Thermal Conductivity Of Nanocomposites Research Articles

Thermal Conductivity Enhancement of Graphene/Epoxy Nanocomposites by Reducing Interfacial Thermal Resistance

The application of graphene/epoxy composites in microelectronic devices has been greatly limited by interfacial thermal resistance (ITR), which has been widely studied to improve the composites’ thermal conductivity. However, the effect of changing ITR on the thermal conductivity of nanocomposites at the nanoscale remains unclear. Here, several common methods are used to decrease graphene–epoxy ITR and graphene–graphene ITR, and the enhanced degree of nanocomposites’ thermal conductivity is investigated by molecular dynamics. First, the graphene concentration is proven to influence thermal conductivity slightly. Then, nanocomposites are simplified as three representative volume element models: the non-contacted model, the stacked model, and the intersected model. For the non-contacted model, the graphene–epoxy interfacial heat transfer coefficient is increased by 303% by functionalizing the graphene edge with amino groups, and the thermal conductivity is improved by 45.3%. For the stacked model, the graphene–graphene ITR is decreased by 220% when vacancy defects are constructed in the stacking region, and the thermal conductivity is improved by 130%. The intersected model’s heat transfer coefficient in the intersecting node is increased by 590% by connecting two graphene sheets by covalent interactions, and the thermal conductivity is improved by 590%. Finally, the stacked and intersected models are combined to construct the graphene/epoxy nanocomposites with a graphene network, and the thermal conductivity can be adjusted by changing the vacancy coverage rate.

Investigating the thermal properties of n-hexacosane/graphene composite: A highly stable nanocomposite material for energy storage application

The present work demonstrates a modified chemical synthesis route (chemical, hydrothermal methods, and sonication) for fabricating n-hexacosane-impregnated graphene nanosheets (GrPCM) nanocomposite, exhibiting enhanced thermal stability in energy storage. The exfoliation of the graphene sheet during the hydrothermal and sonication process increases the surface area that can absorb n-hexacosane, improving the impregnation and interaction between them. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy were used to examine the morphological and structural characteristics of the GrPCM nanocomposite. The findings demonstrate the loading of n-hexacoreferesane PCM materials into porous nanosheet structures without any chemical reactions. Thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and infrared thermography (IR) were used to measure the latent heat, mass loss, thermal conductivity, and stability of as-synthesized GrPCM nanocomposites. The melting and solidification of GrPCM nanocomposite were observed at 57.11 ◦C with a latent heat of 154.61 J/g and 49.28 ◦C with a latent heat of 147.58 J/g, respectively. The GrPCM nanocomposites showed a thermal conductivity of 12.63 W/m K, which is enhanced compared to that of pure PCM materials of around 0.26 W/m K. Thermal performance measurements using infrared thermography revealed a significant increase in the nanocomposite's thermal conductivity over n-hexacosane, which was attributed to the reduced graphene nanosheet. Further, to study the heat transfer between fluid and different nanocomposites, the GrPCM nanocomposites were investigated inside a thermal storage tank. The experimental results were found in agreement with the COMSOL simulation and confirms GrPCM3 to be an excellent composite material for efficient heat transfer processes.

Interaction of phonons with spherical nanoparticles embedded densely in simple crystalline matrix. Case of nitrogen-palladium nanocomposite

