Thermal Conductivity Of Epoxy Composites Research Articles

Construction of AlN oriented skeletons using in-situ reaction strategy and their enhancement effect on the thermal conductivity of epoxy composites

The development of electronic devices towards miniaturization and integration has put forward higher requirements for polymer-based composites with high thermal conductivity (TC). Aluminum nitride (AlN) is one of the most promising fillers thanks to its high TC (∼320 W m−1 K−1) and outstanding physicochemical properties. However, the traditional composites filled with randomly dispersed AlN particles generally require extremely high filling fraction to enhance the TC, leading to increased production cost and degraded mechanical performance. To address this issue, an innovative strategy combining freezing casting and in-situ reaction process was proposed to directly construct vertically aligned AlN skeletons, which was further used as reinforcements to enhance the TC of epoxy (EP) composites. The close arrangement of AlN particles along the vertical direction was not only beneficial for enhancing the TC, but also improving the mechanical strength. The AlN/EP composites achieved an extremely high TC of ∼8.25 W m−1 K−1 at the AlN filling fraction of 56.2 vol%, which was 45.83 times higher than that of pure EP. The actual thermal management applications and finite element simulations also demonstrated the oriented AlN skeletons exhibited a more significant TC enhancement than that of randomly arranged AlN. Furthermore, the as-prepared AlN/EP composites also exhibited superior thermal stability and dielectric properties, presenting a broad application prospect as thermal management materials for the next-generation electronic devices.

Improving thermal conductivity of epoxy composite by three-dimensional filler network constructed with two different diameters aluminum nitride and cellulose nanofiber

Improving thermal conductivity of epoxy composite by three-dimensional filler network constructed with two different diameters aluminum nitride and cellulose nanofiber

Enhancing the Thermal Conductivity of Epoxy Composites via Constructing Oriented ZnO Nanowire-Decorated Carbon Fibers Networks.

With the miniaturization and high integration of electronic devices, high-performance thermally conductive composites have received increasing attention. The construction of hierarchical structures is an effective strategy to reduce interfacial thermal resistance and enhance composite thermal conductivity. In this study, by decorating carbon fibers (CF) with needle-like ZnO nanowires, hierarchical hybrid fillers (CF@ZnO) were rationally designed and synthesized using the hydrothermal method, which was further used to construct oriented aligned filler networks via the simple freeze-casting process. Subsequently, epoxy (EP)-based composites were prepared using the vacuum impregnation method. Compared with the pure CF, the CF@ZnO hybrid fillers led to a significant increase in thermal conductivity, which was mainly due to the fact that the ZnO nanowires could act as bridging links between CF to increase more thermally conductive pathways, which in turn reduced interfacial thermal resistance. In addition, the introduction of CF@ZnO fillers was also beneficial in improving the thermal stability of the EP-based composites, which was favorable for practical thermal management applications.

Theoretical study on thermal conductivity of epoxy composites doped with boron nitride with multiple dimensions

Epoxy is widely used in electrical equipment owing to its exceptional physical, chemical, and electrical insulation properties. However, its low conductivity limits its applications. The incorporation of fillers with high thermal conductivities into epoxy matrices is one of the most effective and common methods for enhancing the thermal conductivities of epoxy composites. In this study, Digimat software was used to construct the models, and a numerical simulation based on representative volume elements (RVEs) was employed to investigate the relationship between the thermal conductivity and microstructure of the epoxy composites. The epoxy composites exhibited different thermal conductivities in various directions owing to the pronounced anisotropy of the boron nitride (BN) fibers. In composites filled with both spherical boron nitride (S-BN) and BN fibers, BN fibers play a dominant role in enhancing the effective thermal conductivity (ETC). However, at the same filling fraction, the composites achieved their maximum ETC when the S-BN-to-BN fiber ratio was 2:8. Furthermore, the ETC increased linearly with the filling fraction of the filler. When the volume fraction of the fillers was kept constant, the smaller S-BN particles increased the ETC of the composites. Similarly, when the number of fillers and volume fraction were kept constant, an increased aspect ratio of the BN fibers resulted in a higher ETC of the composites. An investigation of the electrothermal coupling between pure epoxy resin and epoxy-resin composite materials revealed that the stable temperature of the composites was considerably lower than that of pure epoxy. The heat transfer to the bottom of the composites was faster, which indicated a substantial improvement in the ETC.

