Thermal Transport at Carbon Nanotube-Graphene Junction

Author(s):  
Jungkyu Park ◽  
Vikas Prakash

We present results of a molecular dynamics study to analyze thermal transport at carbon nanotube (CNT)-graphene junctions comprising of single layer graphene and (6,6) armchair single-walled carbon nanotubes (SWCNTs). Two possible junction types with different degrees of sp2 and sp3 hybridization are investigated. Reverse Non-Equilibrium Molecular Dynamics (RNEMD) simulations are used to obtain the thermal conductivities in these hybrid structures and also analyze the role of the interfacial thermal resistance at the SWCNT-graphene junctions in limiting thermal transport. The highest out-of-plane (along the SWCNT axis) thermal conductivity of a hybrid structure with a CNT-graphene junction was obtained to be 158.9±1.2 W/m-K when the junction comprised of only sp2 bonds with an interpillar distance of 15 nm and a pillar height of 200 nm. The highest in-plane thermal conductivity (along the graphene layer plane) with two CNT-graphene junctions was found to be 392.2±9.9 W/m-K with junctions comprising of only sp2 bonds and an interpillar distance of 20 nm and a pillar height of 25 nm. In all cases, junctions with mixed sp2/sp3 hybridization showed higher interfacial thermal resistance than junctions with pure sp2 bonds, and the thermal interfacial resistance was found to be weakly dependent on the length of CNT and the interpillar distance. The highest interfacial thermal resistance measured across the CNT-graphene junction was 3.10×10−6 K-cm2/W when the junction comprised of mixed sp2/sp3 bonds and with 15 nm interpillar distance and 50 nm pillar height.

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Jungkyu Park ◽  
Vikas Prakash

In the present study, reverse nonequilibrium molecular dynamics is employed to study thermal resistance across interfaces comprising dimensionally mismatched junctions of single layer graphene floors with (6,6) single-walled carbon nanotube (SWCNT) pillars in 3D carbon nanomaterials. Results obtained from unit cell analysis indicate the presence of notable interfacial thermal resistance in the out-of-plane direction (along the longitudinal axis of the SWCNTs) but negligible resistance in the in-plane direction along the graphene floor. The interfacial thermal resistance in the out-of-plane direction is understood to be due to the change in dimensionality as well as phonon spectra mismatch as the phonons propagate from SWCNTs to the graphene sheet and then back again to the SWCNTs. The thermal conductivity of the unit cells was observed to increase nearly linearly with an increase in cell size, that is, pillar height as well as interpillar distance, and approaches a plateau as the pillar height and the interpillar distance approach the critical lengths for ballistic thermal transport in SWCNT and single layer graphene. The results indicate that the thermal transport characteristics of these SWCNT-graphene hybrid structures can be tuned by controlling the SWCNT-graphene junction characteristics as well as the unit cell dimensions.


Author(s):  
Sushan Nakarmi ◽  
V. U. Unnikrishnan

The variations in thermal conductivity of nanocomposites are found to depend not only the intrinsic properties of the fiber and matrix phases but also on the interfacial resistance of the reinforcing phase. As we go down the length scales, the interfacial thermal resistance due to size of the nanoparticle becomes significant. In order to address the effect of size (length and diameter) of nanotube on the thermal transport property of nanotube composites, thermal conductivity of different nanotube samples varying in length and diameter will be estimated first using molecular dynamic (MD) simulations with AIREBO potentials. This will be carried out using the ‘Heat-Bath’ method - non-equilibrium molecular dynamics (NEMD) approach. In the heat bath method, constant amount of heat is added to and removed from the hot and cold regions and the resulting temperature gradient is measured and the thermal conductivity is calculated using the Fourier Law. This will be followed by the study of interfacial thermal resistance of these nanostructures. These intrinsic properties are then used with continuum based mathematical formulations to study the effect of size of the nanoparticle on the overall thermal conductivity of the nanocomposite.


2017 ◽  
Vol 5 (21) ◽  
pp. 5119-5127 ◽  
Author(s):  
Xinyu Wang ◽  
Yang Hong ◽  
Dongwei Ma ◽  
Jingchao Zhang

Basal-plane thermal conductivity and cross-plane interfacial thermal resistance in a C2N bilayer structure are comprehensively investigated.