The results of experimental investigations of thermal conductivity of nanocomposites built of palladium spherical nanoparticles embedded in the structure of crystalline nitrogen are presented in this paper. The investigations were carried out on the samples containing the Pd nanospheres of diameters of 6, 8, 10, 12, 18, and 24 nm at the palladium fraction amounting to 15% of the nanocomposite volume. The measurements were performed with a steady-state heat flow method in the temperature interval of 2–35 K. For the analysis of the experimental results, the relaxation time approximation in the frame of the thermal conductivity Debye model was used. The analysis shows that the nitrogen matrix phonons can effectively interact with spherical nanoparticles in, at least, four different mechanisms. Two of those mechanisms, a diffuse scattering by the boundary of two media (which are the matrix and the material of the nanoparticle) and an oscillating resultant of interaction of nanoparticle phonons with the matrix phonons, result in a decrease of the nanocomposite thermal conductivity. The remaining two mechanisms would be considered nonthermal resistive scattering processes: The first of them is the specular scattering of the matrix phonons by the matrix and the nanoparticle material interface. The second one is a forward scattering, in which the matrix phonon penetrates the nanoparticle and afterward penetrates another one without any resistive interaction with phonons of the crystalline matrix. The analysis shows that the nonresistive processes are significantly more frequent in the investigated nanocomposites than the resistive ones. Such a conclusion is in perfect agreement with the results of the analysis of the phonon mean free path in the nitrogen crystal-palladium nanospheres composite.

Multiscale modeling of thermal conductivity of hierarchical CNT-polymer nanocomposite system with progressive agglomeration

Agglomeration of carbon nanotubes (CNTs) is a key phenomenon that affects the effective thermal conductivity of CNT-polymer nanocomposites. This issue needs to be adequately studied especially in the practice of prediction of the effective thermal properties of CNT nanocomposites. In this study, we developed a multiscale model within the framework of effective medium theory to predict the effect of CNT agglomeration on the overall thermal conductivity of the hierarchical CNT-polymer nanocomposite system over a wide range of CNT loading. With an introduced Cauchy cumulative probability function, we developed a new model of CNT agglomeration wherein the CNT volume fraction progressively evolves with the total loading of the CNT fillers in the composite. This model is self-consistent and it leads to a very good agreement with experimental observations. The entire multiscale approach consists of the newly developed model of the progressive agglomeration as well as models that altogether take into account the effect of two types of CNT interfacial thermal resistance and the unique feature of the CNT nanostructure. We highlighted this multiscale approach with its implementation in the prediction of the overall thermal conductivity. Good agreement was confirmed between the prediction and the experimental data. The study shows that the existence of CNT agglomerates downgrades the thermal percolation networks and it can cause a decrease up to 50% in the overall thermal conductivity of the nanocomposite. Two important parameters for the progressive agglomeration model were identified and their influences to the predicted results were examined.

Influence on the thermophysical properties of nanocomposites of the duration of mixing of components in the polymer melt

A set of experimental studies has been carried out to establish the effect of the mixing time of components of nanocomposite materials on their thermal conductivity, specific heat, and density. The physical properties of polypropylene-carbon nanotube composites were to be studied. During the experiments, the duration of mixing of the components in the melt of the polymer varied from 5 to 52 minutes, the mass fraction of the filler ‒ in the range of 0.3...10 %, and nanocomposite temperature – from 290 K to 475 K. It was found that an increase in the mixing time of components of nanocomposite materials could lead to a significant (more than 70 times) increase in their thermal conductivity. It is also shown that the influence of the specified time is limited to its value equal to 27 minutes, above which the change in the thermal conductivity of nanocomposites can be neglected. It was found that the sensitivity of the thermal conductivity of nanocomposites to the time of mixing of their components decreases with a decrease in the mass fraction of the filler. Temperature dependences of the specific heat capacity of the studied composites were obtained by varying the mixing time of their components and the mass fraction of the filler. It was found that with an increase in the specified time, there is a decrease in the heat capacity of nanocomposites, which is significantly manifested only in the region of temperatures close to the melting point of the composite matrix. It is shown that the dependence of the density of nanocomposites on the mixing time of their components in qualitative terms is similar to the corresponding dependence for their thermal conductivity. The obtained data can be used to choose the mixing time of components of nanocomposite materials in the development of appropriate technology for their production

Nanocomposites transformed from polystyrene waste/antimony, barium and nickel oxides nanoparticles with improved thermal and electrical properties

