Mussel Inspired Modification for Aluminum Oxide/Silicone Elastomer Composites with Largely Improved Thermal Conductivity and Low Dielectric Constant

Effect of the alumina micro-particle sizes on the thermal conductivity and dynamic mechanical property of epoxy resin

Epoxy thermal conductive adhesives with high thermal conductivity and dynamic mechanical properties are important thermally conductive materials for fabricating highly integrated electronic devices. In this paper, micro-Al2O3 is used as a thermally conductive filler for the epoxy resin composite and investigated the effect of micron-sized alumina particle size on the thermal conductivity and dynamic mechanical property of epoxy resin by the transient planar hot plate method and DMA (Dynamic mechanical analysis). The experimental results show that with the same amount of alumina filling, the thermal conductivity and Tg (glass transition temperature) of epoxy/Al2O3 composite material decrease with the increase of alumina particle size. The maximum thermal conductivity of the composite material is 0.679 (W/mK), while the energy storage modulus of epoxy/Al2O3 composite material increases with the increase of alumina particle size, and the maximum energy storage modulus of the composite material is 160MPa. Compared with pure epoxy resin, the thermal conductivity and energy storage modulus have increased by 2.7 and 3.2 times, respectively. The epoxy/Al2O3 composite was applied to the COB (Chips On Board) type LED package, and the substrate temperature of the LED dropped to the lowest after 1.5 hours of operation using EP-A5 composite, and the temperature was stabilized at 38.2°C, indicating that the addition of 5-micron alumina composite has the best heat dissipation in the COB type LED package. These results are critical for the implementation of particulate-filled polymer composites in practical applications because relaxed material specifications and handling procedures can be incorporated in production environments to improve efficiency.

Impact of silver-doped alumina nanocomposite on water decontamination by remodeling of biogenic waste

The main cause of various fatal diseases in humans and animals is environmental pollution. Ag-doped alumina nanocomposite was prepared using coffee husk extract with a large BET surface area of 126.58 m² g^-1 and investigated for its antibacterial potential against both bacterial strains Escherichia coli and Salmonella typhimurium, and observed as an effective sorbent for removing the water pollution dye indigo carmine (IGC). The lowest concentration of the nanocomposite and the maximum contact time required to achieve complete inhibition of bacteria present in the contaminated water, as well as the capacity of sorption of IGC, were investigated. The results showed that the minimum inhibitory concentration of the Ag-doped alumina nanocomposite was 12 µg mL^-1 for both bacterial strains, with the highest inhibition occurring in E. coli. Moreover, the nanocomposite exhibited an experimental qt of 462.7 mg g^-1 from 160 mg L^-1 IGC solution at 50 °C and followed the Langmuir model. The thermodynamic results showed that the process was endothermic, spontaneous, and physisorptive. The nanocomposite was used to fully treat water samples contaminated with 10 mg L^-1 concentrations of IGC. For six consecutive cycles, the reuse research showed an average efficiency of 95.72 ± 3.6%. Consequently, the synthesized Ag-doped alumina nanocomposite is suitable for treatments of contaminated water.

Development and Perspectives of Thermal Conductive Polymer Composites

With the development of electronic appliances and electronic equipment towards miniaturization, lightweight and high-power density, the heat generated and accumulated by devices during high-speed operation seriously reduces the working efficiency and service life of the equipment. The key to solving this problem is to develop high-performance thermal management materials and improve the heat dissipation efficiency of the equipment. This paper mainly summarizes the research progress of polymer composites with high thermal conductivity and electrical insulation, including the thermal conductivity mechanism of composites, the factors affecting the thermal conductivity of composites, and the research status of thermally conductive and electrical insulation polymer composites in recent years. Finally, we look forward to the research focus and urgent problems that should be addressed of high-performance thermal conductive composites, which will provide strategies for further development and application of advanced thermal and electrical insulation composites.

Synchronously improved thermal conductivity and dielectric constant for epoxy composites by introducing functionalized silicon carbide nanoparticles and boron nitride microspheres

Polymer-based dielectrics with high thermal conductivity and superb dielectric properties hold great promising for advanced electronic packaging and thermal management application. However, integrating these properties into a single material remains challenging due to their mutually exclusive physical connotations. Here, an ideal dielectric thermally conductive epoxy composite is successfully prepared by incorporating multiscale hybrid fillers of boron nitride microsphere (BNMS) and silicon dioxide coated silicon carbide nanoparticles (SiC@SiO₂). In the resultant composites, the microscale BNMS serve as the principal building blocks to establish the thermally conductive network, while the nanoscale SiC@SiO₂ as bridges to optimize the heat transfer and suppress the interfacial phonon scattering. In addition, the special core-shell nanoarchitecture of SiC@SiO₂ can significantly impede the leakage current and generate a great deal of minicapacitors in the composites. Consequently, favorable thermal conductivity (0.76 W/mK) and dielectric constant (∼8.19) are simultaneously achieved in the BNMS/SiC@SiO₂/Epoxy composites without compromising the dielectric loss (∼0.022). The strategy described in this study provides important insights into the design of high-performance dielectric composites by capitalizing on the merits of different particles.

