The superior effect of edge functionalization relative to basal plane functionalization of graphene in enhancing the thermal conductivity of polymer–graphene nanocomposites – a combined molecular dynamics and Green's functions study (original) (raw)
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2022
To achieve high thermal conductivity (k) of polymer graphene nanocomposites, it is critically important to achieve efficient thermal coupling between graphene and its surrounding polymers through effective functionalization schemes. In this work, we demonstrate that edge-functionalization of graphene nanoplatelets (GnPs) can enable a larger enhancement of effective thermal conductivity in polymer-graphene nanocomposites, relative to basal plane functionalization. Effective thermal conductivity for edge case is predicted, through molecular dynamics simulations, to be up to 48% higher relative to basal plane bonding for 35 wt.% graphene loading with 10 layers thick nanoplatelets. This unique result opens up promising new avenues for achieving high thermal-conductivity polymer materials, which is of key importance for a wide range of thermal management technologies. The anisotropy of thermal transport in single layer graphene leads to very high in-plane thermal conductivity (~2000 W/mK...
Model Approach to Thermal Conductivity in Hybrid Graphene–Polymer Nanocomposites
Molecules
The thermal conductivity of epoxy nanocomposites filled with self-assembled hybrid nanoparticles composed of multilayered graphene nanoplatelets and anatase nanoparticles was described using an analytical model based on the effective medium approximation with a reasonable amount of input data. The proposed effective thickness approach allowed for the simplification of the thermal conductivity simulations in hybrid graphene@anatase TiO2 nanosheets by including the phenomenological thermal boundary resistance. The sensitivity of the modeled thermal conductivity to the geometrical and material parameters of filling particles and the host polymer matrix, filler’s mass concentration, self-assembling degree, and Kapitza thermal boundary resistances at emerging interfaces was numerically evaluated. A fair agreement of the calculated and measured room-temperature thermal conductivity was obtained.
Duality of the interfacial thermal conductance in graphene-based nanocomposites
Carbon, 2014
The thermal conductance of graphene-matrix interfaces plays a key role in controlling the thermal properties of graphene-based nanocomposites. Using atomistic simulations, we found that the interfacial thermal conductance depends strongly on the mode of heat transfer at graphene-matrix interfaces: if heat enters graphene from one side of its basal plane and immediately leaves it through the other side, the corresponding interfacial thermal conductance, G across , is large; if heat enters graphene from both sides of its basal plane and leaves it at a position far away on its basal plane, the corresponding interfacial thermal conductance, G non-across , is small. For a single-layer graphene immersed in liquid octane, G across is 150MW/m2KwhileGnon−acrossis150 MW/m 2 K while G non-across is 150MW/m2KwhileGnon−acrossis5 MW/m 2 K. G across decreases with increasing multi-layer graphene thickness (i.e., number of layers in graphene) and approaches an asymptotic value of 100 MW/m 2 K for 7-layer graphenes. G non-across increases only marginally as the graphene sheet thickness increases. Such a duality of the interface thermal conductance for different probing methods and its dependence on graphene sheet thickness can be traced ultimately to the unique physical and chemical structure of graphene materials. The ramifications of these results in areas such as the optimal design of graphene-based thermal nanocomposites are discussed.
Nanomaterials, 2020
Thermal conductivity (k) of polymers is usually limited to low values of ~0.5 Wm−1K−1 in comparison to metals (>20 Wm−1K−1). (100)T3//(926)T4 The goal of this work is to enhance thermal conductivity (k) of polyethylene–graphene nanocomposites through simultaneous alignment of polyethylene (PE) lamellae and graphene nanoplatelets (GnP). Alignment is achieved through the application of strain. Measured values are compared with predictions from effective medium theory. A twin conical screw micro compounder is used to prepare polyethylene–graphene nanoplatelet (PE-GnP) composites. Enhancement in k value is studied for two different compositions with GnP content of 9 wt% and 13 wt% and for applied strains ranging from 0% to 300%. Aligned PE-GnP composites with 13 wt% GnP displays ~1000% enhancement in k at an applied strain of 300%, relative to k of pristine unstrained polymer. Laser Scanning Confocal Microscopy (LSCM) is used to quantitatively characterize the alignment of GnP flakes...
