High Thermal Conductive Composites Research Articles

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.

Surface micro-welding strategy of h-BN assembled microspheres for composites with desirable thermal conductivity and a low dielectric constant

As electronic devices strive for higher integration and faster signal transmission, the demand rises for polymer composites with high thermal conductivity (TC) and low dielectric constant (εr). However, high TC composites often come with a high filler content, leading to a reduction in processibility and dielectric properties. Herein, by surface micro-welding strategy, we fabricated cohesive h-BN microspheres (SBO) with a quasi-hollow structure. The pre-constructed micro-nano network of h-BN inside the microsphere serves as a continuous pathway for heat transfer, while the internal space of the microsphere is divided into numerous gas chambers, establishing a foundation for low εr. Benefiting from this structure, the TC of the prepared composite is 2.12 W/m·K, and its εr is remarkably low at 3.24 (103 Hz), effectively balancing the TC and dielectric properties at a high filler loading. Furthermore, this designed structure significantly reduces the viscosity of the composite (measured 309 Pa s with a filler content of 50 wt% at 1s−1) due to the smooth surface of the microsphere. This strategy offers a facile approach for fabricating composites characterized by desirable TC, low εr and excellent processibility, showcasing promising prospects for advancement in the realm of microelectronics.

Highly thermal conductivity polymer composites reinforced by BNNS/UHMWPE fabric for reliable electronic thermal protection and management

With the rapid development of 5G communication and microelectronics technology, the heat accumulation of high-power electronic devices puts forward an urgent demand for high thermal conductivity (TC) composites. However, it's still a great challenge through electrically insulating polymer to achieve good comprehensive performance of high TC, flexibility, and safety reliability. Herein, ultra-high molecular weight polyethylene (UHMWPE) fabric was coated with boron nitride nanosheets (BNNS) by dispersion and interfacial reinforcement of cellulose nanofibers (CNFs), and the BNNS/UHMWPE fabric-reinforced polymer composite (B/UF-PC) with 3D continuous thermal pathway was obtained by further composite with polydimethylsiloxane (PDMS). The continuous thermal pathways of highly aligned UHMWPE fibers in the fabric and the synergistic effect of the BNNS network enhance the out-of-plane and in-plane TC to 6.02 and 11.78 W/m K, respectively. Moreover, B/UF-PC exhibits flexible, lightweight (0.89 g/cm3), and significantly higher tensile strength (87.40 MPa) and energy absorption efficiency (98 %) than those of polymer composites, which allows it to be used in reliable electronic thermal management to prevent heat accumulation and external mechanical impact. This work provides a strategy for efficiently preparing flexible polymer composites with high TC and insulation properties.

Preparation of high performance thermal conductive composites from aluminum plastic packaging waste via Solid-state Drawing

Aluminum-plastic multilayer films have been widely used as the top-grade packaging material due to their exceptional barrier properties. However, the recycling of aluminum plastic packaging waste (APPW) poses a great challenge. To address this issue, we proposed a facile method for recycling APPW using solid-state drawing technology to produce high performance thermal conductivity composites for the first time. The ultrafine APPW with good processability was obtained by solid-state shear milling (S3M), with a low electrical conductivity of less than 10−12 S/cm. The subsequent solid-state drawing of both the aluminum sheet and polymer chain resulted in the formation of an oriented crystalline structure, with the Al sheet acting as an effective nucleating agent. This resulted in a significant increase in tensile strength for HDPE/APPW (30 %) composites, from 21.4 MPa to 116.1 MPa at the drawing ratio of 5. In addition, the in-plane thermal conductivity of HDPE/APPW (50 %) composites reached an impressive 2.5 W/mK, with the tensile strength of 78.8 MPa. Our findings demonstrate the potential of utilizing APPW for the production of value-added composites without requiring separation, with possible applications in heat management for emerging electrical systems and electronic devices.

Vertically aligned and conformal BN-coated carbon fiber to achieve enhanced thermal conductivity and electrical insulation of a thermal interface material

