High Thermal Conductivity Values Research Articles

Manufacture and study the mechanical, thermal and physical properties of plastic wood

Abstract This study focuses on evaluating the mechanical properties and thermal conductivity of unsaturated polyester (UPE) composites reinforced with Pistacia shells (Pi-S). Wood-plastic composites were prepared using UPE reinforced with Pi-S at different weight ratios (50%, 60%, 70%). The main objective of this work is to recycle Pistacia shells in significant proportions and assess the impact of using Pi-S as reinforcing materials in UPE. Mechanical tests, such as Shore D hardness, impact resistance, and compressive strength, were employed to evaluate the mechanical properties of the composites. The results showed that the 50% weight ratio achieved the highest values in all tests compared to other ratios (60%, 70%). Impact resistance increased to 10.15 Kj/m2 at the 50% weight ratio, followed by the 60% weight ratio with the highest impact resistance. The results also indicated a slight decrease in Shore D hardness with an increase in the weight ratio and a decrease in compressive strength. Regarding thermal conductivity, the highest thermal conductivity value was at the 50% weight ratio, with a value of 0.68118762 W/mk. It then decreased at the other weight ratios but remained higher than the thermal conductivity of pure unsaturated polyester. This technique allows for the full utilization of Pistacia shells in the wood-plastic industry, contributing to various applications such as wooden and plastic flooring, surfaces, doors, and more.

Thermal Conductivity of 3D Printed Metal using Extrusion-based Metal Additive Manufacturing Process

Abstract In this study, the thermal conductivity of 3D-printed 316L stainless steel parts using the bound metal deposition (BMD) method, an extrusion-based 3D printing technology, were examined experimentally and validated numerically using finite element analysis (FEA). Various critical printing parameters were examined, including infill density, skin overlap percentage, and print sequence to study their effect on the printed thermal conductivity. A heat conduction experiment was performed on the 3D-printed samples of 316L stainless steel followed by a FEA. The results from this investigation revealed that an increase in 3D printing infill density correlated with a rise in effective thermal conductivity. Conversely, a substantial decrease in thermal conductivity was observed as porosity increased. For instance, at a porosity level of 16.5%, the thermal conductivity experienced a notable 33% reduction compared to the base material. The skin overlap percentage, which governs how much the outer shell of adjacent layers overlaps, was found to impact heat transfer across the overall part surface. A higher overlap percentage was associated with improved thermal conductivity, although it could affect the surface finish of the part. Furthermore, the study explored the print sequence, focusing on whether the outer wall or infill was printed first. Printing the outer wall first resulted in higher thermal conductivity values than that obtained from printing the infill first. Therefore, it is crucial to carefully consider these factors during the BMD 3D printing process to achieve the desired thermal conductivity properties.

Nanostructured inclusions enhancing the thermoelectric performance of Higher Manganese Silicide by modulating the transport properties

Higher Manganese Silicides (HMS) are the best p-type materials beneficial for intermediate-temperature range thermoelectric device applications due to their high thermal stability and inexpensive constituent elements. Although the cost-effective HMS materials possess high thermal stability, they are concerned with high thermal conductivity values. The nanocomposite approach was promised to lower the thermal transport properties without affecting the electrical transport properties, which is experimented in the present work. The higher manganese silicide with varying weight percentages of nano-structured Si0.8Ge0.2B0.02 inclusions was experimented to decrease the thermal conductivity and to enhance the electrical properties. The lowest thermal conductivity value of ≃ 2.24 W/mK was reported with 2 wt% Si0.8Ge0.2B0.02 addition in HMS material. Also, the HMS-2 wt. % Si0.8Ge0.2B0.02 improved the transport properties, electrical conductivity and Seebeck coefficient values of ≃ 4 × 104 S/m and ≃ 220 μV/K respectively. Furthermore, various mathematical models were proposed here to simulate the composite approach results, which were then correlated with experimental results.

Heavy elemental compound addition enhancing thermoelectric performance of Chromium Silicide synthesized by Spark plasma sintering

Silicide-based materials drive great potential in developing mid-temperature range thermoelectric generators (TEGs) applications. However, realizing the efficient and stable silicide materials is still a constraint for its real potential device applications. Chromium silicide will likely become p-type thermoelectric materials in this direction for thermoelectric power generation applications. However, high thermal conductivity values impede the figure-of-merit (zT). The present work adopts the chromium silicide, adding different weight percentages of well-known ZrCoSbSn compounds employing the compaction spark plasma sintering (SPS) technique. By adopting these combinations, the thermal conductivity is significantly reduced by enhanced scattering of heat-carrying phonons by multiple interfaces. Also, the maximum power factor value of ≃ 2.1 × 10−3 W/mK2 is achieved by employing a CrSi2 -ZrCoSbSn compound addition. The enhanced figure-of-merit value (zT) ≃ 0.26 is realized in the temperature at 623 K for the CrSi2-5wt% ZrCoSbSn compound material.