Thermal transmittance in graphene based networks for polymer matrix composites
Graphene nanoribbons (GNRs) can be added as llers in polymer matrix composites for enhancing their thermo-mechanical properties. In the present study, we focus on the eect of chemical and geometrical characteristics of GNRs on the thermal conduction properties of composite materials. Congurations consisting of single and triple GNRs are here considered as representative building blocks of larger ller networks. In particular, GNRs with dierent length, relative orientation and number of cross-linkers are investigated. Based on results obtained by Reverse Non-equilibrium Molecular Dynamics simulations, we report correlations relating thermal conductivity and thermal boundary resistance of GNRs with their geometrical and chemical characteristics. These eects in turn aect the overall thermal transmittance of graphene based networks. In the broader context of eective medium theory, such results could be benecial to predict the thermal transport properties of devices made of polymer matrix composites, which currently nd application in energy, automotive, aerospace, electronics, sporting goods, and infrastructure industries.
Thermally Conductive Graphene-Polymer Composites: Size, Percolation, and Synergy Effects
The rapidly increasing device densities in electronics dictate the need for efficient thermal management. If successfully exploited, graphene, which possesses extraordinary thermal properties, can be commercially utilized in polymer composites with ultrahigh thermal conductivity (TC). The total potential of graphene to enhance TC, however, is restricted by the large interfacial thermal resistance between the polymer mediated graphene boundaries. We report a facile and scalable dispersion of commercially available graphene nanoplatelets (GnPs) in a polymer matrix, which formed composite with an ultrahigh TC of 12.4 W/m K (vs 0.2 W/m K for neat polymer). This ultrahigh TC was achieved by applying high compression forces during the dispersion that resulted in the closure of gaps between adjacent GnPs with large lateral dimensions and low defect densities. We also found strong evidence for the existence of a thermal percolation threshold. Finally, the addition of electrically insulating boron-nitride nanoparticles to the thermally conductive GnP-polymer composite significantly reduces its electrical conductivity (to avoid short circuit) and synergistically increases the TC. The efficient dispersion of commercially available GnPs in polymer matrix provides the ideal framework for substantial progress toward the large-scale production and commercialization of GnP-based thermally conductive composites.
Heat conduction in graphite-nanoplatelet-reinforced polymer nanocomposites
Applied Physics Letters, 2006
Heat transport in polymer nanocomposites reinforced with graphite nanoplatelets (GNPs) is studied using high-precision thermal conductivity measurements. The resistance to heat conduction across interfaces between GNPs and the polymer matrix has a strong effect on energy transport in the nanocomposites. The thermal conductivity is observed to increase when GNPs are pretreated with nitric acid to improve interfacial bonding. The improvement in the thermal conductivity, however, is much smaller than the corresponding improvement in mechanical properties. The thermal interface resistance extracted from the present thermal conductivity data is comparable to that obtained from the previously reported data on carbon nanotube suspensions. (
Nanoscale, 2017
The effect of simultaneous alignment of polyethylene (PE) lamellae and graphene nanoplatelets (GnP) on the thermal conductivity (k) of PE-GnP composites is investigated. Measurements reveal a large increase of 1100% in k of the aligned PE-GnP composite using 10 wt% GnPs relative to unoriented pure PE. The rate of increase of k with applied strain for the pure PE-GnP composite with 10 wt% GnP is found to be almost a factor of two higher than the pure PE sample, pointing to the beneficial effect of GnP alignment on k enhancement. Aligned GnPs are further found to be 3 times as effective in enhancing k as in the randomly oriented configuration. Enhancement in k is correlated with the alignment of PE lamellae and GnPs through wide-angle X-ray scattering and polarized Raman spectroscopy. At the maximum applied strain of 400% and using 10 wt% GnPs, a composite k of 5.9 W mK(-1) is achieved. These results demonstrate the great potential of simultaneous alignment effects in achieving high k...
Enhanced thermal conductivity of graphene nanoplatelets epoxy composites
Materials Science-Poland
Efficient heat dissipation from modern electronic devices is a key issue for their proper performance. An important role in the assembly of electronic devices is played by polymers, due to their simple application and easiness of processing. The thermal conductivity of pure polymers is relatively low and addition of thermally conductive particles into polymer matrix is the method to enhance the overall thermal conductivity of the composite. The aim of the presented work is to examine a possibility of increasing the thermal conductivity of the filled epoxy resin systems, applicable for electrical insulation, by the use of composites filled with graphene nanoplatelets. It is remarkable that the addition of only 4 wt.% of graphene could lead to 132 % increase in thermal conductivity. In this study, several new aspects of graphene composites such as sedimentation effects or temperature dependence of thermal conductivity have been presented. The thermal conductivity results were also com...