Enhancing cryogenic thermal conductivity of epoxy composites through the incorporation of boron nitride nanosheets/nanodiamond aerogels prepared by directional‐freezing method

AbstractIn the realm of electronic circuits, materials with high thermal conductivity are sought after as ideal packaging components. It is crucial that such materials not only possess excellent thermal conductivity, but also maintain desirable dielectric properties. To this end, boron nitride nanosheets (BNNS) and BNNS/nanodiamond (ND) aerogels with a three‐dimensional (3D) structure using the ice‐template method were prepared. Subsequently, these aerogels were utilized as a framework to produce 3D‐BNNS/epoxy and 3D‐BNNS/ND/epoxy composites via the vacuum‐assisted impregnation method, which exhibit enhanced anisotropic thermal conductivity. Furthermore, the thermal conductivity exhibited by the 3D‐BNNS/epoxy composites outperforms those containing randomly distributed BNNS. The experiment also reveals sintering the aerogel at elevated temperatures to remove the PVA can significantly improve the thermal conductivity exhibited by the 3D‐BNNS/epoxy and 3D‐BNNS/ND/epoxy composites. Importantly, the 3D‐BNNS/ND/epoxy composites illustrate exceptional thermal conductivity values of 1.326 W/(m·K), indicating a remarkable synergistic effect of BNNS and ND in improving thermal conductivity. It is noteworthy to state that the relative thermal conductivity ratio of the 3D‐BNNS/epoxy and 3D‐BNNS/ND/epoxy composites to pure epoxy resin was markedly higher at lower temperatures than the values measured at room temperature, signifying their superior heat transfer performance at lower temperatures. In addition, the composites depict excellent dielectric properties and lower coefficients of thermal expansion values. Finally, the 3D‐BNNS/ND/epoxy composites also have significantly improved Tg (132.5 and 152.6°C). The high‐performance polymer composites described in this study are envisaged for implementation within the realm of electronic packaging materials.

Oriented Three-Dimensional Skeletons Assembled by Si3N4 Nanowires/AlN Particles as Fillers for Improving Thermal Conductivity of Epoxy Composites.

With the miniaturization of current electronic products, ceramic/polymer composites with excellent thermal conductivity have become of increasing interest. Traditionally, higher filler fractions are required to obtain a high thermal conductivity, but this leads to a decrease in the mechanical properties of the composites and increases the cost. In this study, silicon nitride nanowires (Si3N4NWs) with high aspect ratios were successfully prepared by a modified carbothermal reduction method, which was further combined with AlN particles to prepare the epoxy-based composites. The results showed that the Si3N4NWs were beneficial for constructing a continuous thermal conductive pathway as a connecting bridge. On this basis, an aligned three-dimensional skeleton was constructed by the ice template method, which further favored improving the thermal conductivity of the composites. When the mass fraction of Si3N4NWs added was 1.5 wt% and the mass fraction of AlN was 65 wt%, the composites prepared by ice templates reached a thermal conductivity of 1.64 W·m-1·K-1, which was ~ 720% of the thermal conductivity of the pure EP (0.2 W·m-1·K-1). The enhancement effect of Si3N4NWs and directional filler skeletons on the composite thermal conductivity were further demonstrated through the actual heat transfer process and finite element simulations. Furthermore, the thermal stability and mechanical properties of the composites were also improved by the introduction of Si3N4NWs, suggesting that prepared composites exhibit broad prospects in the field of thermal management.

Improved thermal conductivity of epoxy composites filled with three-dimensional boron nitride ceramics-carbon hybrids

Epoxy (EP) is the preferred packaging materials used as a crucial component in power semiconductor devices. However, its low thermal conductivity (TC) always has negative impact in the heat dissipation of electronic devices. In this paper, we use hole-making method to prepare three-dimensional boron nitride ceramics-carbon (3D-BN-C) hybrids which are filled in EP matrix to improve the TC of the 3D-BN-C/EP composites. The results show that TC values of 3D-BN-C/EP composites are much superior to the BN/EP composite with random distribution of BN and 3D-BN/EP composite without carbon. The improved TC is mainly attributed to the high TC-3D skeleton structure and the low interface thermal resistance (R) due to the carbon connected with BN fillers. Infrared thermal images and Comsol simulation demonstrate that high TC 3D-BN-C/EP composite offers excellent heat dissipation capability of EP composites used as packing insulation materials. In addition, the dielectric loss of 3D-BN-C/EP composite still remains at a relative low level in a wide frequency range, exhibiting good insulation property and great potential to be used as high-performance packing insulation materials in electronic device applications.