Effect of Weave and Weft Type on Mechanical and Comfort Properties of Hemp-Linen Fabrics.

In this study the influence of fabric weave (plain, twill, and panama) and weft type (flax and hemp yarns) on selected mechanical and comfort properties of six fabrics was analyzed. The results showed that tear and abrasion properties were most affected by the weave. The tensile properties of the linen fabrics were not significantly different when weft hemp yarns were used instead of flax. Fabrics with the same weave seemed to be equally resilient to abrasion regardless of the type of weft. By contrast, the hemp weft yarns favorized the physical and comfort properties of the investigated fabrics. For the same weave, the hemp-linen fabrics were slightly lighter and exhibited lower bulk density, significantly larger air permeability, and improved moisture management properties. Although the results of maximum thermal flux (Qmax) suggested a cooler sensation of the linen fabrics with panama and twill, the hemp-linen fabric with a plain weave seemed to be the optimal choice when a cool sensation was desired. Higher thermal conductivity values also suggested slightly better heat transfer properties of the hemp-linen fabrics, and these were significantly influenced by the weave type. The results clearly indicated the advantages of using hemp for improving physical and specific comfort properties of linen fabrics.

Glass fiber strengthened BNNS/ST/polyolefin composites with high dielectric constant and high thermal conductivity

The present research presents an examination of the consequential effects brought about by the introduction of short-cut E-glass fibers (GF) on the properties of high-dielectric constant, high-thermal conductivity microwave composite systems (xGF/(8-x)BNNS/78 wt%ST/polyolefin, x = 0-8 wt%, BNNS: hexagonal boron nitride nanosheets). The GF is modified using KH550, with the success of the surface modification definitively confirmed by X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR). All components are found to exhibit consistently ultra-high and stable dielectric constants within the 8–12 GHz frequency range (Dk = 17.7–18.08). Based on thermogravimetry analysis (TGA) and dynamic mechanical analysis (DMA) results, the incorporation of modified GF improve the thermal stability of the composite materials, enhancing thermal decomposition temperature, residual carbon content and glass transition temperature. Furthermore, replacing BNNS with GF significantly amplifies the mechanical properties of the composite substrate. This substitution leads to a notable reduction in the coefficient of thermal expansion (CTE) in all directions while simultaneously increasing the bending and tensile strength. At the same time, the composites can maintain reasonably high thermal conductivity values. Overall, with a GF concentration of 4 wt%, the composite showcases an appreciable increase in dielectric constants (17.81), a high thermal conductivity (1.3 W/m·K) and enhances mechanical properties (cross-plane CTE: 15.44 μm/(m·°C), in-plane CTE: 26.06 μm/(m·°C), bending strength: 65.6 MPa, tensile strength: 17.42 MPa). Considering its superior performance metrics, the composite can be identified as an optimal choice for microwave composite dielectric substrate material.

Mesoscopic glass transition model: Influence of the cooling rate on the structure refinement

<p>The process of glass transition during the quenching in the domain with the cold wall has been numerically simulated. We have implemented the temperature-dependent form of the previously proposed theoretical model, which combined the heat transfer in the domain and the gauge theory of glass transition, assuming the presence of topologically stable distortions (disclinations) in the forming solid. The competition between crystallization (formation of polycrystalline structure) and the formation of the amorphous disordered phase has been shown. At the relatively slow cooling rates corresponding to the formation of the crystalline phase, we observed a columnar to equiaxed transition qualitatively similar to the observed in many metallic alloys. The moving front followed the equilibrium isotherm corresponding to the equilibrium temperature of transition in the disclinations subsystem, although front drag resulted in the effect of kinetic undercooling and the emergence of the maximum velocity of the crystallization front. High thermal conductivity values associated with the substantial heat flux lead to the bulk amorphous state. The dynamics of the coarsening of the primary amorphous structure depended on the annealing temperature.</p>

Effects of a liquid metal co‐filler on the properties of epoxy/binary filler composites

