High Thermal Conductive Filler Research Articles

Study on the improvement of geothermal cement properties by nanofluid composed of deep eutectic solvent and graphene oxide

Guided by the goal of improving the heat transfer efficiency of geothermal cement, the development of high thermal conductivity fillers is urgently needed. Considering the drawbacks of carbon-based fillers in deteriorating the strength and fluidity of cement, this study proposes the use of green and low-cost deep eutectic solvents (DES) loaded with graphene oxide to form nanofluids (GONF) to improve the connection between graphene oxide and cement. The thermal conductivity and basic properties of GONF-cement under thermal storage conditions (60–100 °C, 0–36%NaCl) were reported, and the influence mechanism of nanofluids was analyzed. The following interesting conclusions were found: (1) The oxygen-containing functional groups on the surface of graphene oxide were connected to active sites of DES through the formation of the hydrogen bond network, forming thermal stable nanofluids. (2) Nanofluids was proven to be a low-cost (reduce material costs of graphene oxide by 90%) and effective material for enhancing the thermal conductivity and mechanical properties of geothermal cement while maintaining appropriate fluidity and low variation of density. (3) The synergistic mechanism between nanofluids and cement is due to the fact that nanofluids promotes hydration process by providing stable reaction sites, significantly reducing the porosity and pore size of cement. The dense structure enhances compressive strength and shortens the heat transfer path. This study enriches geothermal cementing technology and provides support for the low-cost application of graphene oxide in exploration engineering.

Surfactant hydrophilic modification of expanded graphite to fabricate water-based composite phase change material with high latent heat for cold energy storage

Glycine water-based (GW) phase change material (PCM) is considered a promising candidate for cold energy storage due to its lower cost and high latent heat. However, low thermal conductivity hinders its practical application. Adding high thermal conductive fillers can effectively enhance the thermal conductivity of PCM, but it also leads to a decrease in enthalpy. Thus, the study employed a non-covalent functionalization method to modify the thermal conductivity filler of expanded graphite (EG) using the surfactant Triton X-100 (TX-100) in this study. The hydrophilic groups in TX-100 facilitated the formation of hydrogen bonds between modified expanded graphite (MEG) and GW PCM, thereby inhibiting the enthalpy loss of GW/MEG materials. The prepared GW/MEG composites containing 2 to 8 wt% of MEG exhibited thermal conductivities ranging from 0.88 to 1.28 W/(m·K), representing an increase of 46.47 % ∼ 113.35 %. Simultaneously, the melting temperature ranged from −5.35 to −5.65 °C, with a high melting latent heat of 284.6 to 264.5 J/g. After 100 thermal cycles, only minor fluctuations in melting temperature (−1.62 % ∼ +2.20 %) and latent heat (−2.18 % ∼ −4.66 %) were observed. Furthermore, the application of GW/MEG2 in cold storage of strawberries resulted in a significant reduction in pre-cooling time by 56.60 % compared to that of ice storage. The GW/MEG2 materials allow strawberries to be refrigerated for up to 17.86 h within the temperature range of 1.54 ∼ 3.39 °C. This study provides an effective solution for short-distance transportation of perishable food within cold chain logistics system.

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.

Multi‐layer graphene nanosheets bridging binary aluminium oxide for the synergistic enhancement of thermal conductivity and electrical insulation of silicone resin composite

