Thermal Conductive Networks Research Articles

Preparation of phosphorous ionic liquids and its effect on the properties of ABS

AbstractTo improve the thermal conductivity and mechanical properties of graphene‐acrylonitrile butadiene‐styrene plastic (ABS) composite, sub‐phosphite‐based ionic liquid (IL) was synthesized, and its structure was characterized by FTIR, NMR, and mass spectrometry. IL was as a modifier, and graphite powder (G powder) was modified by the ball milling method to obtain functional graphene thermal conductive filler (G‐IL). The structure and morphology of G‐IL were characterized by FTIR, X‐ray photoelectron spectroscopy (XPS), XRD, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results of the Molau test showed that the presence of IL improved the interfacial interaction of G‐IL and ABS, enhanced the dispersion of G‐IL in the ABS matrix, made G‐IL contact with each other, and it was easier to establish a thermal conduction network and promote phonon transfer. The thermal conductivity of 9 wt% G‐IL/ABS composite was 0.392 W·m−1·k−1, which was 96% and 14% higher than that of pure ABS and G/ABS composite, respectively. The tensile strength and bending modulus of 9 wt% G‐IL/ABS composite were 44.89 and 2124.37 MPa, which were 13% and 11% higher than those of pure ABS, respectively. The impact strength of 9 wt% G‐IL/ABS composite was 34.17 kJ/m2. It was 18% and 7% higher than that of pure ABS and 9 wt% G‐IL/ABS, respectively.Highlights Phosphorus imidazole ionic liquids were prepared. Graphene was modified by ionic liquids through non‐covalent. Enhanced mechanical properties and thermal conductivity of G‐IL/ABS composites.

Discussion on the thermal conductive network threshold of Al2O3/Co-continuous phase polymer composites

Achieving high thermal conductivity in polymer composites with micro or nanoparticle fillers are challenging. Typically, over 50 ​vol% filler loading is necessary to form a thermal conductive network. However, even with such a network in place, the increase in thermal conductivity may not be significant compared to that in electrically conductive composites. To clarify the ideal filler network structure, we endeavored to selectively disperse nano-sized Al₂O₃ nanoparticles at the interface of co-continuous SEBS/PA6 blends, with and without various filler surface modification methods. A thermal conductive network forms when all interface areas are fully covered by 2.56 ​vol% of Al2O3 nanoparticles (very close to theoretical loading content 2.29 ​vol%). In this case, the Al2O3 nanoparticle has the highest thermal conductive contribution (TCC). However, the absolute TCC values are extremely low because of the interfacial thermal resistance and it will decrease when the filler content exceeds 2.56 ​vol%, indicating that some nanoparticles are dispersed separately out of the existed thermal conductive network. These findings suggest that the construction of a connected thermal conductive network, relatively lower interfacial thermal resistance and the precise positioning of fillers within this network are essential for achieving high thermal conductivity composites.

Phase Change Thermal Interface Materials with Interface Adaptability and Self-Healing Properties

Thermal stress resulting from excessive temperatures is a major cause of electronic device failure. In this work, with easy installation and good interface adaptability, Phase Change Thermal Interface Materials (PCTIMs) which possess high thermal conductivity were prepared. By incorporating phase change material stearic acid (SA) into the thermal interface material, the instantaneous heat absorption during the solid-liquid phase transition of SA effectively alleviates the problem of instantaneous high heat flux impacting electronic devices. Additionally, the solid-liquid transition reduces the modulus of TIMs, thereby minimizing the contact thermal resistance between the heat source and the heat sink during mechanical installation. To further enhance performance, the thermal interface material utilizes a dynamically cross-linked polyolefin elastomer (POE) with borate bonds, which effectively restricts the flow of SA even at its phase change point due to the three-dimensional cross-linked framework. By constructing a thermal conductive network using carbon fibers and aluminum nitride of different dimensions, the thermal conductivity of the thermal interface material reached 1.82 W∙m−1K−1 with a filler content of only 30 vol% . At 70°C, with a force of 50 N applied to a sample area of 400 mm², the contact thermal resistance was only 2.39×10−4K∙m2W−1. Furthermore, the PCTIMs exhibits excellent self-healing ability under thermal conditions, assuring the permanent encapsulation of small electronic devices.