AbstractLiquid metals (LMs) with high fluidity and high thermal conductivity (TC) are receiving considerable attention in the research on thermal management polymer composites as alternatives to conventional rigid solid fillers or as co‐fillers to overcome the trade‐off between TC and composite processability at high filler loads. While most previous studies have investigated the effects of LM fillers in soft elastomeric matrices, their effects on the composite properties with rigid matrices, such as epoxy‐based polymers, have not been discussed extensively. Herein, we investigated the effects of LM eutectic Ga‐In (EGaIn) as a co‐filler on the properties of rigid epoxy‐based composites with a binary filler (Al2O3/EGaIn) system. The increase in the volume fraction of LM fillers significantly improves the processability of uncured precursor composites but markedly decreases the mechanical strength of the cured composites at their high loads—the latter effects have rarely been examined in previous studies. However, with adequate LM loads, the composites exhibited superior mechanical properties compared with the all‐solid‐filler system, withstanding a surprisingly high compressive load (~100 kN) under which the all‐solid‐filler system fractured. Furthermore, the epoxy/binary filler composites exhibited reasonably high TC values (~1 W/mK) comparable to that of commercial epoxy molding compounds, suggesting their potential applicability for electronic packaging.

Giant adiabatic temperature change and its direct measurement of a barocaloric effect in a charge-transfer solid

Solid refrigerants exhibiting a caloric effect upon applying external stimuli are receiving attention as one of the next-generation refrigeration technologies. Herein, we report a new inorganic refrigerant, rubidium cyano-bridged manganese–iron–cobalt ternary metal assembly (cyano-RbMnFeCo). Cyano-RbMnFeCo shows a reversible barocaloric effect with large reversible adiabatic temperature changes of 74 K (from 57 °C to −17 °C) at 340 MPa, and 85 K (from 88 °C to 3 °C) at 560 MPa. Such large reversible adiabatic temperature changes have yet to be reported among caloric effects in solid–solid phase transition refrigerants. The reversible refrigerant capacity is 26000 J kg−1 and the temperature window is 142 K. Additionally, cyano-RbMnFeCo shows barocaloric effects even at low pressures, e.g., reversible adiabatic temperature change is 21 K at 90 MPa. Furthermore, direct measurement of the temperature change using a thermocouple shows +44 K by applying pressure. The temperature increase and decrease upon pressure application and release are repeated over 100 cycles without any degradation of the performance. This material series also possesses a high thermal conductivity value of 20.4 W m−1 K−1. The present barocaloric material may realize a high-efficiency solid refrigerant.

The Dielectrophoretic Alignment of Biphasic Metal Fillers for Thermal Interface Materials.

Pad-type thermal interface materials (TIMs) with composite structures are required to exhibit high thermal conductivity while maintaining conformal contact with the heat sink, which is strongly influenced by the type and content of the thermally conductive filler. This study presents that biphasic metal particles can be effectively aligned using the dielectrophoretic chaining (DEP-C) mechanism, thereby enhancing the thermal conductivity of a pad-type TIM. A eutectic gallium-indium (EGaIn) alloy liquid metal and solid copper were used as the filler materials with two different phases. The biphasic metal particle mixture of EGaIn and Cu (EGaIn-Cu) were better aligned by DEP-C than when they presented individually because fusion between the two particles increased the effective size. As expected, the thermal conductivity of the TIM composites increased when DEP-C aligned the filler. Notably, TIMs with both EGaIn-Cu fillers showed the largest increase in thermal conductivity, of up to 64.6%, and the highest thermal conductivity values after DEP-C application compared to TIMs with only the EGaIn or Cu filler. Finally, the heat dissipation performance of the TIM composite on a lit light-emitting diode is shown, where the TIM with DEP-C-aligned fillers exhibits improved performance.

Improving the performance of room temperature magnetic regenerators using Al2O3-water nanofluid

The present study examines the use of Al2O3-water nanofluid as the heat transfer fluid in a magnetic regenerator and evaluates the improved cooling capabilities of the device. Room-temperature magnetic refrigeration exploits a special property of some materials, the “magnetocaloric effect”, that is the ability of the material to change its temperature when exposed to rapid changes in an external magnetic field. As adiabatic magnetic field variations of 1 to 1.5 T produce a small temperature change of a few degrees, active magnetic regeneration is often employed to achieve larger temperature spans for practical cooling applications. The effectiveness of this process greatly depends on the properties of the heat transfer fluid, which is usually a water-based mixture. High values of the fluid thermal conductivity enhance heat transfer allowing for higher cooling capacity. This work presents the outcome of a comprehensive simulation study evaluating the improved performance of a gadolinium-based regenerator using a water-based mixture with added Al2O3 nanoparticles as the heat transfer fluid. In this analysis, both the volume concentration of nanofluid and the particle size were varied. The combined effect of heat transfer enhancement and pressure drop increase was also investigated through the second law efficiency. On average, a more than 15 % increase in cooling capacity was observed when using Al2O3 (6 % vol, 20 nm particles), and the COP can be preserved or increased with a properly tuned regulation of the cycle time and the utilization factor of the regenerator.