Due to excellent thermal conductivity, high aspect ratio, and low density, mesophase pitch-based carbon fibers (MPCFs) are highly desired in electronic packaging. However, their thermal conductivity is hard to present in the polymer matrix because of the disordered stacking and low filling. Moreover, few researches are focused on the enhancement of the electrical insulation performance for MPCFs. Herein, we report vertically aligned and insulating boron nitride (BN) coated carbon fiber (CF) powders as significant fillers for polymer composites, endowing markedly improved thermal conductivity and electrical insulation. The high-quality BN coating layer on the surface of the CF is produced by a cooling precipitation method and high-temperature treatment with ingenious use of solubility properties, exhibiting a conformal, dense, and highly crystalline structure. This preparation method overcomes the limitations of coating thickness and particle agglomeration, resulting in a 31-fold enhancement of the electrical resistivity of the CF powders. After orientation treatment in a silicone rubber matrix, such CF@BN-filled pads exhibit good thermal conductivity, significantly improved insulation performance, and excellent mechanical properties. Among them, the optimized pad achieves a thermal conductivity of 12.06 W m−1 K−1, a volume resistivity of 50 × 108 Ω cm and a breakdown voltage of 3100 V mm−1, exceptional flexibility, and a favorable compression ratio (@45 psi) of 41.7 %. This work provides unique insights into constructing carbon fiber fillers as well as the preparation of high thermal conductivity composites, thereby expanding the application scenarios of carbon fiber powder in electronic packaging.

Thermally conductive h-BN/EP composites oriented by AC electric field induction

The excellent electrical insulation properties and mechanical properties of epoxy resin (EP) have led to its rapid development in the field of microelectronic packaging. However, the poor thermal conductivity of epoxy resins (thermal conductivity of only 0.14 W/(m·K)) limits the development of components for high power. Adding h-BN to epoxy resin to prepare composites can effectively improve the thermal conductivity of epoxy resin. In this paper, h-BN/EP high thermal conductivity composites were prepared by means of AC electric field induction with the goal of making the composites low loading and high thermal conductivity (loading of 10 wt%). It was shown that the h-BN/EP composite had the highest thermal conductivity of 0.310 W/(m·K) when applied to an AC electric field of 120 V/mm and 50 Hz for 1 h. It was 2.214 times higher than that of EP and 1.325 times higher than that of the same-loaded h-BN/EP composite (0.234 W/(m·K)). A thermal conductivity model that can predict the thermal conductivity of composites prepared using the same type of method is also developed, which extends the applicability of the thermal conductivity model. The prepared composites have good thermal management capability. The method is easy to be engineered and has great potential for use in electronic packaging and even other high thermal conductivity applications.

Facile synthesis of functionalized boron nitride nanosheets for photo‐cured 3D printing of high thermal conductive composites

AbstractAddressing the concern of heat accumulation in electronic devices, considerable research efforts have been dedicated to develop composites that are thermally conductive yet electrically insulative. Incorporating hexagonal boron nitride (h‐BN) as fillers shows promise in enhancing the thermal conductivity of polymer composites. However, notable challenges arise from difficulties in achieving well dispersion and establishing efficient three‐dimensional thermal conductive networks. This work demonstrated an efficient photocurable direct ink writing (DIW) printing method to fabricate functional h‐BN nanosheets (A‐BNNS)/epoxy acrylate (EA) resin‐based thermal conductive composites (A‐BNNS/EA). Apple polyphenol‐assisted ball milling was employed to fabricate functionalized BN nanosheets (A‐BNNS). Subsequently, A‐BNNS/EA inks were 3D printed using DIW to create thermally conductive composites, which were then UV‐cured. The composite containing 55 wt% A‐BNNS demonstrated an impressive thermal conductivity (TC) of 3.44 W/(m K). The utilization of 3D printing technology enables an onion‐like dispersion of A‐BNNS within the polymer matrix, effectively constructing three‐dimensional thermal conductive networks. This contribution significantly enhances the overall thermal conductivity.Highlights The functional BNNS (A‐BNNS) was achieved by apple polyphenol‐assisted ball milling. The utilization of photocurable 3D printing technology for producing high thermal conductivity materials are efficient. A‐BNNS exhibited an onion‐like distribution and effectively constructed a 3D thermal conductive network within the polymer matrix The composites demonstrate excellent thermal conductivity and favorable heat dissipation property.

Recent advances in 3D interconnected carbon/metal high thermal conductivity composites

Recent advances in 3D interconnected carbon/metal high thermal conductivity composites

A novel polymer composites with high thermal conductivity by Zn2+ interfacial intensification and 3D network construction

Polymer-based composites with high thermal conductivity (TC) have attracted broad attention in electronics and heat exchange fields. However, obtaining desirable TC enhancement at low filler loading by a simple preparation strategy remains challenging. In this study, a simple one-pot method was proposed to fabricate high TC composites with low filler loading. Here, Zn2+ was introduced into the curing agent to directly strengthen the interface of expanded graphite (EG)-epoxy (EP), as opposed to the common method of modifying the filler with interfacial reinforcements. Meanwhile, a connectivity network as the main heat transfer medium was constructed with micro-3D EG by the pre-filling method. Results showed that the TC of the prepared composite with only 30 wt% filler loading was up to 55.49 W/(m·K), which was about 241 times higher than that of pure epoxy. After the experimental data analysis, the key to effectively improving TC was that the dual effect of the effective facilitation of Zn2+ and the presence of a dense and high-quality 3D EG network.

