Thermal Conductivity Of Epoxy Composites Research Articles

In situ growth of graphene on carbon fibers to enhance the mechanical and thermal conductivity of epoxy composites

High-strength and high-thermal-conductivity composite materials have become crucial requirements for thermal control systems in various field. Carbon fiber-reinforced polymer (CFRP) has demonstrated potential superior performance. However, the application of CFRP is limited by the chemical inertness of the carbon fiber surface and the shortness of low surface energy. Therefore, surface modification of carbon fibers is necessary. This research employs a pulse plasma discharge method, to in-situ grow graphene on the surface of carbon fibers by disrupting some polymer structures on the carbon fiber surface in a “bottom-up” approach. This method offers advantages such as rapid, simple, convenient, economical, and environmentally friendly preparation process., the modified carbon fibers used in CFRP exhibit superior mechanical and thermal conductivity properties. The flexural strength increased by 218 % to reach 109.5 MPa, and the thermal conductivity increased by 251 % to achieve 1.153 W/(m*K).

Effects of spherical fillers reinforcement on the efficacy of thermal conductivity in epoxy and polyester matrices: Experimental validation and prediction using finite element method

AbstractThe creation of a theoretical heat conduction model for polymers embedded with spherical inclusions is described in this study. It also contains the experimental confirmation of the suggested correlation for utilizing the model to estimate the effective thermal conductivity (K) of such composites. According to ASTM‐E‐1530, composites are made with varying amounts of aluminium oxide and pine wood dust reinforced in polyester resin. The effective thermal conductivities (Keff) of the composites are then determined using the Unitherm TM model 2022. Ansys 19.R2 software is used to evaluate the effective thermal conductivity of these composites with a uniform filler distribution, while Digimat‐FE software is used determine the thermal conductivity values of such particle filled polymer composites with a random filler distribution. After comparison and validation with experimental data, these values are shown to be fairly good agreement with the theoretical values from the suggested correlation. The investigation is further expanded to determine the thermal conductivities for epoxy composites using wood apple shell dust and coir dust particle. Also epoxy and polyester composites reinforced with SiO2 and TiO2 have been investigated in the similar manner. The main thrust of this report to validate the numerical results of composites by varying numerous polymers. The thermal conductivity all the composites grow monotonically with increase in filler content. The thermal conductivity of silicon dioxide, titanium oxide, and aluminium oxide filled epoxy composites is measured as 1.5, 7, and 35 W/m‐K respectively.Highlights In this study spherical fillers are successfully used as a potential filler material in polyester composites The thermal conductivity predicted by proposed mathematical model of polyester is validated with measured value and found better agreement. The Ansys 19.R2 and digimat software are used to predict the thermal conductivity values of these composites. The mathematical model is further used to predict thermal conductivity of epoxy composites to check the accuracy of the model.

Constructing bidirectional heat flow pathways by curved alumina for enhanced thermal conductivity of epoxy composites

The polymer-based composites filled with high thermal conductive fillers have received much attention in the filed of electronic package. However, traditional Al2O3 filled polymer-based composites always hardly simultaneously achieve high thermal conductivity in both horizontal and vertical directions with a low loading. Herein, curved Al2O3 particles have been fabricated via spray assembly and high-temperature sintering and subsequently are infiltrated by epoxy (EP) to obtain Al2O3/EP composites. The formation mechanism of the curved Al2O3 is analyzed in this work. The curved Al2O3 architectures are orderly stacked in EP matrix, which achieve significantly enhanced in-plane (1.21 W/m·K) and through-plane (1.46 W/m·K) thermal conductivity with a low filler loading (19.9 vol%). Importantly, the wall structure of curved Al2O3 particle consists of continuous network structure and interconnected channels, which reduce the thermal expansion coefficient of the composites. Consequently, the design of curved Al2O3 offers a new strategy for next-generation thermal management materials.

Enhanced mechanical, thermal properties and thermal conductivities of epoxy composites via incorporating graphene oxide‐grafted carbon nanotubes hybrids

AbstractA hetero‐structured hybrid was produced by grafting one‐dimensional (1D) amine‐functionalized multiwalled carbon nanotubes (MWCNTs) onto the basal plane of two‐dimensional (2D) graphene oxide (GO) via an amine‐epoxy ring‐opening reaction, and such hybrid was further applied for reinforcing epoxy composites. Based on this hybrid design, 1D MWCNTs anchored on the 2D GO nanosheets resisted the re‐stacking of GO nanosheets while GO improved the MWCNTs' dispersion state. Attributing to the synergistic effect of GO and MWCNTs, a multi‐dimensional conducting network within epoxy matrix was constructed and efficiently transferred stress and heat between hybrid and matrix. When just 0.5 wt% hybrids were incorporated, the mechanical properties, thermal stability and thermal conductivity of hybrid‐filled epoxy composites were significantly improved, compared with pure epoxies. This work gives a promising method for designing and preparing polymer composites for thermal management and protection applications.Highlights A hetero‐structured hybrid consisting of MWCNTs and GO was obtained. Better dispersion of GO–MWCNTs within matrix was achieved. A multi‐dimensional GO–MWCNTs conducting network in matrix was constructed. Enhanced properties were due to the synergistic effect of GO and MWCNTs. Structural performance of GO and MWCNTs was maximized.

In-situ constructing continuous networks composed of SiC nanowires for enhancing the thermal conductivity of epoxy composites

With the rapid miniaturization and high degree of integration of modern electronic devices, there is an increasing demand for high-performance polymer-based thermal management materials. SiC nanowires (SiCNWs) are very promising fillers benefiting from their large aspect ratio and ease of constructing thermally conductive networks. However, the traditional random mixing method allows the SiCNWs to form a thermally conductive network only through physical overlap, resulting in a high interfacial thermal resistance. To address this problem, an innovative strategy for in-situ generating continuous network composed of SiCNWs was proposed in this study, in which the SiCNWs was formed through impregnation-sintering process using an inexpensive polyurethane (PU) sponge as a template. The porous skeletons were sintered by numerous SiCNWs, which not only conferred more thermally conductive pathways, but also solved the problem of weak bonding at the SiCNWs random lap interface. On this basis, the SiC skeletons were further used as reinforcement to prepare epoxy (EP)-based composites. Benefiting from the continuous thermally conductive networks composed of SiCNWs, the composites achieved a thermal conductivity (TC) of ∼1.17 W m−1 K−1 at a low volume fraction of 21.18 vol%, which was 548.7 % higher than that of pure EP. In addition, the unique SiCNWs skeletons also facilitated the enhancement of mechanical properties and thermal stability of the composites, providing new insight for the preparation of innovative thermal management materials.

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.