal Conductivity Material with Leaves-Branches Structure.

In the realm of thermal interface materials (TIMs), high thermal conductivity and low density are key for effective thermal management and are particularly vital due to the growing compactness and lightweight nature of electronic devices. Efficient directional arrangement is a key control strategy to significantly improve thermal conductivity and comprehensive properties of thermal interface materials. In the present work, drawing inspiration from natural leaf and branch structures, a simple-to-implement approach for fabricating oriented thermal conductivity composites is introduced. Utilizing carbon fibers (CFs), known for their ultra-high thermal conductivity, as branches, this design ensures robust thermal conduction channels. Concurrently, boron nitride (BN) platelets, characterized by their substantial in-plane thermal conductivity, act as leaves. These components not only support the branches but also serve as junctions in the thermal conduction network. Remarkably, the composite achieves a thermal conductivity of 11.08 W/(m·K) with just an 11.1 wt% CF content and a 1.86 g/cm3 density. This study expands the methodologies for achieving highly oriented configurations of fibrous and flake materials, which provides a new design idea for preparing high-thermal conductivity and low-density thermal interface materials.

Preparation of high thermal conductivity vat photopolymerization used UV-curable resin synergistically enhanced by silicon nitride and boron nitride

Additive manufacturing (3D printing) technologies, especially vat photopolymerization (VPP), provide a cost-effective and efficient approach for the fabrication of heat dissipation devices with complex geometric designs. The incorporation of inorganic thermal conductive fillers into resin matrix is widely recognized as an effective way to enhance thermal conductivity. Notably, the synergistic effect of hybrid fillers can further enhance thermal conductivity. However, the consequent drastic increase in viscosity of the UV-curable resin may decrease the success rate and accuracy of printing on commercial VPP 3D printers. In this work, hexagonal boron nitride (h-BN) platelets and spherical h-BN together with β-Si3N4 are introduced into the UV-curable resin system. Corresponding results proved that h-BN together with β-Si3N4 provide a synergistic effect on the thermal conductivity enhancement compared to the filler in single morphology only. Moreover, owing to the spherical structure, low-viscosity UV-curable resin with high solid content can be prepared. In specific, a thermal conductive polymer composite material with a solid content of 60 wt% is prepared, which exhibits high thermal conductivity (1.42 W/mK), representing an enhancement of up to 610 % compared to neat resin. In subsequent application demonstrations, 3D printed heat dissipation devices with as-prepared resin composite material have been shown to effectively enhance the heat dissipation rate for the heating device.

Sequential Dual Alignments Introduce Synergistic Effect on Hexagonal Boron Nitride Platelets for Superior Thermal Performance.

Planarly aligning 2D platelets is challenging due to their additional orientational freedom compared to 1D materials. This study reports a sequential dual-alignment approach, employing an extrusion-printing-induced shear force and rotating-magnetic-field-induced force couple for platelet planarly alignment in a yield-stress support bath. It is hypothesized that the partial alignment induced by a directional shear force facilitates subsequent axial rotation of the platelets for planar alignment under an external force couple, resulting in a synergistic alignment effect. This sequential dual-alignment approach achieves better planar alignment of 2D modified hexagonal boron nitride (mhBN). Specifically, the thermal conductivity of the 40 wt% mhBN/epoxy composite is significantly higher (692%) than that of unaligned composites, surpassing the cumulative effect of individual methods (only 133%) with a 5 times more synergistic effect. For 30, 40, and 50 wt% mhBN composites, the thermal conductivity values (5.9, 9.5, and 13.8W m-1 K-1) show considerable improvement compared to the previously reported highest values (5.3, 6.6, and 8.6W m-1 K-1). Additionally, a 3D mhBN/epoxy heat sink is printed and evaluated to demonstrate the feasibility of device fabrication. The approach enables the planar alignment of electrically or thermally conducting 2D fillers during 3D fabrication.