AbstractThe flexible polymer composites usually require high intrinsic thermal conductivity fillers for the applications in thermal management, such as the well‐known graphene, which can, in turn, compromise their electrical insulation properties. Here, the authors developed the silicone resin (SR) composites filled with multi‐layer graphene nanosheets (MGN) and binary alumina (Al2O3), and the microstructure of composites exhibits the dominant skeleton of large‐sized Al2O3 filler and branching of small‐sized Al2O3 fillers features by the size matching effect of optimal binary Al2O3. The introduction of supplementary MGN fillers further increases the face‐to‐face contact probability and bridges the isolated binary Al2O3, which contributes to the high thermal conductivity of 3.0 W·m−1·K−1 under these synergistic effects. The dense and connected ‘Al2O3‐MGN‐Al2O3’ thermal conductive pathway is successfully built, as supported by the numerical simulation and Agari model fitting. Meanwhile, the electrical conductivity caused by MGN can be blocked by the surrounding insulation Al2O3 filler network, exhibiting a high volume resistivity of 1.7 × 1015 Ω · cm. Moreover, the Al2O3/MGN/SR composite films effectively transfer the heat and diminish the hot‐spot temperature by 53.5°C in cooling light emitting diode chip module application.

Flexible phase change materials based on hexagonal boron nitride (hBN) surface modification and styrene-butadiene-styrene (SBS)/low-density polyethylene (LDPE) crosslinking for battery thermal management applications

In battery thermal management (BTM), flexible phase change materials (FPCMs) emerge as highly promising substances, owing to their simple installment and low contact thermal resistance. However, FPCMs based on high thermal conductivity fillers and polymers always suffer from the enduring challenges of poor high-temperature resistance and poor filler-matrix compatibility. To solve these problems, a novel strategy is reported in this work, wherein FPCMs with excellent filler-matrix compatibility and satisfactory high-temperature resistance are synthesized by two steps: functionalizing the hexagonal boron nitride (hBN) surface and inducing the inter crosslinking between Styrene-Butadiene-Styrene(SBS) and Low-density polyethylene(LDPE). Vinyltrimethoxysilane (VTMS) molecules were introduced on the surface of raw hBN by hydroxylation and silanization surface modification to improve the compatibility of hBN with the matrix. Concluding from the results, the addition of 6.7 wt% LDPE doubled the high-temperature resistance of FPCMs, enabling them to maintain their structural integrity even at 200 °C for 1 h. The prepared FPCMs also exhibited higher thermal conductivity (increased by 20.5 %), low leakage rate (<0.6 wt% after 70 heating–cooling cycles), high enthalpy (122 J g−1), and strong adhesion (>0.1 MPa), etc. In terms of BTM performance, the FPCMs-based passive cooling BTM presents remarkable temperature control capabilities (maximum temperature reduction by 16.3 ℃) and uniform temperature performance (maximum temperature difference < 2.5 ℃). Collectively, this work will provide a promising approach for the fabrication of high-performance FPCMs in BTM and other thermal management applications for electronic devices.

Application and Development of Smart Thermally Conductive Fiber Materials.

In recent years, with the rapid advancement in various high-tech technologies, efficient heat dissipation has become a key issue restricting the further development of high-power-density electronic devices and components. Concurrently, the demand for thermal comfort has increased; making effective personal thermal management a current research hotspot. There is a growing demand for thermally conductive materials that are diversified and specific. Therefore, smart thermally conductive fiber materials characterized by their high thermal conductivity and smart response properties have gained increasing attention. This review provides a comprehensive overview of emerging materials and approaches in the development of smart thermally conductive fiber materials. It categorizes them into composite thermally conductive fibers filled with high thermal conductivity fillers, electrically heated thermally conductive fiber materials, thermally radiative thermally conductive fiber materials, and phase change thermally conductive fiber materials. Finally, the challenges and opportunities faced by smart thermally conductive fiber materials are discussed and prospects for their future development are presented.