Synergistic effects of oriented AlN skeletons and 1D SiC nanowires for enhancing the thermal conductivity of epoxy composites

As electronic devices are moving towards miniaturization and integration, the demand for ceramic/polymer composites with high thermal conductivity (TC) are increasing significantly. Herein, we reported a novel idea for rational design and delicate construction of anisotropic three-dimensional thermally conductive networks via the ice template method, using stearic acid-modified AlN particles (AlNm) as the primary filler and SiC nanowires (SiCNWs) as the secondary. As predicted, the as-prepared epoxy (EP)-based composites achieved a maximum TC of 2.56 W·m−1·K−1 in vertical direction at a filling fraction of 55 vol %, which was 12.8 times higher than that of pure EP. More importantly, the enhancement mechanism of composite TC was further demonstrated by realistic heat transfer process and finite element simulations. Furthermore, the prepared composites also displayed excellent thermal stability, high mechanical strength and good dielectric property, indicating that this strategy provides a promising insight for the design of high-performance thermal interface materials (TIMs).

Enhanced Thermal Conductivity of Epoxy Composites Fabricated with Boron Nitride and Multi-Walled Carbon Nanotubes

Preparation of polymer-based packaging materials with rapid heat dissipation capacity is crucial for ensuring high-power equipment’s service life. To achieve this, boron nitride (BN) and multi-walled carbon nanotubes (MWCNTs) were used in different ratios to prepare thermally conductive epoxy composites. These composites were created through a simple mixing and curing process, resulting in a heat transmission path. Then, BN and MWCNTs were separately functionalized with dopamine and acid to enhance their dispersibility and interfacial compatibility within the epoxy resin. This was done to further explore their influence on the formation of serial heat transfer pathways. The BN/MWCNTs/epoxy composites with a filler ratio of 15:1 and a total filler loading of 30 wt % exhibited a thermal conductivity of 0.92 W/mK, which is 118% higher than pure epoxy. These composites also displayed favorable mechanical properties and thermal stability. This study provides guidance for designing high-performance epoxy composites to meet modern electronic devices’ thermal management requirements.

Facile and Scalable Strategy for Fabricating Highly Thermally Conductive Epoxy Composites Utilizing 3D Graphitic Carbon Nitride Nanosheet Skeleton.

The application of high-performance thermal interface materials (TIMs) for thermal management is commonly used to tackle the problem of heat accumulation, which influences the performance and reliability of microelectronic devices. Herein, a novel three-dimensional (3D) carbon nitride nanosheet (CNNS)/epoxy composite with high thermal conductivity was developed by introducing 3D CNNS skeleton fillers prepared by a facile and scalable strategy assisted by a salt template. Benefiting from the continuous heat transfer pathways formed in the CNNS skeleton, 17.0 wt % 3D CNNS/epoxy composites achieve a superior thermal conductivity of 1.27 W/m·K, which is 6.35 and 1.57 times higher than those of epoxy resin and convention CNNS/epoxy, respectively. With the aid of theoretical model analysis and finite element simulation, the pronounced enhancement effect of the 3D CNNS skeleton on the thermal conductivity of epoxy composites is found to be attributed to the continuous 3D CNNS thermally conductive network, the diminished CNNS-CNNS interfacial thermal resistance, and the effective interfacial interactions between epoxy and CNNS. In addition, the 3D CNNS/epoxy composites possess high electrical insulation and desirable mechanical strength. Therefore, 3D CNNS/epoxy composites are promising TIMs for advanced electronic thermal management.

Construction of 3D framework of BN and silica with advanced thermal conductivity of epoxy composites

Construction of 3D framework of BN and silica with advanced thermal conductivity of epoxy composites

TiO2 nanowire formation and GO reduction through a hydrothermal reaction to improve the thermal conductivity of epoxy composites

AbstractThe thermal path must be properly configured to improve the thermal properties of polymer composites. Three‐dimensional (3D) thermally conductive networks can be used as an excellent means for building high‐speed conductive pathways in polymer composites. Titanium dioxide (TiO2) nanowire (NW)/reduced graphene oxide (rGO)/epoxy (EP) composite material has a 3D foam structure and focuses on TiO2 NW formation and rGO gelation through a hydrothermal process. The thermal conductivity of the synthetic composite material through filler loading at 50 wt.% and heat transfer path formation was 805% higher than that of pure EP, and the thermal conductivity was superior to that of the composite material with randomly dispersed fillers. Therefore, this work describes an advanced process to improve the thermal conductivity of polymer composites significantly.