Thermal dissipation network of hexagonal boron nitride platelets induced by low dielectric polymeric particles for millimeter wave devices

Thermal dissipation network of hexagonal boron nitride platelets induced by low dielectric polymeric particles for millimeter wave devices

Electrostatic flocking assisted aligned boron nitride platelets scaffold for enhancing the through-plane thermal conductivity of flexible thermal interface materials

The composite films filled with anisotropic flaky powders usually have excellent in-plane thermal conductivity, but poor through-plane thermal conductivity. To improve the through-plane thermal conductivity, vertically aligned boron nitride (BN) platelets are scaffolded through electrostatic flocking together with flexible epoxy resin. 17.57 wt% BN loading of the BN/epoxy complexes exhibit 0.65 W/m K of through-plane thermal conductivity, which is 18.6% higher than the random BN/epoxy. The method effectively utilizes each anisotropy of the two-dimensional material BN, exploiting the higher thermal conductivity of BN in-plane, and providing a new strategy for the preparation of thermal interface materials.

Fabrication of wear-resistant PA6 composites with superior thermal conductivity and mechanical properties via constructing highly oriented hybrid network of SiC-packed BN platelets

Herein, a strong extensional and shearing field was introduced to construct highly oriented hybrid networks of silicon carbide (SiC)-packed boron nitride (BN) platelets to fabricate high-performance wear-resistant PA6 composites. Results show that in-plane and through-plane thermal conductivity (TC) of the prepared PA6 composites with a total filler loading of 20 wt.% reached 1.31 and 0.35 W/(m K), 352% and 25% higher than those of pure PA6, respectively. It is attributed to the highly oriented hybrid network that facilitates the formation of efficient thermal conductivity pathways. Temperature monitoring results during friction confirm that high TC favors the friction heat dissipation performance. Meanwhile, the yield strength of PA6 composites increased by 39.1% and they still have excellent ductility with an elongation at break of 207.1%. Finally, the wear rate of PA6 composites decreased sharply by 92.5%. This method can be used to manufacture advanced linear bearing and guideway parts, etc.

Vertical Alignment of Anisotropic Fillers Assisted by Expansion Flow in Polymer Composites

HighlightsThe vertically aligned structures of anisotropic fillers (using 2D boron nitride (BN) platelets as a proof-of-concept) in composites are constructed assisted by the expansion flow.BN platelets in composites are aligned in a curved shape that includes vertical alignment in the central area and horizontal alignment close to strip surfaces.The shape of expansion channels affects the vertical orientation order and the through-plane thermal conductivity of composites.

Enhancing Heat Dissipation of Photoluminescent Composite in White-Light-Emitting Diodes by 3D-Interconnected Thermal Conducting Pathways.

The photoluminescent composite, which consists of micro-/nanoscale photoluminescent particles and a polymer matrix, plays a key role in optical wavelength conversion in white-light-emitting diodes (WLEDs). Heat is inevitably generated within the composite due to the energy lost through conversion and cannot be easily dissipated due to the extremely low thermal conductivity of the polymer matrix. Consequently, the composite suffers from a high working temperature, which severely deteriorates its optical performance as well as its long-term stability in WLEDs. To tackle this thermal issue, in this work three-dimensional (3D)-interconnected thermal conducting pathways composed of hexagonal boron nitride (hBN) platelets were constructed inside a photoluminescent composite, using a simplified bubbles-templating method. The thermal conductivity of the composite was efficiently enhanced from 0.158 to 0.318 W/(m∙K) under an ultralow hBN loading condition of 2.67 wt%. As a result, the working temperature of the photoluminescent composite in WLEDs was significantly reduced by 32.9 °C (from 102.3 °C to 69.4 °C, under 500 mA). Therefore, the proposed strategy can improve the heat accumulation issue in photoluminescent composites and thus improve the optical stability of WLEDs.