Accelerating the kinetics of curing reaction of SBR/BR blend by silicon carbide via modification of thermal diffusivity

In this work, the accelerating effect of nano-silicon carbide (SiC) as a high thermal conductive filler on the kinetics of curing reaction of styrene-butadiene rubber/butadiene rubber (SBR/BR) as a compound for tire tread was investigated. The oscillating disk rheometer (ODR) showed that the SiC filler reduced the scorch and optimum curing times by ∼10%. The SiC amount of 5 phr caused an unparalleled reduction of ∼50% in the time difference between the scorch and curing times. The calculated parameters of the autocatalytic kinetic model of Kamal–Sourour using ODR results indicated that SiC accelerated the curing reaction by ∼1.25 times. To find the main mechanism of action of SiC in the improvement of vulcanization kinetic of SBR/BR-SiC, thermal diffusivity of the compound was detected in the thermalization process using a special setup during the curing and also the dethermalization process after that. The results exhibited that the SiC particles led to enhanced heat transfer rate into the compound during the vulcanization by ∼30% and into the cured composite by ∼50%, particularly at 5 phr of SiC. Moreover, fitting the heat transfer equation on the dethermalization data showed that the amount of 5 phr SiC in the recipe enhanced the thermal diffusivity by ∼97%, which can prevent the tire explosion while deriving due to the increment of the air temperature within the tire. The SiC filler can save significant energy in the manufacturing process of the tire tread, which has been neglected so far.

High thermal conductivity electrical insulation composite EP/h‐BN obtained by DC electric field induction

AbstractEpoxy resin, as an adhesive for the main insulation system of large generators, has excellent insulation properties. But its poor thermal conductivity limits the capacity enhancement of large generators. Forming thermally conductive pathways by using electric field to induce high thermal conductivity fillers in the polymer can effectively improve the thermal conductivity of the composite at low loading condition. In this article, a DC electric field is used in epoxy resin (EP) to induce two‐dimensional inorganic fillers h‐BN deflection and head‐to‐tail lap, which can make the heat flow transfer along the in‐plane of the particles and contribute to the more efficient thermal conductivity network. A high thermal conductivity of 0.544 W/(m K) was achieved at a low load of 10 wt%, which has an improvement of 289% compared to pure EP (0.14 W/[m K]) and 130% compared to the randomly dispersed composite with the same load. The composites have excellent thermal conductivity as well as insulating properties, among which volume resistivity is 1.46 × 1012 Ω/cm, increasing by 61.4% compared to pure EP. This method is easy to be carried out in engineering and has great possibilities for the main insulation of large generators and even for other applications with high thermal conductivity electrical insulation.Highlights The structure of composites was adjusted by direct current electric field. The high in‐plane thermal conductivity of h‐BN is fully exploited. The relationship between deflection angle of BN and thermal conductivity of composites was built.

Copolymerization of Phase Change Materials with Water Resistance Poly(Acrylamide‐Co‐Polyacrylic Acid) Copolymer Encapsulation: Photothermal Conversion and Storage Performance Under Solar Conditions

Currently, the majority of composite phase change materials (PCM) are only available in solid‐phase environments. Therefore, it is important to prepare composite PCM with photothermal conversion capacity, high thermal conductivity, and stability in both solid and aqueous phase conditions. Herein, a composite PCM with high photothermal conversion storage efficiency (92.6%), high energy storage density (147.6 J g−1), and high thermal conductivity (1.19 W m−1 K) is prepared using poly(acrylamide‐co‐polyacrylic acid) copolymer (PAAAM) as the supporting material, boron nitride as the high thermal conductivity filler, and carboxyl‐rich carbon as the photothermal conversion agent and key bridge. With the help of the characteristics of PAAAM, although the PAAAM chain is swollen not broken, it still maintains cross interconnection with PCM in the water‐phase environment, which has excellent encapsulation performance in both the water/solid phase environment. This provides another option for broadening the application of PCM in aqueous solvent conditions.