Cactus-like double-oriented magnetic SiC and BN networks leading to simultaneously enhanced dielectric strength and thermal conductivity of epoxy composites

Epoxy-based composites with high insulation and thermal conductivity are desirable materials for electronic and electrical applications. However, resolving the tradeoff between insulation and thermal conductivity remains challenging. Based on the functional requirement, we designed and fabricated a cactus-like double-oriented epoxy composite by combining magnetic orientation and ice-templated methods. Semiconducting SiC endowed the composite with field-grading characteristics, thus relieving local electric field stress along the horizontal direction, while BN with high thermal conductivity promoted heat dissipation along the vertical direction. The composite exhibited its highest performance with 15 vol% filler, improving the breakdown voltage and thermal conductivity by 43.7% and 1312% compared with pure epoxy, respectively, outperforming recently developed packaging materials. It is believed that this work offers an efficient strategy for the fabrication of the filler structure and provides insights on the simultaneous enhancement in insulation and thermal conductivity of polymer composites.

Enhancing thermal conductivity of epoxy composites via f‐BN@f‐MgO hybrid fillers assisted by hot pressing

AbstractHigh thermal conductive polymeric composites are extremely desired for the thermal management of electronic devices due to the rapid development of the modern microelectronic industry. Herein, the functionalized boron nitride (BN) and magnesium oxide (MgO) hybrid fillers (f‐BN@f‐MgO) were synthesized and used to prepare the enhanced thermal conductive epoxy (EP) composites through the hot‐pressing method. The results demonstrated that the covalent binding of BN and MgO in the hybrid fillers reduced the interface thermal resistance effectively between fillers and matrix and the hot‐pressing induced force facilitated the construction of the continuous thermal conduction paths. Consequently, the as‐prepared epoxy composite at 40 wt% hybrid fillers loading had high thermal conductivity (TC) (1.97 W/[m·K]), outstanding insulating performance (6.9 × 1015 Ω cm) and excellent thermal stability. Furthermore, a probable thermal conduction mechanism was proposed to illustrate the high TC of the epoxy composite. Therefore, this study provides a new approach to preparing epoxy composites with outstanding performances.

Enhanced Thermal Conductivity of Epoxy Composites by Introducing 1D AlN Whiskers and Constructing Directionally Aligned 3D AlN Filler Skeletons

With the miniaturization of current electronic products, ceramic/polymer composites with excellent thermal conductivity have attracted increasing attention. For regular ceramic particles as fillers, it is necessary to achieve the highest filling fraction to obtain high thermal conductivity, yet leading to higher production cost and reduced mechanical properties. In this paper, AlN whiskers with a high aspect ratio were successfully prepared using a modified direct nitriding method, which was further paired with AlN particles as fillers to prepare the AlN/epoxy composites. It is indicated that AlN whiskers could form bridging links between AlN particles, which favored the establishment of thermal pathways inside the polymer matrix. On this basis, we constructed the 3D AlN skeletons as a thermal conductivity pathway by the freeze-casting method, which could further enhance the thermal conductivity of the composites. The synergistic enhancement effect of 1D AlN whiskers and directional filler skeletons on the composite thermal conductivity was further demonstrated by the actual heat transfer process and finite element simulations. More significantly, the experimental results showed that the addition of one-dimensional fillers could also effectively improve the thermal stability and mechanical properties of the composites, which was beneficial for preparing high-performance TIMs.

Thermal conductivity of epoxy composites modified by microspheric molybdenum disulfide

In order to improve the thermal conductivity of epoxy resins (EP) without damaging their dielectric properties, a kind of molybdenum disulfide with microspheres structure (S-MoS2) was used as modifiers to add into EP matrix, which were prepared via the surfactant promoting hydrothermal process, and a new kind of S-MoS2/EP composites was finally obtained. The morphology of the prepared S-MoS2 was observed by X-ray diffraction (XRD) scanning electron microscopy (SEM), while the influence of different S-MoS2 loading on the dielectric properties, thermal conductivity and thermal resistance of S-MoS2/EP composites was also researched. The results suggested that the reasonable content of S-MoS2 can highly improve the thermal conductivity of S-MoS2/EP, which can be attributed to the excellent thermal resistant and uniform dispersion of S-MoS2 in EP matrix.