Thermal Dissipation Network of Hexagonal Boron Nitride Platelets Induced by Low Dielectric Polymeric Particles for Millimeter Wave Devices

Thermal Dissipation Network of Hexagonal Boron Nitride Platelets Induced by Low Dielectric Polymeric Particles for Millimeter Wave Devices

Estudio de materiales compuestos multifuncionales de matriz epoxi con nanopartículas cerámicas

The research about multifunctional materials has gained special relevance in recent years. In this sense, properties such as hydrophobicity, due to their potential applications (water repellent surfaces, self-cleaning, anti-icing, protective against corrosion, etc.) in combination with others, such as thermal conductivity or electrical insulation, can lead to new materials and coatings suitable for use in the field of energy and electronics.The present work focuses on the development of multifunctional materials of epoxy resins with inorganic nanoparticles with hydrophobic properties and better heat transfer capacity. To achieve this goal, nano-reinforcements of zinc and titanium oxides of different sizes and morphologies have been selected to obtain hydrophobicity, in addition to boron nitride platelets to improve the thermal conductivity of the nanocomposites coating.Among the possible applications of these coatings would be their use as electrical insulators for high voltage applications, such as self-cleaning surfaces, scratch resistance, etc. The addition of hydrophobic coatings, which also achieve a remarkable mechanical and thermal stability, could lead to new designs of greater reliability and durability in their functions.

Ordered stacking of oriented BN in confined space to construct effective heat transfer pathways

High orientation of thermally conductive fillers has been proved to improve thermal conductivity of polymer-matrix composites effectively. Thus, constructing effective heat transfer pathways of the oriented fillers is a key issue. In this work, the multilayered ribbon network was in-situ formed to confine the stack space of boron nitride (BN) platelets, which was beneficial to increase the local concentration of BN. Further, the ordered stacking of oriented BN was constructed in confined 2D space during the multistage stretching extrusion, and then effective heat transfer pathways of the oriented BN were achieved. Meanwhile, the multilayered ribbon network could improve the strength and toughness of thermally conductive composites, simultaneously. Consequently, in-plane thermal conductivity, yield strength and impact strength of the obtained composite with the multilayered ribbon network at 30 wt % BN were 319%, 60% and 160% higher than those of the traditional compression molding composites, respectively. Therefore, this work offers a new method for the construction of effective heat transfer pathways in polymer-matrix composites to achieve both high thermal conductivity and good mechanical properties.

Enhanced thermal conductivity and mechanical properties of polymeric composites through formation of covalent bonds between boron nitride and rubber chains

AbstractHexagonal boron nitride (BN) platelets, also known as white graphite, are often used to improve the thermal conductivities of polymeric matrices. Due to the poor interfacial compatibility between BN platelets and polymeric matrices, in this study, polyrhodanine (PRd) was used to modify BN platelets and prepared functionalized BN‐PRd platelets, thereby enhancing the interfacial interaction between the thermal conductive filler and polymeric matrix. Then, BN‐PRd platelets were dispersed into the nitrile butadiene rubber (NBR) matrix to yield high thermally conductive composites. The presence of NC═S groups in PRd allowed the combination of PRd and NBR chains containing stable covalent bonds via vulcanization reaction. The thermal conductivity of the as‐prepared 30 vol% BN‐PRd/NBR composite reached 0.40 W/mK, representing an increment of 135% over pure NBR (0.17 W/mK). In addition, the largest tensile strength of NBR composite containing 30 vol% BN‐PRd platelets was 880% times of pure NBR. The 30 vol% BN‐PRd/NBR composite also displayed a relatively high dielectric constant (9.35 at 100 Hz) and a low dielectric loss tangent value (0.07 at 100 Hz), indicating their usefulness as dielectric flexible materials of microelectronics. In sum, the simplicity and good efficiency of formation of covalent bonds between boron nitride and rubber chains look very promising for large‐scale industrial production of high thermally conductive composites.