Electric field-induced orientation of silicon carbide whiskers for directional and localized thermal management

Incorporating high thermal conductivity fillers into the matrix material and optimizing their distribution offers a targeted approach to controlling heat flow conduction. However, the design of composite microstructure, particularly the precise orientation of fillers in the micro-nano domain, remains a formidable challenge to date. Here, we report a novel method for constructing directional/localized thermal conduction pathways based on silicon carbide whiskers (SiCWs) in the polyacrylamide (PAM) gel matrix using micro-structured electrodes. SiCWs are one-dimensional nanomaterials with ultra-high thermal conductivity, strength, and hardness. The outstanding properties of SiCWs can be maximized through ordered orientation. Under the conditions of 18 V voltage and 5 MHz frequency, SiCWs can achieve complete orientation in only about 3 s. In addition, the prepared SiCWs/PAM composite exhibits interesting properties, including enhanced thermal conductivity and localized conduction of heat flow. When the SiCWs concentration is 0.5 g·L−1, the thermal conductivity of SiCWs/PAM composite is about 0.7 W·m−1·K−1, which is 0.3 W·m−1·K−1 higher than that of PAM gel. This work achieved structural modulation of the thermal conductivity by constructing a specific spatial distribution of SiCWs units in the micro-nanoscale domain. The resulting SiCWs/PAM composite has unique localized heat conduction properties and is expected to become a new generation of composites with better characteristics and functions in thermal transmission and thermal management.

Thermal percolation network in alumina based thermal conductive polymer

Polymers incorporated with high thermal conductivity fillers have numerous applications in thermal interface materials. Plenty of efforts have been made to improve the thermal conductivity of polymer composite. A possible method is to choose fillers with different morphologies, which can combine the advantages of various fillers. However, owing to the limitations of the effective medium theory as well as lack of researches of thermal percolation, there is still little understanding of the synergistic mechanism of fillers with different morphologies. In order to avoid the coupling effect of different materials, this work uses the same kind of alumina but with different morphologies to prepare different kinds of epoxy composites incorporated with spherical alumina, plate-like alumina and fillers mixed of 1:1 ratio. The thermal conductivity of each sample is measured by the steady state method. With the fitting of the thermal percolation theory, the synergistic effect of plate-like fillers and that of spherical fillers are verified to promote the formation of thermal percolation network. In addition, by observing the microscopic distribution of fillers, we try to explain the mechanism of this synergistic effect.

Thermal percolation network in Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; based thermal conductive polymer

Polymers incorporated with high thermal conductivity fillers have numerous applications in thermal interface materials. Plenty of efforts have been made to improve the thermal conductivity of polymer composite. A possible method is to choose fillers with different morphologies, which can combine the advantages of various fillers. However, owing to the limitations of the effective medium theory as well as lack of researches of thermal percolation, there is still little understanding of the synergistic mechanism of fillers with different morphologies. In order to avoid the coupling effect of different materials, this work uses the same kind of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; but with different morphologies to prepare different kinds of epoxy composites incorporated with spherical Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;, plate-like Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; and fillers mixed of 1∶1 ratio. The thermal conductivity of each sample is measured by the steady state method. With the fitting of the thermal percolation theory, the synergistic effect of plate-like fillers and that of spherical fillers are verified to promote the formation of thermal percolation network. In addition, by observing the microscopic distribution of fillers, we try to explain the mechanism of this synergistic effect.

An Efficient Method to Determine the Thermal Behavior of Composite Material with Loading High Thermal Conductivity Fillers

Improvement of the thermal conductivity of encapsulant material using doping filler is an important requirement for electronic device packaging. We proposed a simple method for determining the thermal characteristics of composite material that can help save time, increase research performance, and reduce the cost of buying testing equipment. Based on the theory of Fourier law, a general 3D model is simplified into a 2D model, which can then be applied to calculate the thermal conductivity of the tested sample. The temperature distribution inside the sample is simulated by the finite element method using MATLAB software; this is a simple and useful option for researchers who conduct studies on thermal conduction. In addition, an experimental setup is proposed to help determine the extent of thermal conductivity improvement in a sample with doping filler compared to a bare sample. This method is helpful for research on optoelectronics packaging, which relates to the enhancement of thermal conductivity composite material.