Conflicting primary and secondary properties of thermoelectric devices – A case study on the thermomechanical behavior of ZrNiSn

While the primary properties of thermoelectric devices, directly related to the conversion efficiency, are considered in design efforts, the secondary (thermomechanical) properties are often ignored or overlooked even though they can lead to failure. Here, thermomechanical properties of thermoelectric ZrNiSn in the amorphous and crystalline state (space group F-43m), comprising thermal conductivity, thermal expansion, elastic (Young’s) modulus, and thermal shock, are studied using density functional theory and two phonon models. Thermal conductivity is also a key primary property for thermoelectric applications. Amorphous ZrNiSn exhibits a fourfold lower thermal conductivity than the crystalline counterpart due to high phonon–phonon scattering, which is conducive to thermoelectric performance. However, this is conflicting since a high thermal conductivity value is required to attain high resistance to thermal shock. Due to stronger bonds in the crystalline counterpart, facilitated by the stronger Zr3d–Ni3d and Sn5p–Ni3d hybridization and higher coordination than in the amorphous state, the linear coefficient of thermal expansion is lower, and the elastic modulus is higher. Hence, the crystalline state yields higher resistance to thermal shock. It is suggested that samples entailing both amorphous and crystalline regions can concurrently satisfy the primary and secondary requirements for enhanced efficiency and durability.

Experimental Investigation on Thermal Conductivity of Palm Oil and Zinc Oxide PFAE-based Nanofluids

Vegetable oil (VO) have been constantly researched as an alternative to the conventional mineral oil (MO) in the application of transformer insulation liquid. VO is deemed as a suitable replacement for MO as they are a renewable source, cheaper in price, and have a high thermal conductivity, high flashpoint, and high breakdown voltage value. In addition, the trending interest in nanofluids has made it possible to further improved the insulating properties of VOs. This paper reports the experimental results of thermal conductivity test of Palm oil-based nanofluids and Palm fatty acid ester (PFAE)-based nanofluids. The nanoparticles used in this work is Zinc Oxide (ZnO) <50nm nano powder and the nanofluid (NF) samples are varied by low, medium and high concentrations. The test was conducted at 9 different temperatures from 25°C to 65°C with 5°C gap. The result shows that a low and medium concentration nanofluid has an improvement in thermal conductivity value, up to 42.6% and 59.5% respectively for palm oil-based nanofluid. Meanwhile, the high concentration palm oil-based nanofluid has lower enhancement in thermal conductivity value at certain temperatures. As for PFAE-based nanofluids, the thermal conductivity value has improved by up to 27% and 14.4% for medium and high concentration respectively. Nanofluids with medium concentration of ZnO, has the highest enhancement in insulating and cooling properties for both palm oil and PFAE-based nanofluids. This observation is supported by the kinematic viscosity value of the mentioned nanofluid.

NiTiCu shape memory alloys with ultra-low phase transformation range as solid-state phase change materials

Shape memory alloys (SMAs) have been demonstrated as effective phase change materials (PCMs) for thermal energy storage (TES) applications. NiTi and NiTiHf SMAs have shown high TES performance, as quantified by PCM figure of merit (FOM) but their use in applications requiring narrow operation temperature windows is limited by large overall phase transformation ranges (OTR). This work investigates NiTiCu SMAs as PCMs with high FOM and low OTR. A full-factorial design of experiments is used to examine 24 NiTiCu compositions. The compositions were fabricated using vacuum arc melting and their phase transformation and thermophysical properties were characterized using calorimetry, thermal diffusivity, and density measurements. The NiTiCu compositions spanned martensitic transformation temperatures between -22 and 84 °C and exhibited greater FOM (250–1050 106J2K−1s−1m−4), compared to traditional PCMs (typically <100 106J2K−1s−1m−4), with major benefits associated with higher density and higher thermal conductivity values. In addition, the NiTiCu compositions in this study show ultra-low OTR (12–20 °C) compared to NiTi and NiTiHf SMAs (>50 °C), enabling utility in narrow operating temperature windows. Thermal cycling was also performed revealing extreme stability of martensitic transformation with only 0.04 °C shift in transformation temperatures after 80 thermal cycles, which is the lowest reported to date in SMA literature.