Size and surface effects of hexagonal boron nitrides on the physicochemical properties of monolithic phase change materials synthesized via sol–gel route

Monolithic shape-stabilized phase change materials (ss-PCMs) are among the most promising materials to store large amounts of solar energy, waste heat and off-peak electricity as heat in energy-saving buildings, battery- and water-heating systems. Generally, graphite-like additives, such as hexagonal boron nitride platelets (BN), are used to increase the thermal conductivity of ss-PCMs. However, it is still unknown which particle size and surface type of graphite-like additives increase the thermal conductivity of ss-PCMs to the highest extent. Here, we present the first experimental study about the influence of BN with different particle sizes and specific surface areas on the physicochemical properties of ss-PCMs synthesized via the sol–gel route. With a BN particle size of 25 µm, the average thermal conductivity of ss-PCMs containing 5–20 wt% BN increased by 57% when compared to the same ss-PCMs prepared with smaller BN particles (3 µm). This effect possibly results from the stronger exfoliation of the larger BN particles during synthesis and a larger amount of BN particles ordered in the same alignment in the silica structure. BN particles larger than 25 µm hinder the formation of mechanically stable silica structures. Smaller BN particles lead to higher viscous reaction mixtures with shorter gelation times and, thus, result in smaller silica macropores with diameters below 1 µm and higher compressive strengths of ss-PCMs up to 2.4 MPa at 10 °C and 1.7 MPa at 30 °C. An increasing specific surface area of BN up to 20 m2/g decreases the thermal conductivity by 0.11 W/mK (30 °C) and the compressive strength by 0.28 MPa (30 °C) of ss-PCMs with 20 wt% BN because of more BN agglomeration. Therefore, ss-PCMs containing 20 wt% BN with a particle size of 25 µm and a specific surface area of 3 m2/g have the highest thermal conductivity of 1.14 W/mK at 10 °C and 0.62 W/mK at 30 °C, but a 0.7–0.3 MPa lower compressive strength (10 °C) than the ss-PCM synthesized using 3 µm sized BN particles and specific surface areas of 12–20 m2/g.

Enhanced thermal conductivity and wear resistance of polytetrafluoroethylene via incorporating hexagonal boron nitride and alumina particles

AbstractPolytetrafluoroethylene (PTFE) receives wide attention in electronic packaging materials due to its excellent dielectric properties, friction properties and thermal stability. However, its extremely low thermal conductivity limits its further application. In this work, hexagonal boron nitride (h‐BN) platelets are added into PTFE matrix to improve the thermal conductivity as the expense of largely deteriorated friction property. To make up the loss of friction property, alumina particles (AO) are also added and the effects of filler ratio between h‐BN and alumina on the thermal conductivity and tribological performance of PTFE composites are investigated. It is interesting to find that when the filler ratio of h‐BN and alumina is fixed at 2:1, the through‐plane and in‐plane thermal conductivity of PTFE composite filled with 30 vol% hybrid filler can be increased to 1.544 Wm−1 K−1 and 2.029 Wm−1 K−1 (5.5 and 5.7 times that of PTFE), respectively. Furthermore, the coefficient of friction of PTFE composites only increases by 21.32% and the wear rate decreased by 48.09%, compared with that of PTFE. Our work demonstrates a facile method to achieve much improved thermal conductivity of PTFE while maintaining its excellent dielectric properties and friction properties by using hybrid filler of h‐BN and AO.

Multi-functional 2D hybrid aerogels for gas absorption applications

Aerogels have attracted significant attention recently due to their ultra-light weight porous structure, mechanical robustness, high electrical conductivity, facile scalability and their use as gas and oil absorbers. Herein, we examine the multi-functional properties of hybrid aerogels consisting of reduced graphene oxide (rGO) integrated with hexagonal boron nitride (hBN) platelets. Using a freeze-drying approach, hybrid aerogels are fabricated by simple mixing with various volume fractions of hBN and rGO up to 0.5/0.5 ratio. The fabrication method is simple, cost effective, scalable and can be extended to other 2D materials combinations. The hybrid rGO/hBN aerogels (HAs) are mechanically robust and highly compressible with mechanical properties similar to those of the pure rGO aerogel. We show that the presence of hBN in the HAs enhances the gas absorption capacities of formaldehyde and water vapour up to ~ 7 and > 8 times, respectively, as compared to pure rGO aerogel. Moreover, the samples show good recoverability, making them highly efficient materials for gas absorption applications and for the protection of artefacts such as paintings in storage facilities. Finally, even in the presence of large quantity of insulating hBN, the HAs are electrically conductive, extending the potential application spectrum of the proposed hybrids to the field of electro-thermal actuators. The work proposed here paves the way for the design and production of novel 2D materials combinations with tailored multi-functionalities suited for a large variety of modern applications.