Significant enhancement of bi-directional ultrahigh thermal conductivity in polymer composites fabricated via Polyetherimide@Silver core–shell structured microspheres

Nowadays, the polymer-based composites with excellent thermal-conductive ability and ideal electromagnetic interference shielding performance are in great demand with the advent of developing modern electronic technology. However, most conventional thermal-conductive materials were typically designed to enhance thermal conductivity in just one single direction (through-plane or in-plane direction), which will be inadequate to meet increasing heat-dissipation requirements. Hence, polyetherimide/Silver (PEI/Ag) composites with unique segregated thermal-conductive network were fabricated via hot-pressing the core–shell (PEI@Ag) particles, which was endowed with superior thermal-conductive ability in bi-directions. By this process, the Ag shell was deposited on the surface of various polymer microsphere, and diverse morphology of composite particles would lead to different findings. The results show the PEI@Ag composites with filler content of 18.9 vol% exhibited high in-plane thermal conductivity and through-plane thermal conductivity of 19.9 and 14.0 W/mK, respectively. Particularly, these results achieved obvious improvements of 331 % and 1264 % higher than the composites with filler random distribution, indicating the composite materials obtained outstanding advantage in both horizontal and vertical direction. The research also found that the composites prepared from PEI@Ag core–shell structures possess better properties than those prepared with Ag nanoparticles growing on polymers, indicating the importance of continuous heat-transfer path, and their heat transfer behavior was further demonstrated by finite element analysis. Besides, the composites also exhibited remarkable EMI shielding performance (40.1 dB)). In a word, this study provides viable strategies to enhance the thermal conductivity of composites based on organic solvent-soluble polymer with EMI capability for the development of electronic devices.

Exploring the thermal and optical characteristics of Ti3C2 MXene for enhanced photothermal conversion

Ti3C2 MXene, a member of the two-dimensional (2D) transition metal carbides family, has garnered significant attention for its exceptional photothermal properties. To understand the mechanistic underpinnings of this feature, we conducted a comprehensive first-principles density functional theory analysis. This study was aimed at investigating the electronic band structure and vibrational characteristics of Ti3C2 MXene to unravel its microscopic process of photothermal conversion. After obtaining its optical and thermal properties, the process by which the material moves from light absorption to heat release is elucidated. The presence of localized surface plasmon resonance (LSPR) effects in Ti3C2 is proved by Finite-difference time-domain (FDTD) simulations. The synergy between the high thermal conductivity network in the Ti layers and the LSPR phenomenon is believed to be responsible for the superior photothermal conversion capabilities. This investigation enhances the understanding of the intrinsic properties of Ti3C2 MXene, confirming its status as an ultrahigh photothermal conversion material.

Phase change thermal interface film with bicontinuous and textured filler network for efficient wearable heat dissipation

Wearable thermal management needs to simultaneously meet thermal conductivity, heat storage capacity, stability, flexibility, and economy, but these characteristics constrain each other in the development of phase change thermal interface materials (PhC-TIM). Therefore, relying on the economic bicontinuous structure for fillers’ orientation, a new type of bicontinuous phase change thermal interface material (BPTIM) was designed, which includes thermal storage phase composed of paraffin (PCMs) and flexible molecule styrene–butadiene–styrene (SBS), and thermal conductivity phase composed of adhesive polyurethane (PU) and thermal conductive medium boron nitride (h-BN). In the experiment, shear force generated by stirring and optimized two-phase volume ratio resulted in the stretching and compressing of the thermal conductive phase, promoting the orientation of h-BN and ultimately forming a textured thermal-conductive network in a high PCMs content bicontinuous structure. Moreover, the introduction of SBS had brought bending resistance and thermal stability. These characteristics enabled BPTIMs to significantly reduce the surface temperature of the wearable device by 23 °C. Overall, this design provides a certain reference for the widespread application of PhC-TIM in thermal management of wearable electronic products.