Construction of three-dimensional interconnected boron nitride/sliver networks within epoxy composites for enhanced thermal conductivity

With the advent of the 5G era, the conspicuous increases in operating power and thermogenic capacity of integrated electronic components necessitated the development of enhanced thermal conductive polymeric composites with excellent heat dissipation properties. Herein, the polydopamine (PDA) and silver (Ag) modified BN (BN-PDA-Ag) was synthesized and a three-dimensional (3D) interconnected BN-PDA-Ag porous network was successfully fabricated by the salt template-assisted method to improve the thermal conductivity property of epoxy based composites. The high thermal conductive epoxy resin composites (3D BN-PDA-Ag/EP) were obtained by infiltrating epoxy into the 3D BN-PDA-Ag porous network. On one hand, the 3D BN-PDA-Ag porous skeleton provided continuous transfer paths for phonons, which was conducive to reducing phonon scattering. On the other hand, the Ag nanoparticles loaded on the BN surface bridged the adjacent BN sheets, significantly decreasing the thermal contact resistance between adjacent fillers. The isotropic thermal conductivity (TC) of 3D BN-PDA-Ag/EP composite with a BN-PDA-Ag content of 20.3 wt% reached 1.37 W/(m·K), which exhibited a evident enhancement of 661% compared with pure epoxy. The thermal management simulation and application results showed the composite had enormous application potential for electronic devices and components in heat dissipation.

High thermal conductivity and flame-retardant epoxy-based composites with low filler content via hydrazine foaming of graphene oxide and boron nitride hybrid fillers

In this study, we developed a composite material for thermal conductivity by creating a hyperbolic boron nitride (BN) and graphene oxide (GO) structure with surface treatment using phosphorus-containing functional groups. The resulting composite, with a 4.04 vol % hybrid filler content, was impregnated with epoxy resin. The composite achieved a thermal conductivity of 0.95 W/mK and exhibited a significant thermal conductivity enhancement (TCE) when compared to the neat EP (377 %), demonstrating its potential for mitigating thermal accumulation in industrial applications. Additionally, the tensile strength of the composite significantly improved up to 45.3 MPa and had excellent flame-retardant properties. These results highlight the effectiveness of the hybrid filler approach in enhancing thermal and mechanical properties. The developed composite holds promise for various applications that require improved heat transfer and enhanced mechanical performance.

The Interfacial Thermal Resistance Properties Of GNPs/Epoxy Thermally Conductive Composites By Molecular Dynamics Simulation

With the increasing power density and integration degree of electrical equipment, the problem of excess heat production is serious. Existing data show that the thermal management capability of electrical equipment is a key factor affecting the performance of electrical equipment. Therefore, the development of high thermal conductivity composites is an effective solution to improve the thermal management ability of equipment and extend the working life of equipment. With the purpose of enhancing the heat conduction of epoxy resin, graphene sheets (GNPs) with high thermal conductivity were added. Based on the reverse nonequilibrium molecular dynamics simulation (RNEMD) method, the thermal conductivity simulation of epoxy resin equipped with GNPs was carried out. The simulation results showed that the heat conductivity of epoxy resin equipped with GNPs had been greatly improved.

Highly thermally conductive polymer composite enhanced by constructing a dual thermal conductivity network

AbstractConstructing interconnected thermally conductive networks in a polymer matrix is essential for efficient heat transport in thermally managed materials. Thermally conductive network structures typically have meager thermal resistance, and heat transfer into the material is rapidly exported along such networks. However, increasing the thermally conductive networks inside the polymer matrix is still challenging. This paper prepared high thermal conductivity composites with “primary‐secondary” thermal conductivity networks by combining two processes: constructing three‐dimensional thermally conductive skeletal networks and physically blending fillers, using epoxy resin as the matrix. The performance test results showed that the thermal conductivity of the composites reached 1.65 W/(m K) when the boron nitride (BN) content reached 33.5 wt%, which was 842.8% and 150% higher than that of pure epoxy (EP) and composites with randomly dispersed fillers. This highly efficient heat transfer behavior is mainly due to the synergistic effect of the two‐level thermally conductive network, which weakens the scattering effect of phonons to a great extent. Also, the dielectric properties of the composite material, especially the transport of carriers inside the material under strong electric fields, were discussed in this paper. This work provides ideas and methods for preparing electrical and electronic devices applied to high power density.