Thermally Conductive and Electrically Insulated Silicone Rubber Composites Incorporated with Boron Nitride−Multilayer Graphene Hybrid Nanofiller

Thermally conductive and electrically insulating composites are important for the thermal management of new generation integrated and miniaturized electronic devices. A practical and eco−friendly electrostatic self−assembly method was developed to prepare boron nitride−multilayer graphene (BN−MG) hybrid nanosheets. Then, BN−MG was filled into silicone rubber (SR) to fabricate BN−MG/SR composites. Compared with MG/SR composites with the same filler loadings, BN−MG/SR composites exhibit dramatically enhanced electrical insulation properties while still maintaining excellent thermal conductivity. The BN−MG/SR with 10 wt.% filler loading shows a thermal conductivity of 0.69 W·m⁻¹·K⁻¹, which is 475% higher than that of SR (0.12 W·m⁻¹·K⁻¹) and only 9.2% lower than that of MG/SR (0.76 W·m⁻¹·K⁻¹). More importantly, owing to the electron blocking effect of BN, the electron transport among MG sheets is greatly decreased, thus contributing to the high−volume resistivity of 4 × 10¹¹ Ω cm for BN−MG/SR (10 wt.%), which is fourorders higher than that of MG/SR (2 × 10⁷ Ω·cm). The development of BN−MG/SR composites with synergetic properties of high thermal conductivity and satisfactory electrical insulation is supposed to be a promising candidate for practical application in the electronic packaging field.

Interfacial assembled mesoporous polydopamine nanoparticles reduced graphene oxide for high performance of waterborne epoxy-based anticorrosive coatings

Embedding two-dimension micro/nanocontainers containing corrosion inhibitors into organic coating is a well-established concept to impart the coating with enhanced barrier and self-healing feature. Herein, a versatile nanoemulsion assembly approach was used to synthesis nanocarriers combing mesoporous polydopamine nanoparticles (MPDA) with reduced graphene oxide (GO), which was employed to encapsulate corrosion inhibitors (benzotriazole, BTA) to improve the anticorrosion performance of waterborne epoxy coating. The BTA release profiles from synthesized GO with MPDA (PDAG) demonstrated the rapid pH-triggered activities to acidic corrosion environment. With the addition of BTA-loaded PDAG, the composited epoxy coatings presented self-repairing behavior and enhanced corrosion resistance during long-term immersion. The outstanding anticorrosion performance is attributed to dual-protection mechanism provided by BTA-loaded PDAG: (1) MPDA endows GO with satisfactory interface compatibilities and thus provides impermeable barrier to delay the penetration process of corrosive electrolyte; (2) corrosion inhibitors including BTA and polydopamine form the adsorption layers on bare steel surface to resist continuous corrosion at metal/coating interface.

A Novel Branched Al2O3/Silicon Rubber Composite with Improved Thermal Conductivity and Excellent Electrical Insulation Performance

In this paper, we report a thermal conductive polymer composite that consists of silicone rubber (SR) and branched Al₂O₃ (B-Al₂O₃). Owing to the unique two-dimensional branched structure, B-Al₂O₃ particles form a continuous three-dimensional network structure by overlapping each other in the matrix, serving as a continuous heat conductive pathway. As a result, the polymer composite with a 70 wt% filler achieves a maximum thermal conductivity of 1.242 Wm⁻¹ K⁻¹, which is equivalent to a significant enhancement of 521% compared to that of a pure matrix. In addition, the composite maintains a high volume resistivity of 7.94 × 10¹⁴ Ω·cm with the loading of 70 wt%, indicating that it meets the requirements in the field of electrical insulation. Moreover, B-Al₂O₃ fillers are well dispersed (no large agglomerates) and form a strong interfacial adhesion with the matrix. Therefore, the thermal decomposition temperature, residual mass, tensile strength, modulus and modulus of toughness of composites are significantly improved simultaneously. This strategy provides new insights for the design of high-performance polymer composites with potential application in advanced thermal management in modern electronics.