Carbides of transition metals: Properties, application and production. Review. Part 2. Chromium and zirconium carbides

The properties, application, and methods for producing chromium and zirconium carbides are considered. These carbides are oxygen-free refractory metal-like compounds. As a result, they are characterized by high values of thermal and electrical conductivity. Their hardness is relatively high. Chromium and zirconium carbides exhibit significant chemical resistance in aggressive environments. For these reasons, they have found application in modern technology. Chromium carbide is used mainly as component of surfacing mixtures to create protective coatings that resist intensive abrasive wear, including at elevated temperatures (up to 800 °C) in oxidizing environments. This compound is also used in the manufacture of tungsten-free hard alloys and carbide steels. Chromium carbide, along with vanadium carbide, is used as a grain growth inhibitor in WC – Co hard alloys. Powdered zirconium carbide can be used to polish the surface of items made of ferrous and non-ferrous metals. The properties of refractory compounds depend on the content of impurities and dispersion (particle size). To solve a specific problem associated with the use of refractory compounds, it is important to choose the right method for their preparation, to determine the permissible content of impurities in the initial components. This leads to the existence of different methods for the synthesis of carbides. The main methods for their preparation are: synthesis from simple substances (metals and carbon), metallothermal and carbothermal reduction. Plasma-chemical synthesis (vapor-gas phase deposition) is also used to obtain carbide nanopowders. A characteristic is given to each of these methods. Information on the possible mechanism of the processes of carbothermal synthesis is presented.

Improving the thermophysical aspects of innovative clay brick composites for sustainable development via TiO2 and rGO nanosheets

In the current work, distinctive nanoscale fillers, such as reduced graphene oxide (rGO) and titanium oxide (TiO2), were synthesized to open up novel opportunities to enhance the thermal performance of clay brick composites. Innovative clay-based nanocomposite bricks with various doping levels, including untreated clay, clay–rGO, clay–TiO2 and clay–rGO–TiO2, were synthesized for the first time to enhance brick's thermophysical performance. Physical observations of microstructure, shrinkage, morphology, density, porosity, as well as thermophysical characteristics of the composite clay bricks were investigated. Incorporating a varying quantity of rGO and TiO2 nanoparticles (NPs) into the clay matrix resulted in a variation in peak intensity within the lattice structure, along with a rise in the estimated crystallite size to 30.3 nm of clay–rGO–TiO2 composites. Meanwhile, the wealthy hydroxyl groups of TiO2 and rGO NPs boost the formation of many hydrogen bonds well distributed within clay structures, leading to rigid filler adherence. Moreover, the apparent porosity rose (i.e. from 24.01% to 43.64%) due to the creation of new intermolecular covalent bonds and hydrogen bonds between clay–H2O and metal oxides–OH groups. This porosity results in lighter bricks (i.e. bulk density decomposes from 2.02 to 1.41 g/cm3) with a pore size on the order of 3.5 µm. These variations are supported by the differ-dense microstructure presented in the SEM images. Interestingly, the Clay–rGO–TiO2 mixture not only has a high thermal conductivity value (0.44 W/mK), but also exhibits exceptional thermal diffusivity (4.1 mm2/S). The existence of TiO2 NPs, along with rGO nanosheets with a large surface area and high porosity features, which efficiently permits liquid absorption of the interlayers is the main explanation for these findings.

THERMAL CONDUCTIVITY OF PARTITION BOARD BY POLYMER COMPOSITE WITH FILLER EMPTY FRIUT BUNCHES FIBRES

Utilization and management of Empty Fruit Bunches (EFB) fibre continue to develop as the main ingredient and additional material used in various industrial products. The technological breakthrough targeted in this study is the developed EFB fibre as a filler in polymer composite partition boards which are used as heat retainers in the interior construction of buildings. The partition board is a heat insulator, and its thermal conductivity is affected by mass density and porosity. The purpose of this study was to determine the heat resistance of partition board products to reduce the heat entering the room from outside by propagating through walls exposed to direct sunlight. The test method used is adopted from ASTM C177-13, namely the measurement of heat propagation with a modification of the heat source of 40 watts. In addition, mass density tests (referring to SNI 03-2105-2006) and water absorption (referring to ASTM D5229M-12) were also carried out on the product. The specimens were based on the formation of Singapore Highpolymer Chemical Product (SHCP) 2667 WNC polyester resin matrix partition board with weight fractions of 25%, 30%, and 35% chop strand mat (CSM). The test results show that the highest thermal conductivity value is found on the board with a weight fraction of 25%, namely 0.153 W/m.°C with a mass density of 1.16 g/cm3 and a water absorption capacity of 3.38%. However, the lowest thermal conductivity value was found in the fibre with weight fraction of 35%, namely 0.147 W/m. °C at a mass density of 1.24 g/cm3 and a water absorption capacity of 3.75%.