Extremely high thermal conductive cement-based composites with diamond/ZnO/expanded graphite thermal conductivity network for cooling road

In recent years, the deterioration of traffic safety due to high road temperatures and the increase in transport costs have led to an urgent need for road users to reduce the temperature of the road surface. In this paper, high thermal conductivity diamond/ZnO/expanded graphite (D/ZnO/EG)11Diamond: D; Expanded graphite: EG. cement-based composites were prepared by constructing and optimizing a thermal conductivity network in a cement matrix to achieve road cooling. Thermal network structure and porosity’s impact on thermal conductivity had both been investigated, and the mechanism governing thermal conductivity had also been analyzed. With a thermal conductivity of 6.338 W/(m·K), 732 % of the cement matrix, the result showed that the expanded graphite (EG) thermal conductivity network and D/ZnO significantly enhanced heat transfer. The excellent thermal transfer capacity of D/ZnO/EG cement-based composites was also shown to be beneficial in reducing pavement temperatures in the temperature distribution simulations at the road surface under solar irradiation. The above results illustrated the EG network thermal’s conductivity, the impact of D in shortening the EG spacing, and the impact of ZnO in filling the gaps, all of which were effective in enhancing thermal conductivity. In addition, D/ZnO/EG prevented crack extension and thus attenuated the damage to thermal conductivity caused by freeze–thaw cycles. This work confirms that the D/ZnO/EG cement-based composite can achieve effective heat dissipation from pavements, thereby improving traffic safety and reducing the long-term costs of road traffic.

Oriented High Thermal Conductivity Solid-Solid Phase Change Materials for Mid-Temperature Solar-Thermal Energy Storage.

As the global energy crisis intensifies, the development of solar energy has become a vital area of focus for many nations. The utilization of phase change materials (PCMs) for photothermal energy storage in the medium temperature range holds great potential for various applications, but their conventional forms face several challenges. For instance, the longitudinal thermal conductivity of photothermal PCMs is inadequate for effective heat storage on the photothermal conversion surface, and there is a risk of leakage due to repeated solid-liquid phase transitions. Here, we report a solid-solid phase change material, tris(hydroxymethyl)aminomethane (TRIS), which has a phase change temperature of 132 °C in the medium temperature range, enabling high-grade and stable solar energy storage. To overcome the low thermal conductivity problem, we propose a large-scale production of oriented high thermal conductivity composites by compressing a mixture of TRIS and expanded graphite (EG) using the pressure induction method to create in-plane highly thermally conductive channels. Remarkably, the resulting phase change composites (PCCs) exhibit a directional thermal conductivity of 21.3 W/(m·K). Furthermore, the high phase change temperature (132 °C) and large phase change entropy (213.47 J/g) enable a large-capacity high-grade thermal energy to be used. The developed PCCs, when combined with selected photo-absorbers, exhibit efficient integration of solar-thermal conversion and storage. Additionally, we also demonstrated a solar-thermoelectric generator device with an energy output of 93.1 W/m2, which is close to the power of photovoltaic systems. Overall, this work provides a technological route to the large-scale fabrication of mid-temperature solar energy storage materials with high thermal conductivity, high phase change enthalpy, and no risk of leakage, and also offers a potential alternative to photovoltaic technology.

Self-Stacked 3D Anisotropic BNNS Network Guided by Para-Aramid Nanofibers for Highly Thermal Conductive Dielectric Nanocomposites.

The enhancement of the heat-dissipation property of polymer-based composites is of great practical interest in modern electronics. Recently, the construction of a three-dimensional (3D) thermal pathway network structure for composites has become an attractive way. However, for most reported high thermal conductive composites, excellent properties are achieved at a high filler loading and the building of a 3D network structure usually requires complex steps, which greatly restrict the large-scale preparation and application of high thermal conductive polymer-based materials. Herein, utilizing the framework-forming characteristic of polymerization-induced para-aramid nanofibers (PANF) and the high thermal conductivity of hexagonal boron nitride nanosheets (BNNS), a 3D-laminated PANF-supported BNNS aerogel was successfully prepared via a simple vacuum-assisted self-stacking method, which could be used as a thermal conductive skeleton for epoxy resin (EP). The obtained PANF-BNNS/EP nanocomposite exhibits a high thermal conductivity of 3.66 W m-1 K-1 at only 13.2 vol % BNNS loading. The effectiveness of the heat conduction path was proved by finite element analysis. The PANF-BNNS/EP nanocomposite shows outstanding practical thermal management capability, excellent thermal stability, low dielectric constant, and dielectric loss, making it a reliable material for electronic packaging applications. This work also offers a potential and promotable strategy for the easy manufacture of 3D anisotropic high-efficiency thermal conductive network structures.