Preparation and mechanism research of bio-inspired dopamine decorated expanded graphite/silicone rubber composite with high thermal conductivity and excellent insulation

This study looked at the process of designing and synthesized expanded graphite (EG) and modifying it with bio-inspired dopamine (DOPA). This is a process used to improve the thermal conductivity and dielectric properties of methyl vinyl silicone rubber (VMQ). The results demonstrated that the EG-DOPA-VMQ composites acquired an exceptional thermal conductivity of 1.015 W mK^-1at the loading of 10 wt%, approximately 480% higher than that of pure silicone rubber (0.175 W mK^-1). This enhancement is mainly attributed to the improved dispersion capability of EG-DOPA and the robust interfacial interaction between EG-DOPA-VMQ interfaces; specifically, this is the result when compared with pristine EG. Moreover, throughout this process, the composites maintained an excellent insulating property with a resistance of ≈10¹²Ω · cm; this particular result was due to the DOPA deposited on EG surfaces because they acted as an insulating layer, inhibiting the electron transfer in composites. Overall, this work demonstrated that it could present a promising strategy for synchronized manufacturing of polymer composites with high thermal conductivity and insulating capability.

Recent developments in the synthesis of chemically modified nanomaterials for use in dielectric and electronics applications

Polymer nanocomposites (PNC) have attracted enormous scientific and technological interest due to their applications in energy storage, electronics, biosensing, drug delivery, cosmetics and packaging industry. Nanomaterials (platelet, fibers, spheroids, whiskers, rods) dispersed in different types of polymer matrices constitute such PNC. The degree of dispersion of the inorganic nanomaterials in the polymer matrix, as well as the structured arrangement of the nanomaterials, are some of the key factors influencing the overall performance of the nanocomposite. To this end, the surface functionalization of the nanomaterials determines its state of dispersion within the polymer matrix. For energy storage and electronics, these nanomaterials are usually chosen for their dielectric properties for enhancing the performance of device applications. Although several reviews on surface modification of nanomaterials have been reported, a review on the surface functionalization of nanomaterials as it pertains to polymer dielectrics is currently lacking. This review summarizes the recent developments in the surface modification of important metal oxide dielectric nanomaterials including Silicon dioxide (SiO₂), titanium dioxide (TiO₂), barium titanate (BaTiO₃), and aluminum oxide (Al₂O₃) by chemical agents such as silanes, phosphonic acids, and dopamine. We report the impact of chemical modification of the nanomaterial on the dielectric performance (dielectric constant, breakdown strength, and energy density) of the nanocomposite. Aside from bringing novice and experts up to speed in the area of polymer dielectric nanocomposites, this review will serve as an intellectual resource in the selection of appropriate chemical agents for functionalizing nanomaterials for use in specific polymer matrix so as to potentially tune the final performance of nanocomposite.

Preparation of Boron Nitride and Silicone Rubber Composite Material for Application in Lithium Batteries

Hexagonal boron nitride and silicone rubber (h-BN/SR) composites were prepared by the mechanical stirring method, and their crystal morphology, chemical structure, thermal properties, and compression stress–strain performance were investigated. The experimental results suggest that silicone rubber combined with h-BN exhibits better thermal conductivity and mechanical properties. When the proportion of h-BN is 30 wt%, the thermal conductivity of the h-BN/SR composite material is 0.58 W/m∙K, which is 3.4 times that of pure silicone rubber. At the same time, the compressive strength of h-BN/SR is 4.27 MPa, which is 6.7 times that of pure silicone rubber. Furthermore, the finite element model was employed to numerically analyze the thermal behavior of a battery with a h-BN/SR composite as the thermal interface material. The analytical results show that the highest temperature of the battery decreased when using h-BN/SR as the thermal interface material in the battery thermal management system. The h-BN/SR composite can thus effectively improve the safety properties of batteries.

Highly Thermally Conductive and Superior Electrical Insulation Polymer Composites via In Situ Thermal Expansion of Expanded Graphite and In Situ Oxidation of Aluminum Nanoflakes

Polymer composites with highly thermally conductive and electrical insulation are urgently demanded for thermal management in modern electrical and energy applications. However, the incorporation of metal fillers in traditional polymeric composites usually fails to meet the requirements for simultaneously high thermal conductivity and high electrical insulation. Here, we successfully fabricated composites with high thermal conductivity and high electrical insulation by in situ thermal expansion of expandable graphite (EG) and in situ oxidation of aluminum (Al) nanoflakes in aluminum-plastic package waste (APPW). Due to the synergistic effect of the hybrid filler framework, the maximum thermal conductivity reached as high as 8.7 W m^-1 K^-1 for APPW/EG₁₀/Al₆₀-F composites. In addition, the formation of the nano Al₂O₃ layer around the Al filler surface brings extremely low electrical conductivity (<10^-14 S cm^-1) and low dielectric loss (<0.06). Based on the results of finite element simulation, the heat flowed mainly along the effective filler framework and the high thermal conductivity is attributed to the interconnection of the high aspect ratio filler. Furthermore, the strong thermal management capability of the prepared composites was demonstrated in the heat dissipation experiment. The present work suggests that surface-oxidized Al nanoflakes demonstrate fascinating performance and show promising application as thermal management materials in emerging electrical systems and electronic devices.