Enhancing Thermal Insulation of EPDM Ablators via Constructing Alternating Planar Architectures.

Ethylene–propylene–diene monomer (EPDM) composites were usually enhanced with ablative additives to protect solid rocket motor (SRMs) casings. However, the poor thermal insulation caused by the high thermal conductive ablative fillers can lead to rocket motor failure. Herein, the novel EPDM composites containing alternating layers of ablative EPDM (AM) and heat-insulated EPDM (HM) were prepared through layer-multiplying extrusion. Compared with conventional EPDM ablative material, the multilayer composites showed enhanced thermal insulation and mechanical properties that could be further improved by tuning the number of layers. The ablation and thermal insulation properties possessing in AM and HM layers could be combined by forced assembly during co-extrusion, and the alternating multilayer composite was capable of showing the effect of each component. In particular, compared with AM, the maximum back-face temperature with 40 alternating layers of AM/HM decreased from 96.2 °C to 75.6 °C during oxyacetylene test, while the good ablation properties were preserved in the AM component. This significant improvement was attributed to the planar orientation and densification of ablative additives, and the interruption of conductive pathways in the through-plane direction of AM/HM alternating laminate. The anisotropic EPDM composites featuring mechanical robustness, good ablative resistance and thermal insulation suggest considerable potential application in the aerospace industry.

Three-dimensional micro-pipelines high thermal conductive C/SiC composites

Carbon/silicon carbide (C/SiC) composites are usually regarded as thermal protective system materials and widely applied in hypersonic vehicles or ramjet. However, poor thermal conductivity of C/SiC composites, leading to severe heat concentration and thermal stress during the high-speed operation of hypersonic vehicle, limits their broad-range of practical applications. Modification with high thermal conductive fillers is an optional method; however, controllable dispersion and orientation of the fillers to construct continuous and ordered heat conductive channel has been proven to be a challenging task. Herein, based on high thermal conductivity fibers, a three-dimensional micro-pipeline preform was developed for the preparation of structure–function integrated C/SiC composites. The technical feasibility of the method, the characteristics of microstructures, and the thermal conductivity and bending strength of the as-obtained composites were systematically studied. Results revealed that the thermal conductivities of as-obtained composites reached 150.2 and 46.7 W m −1 K −1 for in-plane and out-of-plane direction, respectively. The bending strength obtained herein is 264.4 MPa, which is lower than that of polyacrylonitrile C/SiC composites. However, the fine control over the component and microstructure or densification could provide a higher value in the future research. In sum, the proposed method provides a convenient and feasible approach to prepare high thermal conductive C/SiC composites.

Improving the local thermal conductivity of flexible films by microchannels filled with graphene

Low thermal conductivity is an outstanding problem that hinders the application of polymer substrates in flexible devices. Incorporating high thermal conductivity fillers into polymer to enhance its thermal conductivity usually requires a large mass fraction of fillers at the expense of the flexibility and the insulation capabilities of polymer substrates. The non-uniform heat distribution in flexible devices allows for improving the local thermal conductivity of the core areas via microchannels, a strategy which is an effective method in thermal engineering and can be well designed to adapt to large deformation of flexible devices. Here, we report the fabrication of microchannels in polyimide (PI) composite film by oxygen plasma etching and subsequent filling the microchannels with graphene. Utilizing the time-domain thermoreflectance method and the finite element method, we confirmed that the local thermal conductivity of graphene-filled region is about 10 times larger than that of the unfilled region, which is comparable to that of the PI composite filled heavily with traditional high thermal conductive fillers. In addition, it was also found that stretching the film did not lower the thermal conductivity of the same region.