Grafting of epoxidized natural rubber chains with BN platelets to obtain flexible and thermally conductive papers

Owing to the rapid development of high-power and minimized electronic devices, the materials with ultra-flexibility and effective heat dissipation have attracted much interest. Herein, the high thermally conductive epoxidized natural rubber (ENR) papers with layered structures based on boron nitride (BN) platelets are reported. First, polyrhodanine (PRd) was coated on the surface of BN platelets via oxidative polymerization of rhodanine (Rhd), which was initiated by the absorbed (S2O8)2- ions. Then, BN-PRd platelets were grafted with ENR chains using a mechanochemical method due to the presence of N–CS groups in PRd, allowing the combination of PRd and ENR chains with stable covalent bonds. Moreover, the grafted ENR chains acted as bridges between adjacent BN platelets and improved the heat transfer ability of BN-PRd/ENR thermally conductive composite papers. The as-prepared ultra-flexible 30 wt% BN-PRd/ENR thermally conductive composite papers rendered high in-plane (λ∥) and through-plane (λ⊥) thermal conductivity of 14.57 and 0.52 W/(mK), respectively, which were correspondingly 8094% and 289% of pure ENR paper (0.18 W/(mK)). Also, Young's modulus of the 30 wt% BN-PRd/ENR thermally conductive composite paper was 25.90 MPa. Overall, the as-fabricated BN-PRd/ENR thermally conductive composite papers demonstrated high flexibility, excellent mechanical robustness, outstanding thermal conductivity, and superior electronic illustration, indicating potential applications in areas of electronic components as thermal interface materials.

Modelling of Effective Thermal Conductivity of Composites Filled with Core-Shell Fillers.

An effective model to calculate thermal conductivity of polymer composites using core-shell fillers is presented, wherein a core material of filler grains is covered by a layer of a high-thermal-conductivity (HTC) material. Such fillers can provide a significant increase of the composite thermal conductivity by an addition of a small amount of the HTC material. The model employs the Lewis-Nielsen formula describing filled systems. The effective thermal conductivity of the core-shell filler grains is calculated using the Russel model for porous materials. Modelling results are compared with recent measurements made on composites filled with cellulose microbeads coated with hexagonal boron nitride (h-BN) platelets and good agreement is demonstrated. Comparison with measurements made on epoxy composites, using silver-coated glass spheres as a filler, is also provided. It is demonstrated how the modelling procedure can improve understanding of properties of materials and structures used and mechanisms of thermal conduction within the composite.

Natural rubber composites with enhanced thermal conductivity fabricated via modification of boron nitride by covalent and non-covalent interactions

Hexagonal boron nitride (BN) platelets are often used as fillers to improve the thermal conductivity (λ) of polymer matrix composites thanks to their good insulation and relative high λ. However, the low compatibility between polymeric matrices and BN platelets results in interfacial phonon scattering, interfering with the composites' heat transfer. In this paper, functionalized BN platelets were first modified with poly(catechol/polyamine) (PCPA) and then grafted with bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si69) to yield BN-PCPA-Si69/natural rubber (denoted as BN-PCPA-Si69/NR) composites. PCPA coating declined the interfacial phonon scattering between the matrix and fillers, while silane grafting improved the interfacial interaction via NR vulcanization with tetrasulfide bonds in Si69. In turn, these features led to improved dielectric characteristics, thermal conductivities, and mechanical properties. Among prepared samples, NR composite filled with 30% volume BN-PCPA-Si69 platelets content yielded a thermal conductivity 5.4-fold higher (λ = 0.81 W/mK) than that of neat NR (λ = 0.15 W/mK). The mechanical performances of BN-PCPA-Si69/NR composites also improved significantly with the maximum tensile strength reaching up 17.0 MPa. In sum, the proposed method looks inexpensive and feasible for the fabrication of high thermal conductive polymer composites for use in future advanced electronic devices, such as insulating and packaging electronic materials.