Construction of 3D modified hexagonal boron nitride thermal conductivity network by ice template method and research of high heat‐conducting coefficient of epoxy resin matrix composite material

Construction of <scp>3D</scp> modified <scp>hexagonal boron nitride</scp> thermal conductivity network by ice template method and research of high heat‐conducting coefficient of epoxy resin matrix composite material

MXene quantum dots modified pitaya peel-based composite phase change material with excellent thermal properties for building energy efficiency applications

Bio-based materials have attracted much attention because their application in the construction field is conducive to energy saving and emission reduction. In this paper, a bio-based composite phase change material (CPCM) was prepared by utilizing pitaya peel as a bio-based material, MXene quantum dots (MQDs) as a modified material, and polyethylene glycol (PEG) as a phase change medium. MXene quantum dots dispersed in the pitaya peel-based porous carbon skeleton enhanced the three-dimensional thermal conductivity network of the porous carbon skeleton somewhat improved the thermal conductivity (0.676 W/mK) of the polyethylene glycol/MXene quantum dots-modified pitaya peel-based porous carbon foam (PPF) composite phase change material (PEG/PPF@M). It is worth noting that PEG/PPF@M has excellent thermal stability and its enthalpy is basically unchanged after 100 cycles, which proves the recyclable stability of PEG/PPF@M in practical applications. PEG/PPF@M has great potential for thermal management of buildings and electronic components. Overall, a novel multifunctional CPCM was prepared in this study using a simple process method, which can not only be applied in electronic products to improve the service life of electronic components, but also in the field of construction to realize energy saving and emission reduction, as well as the recycling and reuse of waste.

Investigation on the fabrication and mechanism of thermally conductive bismaleimide composites with low dielectric constant via a branched crosslink structure

In order to address the challenges associated with the low mechanical strength and inadequate thermal conductivity of bismaleimide resin(BMI), trifunctional maleimide (TMI) was synthesized by reacting toluene diisocyanate (TDI trimer) with maleic anhydride (MA) in this study and reacted with diallyl bisphenol A (DBA) and BMI to prepare BMI-TMI resin with a micro-branching structure. This well-designed micro-branching structure resulted in an 8.8 % decrease in the dielectric constant by increasing the free volume of BMI. Additionally, the micro-branching structure endowed BMI resin with improved mechanical properties, as evidenced by a 140 % increase in bending strength and a 149 % increase in impact strength of the cured product. Similarly, utilizing the free volume in micro-branched polymers to construct voids in molecular chain segments facilitates better dispersion of aluminium oxide (Al2O3) thermal conductive fillers, forming a continuous thermal conductive network and providing a high-speed channel for phonon transport, thereby significantly improving the thermal conductivity of the composite material.

PVA-assisted graphene aerogels composite phase change materials with anisotropic porous structure for thermal management

The rapid development of spacecraft thermal control systems necessitates high-performance phase change materials (PCMs) with low density, high thermal conductivity and high enthalpy. Graphene aerogels (GAs) prepared by unidirectional freezing are ideal candidates as thermal conductive networks for PCMs due to the anisotropic porous structures. However, constructing anisotropic thermal conductive composite PCMs with low graphene aerogel loading while employing environmentally friendly cross-linking agents remains challenging. To fulfill the research gap, this study explores the synthesis of poly(vinyl alcohol) (PVA)/graphene aerogels (PGAs) by hydrothermal reaction and conventional freeze-drying. Anisotropic PGAs with oriented porous structures were fabricated by unidirectional freezing. After annealing and impregnation with paraffin wax, composite PCMs with excellent shape stability were obtained. The prepared composite exhibits low density (0.82 g cm−3) and high enthalpy (165 J g−1). The combination of PVA and graphene enables the composite to achieve an ultralow graphene aerogel loading (0.85 wt%) while maintaining high thermal conductivity (1.37 W m−1 K−1), leading to a high specific thermal conductivity enhancement up to 477. This work sheds light on the potential of combing PVA and graphene to construct thermal conductive aerogels, intending to provide feasible means to develop high-performance PCMs for spacecraft thermal management.