In this experiment, the oxide nanoparticles were synthesized via chemical precipitation and the nanocomposites were produced using in situ polymerization method with varying nanoparticles contents ranged from 0.1 g to 1.0 g for electrical conductivity and from 0.05 g to 0.25 g for thermal conductivity. The electrical and thermal conductivities of nanocomposites were investigated and compared with the values obtained for untreated polystyrene. It was observed that the electrical and thermal properties were higher for the nanocomposites and increase with increasing nanoparticle concentrations in the samples. It can be observed that nanocomposite containing NiO nanoparticles gave a better electrical and thermal conductivity followed by nanocomposite containing BaO nanoparticles and nanocomposite containing Sb2O3 nanoparticles respectively. It can also be observed that nanocomposite containing NiO nanoparticle showed increase in rate of heat transfer from 1.60 W to 2.60 W, while nanocomposite containing BaO nanoparticles recorded increase in rate of heat transfer from 1.40 W to 2.45 W and nanoomposite containing Sb2O3 nanoparticle showed increase in rate of heat transfer from 1.07 W to 2.21 W, as concentration of nanoparticles increased from 0.05 g to 0.25 g respectively. Conclusively, with these results, the nanocomposite containing NiO nanoparticles gave a better thermal and electrical conductivity by having a better conducting filler network inside the matrix than nanocomposite containing BaO nanoparticles and nanocomposite containing Sb2O3 nanoparticles. It is recommended that during the production of polymer nanocomposite, PS/NiO, PS/BaO and PS/Sb2O3 nanocomposites could be used in electrically conductive devices as well as suitable materials for heat transfer applications.

Thermal Percolation Behavior in Thermal Conductivity of Polymer Nanocomposite with Lateral Size of Graphene Nanoplatelet.

In this study, the thermal percolation behavior for the thermal conductivity of nanocomposites according to the lateral size of graphene nanoplatelets (GNPs) was studied. When the amount of GNPs reached the critical concentration, a rapid increase in thermal conductivity and thermal percolation behavior of the nanocomposites were induced by the GNP network. Interestingly, as the size of GNPs increased, higher thermal conductivity and a lower percolation threshold were observed. The in-plane thermal conductivity of the nanocomposite containing 30 wt.% M25 GNP (the largest size) was 8.094 W/m·K, and it was improved by 1518.8% compared to the polymer matrix. These experimentally obtained thermal conductivity results for below and above the critical content were theoretically explained by applying Nan’s model and the percolation model, respectively, in relation to the GNP size. The thermal percolation behavior according to the GNP size identified in this study can provide insight into the design of nanocomposite materials with excellent heat dissipation properties.

ЗАЛЕЖНІСТЬ КОЕФІЦІЄНТА ТЕПЛОПРОВІДНОСТІ НАНОКОМПОЗИТІВ НА ОСНОВІ ПОЛІПРОПИЛЕНУ ВІД ЧАСУ ЗМІШУВАННЯ КОМПОНЕНТІВ

The influence of the duration of the process of mixing components in a polymer melt on the thermal conductivity of nanocomposites has been studied. Recommendations for choosing an energetically rational duration of the mixing process are given.

Temperature-affected mechanical properties of polymer nanocomposites from glassy-state to glass transition temperature

In this study, the effects of nanoparticle content, polymer/particle interphase, aggregation/agglomeration, and temperature variation on the thermo-mechanical properties of polymer nanocomposites, containing spherical nanoparticles, were investigated. The temperature distribution in the samples was evaluated using a new proposed model on the thermal conductivity of nanocomposites (error < 4%) which also represented unique information about the thermal and physical characteristics of the interphase region. Consequently, the temperature dependency of all physical/mechanical parameters (tensile modulus, yield strength, density, specific heat capacity, etc.) was defined and the results were used to simulate the response mechanism of under-stress nanocomposite samples at a specific thermal condition. PS and PMMA nanocomposites samples containing 1, 2, 3 and 4 vol % of the surface-modified silica nanoparticles were prepared via melt mixing and subjected to tensile, rheology, heat conduction and DMA tests whose results were used to evaluate the accuracy and analyzing the theoretical obtained data. It was revealed that the increment of the nanoparticle content increases the thermal conduction coefficients of the polymer/particle interphase region and the entire system while it decreases the interphase thickness. This led to more significant negative effects of the temperature on the mechanical properties of the nanocomposites. Also, at temperatures about Tg, the under-stress samples with the nanoparticle content of 4 vol% experienced the plastic deformation sooner than the samples with nanoparticle content of 1 vol%.

