scholarly journals A Multiscale Investigation on the Thermal Transport in Polydimethylsiloxane Nanocomposites: Graphene vs. Borophene

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1252
Author(s):  
Alessandro Di Pierro ◽  
Bohayra Mortazavi ◽  
Hamidreza Noori ◽  
Timon Rabczuk ◽  
Alberto Fina
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Effective Thermal Conductivity ◽  
Polymer Nanocomposites ◽  
Volume Content ◽  
Thermal Conductance ◽  
Single Layer ◽  
Md Simulations ◽  
Aspect Ratios ◽  
Wide Range

Graphene and borophene are highly attractive two-dimensional materials with outstanding physical properties. In this study we employed combined atomistic continuum multi-scale modeling to explore the effective thermal conductivity of polymer nanocomposites made of polydimethylsiloxane (PDMS) polymer as the matrix and graphene and borophene as nanofillers. PDMS is a versatile polymer due to its chemical inertia, flexibility and a wide range of properties that can be tuned during synthesis. We first conducted classical Molecular Dynamics (MD) simulations to calculate the thermal conductance at the interfaces between graphene and PDMS and between borophene and PDMS. Acquired results confirm that the interfacial thermal conductance between nanosheets and polymer increases from the single-layer to multilayered nanosheets and finally converges, in the case of graphene, to about 30 MWm−2 K−1 and, for borophene, up to 33 MWm−2 K−1. The data provided by the atomistic simulations were then used in the Finite Element Method (FEM) simulations to evaluate the effective thermal conductivity of polymer nanocomposites at the continuum level. We explored the effects of nanofiller type, volume content, geometry aspect ratio and thickness on the nanocomposite effective thermal conductivity. As a very interesting finding, we found that borophene nanosheets, despite having almost two orders of magnitude lower thermal conductivity than graphene, can yield very close enhancement in the effective thermal conductivity in comparison with graphene, particularly for low volume content and small aspect ratios and thicknesses. We conclude that, for the polymer-based nanocomposites, significant improvement in the thermal conductivity can be reached by improving the bonding between the fillers and polymer, or in other words, by enhancing the thermal conductance at the interface. By taking into account the high electrical conductivity of borophene, our results suggest borophene nanosheets as promising nanofillers to simultaneously enhance the polymers’ thermal and electrical conductivity.

scholarly journals A Multiscale Investigation on the Thermal Transport in Polydimethylsiloxane Nanocomposites: Graphene vs Borophene

2021 ◽  
Author(s):  
Alessandro Di Pierro ◽  
Bohayra Mortazavi ◽  
Hamidreza Noori ◽  
Timon Rabczuk ◽  
Alberto Fina
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Effective Thermal Conductivity ◽  
Volume Content ◽  
Thermal Conductance ◽  
Single Layer ◽  
Interfacial Thermal Conductance ◽  
Aspect Ratios ◽  
The Matrix ◽  
Dynamics Simulations

Graphene and borophene are highly attractive two-dimensional materials with outstanding physical properties. In this study we employed a combined atomistic continuum multiscale modeling to explore the effective thermal conductivity of polymers nanocomposites made of PDMS polymer as the matrix and graphene and borophene as nanofillers. We first conduct classical molecular dynamics simulations to investigate the interfacial thermal conductance between graphene/PDMS and borophene/PDMS interfaces. Acquired results confirm that the interfacial thermal conductance between nanosheets and polymer increases from the single-layer to multilayered nanosheets and finally converges. The data provided by the atomistic simulations were then used in the finite element method simulations to evaluate the effective thermal conductivity of polymer nanocomposites at continuum level. We explore the effects of nanofillers type, their volume content, geometry aspect ratio and thickness on the nanocomposites effective thermal conductivity. As a very interesting finding, we show that borophene nanosheets, despite almost two orders of magnitude lower thermal conductivity than graphene, can yield very close enhancement in the effective thermal conductivity in comparison with graphene, particularly for low volume content and small aspect ratios and thicknesses. We conclude that for the polymer-based nanocomposites, significant improvement in the thermal conductivity can be reached by improving the bonding between the fillers and polymer or in another word enhancing the thermal conductance at the interface. By taking into account the high electrical conductivity of borophene, our results suggest borophene nanosheets as promising nanofillers to simultaneously enhance the polymers thermal and electrical conductivity.

Qualitative Equivalence Between Electrical Percolation Threshold and Effective Thermal Conductivity in Polymer/Carbon Nanocomposites

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Majid Baniassadi ◽  
Akbar Ghazavizadeh ◽  
Yves Rémond ◽  
Said Ahzi ◽  
David Ruch ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Percolation Threshold ◽  
Effective Thermal Conductivity ◽  
Electrical Percolation ◽  
Aspect Ratios ◽  
Wide Range ◽  
Statistical Continuum ◽  
Electrical Percolation Threshold

In this study, a qualitative equivalence between the electrical percolation threshold and the effective thermal conductivity of composites filled with cylindrical nanofillers has been recognized. The two properties are qualitatively compared on a wide range of aspect ratios, from thin nanoplatelets to long nanotubes. Statistical continuum theory of strong-contrast is utilized to estimate the thermal conductivity of this type of heterogeneous medium, while the percolation threshold is simultaneously evaluated using the Monte Carlo simulations. Statistical two-point probability distribution functions are used as microstructure descriptors for implementing the statistical continuum approach. Monte Carlo simulations are carried out for calculating the two-point correlation functions of computer generated microstructures. Finally, the similarities between the effective conductivity properties and percolation threshold are discussed.