The thermal conductivity of 3D network reinforced polypropylene matrix composites was constructed by the pickering‐like emulsion method

AbstractPolypropylene (PP) has the advantages of corrosion resistance, easy processing, and low dielectric loss, but its low thermal conductivity limits the application of its composites in fields such as electronic packaging. To solve this problem, in this work, composite microspheres with the segregated structure were prepared by coating boron nitride nanosheets (BNNSs) on the PP surface by Pickering‐like emulsion method, and BNNSs@PP composites with three‐dimensional thermal conductivity network were obtained after molding. Due to the high thermal conductivity of BNNSs and the formation of perfect thermal conduction pathways, the thermal conductivity of the composites reached 1.71 W m−1 K−1 when the content of BNNSs was 10.1 wt%, which was a 713% increase in thermal conductivity for that of pure PP. At the same time, the mechanical properties of the composites were ensured. This method provides a simple and effective technique to improve the thermal conductivity of PP‐based thermally conductive composites, which has a wide application potential in electronic packaging.

Constructing highly thermally conductive polystyrene-based composites by introducing multi-walled carbon nanotubes into melamine foam-supported boron nitride network

High-density 3D thermally conductive nanofiller network plays a vital role in the fabrication of polymer-based composites with high thermal conductivity (TC) for thermal management systems. In this work, highly thermally conductive polystyrene (PS)-based composites were prepared by introducing boron nitride nanosheets-coated melamine foam (MF@BNNSs) and carboxylated multi-walled carbon nanotubes (MWCNT–COOH). In this unique structure, MF@BNNSs can provide a 3D thermally conductive network, while MWCNT–COOH is embedded into the MF@BNNSs skeleton to improve the network-density. Specifically, the TC of PS/MWCNT/MF@BNNSs composite with 0.6 wt% MWCNT–COOH loading reaches 5.33 W /m· K, about 4.4-fold as high as that of the PS/MF@BNNSs. Moreover, the PS/MWCNT/MF@BNNSs composite exhibits effective heat dissipation capacity after assembling the power LED chip. Due to the isolation effect of MF@BNNSs skeleton, the PS/MWCNT/MF@BNNSs maintain electrical insulation properties. Consequently, the design of the thermal conductive network based on MF@BNNSs and MWCNT–COOH offered a substantial potential avenue for the preparation of polymer-based composites with high TC and insulating properties.

Significantly improved thermal conductivity of C/C composite by constructing 3D SiC nanowires network in carbon felt via vacuum thermal evaporation

Developing a nanoscale secondary thermal conduction network within carbon fiber performs is a challenging yet effective method to substantially enhance the thermal conductivity of C/C composites. In this study, a strategy for creating a three-dimensional (3D) SiC nanowires (SiCNWs) thermal conductivity network in carbon felts (CFs) was implemented using vacuum thermal evaporation technology to fabricate SiCNWs modified C/C composites (SiCNW–C/C). The growth mechanism of SiC nanowires within CFs and their impact on the microstructure and thermal conductivity of the C/C composite were thoroughly investigated. The findings indicate that a SiC nanowires thermal conduction network can be successfully established within carbon felts without catalysts by initiating nucleation sites and managing reaction pressure. An appropriate reaction pressure is crucial not only for the uniform growth of SiC nanowires but also as a key factor in modulating the content and microstructure of the SiC nanowires. SiC nanowires prepared at 150 Pa exhibit minimal structural defects and are evenly distributed throughout the carbon felts, markedly enhancing the thermal response rate of the felts. The thermal conductivity of these SiCNW-modified C/C composites, both parallel and perpendicular to the carbon fibers, increased to 173 W/m•K and 112 W/m•K, respectively, approximately tripling that of the pure C/C composite. The exceptional thermal management capabilities of SiCNW–C/C were empirically validated through simulated operational chips and finite element simulation. This work presents an effective approach for producing C/C composite with high thermal conductivity particularly through the thickness, offering promising applications in the thermal management of advanced electronics.