Synthesis and characterization of conducting Polyaniline@cobalt-Paraffin wax nanocomposite as nano-phase change material: Enhanced thermophysical properties

Dispersion of conducting polymer-based nanocomposite in Phase Change Materials (PCMs) tends to enhance the thermophysical properties. Present work aims to synthesize and disperse conducting polyaniline@cobalt nanocomposite within the Paraffin matrix to improve the thermo-physical property. Polyaniline based nanocomposites with 1.0 and 2.0 wt% cobalt (PC1 and PC2) were sonicated with paraffin at different weight ratio of 0.1%, 0.5%, 1%, and 5% and characterization of nanocomposite dispersed phase change material was performed. Thermo-physical properties were analysed by using thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). Thermal conductivity of nanocomposite enhanced paraffin increased with increase in weight% of both PC1 and PC2 till 1% of its weight in paraffin and decreased for 5% of PC1 and PC2 concentration with paraffin. TGA readings observed drop in initial decomposition temperature of PPC1-5% (Paraffin with PC1 in 5% concentration) and PPC2-5% (Paraffin with PC2 in 5% concentration) by an amount of 08% and 12.4% respectively compared with base PCM Paraffin wax. DSC results of PPC1-0.1% and PPC2-0.5% showed 182.04 J/g and 170.86 J/g latent heat of fusion as compared to Paraffin wax. The samples were tested for 200 thermal cycles and the chemical stability and thermal property were compared with the fresh samples.

Enhanced Thermal Conductivity of Polyamide-Based Nanocomposites Containing Graphene Oxide Sheets Decorated with Compatible Polymer Brushes.

Polyamide-based nanocomposites containing graphene platelets decorated with poly(acrylamide) brushes were prepared and characterized. The brushes were grafted from the surface of graphene oxide (GO), a thermally conductive additive, using atom transfer radical polymerization, which led to the formation of the platelets coated with covalently tethered polymer layers (GO_PAAM), accounting for ca. 31% of the total mass. Polyamide-6 (PA6) nanocomposites containing 1% of GO_PAAM were formed by extrusion followed by injection molding. The thermal conductivity of the nanocomposite was 54% higher than that of PA6 even for such a low content of GO. The result was assigned to strong interfacial interactions between the brushes and PA6 matrix related to hydrogen bonding. Control nanocomposites containing similarly prepared GO decorated with other polymer brushes that are not able to form hydrogen bonds with PA6 revealed no enhancement of the conductivity. Importantly, the nanocomposite containing GO_PAAM also demonstrated larger tensile strength without deteriorating the elongation at break value, which was significantly decreased for the other coated platelets. The proposed approach enhances the interfacial interactions thanks to the covalent tethering of dense polymer brushes on 2D fillers and may be used to improve thermal properties of other polymer-based nanocomposites with simultaneous enhancement of their mechanical properties.

A Micromechanics-Based Hierarchical Analysis of Thermal Conductivity of Metallic Nanocomposites with Agglomerated Ceramic Nanoparticles