Transient thermal behaviour of high thermal conductivity graphene based composite materials: Experiments and theoretical models

High thermal conductivity composites could be a valid alternative to traditional materials in many engineering applications. This work presents the realization of high thermal conductivity composites based on multilayer graphene sheets (GS) impregnated with polydimethylsiloxane (PDMS). Three composite configurations were prepared: discs, slab, and roll. The in-plane and out-of-plane effective thermophysical properties of GS/PDMS composites have been measured. Thermal diffusivity has been measured by a homemade Flash Method (FM) and the density by a gravimetric method. Specific heat and thermal conductivity have been calculated. The experiment results showed that the GS/PDMS composite has an in-plane thermal conductivity up to 430 W m−1K−1 with a GS loading of 70 wt%, higher than standard metals used in heat exchangers (e.g. copper, aluminum). The out-of-plane effective thermal conductivity reached up to 1 W m−1K−1 with a GS loading of 95 wt%, comparable with other high thermal conductivity composites that work as thermal interface materials in electronic applications. Two analytical models to predict the effective thermophysical properties of the multiphase composites were developed and presented.

富山県立大学 工学部 機械システム工学科 材料設計加工学講座 真田研究室

The objective of our laboratory is development of new polymer composites with superior performance and reliability using experimental and analytical approaches. Nowadays, we have been working on three research themes for new polymer composites: self-healing polymer composites, high thermal conductive polymer composites, and polymer composites with cellulose nanofibers. This article introduces research facilities and outline of three research themes in our laboratory.

Hydroxy silicone oil modified boron nitride for high thermal conductivity and low dielectric loss silicone rubber composites: experimental and molecular simulation studies.

Polymer-based composites are widely used in microelectronics and wireless communications, which require high thermal conductivity and low dielectric loss for effective heat dispersion and signal transmission. Different lengths of hydroxyl silicone oil chains modified boron nitride/silicone rubber composites were explored and prepared in this work. Experiments demonstrate that the long-chain modified BN improves the thermal conductivity and decreases the dielectric loss of composites. A molecular dynamics simulation was employed to study the mechanism and affecting variables. The calculated results indicated that the improvement of the thermal and dielectric properties is mainly related to the interfacial behavior, including interfacial compatibility, interfacial bond strength, and phonon matching. Based on the simulated interfacial behavior and thermal conductivity, the thermal and dielectric properties of different chain-length modified boron nitride/silicone rubber composites have been anticipated. The results show that the longer-chain modified boron nitride/silicone rubber composites have better thermal and dielectric properties. This research may give a theoretical foundation for the development of materials with designable performance for electronic devices.

Preparation of polymer composites with high thermal conductivity by constructing a “double thermal conductive network” via electrostatic spinning

With the advancement of information technology, there is a boom of demand for high-performance thermal conductive polymer-based materials applied in microelectronic devices. Fillers with high thermal conductivity, such as boron nitride nanosheets (BNNS), are often incorporated to improve the comprehensive thermal conductivity of polymer matrix. However, the fillers dispersed in composites often fail to form continuous heat transfer pathways due to the occurrence of interfaces, resulting in a suppressed thermal conductivity. In this paper, BNNS was confined in carbon nanofibers by electrostatic spinning (e-spin). The resultant fibrous carbon-boron nitride hybrid skeleton was combined with silicone rubber to form an elastic composite film. The effects of BNNS contents on the hybrid skeleton morphology and the composite conductivity were rigorously resolved. It was found that the hybrid skeleton consisted of continuous long-stacked carbon fibers, with high thermal conductivity intrinsically. And BNNS was tightly stacked, confined, and oriented along the fibers. The maximum thermal conductivity of the composite film was 4.09 W m−1 K−1, about 16 times higher than that of pure PDMS. A double thermal conductive network mechanism was proposed. That is, the two thermal pathways were formed by the overlapped BNNS and the carbon fibers, respectively. And the optimal thermal conductivity was achieved as the two pathways composited together by spinning and carbonization. The composite films with vertical alignment of the hybrid fibers were also prepared. Our work provides an essential and innovative strategy for the preparation of high thermal conductivity composites.