Developing PEEK composites with exceptional thermal conductivity and electromagnetic shielding properties by constructing a dense dual-continuous filler network

Polyether ether ketone (PEEK) has regular and rigid molecular chain and is insoluble in most organic solvents. Therefore, it is challenging to use PEEK matrix composites for thermal conductivity (TC) and electromagnetic interference (EMI) shielding applications. Herein, PEEK composites with hybrid fillers were fabricated by solution blending and non-solvent-induced phase separation (NIPS) methods based on a chemical conversion reaction between soluble precursor PEEK-dithiolane and PEEK. Synergistic interaction between hybrid fillers (graphene nanosheets and multiwalled carbon nanotubes) improves the thermal and electrical conductivity of the composites. The effect of the hot-pressing pressure on the conductive/thermal network densification was investigated. The composites performed optimally at a hot pressure of 200 MPa and a filler content of 20.08 vol%. The maximum in-plane and out-of-plane TC reached 10.46 W·m–1·K–1 and 4.8 W·m–1·K–1, respectively, which were 4619 % and 2414 % higher than the corresponding TC of PEEK. Simultaneously, the optimised composite demonstrated significantly improved electrical conductivity (3517 S/m) and EMI shielding effectiveness (66.1 dB). These excellent characteristics are attributed to the solution blending–NIPS method, which improves the dispersion of hybrid fillers in the matrix and forms an internal and external dual-continuous thermal conductive network. The dual-continuous network creates effective channels for phonon and electron transport and enhances EM wave loss. This work provides inspiration for the preparation of PEEK composites as advanced EMI protection and thermal management materials.

Highly thermally conductive BNNS/PANF dielectric composite boards prepared by a facile compression moulding process

The structural design of an efficient heat conduction channel is critical for heat dissipation in electronic packaging material. The build of oriented boron nitride nanosheet (BNNS) network inside polymers has attracted much attention due to its excellent thermal conductivity and dielectric properties. However, to fabricate a BNNS/polymer composite, complex method and low thermal conductive resin for binding BNNS network are commonly involved, which severely restrict its facile production and enhancement in thermal conductivity. Herein, by utilizing para-aramid nanofibers (PANF) as assistance to BNNS to form thermal conduction network, we obtained high performance composite boards with good formability and adjustable sizes via a simple compression moulding of the BNNS/PANF aerogels. The composite boards exhibit a remarkable in-plane thermal conductivity of 10.62 W/m K−1 at 50 wt% BNNS loading, outstanding practical thermal management capability, excellent thermal stability, low dielectric constant and loss, showing great potential for electronic packaging applications. This facile construction strategy provides a feasible way for the large-scale production and application of high-performance thermal management materials in the future.

Flexible hexagonal boron nitride@liquid metal/polydimethylsiloxane composites with excellent thermal conductivity and superior mechanical properties

AbstractHexagonal boron nitride (h‐BN) has a layered lattice structure, high intrinsic thermal conductivity, and good chemical stability, and it has a promising applications in thermal management materials. However, poor interfacial compatibility and dispersion of BN flakes in the polymer matrix cause thermal contact resistance and gaps, directly impairing the performance of the composites and limiting their thermal conduction applications. Herein, the P‐BN@LM/PDMS thermally conductive composites with superior mechanical properties were fabricated by incorporating dopamine and liquid metal (LM) into BN flakes. The dopamine self‐polymerizes to form polydopamine (PDA) on the BN surface, denoted as P‐BN, which effectively improves interface compatibility and dispersion. The LM attaches to the functionalized P‐BN surface by mechanical grinding, acting as a bridge between adjacent BN flakes to enhance the integrity of the thermal conductive network within the composites. The coordination between P‐BN and LM increases interface strength, effectively improving mechanical performance. Hence, the P‐BN@LM/PDMS composites exhibit excellent thermal conductivity (4.0 W/mK) and an enhancement factor of 1373%, which is 2.22 times that of BN/PDMS composites with the same 30 wt% loading. Additionally, the composite shows superior tensile strength (2.11 MPa) and elongation at break (121%), representing 441% and 203% improvements compared with pure polydimethylsiloxane (PDMS). The P‐BN@LM/PDMS composites, with significant advantages in thermal conductivity and mechanical properties, are promising for future applications as flexible thermal interface materials in thermal management.Highlights The P‐BN@LM/PDMS composites exhibit excellent thermal conductivity (4.0 W/mK) and an enhancement factor of 1373%, making them promising for future applications as flexible thermal interface materials in thermal management. The P‐BN@LM/PDMS composites present a superior tensile strength (2.11 MPa) and elongation at break (121%). PDA formed by the self‐polymerization of dopamine on the BN surface effectively enhances interfacial compatibility and dispersion. LM attaches to the functionalized BN surface through mechanical grinding, acting as a bridge between adjacent BN flakes, thus enhancing the integrity of the thermal conductive network within the composites.