The influence of agglomeration of SiC nanoparticles on the bulk thermal conducting behavior of aluminum (Al)-based nanocomposites is examined using a micromechanics-based hierarchical technique. The interfacial thermal resistance (ITR) between the ceramic nano-scale particles and the metallic matrix is included in the analysis. The predictions of the micromechanical model considering the agglomeration and ITR are in very good agreement with the available experimental results. The agglomeration of ceramic nanoparticles greatly reduces the thermal conducting coefficient of the Al-based nanocomposites. When the nanoparticle volume fraction is 10%, the thermal conductivity decreases from 132 to 115 W/mK with the formation of nanoparticle agglomeration. The uniform distribution of nanoparticles and the elimination of ITR can lead to a substantial enhancement in the nanocomposite thermal conductivity. When the volume fraction is 10%, the thermal conductivity increases from 115 to 188 W/mK by uniform dispersing the nanoparticles and removing the SiC/Al ITR. Moreover, the effects of amount, and diameter of nano-scale particles as well as the constituent material properties on the bulk thermal conductivity of the SiC nanoparticle-filled Al nanocomposites are examined. When the SiC diameter increases from 35 nm to 3.5 µm, the thermal conductivity of the Al-based composite increases from 132 to 173 W/mK.

A multiscale study of the filler-size and temperature dependence of the thermal conductivity of graphene-polymer nanocomposites

The size of graphene nanofillers and the ambient temperature are two important factors for the effective thermal conductivity of graphene nanocomposites. However, these two issues together are seldom considered in theoretical evaluation of the overall thermal property. By introducing the size-dependent thermal transport mechanisms (quasi-ballistic heat flow and diffusive heat transport) to the Landauer-like theory, we established a new method to calculate the in-plane size and temperature dependence of the thermal conductivity of graphene nanofillers from the nanoscale perspective, which is crucial for the overall thermal conductivity of the nanocomposites. The validity of this approach was confirmed by nonequilibrium molecular dynamics simulation. Then the filler-size- and temperature-dependent thermal conductivity of graphene nanocomposites was calculated via an effective-medium approximation based on Maxwell’s far-field matching at a microscopic level. We highlight this multiscale approach with its implementation in the estimation of the overall thermal conductivity of graphene-polymer nanocomposites. The results are shown to be in close agreement with the experimental observations over the average filler size from 200 to 1000 nm and over the temperature from 300 to 360 K, respectively. This study revealed the significant effects of the graphene-filler size and the ambient temperature on the thermal conductivity of the nanocomposites.

Effect of nanoinclusions on the lattice thermal conductivity of SnSe

We theoretically investigate the effect of nanoparticle(NP) inclusion on the lattice thermal conductivity (κ l ) of SnSe matrix. The theoretical approach involves the prediction of κ l by varying the radius (R), density (D 1), and volume fraction (ε) of NP in SnSe matrix. NP has strong anisotropic effect on the lattice thermal conductivity reduction along the crystallographic direction. We observe the existence of an optimal NP volume fraction that minimizes the nanocomposite's thermal conductivity. At room temperature, this value is found to be ε = 0.317 for which lattice thermal conductivity reduces by 35% with NP (R = 5 nm) compared to pure SnSe. An enhancement in the figure of merit (ZT) around room temperature opens up new opportunities for thermoelectric power generation at moderate temperatures. Even larger enhancement is possible in polycrystalline SnSe which will be helpful for thermoelectric devices.

Self-Healing Polyurethane-Based Nanocomposites Modified with Carbon Fibres and Carbon Nanotubes

Self-healing polyurethanes (PUs) were synthesized as a matrix of nanocomposites containing two fibrous carbon components, i.e., functionalized carbon nanotubes (CNF-OH) and short carbon fibers (CF). Two types of PUs differing in the content of flexible chain segments (40% and 50%) were used. Changes in mechanical strength were analyzed to assess the ability to self-healing of PU-based matrix nanocomposites with experimentally introduced damage in the form of an incision. The healing process was activated by heating the damaged samples at 60°C, for 30 minutes. The addition of CNT-OH and CF caused a slight reduction in the self-healing ability of the nanocomposites as compared to the neat PUs. After heating to 60°C, the nanocomposites self-healed up to 72% of the initial strength of the undamaged samples. The introduction of fibrous components to the polymer matrix improved the thermal conductivity of nanocomposites and facilitated heat transfer from the environment to the interior of the samples, necessary to initiate self-healing. Low content of carbon components in the PU matrix, i.e., 3 wt% of CF and 2 wt% of CNF-OH increased the total work up to fracture of samples after healing by about 53%.