Effective Thermal Conductivity in Multidimensional Bodies

1994 ◽  
Vol 116 (1) ◽  
pp. 17-27 ◽  
Author(s):  
Y.-M. Lee ◽  
A. Haji-Sheikh ◽  
L. S. Fletcher ◽  
G. P. Peterson
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Spherical Inclusion ◽  
Applied Pressure ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Surface Conductance ◽  
Three Dimensional Model ◽  
Elliptical Inclusion ◽  
Aspect Ratios

The effective thermal conductivity in three-dimensional bodies is studied analytically. The three-dimensional model considers a spherical inclusion centrally located in a cubical body. Later, the spherical inclusion is replaced by an elliptical inclusion to study the biased effect or directionality of heat flux. Two different aspect ratios for the elliptical inclusion are considered. It is shown that the effective thermal conductivity is influenced by surface conductance in addition to geometric factors. Also, the effective thermal conductivity is measured for different samples. Spherical inclusions are placed inside cylindrical bodies for convenience of the experiments. The data show that cracks induced by applied pressure and thermal stress during the experiment reduce the thermal conductance. Using the measured effective thermal conductivity data, an analytical procedure is used to calculate the average values of the apparent contact conductance.

Natural Convection of Cu-Gallium Nanofluid in Enclosures

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Cong Qi ◽  
Yurong He ◽  
Yanwei Hu ◽  
Juancheng Yang ◽  
Fengchen Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Nusselt Number ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Convection Heat Transfer ◽  
Low Velocity ◽  
Grashof Number ◽  
Aspect Ratios ◽  
Wide Range ◽  
Temperature Dependent Properties

In this work, the natural convection heat transfer of Cu-gallium nanofluid in a differentially heated enclosure is investigated. A single-phase model is employed with constant or temperature-dependent properties of the fluid. The results are shown over a wide range of Grashof numbers, volume fractions of nanoparticles, and aspect ratios. The Nusselt number is demonstrated to be sensitive to the aspect ratio. It is found that the Nusselt number is more sensitive to thermal conductivity than viscosity at a low velocity (especially for a low aspect ratio and a low Grashof number), however, it is more sensitive to the viscosity than the thermal conductivity at a high velocity (high aspect ratio and high Grashof number). In addition, the evolution of velocity vectors, isotherms, and Nusselt number for a small aspect ratio is investigated.

Analysis of Clustering and Interphase Region Effects on the Electrical Conductivity of Carbon Nanotube-Polymer Nanocomposites via Computational Micromechanics

2008 ◽  
Author(s):  
Gary D. Seidel ◽  
Kelli L. Boehringer ◽  
Dimitris C. Lagoudas
Keyword(s):  
Electrical Conductivity ◽  
Polymer Nanocomposites ◽  
Effective Conductivity ◽  
Interphase Layer ◽  
Finite Element Software ◽  
Interphase Region ◽  
Effective Electrical Conductivity ◽  
Wide Range ◽  
Electrical Conductivities ◽  
Computational Micromechanics

In the present work, computational micromechanics techniques are applied towards predicting the effective electrical conductivities of polymer nanocomposites containing aligned bundles of SWCNTs at wide range of volume fractions. Periodic arrangements of well-dispersed and clustered/bundled SWCNTs are studied using the commercially available finite element software COMSOL Multiphysics 3.4. The volume averaged electric field and electric flux obtained are used to calculate the effective electrical conductivity of nanocomposites in both cases, therefore indicating the influence of clustering on the effective electrical conductivity. In addition, the influence of the presence of an interphase region on the effective electrical conductivity is considered in a parametric study in terms of both interphase thickness and conductivity for both the well dispersed case and for the clustered arrangements. Comparing the well-dispersed case with an interphase layer to the same arrangement without the interphase layer allows for the assessment of the influence of the interphase layer on the effective electrical conductivities, while similar comparisons for the clustered arrangements yield information about the combined effects of clustering and interphase regions. Initial results indicate that there is very little influence of the interphase layer on the effective conductivity prior to what is identified as the interphase percolation concentration, and that there is an appreciable combined effect of clustering in the presence of interphase regions which leads to increases in conductivity larger than the sum of the two effects independently.