Epoxy-matrix composite with low dielectric constant and high thermal conductivity fabricated by HGMs/Al2O3 co-continuous skeleton

Electronic packaging materials with low dielectric constant (Dk) and high thermal conductivity (TC) are of vital importance in mitigating signal delay and enhancing heat dissipation efficiency in modern electronics. However, low Dk and high TC are difficult to complement each other, because high TC filler usually possesses a high Dk. Herein, we have newly designed a composite material simultaneously with low Dk and high TC through hollow glass microspheres (HGMs), boron nitride particles, epoxy resin and reticulated porous ceramic (RPC). The composite material prepared by sintering HGMs and RPC is more effective in improving TC while keeping low Dk. Specifically, the Dk of the newly designed composite is lower than 3.0 with a large TC of 0.96 W/m·K. This new epoxy-matrix composite with both low Dk and high TC can shed new light on designing electronic packaging materials for advanced miniaturized electronics.

A Review on Thermal Properties of Hybrid Polymer Matrix Composites

The requirement and demand of hybrid polymer composites increasing in every filed of applications day by day due to low weight high strength. Since the polymers have found low thermal properties and low strength to high temperature conditions, similarly glass fibre reinforced epoxy resin composites are high strength and stiffness but poor in thermal stability and easily degrades at high temperatures. Which encourages to enhance thermal properties to increase the thermal stability of glass fibre reinforced epoxy resin composites without compromising the strength and stiffness, solution of that is adding high thermal conductivity filler particles to glass fibre reinforced epoxy resin composites, increases the thermal stability and thermal resistivity.

Enhanced the Thermal Conductivity of Polydimethylsiloxane via a Three-Dimensional Hybrid Boron Nitride@Silver Nanowires Thermal Network Filler.

In this work, polydimethylsiloxane (PDMS)-based composites with high thermal conductivity were fabricated via a three-dimensional hybrid boron nitride@silver nanowires (BN@AgNWs) filler thermal network, and their thermal conductivity was investigated. A new thermal conductive BN@AgNWs hybrid filler was prepared by an in situ growth method. Silver ions with the different concentrations were reduced, and AgNWs crystallized and grew on the surface of BN sheets. PDMS-based composites were fabricated by the BN@AgNWs hybrid filler added. SEM, XPS, and XRD were used to characterize the structure and morphology of BN@AgNWs hybrid fillers. The thermal conductivity performances of PDMS-based composites with different silver concentrates were investigated. The results showed that the thermal conductivity of PDMS-based composite filled with 20 vol% BN@15AgNWs hybrid filler is 0.914 W/(m·K), which is 5.05 times that of pure PDMS and 23% higher than the thermal conductivity of 20 vol% PDMS-based composite with BN filled. The enhanced thermal conductivity mechanism was provided based on the hybrid filler structure. This work offers a new way to design and fabricate the high thermal conductive hybrid filler for thermal management materials.

Interfacial thermal conductance across hexagonal boron nitride &amp; paraffin based thermal energy storage materials

It is of vital importance to understand the interfacial thermal conductance between the high thermal conductivity fillers and the phase change thermal energy storage materials in order to enhance the energy storage efficiency. The interfacial thermal conductance across low-dimensional hexagonal boron nitride layers (h-BN) and n-octadecane was calculated with reverse non-equilibrium molecular dynamics methods in this paper. The influences of size effect, molecular arrangement of n-octadecane, layer number of h-BN as well as the defects modified with various functional groups on the interfacial thermal conductance within the temperature range from 273.15 to 373.15 K were investigated, respectively. The results showed that the interfacial thermal conductance of all systems increase with rising temperature and the size effect is inconspicuous. And systems with n-octadecane molecules parallel to the h-BN surface possess the highest interfacial thermal conductance with respect to the vertical and amorphous arrangements. In addition, the interfacial thermal conductance will reduce when the layer number of h-BN increases. In terms of the effect of defects, the systems with h-BN containing the defects modified with hydrogen atoms, i.e., lighter atom, possess higher interfacial thermal conductance. At last, for interpreting deeper mechanism, the vibration power spectrum of the velocity autocorrelation function and the components in different directions were also calculated.