Thermal conductivity of aligned CNT‐polyethylene nanocomposites and correlation with the interfacial thermal resistance

AbstractCarbon nanotube (CNT) reinforced polymer composites have higher thermal conductivity than polymers themselves, so they have wide application prospects in many thermodynamic applications. It is of great significance to deeply understand the thermal conductivity of polymer nanocomposites and its creations, especially with the CNT‐polymer interface. In this article, for CNT‐polyethylene (PE) nanocomposites, the temperature distribution and thermal conductivity, and its correlation with the CNT volume fraction, the interfacial thermal resistance caused by interfacial defects in the CNT‐PE interface region, and mechanical strain were comprehensively studied through molecular dynamics simulation. The results show that the CNT volume fraction and mechanical stretches have remarkable effects on the thermal conductivity of the nanocomposite, and comparatively the influence of the interfacial defects is weak just in the range of the CNT volume fraction &lt;0.3. The thermal conductivity rapidly increases when the volume fraction of CNTs changes from 0 to 0.20. Under tensile strain, the thermal conductivities κ∥ and κ⊥ (being parallel to and perpendicular to the stretching direction, also the direction of nanotubes) display quite different rules. The κ∥ increases linearly with the tensile strain, while the κ⊥ decreases linearly. After the CNT‐PE interfacial defect degree fd of assessing the defect extent was introduced, its dependence on the interfacial thermal resistance Ri was analytically given, and further the influence of the fd on the thermal conductivity was obtained through comparative studies of with/without interfacial defects. We found that the thermal conductivity has a sharply deduce when the fd is in the range of 30% to 60%.

Mechanical, thermal, and conductivity performances of novel thermoplastic natural rubber/graphene nanoplates/polyaniline composites

ABSTRACTConventional polymer blending has a shortcoming in conductivity characteristic. This research addresses the preparation of conductive thermoplastic natural rubber (TPNR) blends with graphene nanoplates (GNPs)/polyaniline (PANI) through melt blending using an internal mixer. The effect of PANI content (10, 20, 30, and 40 wt %) on the mechanical and thermal properties, thermal and electrical conductivities, and morphology observation of the TPNR/GNPs/PANI nanocomposites was investigated. The results showed that the tensile and impact properties as well as thermal conductivity of nanocomposite had improved with the incorporation of 3 wt % of GNPs and 20 wt % of PANI as compared to neat TPNR and reduced with further increase of the PANI content. It was observed that the GNPs and PANI acted as a critical component to improve the thermal stability and electrical conductivity of the TPNR/GNPs/PANI nanocomposites. The most improved conductivity of 5.22 E‐5 S/cm was observed at 3 wt % GNPs and 40 wt % PANI. Variable‐pressure scanning electron microscopy micrograph revealed the good interaction and distribution of GNPs and PANI within TPNR matrix at PANI loadings lower than 30 wt %. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48873.

Prediction of mechanical and thermal properties of polymer nanocomposites reinforced by coiled carbon nanotubes for possible application as impact absorbent

This paper presents three-dimensional finite element modeling of nanocomposite materials made from polyethylene polymer reinforced by coiled carbon nanotubes. A method of Python scripting was used to generate representative volume elements in order to determine the mechanical behavior in elastic and plastic zones as well as effective thermal conductivity using the finite element software. The properties of the nanocomposites are investigated by considering the interphase zone between carbon nanofillers and matrix. The effects of different volume fractions, geometrical parameters, and orientations of the nanofillers on the elastic and thermal characteristics of the nanocomposites are studied considering both cohesive interaction and perfect bonding between the fillers and matrix. Moreover, the effects of applying strain on the effective thermal conductivity of the representative volume elements are analyzed. The results reveal that both stress–strain curves and thermal conductivity coefficients of the nanocomposites are following similar trends vs. the changes of the volume fractions as well as the geometries and orientations of the coiled carbon nanotubes. Analysis of the tensile toughness of all samples reveals that it is affected by both stress and the number of fillers in the representative volume element. In addition, thermal-displacement analysis shows that thermal conductivity coefficient decreases by increasing the applied strain on the representative volume element, while the intensity of decrease of the nanocomposite thermal conductivity depends on the volume fraction and interaction of the nanofillers and interphase zone. Finally, crashworthiness analysis of the nanocomposite material proves that they are appropriate candidates for absorbing energy under impact loadings in comparison to metals.

