Thermal conductivity of carbon nanotubes and graphene in epoxy nanofluids and nanocomposites (original) (raw)
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Enhanced thermal conductivity of graphene nanoplatelets epoxy composites
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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...
Role of solvent in enhancement of thermal conductivity of epoxy/graphene nanocomposites
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In this work, we demonstrate that dimethylformamide (DMF) leads to better dispersion of graphene nanoplatelets relative to acetone, leading to higher thermal conductivity epoxy-graphene nanocomposites. Uniform dispersion of graphene nanoparticles into epoxy is critical for achieving high thermal conductivity epoxy-graphene nanocomposites. Uniform dispersion of graphene nanoplatelets can improve thermal contact with polymer leading to higher thermal conductivity of the composite. Organic solvents typically lead to efficient dispersion of graphene into the epoxy matrix. In this study, we compare the effect of two organic solvents, dimethylformamide (DMF) and acetone, in terms of their efficiency in dispersing graphene into the epoxy matrix and their effect on enhancing thermal conductivity of the composite. While the effect of solvents on mechanical properties of polymer-graphene nanocomposites has been studied, their effect on thermal conductivity is not well understood. In this stud...
Thermal Conductivity Enhancement of Graphene Epoxy Nanocomposite
Key Engineering Materials, 2016
Graphene was introduced in the epoxy matrix for the enhancement of thermal conductivity properties. Dispersion is a crucial step in nanocomposite processing. Therefore, it is important to tackle the issues and homogenously dispersed the graphene in the epoxy matrix. In this paper, we varied the stirring speed in order to understand its effects on enhancing the thermal conductivity values of the composites. Results show that the thermal conductivity increases up to 17.5% with the 1.5% weight loading of graphene that was stirred at 1500 rpm stirring speed. The experiment results are then compared to theoretical calculation by Maxwell model. Study implied that Maxwell model can predict the thermal conductivity of composites because it applies only for small volume fraction of filler. As the filler loading used in this study only up to 1.5 wt. %, Maxwell model was suitable to be used.
Graphite Nanoplatelets Composite Materials: Role of the Epoxy-System in the Thermal Conductivity
Journal of Materials Science and Chemical Engineering, 2015
Polymers typically have intrinsic thermal conductivity much lower than other materials. Enhancement of this property may be obtained by the addition of conductive fillers. In this research, epoxy nanocomposites with exfoliated graphite nanoplatelets are prepared and characterized. The chosen approach requires no surface treatment and no sophisticated equipments allowing one to produce composites on a pilot scale. A significant increase of the thermal conductivity with the increasing of the graphite fillers content is nevertheless observed on 4 mm thick specimens. Our results viewed in the latest scientific findings suggest that the choice of resin is an important parameter to move towards composite materials with high thermal conductivity.
Thermal conductivity of graphene nanoplatelet/cycloaliphatic epoxy composites: Multiscale modeling
Carbon, 2018
Composite materials using cycloaliphatic epoxy (CE) resins are used in some structural applications that require resistance to aggressive environments. Specifically, CE-based composites are used for structural reinforcement in aluminum conductor composite core (ACCC) high-voltage power lines. However, CE resins have a relatively low thermal conductivity, which makes it difficult to dissipate localized heating due to transmission line faults. Graphene nanoplatelet (GNP) reinforcement can potentially improve the thermal conductivity of CE composites (~0.2 W/m-K) due to its superior in-plane thermal conductivity (~5,300 W/m-K). In this study, the thermal conductivities of GNP/CE composites are investigated by multiscale modeling using molecular dynamics (MD) and micromechanics simulation techniques. Different levels of GNP dispersion and aspect ratio are studied and compared to experimental data established herein and in the literature. The thermal conductivity of GNP/CE composites increases with increased GNP content, dispersion, and aspect ratio. Additionally, covalently functionalized GNP/CE systems are simulated to determine the effect of functionalization on thermal conductivity. The transverse thermal conductivity of GNP/CF/CE hybrid composites is further investigated and validated with experimental values. This study establishes a unique multiscale modeling approach for predicting thermal conductivity of polymer nanocomposite materials (and hybrid composite materials) based on molecular structure of the nanoreinforcement/polymer interface.
Investigation of thermal and electrical conductivity of graphene based nanofluids
Journal of Applied Physics, 2010
We report for the first time, the synthesis of highly stable exfoliated graphene based nanofluids with water and ethylene glycol as base fluids with out any surfactant and the subsequent studies on their thermal and electrical conductivities. Graphene was synthesized by thermal exfoliation of graphene oxide at 1050°C in Ar atmosphere. The as-synthesized graphene has been suitably functionalized and further dispersed it in the base fluids without any surfactant. Thermal and electrical conductivities of these nanofluids were measured for varying volume fractions and at different temperatures. An enhancement in thermal conductivity by about 14% has been achieved at 25°C with deionized water ͑DI͒ as base fluid at a very low volume fraction of 0.056% which increases to about 64% at 50°C. Electrical conductivity measurements for these nanofluids indicate an enormous enhancement at 25°C for a volume fraction of 0.03%in DI water.
Nanotechnology, 2013
Carbon nanomaterials are generally used to promote the thermal conductivity of polymer composites. However, individual graphene nanoplatelets (GNPs) or carbon nanotubes (CNTs) limit the realization of the desirable thermal conductivity of the composite in both throughand in-plane directions. In this work, we present the thermal conductivity enhancement of the epoxy composite with carbon hybrid fillers composed of CNTs directly grown on the GNP support. The composite with 20 wt% hybrid filler loading showed 300% and 50% through-plane thermal conductivity improvements in comparison with the individual CNTs and GNPs, respectively. Moreover, it showed an enhanced thermal conductivity of up to 12% higher than that of the simply mixed GNP and CNT fillers. In more detail, hybrid fillers, whose CNTs were synthesized on the GNP support (Support C, Fe/Mo-MgO:GNP = 1:0.456) for 60 min via chemical vapor deposition process, presented the highest through-plane thermal conductivity of 2.41 W m −1 K −1 in an epoxy composite.
Thermal Conductivity of Carbon Nanoreinforced Epoxy Composites
Journal of Nanomaterials, 2016
The present study attempts to investigate the influence of multiwalled carbon nanotubes (MWCNTs) and graphite nanoplatelets (GNPs) on thermal conductivity (TC) of nanoreinforced polymers and nanomodified carbon fiber epoxy composites (CFRPs). Loading levels from 1 to 3% wt. of MWCNTs and from 1 to 15% wt. of GNPs were used. The results indicate that TC of nanofilled epoxy composites increased with the increase of GNP content. Quantitatively, 176% and 48% increase of TC were achieved in nanoreinforced polymers and nanomodified CFRPs, respectively, with the addition of 15% wt. GNPs into the epoxy matrix. Finally, micromechanical models were applied in order to predict analytically the TC of polymers and CFRPs. Lewis-Nielsen model with optimized parameters provides results very close to the experimental ones in the case of polymers. As far as the composites are concerned, the Hashin and Clayton models proved to be sufficiently accurate for the prediction at lower filler contents.