Influence of Contact Mechanics in the Prediction of the Effective Thermal Conductivity of Spheroid Packed Beds

2003 ◽  
Author(s):  
G. Buonanno ◽  
A. Carotenuto ◽  
G. Giovinco ◽  
L. Vanoli
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Statistical Approach ◽  
Thermal Contact ◽  
Peak Height ◽  
Thermal Contact Conductance ◽  
Curvature Radius ◽  
Packed Beds ◽  
Wide Range ◽  
Thermal Phenomena

Thermal contact conductance is an important parameter in a wide range of thermal phenomena, and consequently a large number of experimental, numerical and statistical investigations have been carried out in literature. In the present paper an analysis of thermal contact resistance is carried out to predict heat transfer between spherical rough surfaces in contact, by means of a statistical approach. The micro-geometry of the surface is described through a probabilistic model based on the peak height variability and invariant asperity curvature radius. The numerical model has been applied to evaluate the effective thermal conductivity of packed beds of steel spheroids and validated through the comparison with the experimental data obtained by means of an apparatus designed and build up for this purpose.

scholarly journals Interfacial Thermal Conductance across Graphene/MoS2 van der Waals Heterostructures

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5851
Author(s):  
Shuang Wu ◽  
Jifen Wang ◽  
Huaqing Xie ◽  
Zhixiong Guo
Keyword(s):  
Thermal Conductivity ◽  
First Principles ◽  
Van Der Waals ◽  
Thermal Conductance ◽  
Md Simulations ◽  
Monolayer Graphene ◽  
Density Of State ◽  
Interfacial Thermal Conductance ◽  
Van Der Waals Heterostructure ◽  
Phonon Spectra

The thermal conductivity and interface thermal conductance of graphene stacked MoS2 (graphene/MoS2) van der Waals heterostructure were studied by the first principles and molecular dynamics (MD) simulations. Firstly, two different heterostructures were established and optimized by VASP. Subsequently, we obtained the thermal conductivity (K) and interfacial thermal conductance (G) via MD simulations. The predicted Κ of monolayer graphene and monolayer MoS2 reached 1458.7 W/m K and 55.27 W/m K, respectively. The thermal conductance across the graphene/MoS2 interface was calculated to be 8.95 MW/m2 K at 300 K. The G increases with temperature and the interface coupling strength. Finally, the phonon spectra and phonon density of state were obtained to analyze the changing mechanism of thermal conductivity and thermal conductance.

scholarly journals Electrical and Thermal Conductivity of Epoxy-Carbon Filler Composites Processed by Calendaring

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1522 ◽  
Author(s):  
Andrea Caradonna ◽  
Claudio Badini ◽  
Elisa Padovano ◽  
Mario Pietroluongo
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Hybrid Composites ◽  
Synergetic Effect ◽  
Multiwall Carbon Nanotubes ◽  
Carbon Filler ◽  
Aspect Ratios ◽  
Roll Mill ◽  
Mill Equipment ◽  
Noticeable Improvement

Electrical and thermal conductivity of composites which contain carbon-based fillers in an epoxy matrix were investigated. The fillers were dispersed in the liquid matrix by using three roll mill equipment. The filler/matrix mixture was cast in a mold and then cured, thus obtaining composite specimens. Multiwall carbon nanotubes, graphene-like nanoplatelets, and graphite were used as fillers and their effect on conductivity was investigated. Electrical and thermal conductivity were measured at different filler loads. It was found that the formation of percolation paths greatly enhanced electrical conductivity, although they were not so effective in improving thermal conductivity. The behavior of composites containing each single filler was compared with that of hybrid composites containing combinations of two different fillers. Results show that fillers with different aspect ratios displayed a synergetic effect resulting in a noticeable improvement of electrical conductivity. However, only a small effect on thermal conductivity was observed.

Thermal Conductivity of Metal-Oxide Nanofluids: Particle Size Dependence and Effect of Laser Irradiation

2006 ◽  
Vol 129 (3) ◽  
pp. 298-307 ◽  
Author(s):  
Sang Hyun Kim ◽  
Sun Rock Choi ◽  
Dongsik Kim
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Effective Thermal Conductivity ◽  
Laser Irradiation ◽  
Volume Fraction ◽  
Suspended Particle ◽  
Titanium Dioxide Nanoparticles ◽  
Size Change ◽  
Conductivity Enhancement ◽  
Wide Range

The thermal conductivity of water- and ethylene glycol-based nanofluids containing alumina, zinc-oxide, and titanium-dioxide nanoparticles is measured using the transient hot-wire method. Measurements are performed by varying the particle size and volume fraction, providing a set of consistent experimental data over a wide range of colloidal conditions. Emphasis is placed on the effect of the suspended particle size on the effective thermal conductivity. Also, the effect of laser-pulse irradiation, i.e., the particle size change by laser ablation, is examined for ZnO nanofluids. The results show that the thermal-conductivity enhancement ratio relative to the base fluid increases linearly with decreasing the particle size but no existing empirical or theoretical correlation can explain the behavior. It is also demonstrated that high-power laser irradiation can lead to substantial enhancement in the effective thermal conductivity although only a small fraction of the particles are fragmented.

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