Enhanced thermal conductivity of epoxy composites reinforced with oriented polydopamine-graphene foam complexed by metal ions

Although graphene has aroused considerable interest in the thermal conductive enhancement of polymer composites for its superb intrinsic thermal conductivity, the enhancement efficiency is still limited by its production-induced defects, misalignment and intense phonon interface scattering. Herein, the three-dimensional (3D) polydopamine-graphene foam (PGF) with high orientation and good interfacial bonding has been prepared by electro-exfoliation, surface modification and unidirectional-freezing. This unique structure imparts excellent thermal conductivity, electrical insulation and good mechanical property to the PGF/epoxy (PGF/EP) composite. The highly arranged and compact stacked PDA-graphene sheets bound by metal ions provide heat conduction paths for effective phonon transport within the matrix. The manufactured PGF/EP shows enhanced through-plane thermal conductivity of 3.48 W/m·K with 3.02 vol% of PGF, excellent surface & volume electrical resistivity (2.7 × 1011 Ω and 1.65 × 1011 Ω·cm) and high mechanical strength (82.74 MPa), as well as the outstanding heat dissipation performance. Therefore, the PGF/EP composites prepared in the present study have a broad application prospect in advanced electronic packaging materials.

Large‐scale plasma grafts voltage stabilizer on hexagonal boron nitride for improving electrical insulation and thermal conductivity of epoxy composite

AbstractBetter electrical insulation and thermal management are both urgently required in integrated power semiconductors. Electrical insulation epoxy encapsulation suffers from poor heat conduction, which has increasingly become a bottleneck of power semiconductors integration. Although incorporating high thermal conductivity ceramics, such as hexagonal boron nitride (hBN), aluminium nitride etc. into epoxy promotes the thermal conductivity, the eco‐friendly scalable fabrication of these composites with sufficient electrical breakdown strength remains a formidable challenge. Suitable voltage stabilizers are known to provide additional benefits to breakdown strength. Herein, a high‐throughput approach combining plasma with roll‐to‐roll was developed. The voltage stabilizer (acetophenone) was grafted on interfaces between hBN and epoxy matrix through plasma. The high‐energy electrons are consumed by the grafted interface, which leads to the significant suppression of partial discharge in Epoxy/hBN. Meanwhile, interfacial phonon scattering is repaired by grafting. Therefore, the epoxy composite concurrently exhibits improved breakdown strength (by 27.4%) and thermal conductivity (by 142.9%) at about 11.9 wt.% filler content, outperforming the pure epoxy. Consequently, a promising modification strategy for mass production is provided for the encapsulation materials in various high‐power‐density semiconductor devices.

Enhanced thermal conductivity of epoxy composites with ternary particle size through the use of hybrid polyhedral α-alumina oxide and aluminum nitride

With the continued trends toward electronic device miniaturization, functionalization, and increased integration, epoxy-based cost-effective polymer composites with excellent thermal conductivity, dielectric performance, and processability are in high demand for the thermal management of electronic devices. An effective and continuous thermal transport pathway for epoxy composites was constructed by using a ternary-particle-size system comprising 22 μm polyhedral α-alumina oxide (Al2O3-22), 3.0 μm aluminum nitride (AlN-3), and 0.35 μm polyhedral α-alumina oxide (Al2O3-03). A distinctly high thermal conductivity (4.27 W/(m·K) and lower viscosity (35.28 Pa·s) were acquired using the ternary filler comprising 61.00 wt% Al2O3-22, 10.76 wt% AlN-3, and 6.24 wt% Al2O3-03. Meanwhile, the epoxy composites exhibited excellent thermo-mechanical properties, thermal stability, and dielectric performance. This work presents an easy and cost-effective approach for preparing highly thermally conductive and low-dielectric-performance polymer-based composites that can be widely used for the thermal management of electronic devices in the 5G era.

Aligning diamond particles inside BN honeycomb for significantly improving thermal conductivity of epoxy composite

Construction of interconnected heat conductive network in polymer is essential to effectively transport heat in thermal management materials. Due to synergistic effect, hybrid fillers are increasingly utilized in composites for higher thermal conductivity, but how to achieve better enhancement is still an open problem. In this paper, a pod-like 3D interconnected heat percolation network was obtained by aligning diamond inside boron nitride (BN) honeycomb. The BN honeycomb used as secondary templets was prepared by ice template method. Subsequently, the epoxy (EP) and diamonds were filled into it simultaneously by vacuum infiltration. SEM and computed tomography results demonstrated that highly ordered thermal conductive channels have been constructed. When the content of BN is 7 vol% and diamond is 12 vol%, the thermal conductivity of the composite is as high as 2.720 W/(m·K), which is 12.5 and 5.8 times higher than that of pure EP and randomly mixed sample, respectively. To better understand the enhance mechanism, through the parallel structural model calculations, the effective thermal conductivity of the local tightly packed diamond part was increased from 1.210 W/(m·K) to 11.318 W/(m·K) in the composite. The findings suggested that the bridging effect of BN wall on connecting diamond particles also contributed to enhanced property of the composite. This study offers a novel strategy for obtaining higher thermal conductivity with low filler loading in hybrid composites.