Influence of powder properties and mixing technique under different conditions, on the densification and thermal conductivity of AlN for solar thermal applications

In this study, a novel approach is presented which can be utilized to enhance the thermal conductivity and densification of sintered AlN pellets. AlN pellets with a CaO additive were produced by spark plasma sintering. The influence of CaO powder properties such as particle size (micron-, submicron- and nano-scale), dispersion, flowability and structural characteristics, on the mixing behavior of AlN and CaO mixed powders, and on the porosity and thermal conductivity of AlN pellets, were investigated. Additionally, the influence of mixing conditions, including additive content and rotational speed in a novel high-shear mixer (Picomix), were studied and various mixing techniques were compared. The results indicate that when the CaO content of the AlN pellets is increased to 3 wt%, their thermal conductivity rises from 48.1 W/m·K to 112.9 W/m·K. This increase can be attributed to the formation of a liquid phase, and to a reduction in pellet porosity during sintering. Furthermore, when the rotational speed of the mixer is increased to 5000 rpm, the pellets’ thermal conductivity further rises to 126.2 W/m·K. This improvement is a result of the enhanced dispersion of CaO in the mixed powder. The shearing forces in the Picomix facilitate the coating of AlN particles with submicron- or nano-scale CaO particles, thereby improving the flowability of the mixed powder and narrowing the particle size distribution. This further improves the liquid phase distribution, thus enhancing the thermal conductivity of the AlN pellets (135.3 W/m·K). The novel high-shear mixer (Picomix) has demonstrated enhanced performance when compared with traditional mixing techniques (ball milling and manual mixing), since it involves a solvent-free process, is faster, has a lower energy consumption, causes less powder-oxidation and leads to a higher value of thermal conductivity, making it an excellent choice for the preparation of mixed powders for solar thermal applications.

The Effect of Porosity on the Thermal Conductivity of Highly Thermally Conductive Adhesives for Advanced Semiconductor Packages.

This study suggests promising candidates as highly thermally conductive adhesives for advanced semiconductor packaging processes such as flip chip ball grid array (fcBGA), flip chip chip scale package (fcCSP), and package on package (PoP). To achieve an extremely high thermal conductivity (TC) of thermally conductive adhesives of around 10 Wm-1K-1, several technical methods have been tried. However, there are few ways to achieve such a high TC value except by using spherical aluminum nitride (AlN) and 99.99% purified aluminum oxide (Al2O3) fillers. Herein, by adapting highly sophisticated blending and dispersion techniques with spherical AlN fillers, the highest TC of 9.83 Wm-1K-1 was achieved. However, there were big differences between theoretically calculated TCs that were based on the conventional Bruggeman asymmetric model and experimentally measured TCs due to the presence of voids or pores in the composites. To narrow the gaps between these two TC values, this study also suggests a new experimental model that contains the porosity effect on the effective TC of composites in high filler loading ranges over 80 vol%, which modifies the conventional Bruggeman asymmetric model.

Modification of Multi-Functional Composites by Using Particles with High Thermal Conductivity to Improve Heat Management and Electromagnetic Shielding Performance

Packaging materials with thermal management and electromagnetic protection are designed to develop miniaturized high-power airborne electronic equipment and meet the overall design requirements. In this study, graphene/paraffin composite material modified by high thermal conductivity particles is used to improve thermal conductivity, thermal management efficiency, and electromagnetic performance. Four kinds of high thermal conductivity particles including nickel, silver, copper, and hexagonal boron nitride were selected. Modified phase change material composite with carbon matrix was prepared by melt blending and pressure molding. Microstructure, thermal conductivity, latent heat, and electromagnetic properties were tested. Particles with different high thermal conductivity values could be uniformly distributed in the composite material by melt blending. Adding particles can improve the thermal conductivity of the composite to varying degrees, and copper and silver can also improve the electromagnetic shielding effectiveness of the composite. The composite material added with silver particles has the best modification effect, with a 92.3% increase in thermal conductivity and a 32.8% increase in shielding efficiency.