Polydopamine-Modified Al2O3/Polyurethane Composites with Largely Improved Thermal and Mechanical Properties

Alumina/polyurethane composites were prepared via in situ polymerization and used as thermal interface materials (TIMs). The surface of alumina particles was modified using polydopamine (PDA) and then evaluated via Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and Raman spectroscopy (Raman). Scanning electron microscope (SEM) images showed that PDA-Al2O3 has better dispersion in a polyurethane (PU) matrix than Al2O3. Compared with pure PU, the 30 wt% PDA-Al2O3/PU had 95% more Young's modulus, 128% more tensile strength, and 76% more elongation at break than the pure PU. Dynamic mechanical analysis (DMA) results showed that the storage modulus of the 30 wt% PDA-Al2O3/PU composite improved, and the glass transition temperature (Tg) shifted to higher temperatures. The thermal conductivity of the 30 wt% PDA-Al2O3/PU composite increased by 138%. Therefore, the results showed that the prepared PDA-coated alumina can simultaneously improve both the mechanical properties and thermal conductivity of PU.

Silicone Rubber Composites with High Breakdown Strength and Low Dielectric Loss Based on Polydopamine Coated Mica

High breakdown strength and low dielectric loss are necessary for the outdoor insulator using silicone rubber (SR) composites. In this work, polydopamine coated mica (mica-PDA) was synthesized via bioinspired dopamine self-polymerization, and mica-PDA-filled SR composite (SR/mica-PDA-VTMS) was prepared using vinyl tri-methoxysilane (VTMS) as a silane coupling agent which serves as the molecular bridges between the organic rubber and the inorganic filler. The SR/mica-PDA-VTMS composite demonstrated dense and uniform morphology where the filler was well dispersed. Due to the strong interfacial interactions between filler and rubber, the SR/mica-PDA-VTMS composite exhibits much lower dielectric loss compared to the other mica-filled SR composites, which was comparable to the prepared alumina-tri-hydrate-filled SR composites. Moreover, the breakdown strength of ~31.7 kV/mm and tensile strength of 5.4 MPa were achieved for the SR/mica-PDA-VTMS composite, much higher than those of the other as-prepared SR composites.

Fabrication of Morphologically Controlled Composites with High Thermal Conductivity and Dielectric Performance from Aluminum Nanoflake and Recycled Plastic Package

Polymer composites with high thermal conductivity are highly desirable for modern electronic and electrical industry because of their wide range of applications. However, conventional polymer composites with high thermal conductivity usually suffer from the deterioration of electrical insulation and high dielectric loss, whereas polymer composite materials with excellent electrical insulation and dielectric properties usually possess low thermal conductivity. In this study, combining surface-oxidized aluminum (Al) nanoflake and multilayer plastic package waste (MPW) by powder mixing technique, we report a novel strategy for polymer composites with high thermal conduction, high electrical insulation, and low dielectric loss. The resultant MPW/Al, MPW/Al₄₀₀, and MPW/Al₅₀₀ composites exhibited the maximum thermal conductivity of 4.8, 3.5, and 1.4 W/mK, respectively, which exceeds those of most of the corresponding composites reported previously. In addition, all the composites still have high insulation (<10^-13 S/cm) and maintain dielectric loss at a relatively low level (<0.025). Such a result is ascribed to the formation of an insulating Al₂O₃ shell and the continuous three-dimensional filler network, which is revealed by Agari model fitting coefficient. The model of effective medium theory qualitatively demonstrates that the lower interfacial thermal resistances of the MPW/Al composite can also benefit the high thermal conduction. This interfacial engineering strategy provides an effectively method for the fabrication of polymer materials with high-performance thermal management.

Synergistic Improvement in Thermal Conductivity of Polyimide Nanocomposite Films Using Boron Nitride Coated Copper Nanoparticles and Nanowires

Electronic devices are increasingly dense, underscoring the need for effective thermal management. A polyimide (PI) matrix nanocomposite film combining boron nitride (BN)-coated copper nanoparticles (CuNPs@BN) and nanowires (CuNWs@BN) was fabricated by a flexible and fast technique for enhanced thermal conductivity and the dielectric properties of nanocomposite films. The thermal conductivity of (CuNPs-CuNWs)@BN/PI composite comprising 10 wt % filler loading rose to 4.32 W/mK, indicating a nearly 24.1-fold increase relative to the value obtained for pure PI matrix. The relative permittivity and dielectric loss approximated 4.92 and 0.026 at 1 MHz, respectively. The results indicated that the surface modification of CuNPs and CuNWs by introducing a ceramic insulating layer BN effectively promoted the formation of thermal conductive networks of nanofillers in the PI matrix. This study enabled the identification of appropriate modifier fillers for polymer matrix nanocomposites to improve electronic applications.