Effects of metal silicide inclusion interface and shape on thermal transport in silicon nanocomposites

While various silicon nanocomposites with their low thermal conductivity have received much attention for thermoelectric applications, the effects of inclusion interface and shape on thermal transport remain unclear. Here, we investigate thermal transport properties of silicon nanocomposites, in which metal silicide inclusions are periodically arranged within silicon. Using the known phonon dispersion relations and the diffuse mismatch model, we explore the effects of different silicide-silicon interfaces, and using Monte Carlo ray tracing simulations, we explore the effects of silicide inclusion shapes. Our investigations show that the thermal conductivity of silicon nanocomposites can be reduced to the range of nanoporous silicon of the same geometry, depending on the interface density, crystal orientation, and acoustic mismatch. For instance, CoSi2 inclusions of [111] orientation can reduce the nanocomposite thermal conductivity more effectively than inclusion materials with lower intrinsic thermal conductivity, such as NiSi2, when the inclusion density is up to 12.5% with an interface density of 7.5 μm−1. Among the silicide inclusion materials investigated in this work, Mn4Si7 leads to the lowest nanocomposite thermal conductivity due to a combination of low intrinsic thermal conductivity and high acoustic mismatch. Compared to widely spaced and symmetric inclusions such as a circular shape, narrowly spaced and asymmetric inclusions such as a triangular shape are more effective in limiting the phonon mean free path and reducing the nanocomposite thermal conductivity. These findings regarding thermal transport in silicon nanocomposites with respect to inclusion interface and shape will guide optimal material designs for thermoelectric cooling and power generation.

Enhanced thermal conductivity of benzoxazine nanocomposites based on non-covalent functionalized hexagonal boron nitride

High thermal conductivity composites with ideal electrical properties have a wide potential application of electronic packaging systems in aerospace, electrical and electronic fields. Hexagonal boron nitride (h-BN) has been widely used in heat conduction systems due to its good insulation and thermally conductivity. However, its application has been limited due to its surface inertness and low strength. In this work, dopamine (DA) was used to provide a polymer coating (PDA) in the hexagonal boron nitride (h-BN) surface to improve its uniform dispersion and interfacial compatibility in the polymer matrix (A-ph/CE). Polymer nanocomposites with different nanofiller loadings were prepared by simple curing casting procedure. Among them, the thermal conductivity of A-ph/CE/h-BN@PDA nanocomposites with 20 wt% h-BN@PDA increases to 0.71 W/m⋅K. The thermal conductivity of nanocomposites was predicted by using the classical equation Agari model. With the nanofiller amounts increasing, the thermal stability of the nanocomposites also improved. The thermal decomposition and Tg with A-ph/CE/h-BN@PDA nanocomposites with 20 wt% h-BN@PDA increase to 350.8 °C and 339.9 °C, respectively. And its dynamic storage modulus reaches 7390 Mpa. And the prepared composites had ideal dielectric properties. The dielectric constant and dielectric loss of 20 wt% A-ph/CE/h-BN@PDA nanocomposites at 1000 Hz were 5.72 and 0.0148 respectively, the volume resistivity was 4.08 × 108 Ω cm, and dielectric breakdown strength was 61.6 kV/mm. The nanofiller (h-BN@PDA) reinforced polymer nanocomposites (A-ph/CE/h-BN@PDA) prepared in this work has good thermal conductivity, ideal electrical properties, and excellent thermal stability, etc., which has great potentiality in the demanding field of electronic packaging.