Highly thermally conductive and flexible nanocomposites prepared by integrating 1D/2D polyethyleneimine-modified boron nitride

Thermally conductive composites rely on efficient heat transfer networks. Here, we employ polyethyleneimine to modify 1D boron nitride nanotubes (BNNTs) and 2D boron nitride nanosheets (BNNSs) to improve their dispersion while enhancing the interfacial interaction between them and the matrix through amide bonds, hydrogen bonds, and Lewis acid-base interactions, thereby reducing interfacial thermal resistance. Moreover, the introduction of 1D BNNTs bridges 2D BNNSs, boosting the thermal conductivity network. This resulted in an enhanced thermal conductivity of the composite film by 17.8 %, reaching 28.71 W/(m·K) at a 30 wt% filler content. Coupled with satisfactory mechanical strength and thermal stability, this heat dissipation capability is highly valuable for applications.

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

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

0D/2D Co-Doping Network Enhancing Thermal Conductivity of Radiative Cooling Film for Electronic Device Thermal Management.

The radiative cooling has great potential for electronic device cooling without requiring any energy consumption. However, a low thermal conductivity of most radiative cooling materials limits their application. Herein, a multishape codoping strategy was proposed to achieve collaborative enhancement of thermal conductivity and radiative properties. The hBN-coated hollow SiO2 particles were prepared based on electrostatic self-assembly technology, which were then mixed with hBN platelets and doped into a poly(vinylidene fluoride-co-hexafluoropropylene) substrate. Discrete dipole approximation theory was employed to reveal the mechanism and optimize the particle size. The results showed that the multishape codoping method can significantly improve the radiative performance, with 94.9% reflectivity and 91.2% emissivity. In addition, this zero-dimensional and two-dimensional composite doping structure facilitated the formation of a thermal conduction network, which enhanced the thermal conductivity of the film up to 1.32 W m-1 K-1. The high thermal conductivity radiative cooling film can decrease the heater temperature from 58.8 to 31.3 °C, with a further reduction of temperature by 7.2 °C compared to the radiative cooling substrates with low thermal conductivity. The net cooling power of the film can reach 102.5 W m-2 under direct sunlight. This work provides a novel strategy for high-efficiency electronic device cooling.

Ternary particle composite synergistically enhances the fluidity and dielectric properties of filled thermal conductive epoxy resin

Abstract Particle-packed epoxy materials are widely used to improve the thermal conductivity of insulation materials. However, the addition of fillers increases the viscosity of the composite which reduces its operability, and is not conducive to the packaging of power electronic equipment such as electric transformers and reactors. Multi-scale particle compounding is one of the effective methods to enhance the co-processing performance of materials by reducing the friction between particles and epoxy matrix while forming an effective thermal conductivity network. Three types of spherical alumina sized around 4 μm, 38 μm, and 125 μm were used as fillers to study the fluidity, thermal conductivity, and dielectric properties of single-filled and ternary compounds. The results showed that the ternary particle composite reduced the viscosity of the precursor by up to 68.8%, achieving a synergistic improvement in operability, thermal conductivity, and electrical performance.