2016 ◽  
Vol 51 (23) ◽  
pp. 3299-3313 ◽  
Author(s):  
Sumit Sharma ◽  
Pramod Kumar ◽  
Rakesh Chandra

Single layer graphene sheets and carbon nanotubes have resulted in the development of new materials for a variety of applications. Though there are a large number of experimental and numerical studies related to these nanofillers, still there is a lack of understanding of the effect of geometrical characteristics of these nanofillers on their mechanical properties. In this study, molecular dynamics simulation has been used to assess this issue. Two different computational models, single layer graphene sheets–copper and carbon nanotube–copper composites have been examined to study the effect of nanofiller geometry on Young’s modulus and thermal conductivity of these nanocomposites. Effect of increase in temperature on Young’s modulus has also been predicted using molecular dynamics. The effect of nanofiller volume fraction ( Vf) on Young’s modulus and thermal conductivity has also been studied. Results of thermal conductivity obtained using molecular dynamics have been compared with theoretical models. Results show that with increase in Vf the Young’s modulus as well as thermal conductivity of single layer graphene sheets–Cu composites increases at a faster rate than that for carbon nanotube–Cu composite. For the same Vf, the Young’s modulus of single layer graphene sheets–Cu composite is higher than carbon nanotube–Cu composite.


Author(s):  
Arian Mayelifartash ◽  
Mohammad Ali Abdol ◽  
Sadegh Sadeghzadeh

In this paper, by employing non-equilibrium molecular dynamics simulations (NEMD), the thermal conductance of hybrid formed by polyaniline (C3N) and boron carbide (BC3) in both armchair and zigzag configurations has...


2015 ◽  
Vol 17 (37) ◽  
pp. 23704-23710 ◽  
Author(s):  
Jingchao Zhang ◽  
Yang Hong ◽  
Zhen Tong ◽  
Zhihuai Xiao ◽  
Hua Bao ◽  
...  

For the first time, the interfacial thermal resistance between silicene and multiple substrates,i.e., crystalline silicon and silica, amorphous silicon and silica are calculated using a transient heating molecular dynamics technique.


Author(s):  
Tad Whiteside ◽  
Marie A. Priest ◽  
Clifford W. Padgett

In this paper, the effect on the interfacial thermal resistance between a composite system composed of a carbon nanotube or diamond nanorod and an octane matrix by the functionalization of those nanostructures with alkyl chains has been examined using molecular dynamics simulations. The effect of functionalization was studied by varying the percent functionalization from 0.00% to 2.00% using octyl as the functional group. As the percent functionalization increased, both systems showed a decrease in the interfacial thermal resistance. At 1.00% functionalization, as the alkyl chain length was increased from one to eight atoms, the interfacial thermal resistance of the carbon nanotube systems decreased to a minimum, while in the diamond nanorod system the interfacial thermal resistance remained constant.


Author(s):  
Tatiana Zolotoukhina

The spectral components of the phonon transport in the locally thermally excited graphene samples were studied by molecular dynamics (MD) method. In order to be able to select and analyze separate phonon modes in the time of propagation, the transient Green-Kubo approach to the definitions of density of states (DOS) and thermal conductivity was tested in quasi-equilibrium regimes for limited region of the graphene sample studied. Propagation of single modes at the background of diffusional phonon distribution and energy decay of such modes are studied by calculation of the DOS and dispersion relations, their dependence on the heating condition and temperature is studied. Similar conditions can be generated at localized heating of small areas of graphene structures in electronic devices. In transient regime, many issues of thermal transport evaluation still remain not sufficiently tested, especially phonon dynamics. Thermal conductivity of graphene samples related to transport of separate phonon modes is still not completely investigated, however, recent result give indication on the difference in the contribution of phonon modes. In the study, we consider mostly high temperature transport modes that are generated at the heated spot in order to be able to define their velocities and lifetimes in the limit of transient MD sampling. The single-layer graphene nanoribbon of 150 nm to 40 nm was relaxed and prepared in equilibrium in zigzag and armchair orientations. REBO potential for graphene was utilized. Our calculation has shown that at the heating to high temperatures of 1000K and higher, the G mode of graphene remains stationary and has a minimal contribution into thermal transport by coherent modes. The coherent phonon mode or modes that contribute the most into thermal transport were confined in the vicinity of 30 THz and can possibly be attributed to the D modes of graphene.


Sign in / Sign up

Export Citation Format

Share Document