Thermal Conductivity Reduction in Few-Layer Graphene

2011 ◽  
Author(s):  
Dhruv Singh ◽  
Jayathi Y. Murthy ◽  
Timothy S. Fisher
Keyword(s):  
Thermal Conductivity ◽  
Weak Coupling ◽  
Phonon Scattering ◽  
Single Layer ◽  
Acoustic Mode ◽  
Single Layer Graphene ◽  
Boltzmann Transport ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Few Layer Graphene

Using the linearized Boltzmann transport equation and perturbation theory, we analyze the reduction in the intrinsic thermal conductivity of few-layer graphene sheets accounting for all possible three-phonon scattering events. Even with weak coupling between layers, a significant reduction in the thermal conductivity of the out-of-plane acoustic modes is apparent. The main effect of this weak coupling is to open many new three-phonon scattering channels that are otherwise absent in graphene. The highly restrictive selection rule that leads to a high thermal conductivity of ZA phonons in single-layer graphene is only weakly broken with the addition of multiple layers, and ZA phonons still dominate thermal conductivity. We also find that the decrease in thermal conductivity is mainly caused by decreased contributions of the higher-order overtones of the fundamental out-of-plane acoustic mode. Moreover, the extent of reduction is largest when going from single to bilayer graphene and saturates for four layers. The results compare remarkably well over the entire temperature range with measurements of of graphene and graphite.

Image Processing To Aid in Graphene Detection

2014 ◽  
Vol 1702 ◽  
Author(s):  
Ryan D. Gorby ◽  
Lihong (Heidi) Jiao
Keyword(s):  
Image Processing ◽  
Single Layer ◽  
Optical Microscope ◽  
Single Layer Graphene ◽  
Camera System ◽  
Layer Graphene ◽  
Sophisticated Equipment ◽  
Processing Software ◽  
Image Processing Software ◽  
Few Layer Graphene

ABSTRACTQualitative techniques for the detection of graphene on a Si/SiO2 substrate, without the use of sophisticated equipment, are presented. Once calibrated, this technique can be used to detect Single Layer Graphene (SLG) and Few Layer Graphene (FLG) with the use of an inexpensive optical microscope (OM), OM camera system, and image processing software. This technique could be transferred to graphene deposited on other substrates or other 2-D materials with minor updates to mathematical theory.

Mode dependent lattice thermal conductivity of single layer graphene

2014 ◽  
Vol 116 (15) ◽  
pp. 153503 ◽  
Author(s):  
Zhiyong Wei ◽  
Juekuan Yang ◽  
Kedong Bi ◽  
Yunfei Chen
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Layer Graphene

scholarly journals Thermal Resistance across Interfaces Comprising Dimensionally Mismatched Carbon Nanotube-Graphene Junctions in 3D Carbon Nanomaterials

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Jungkyu Park ◽  
Vikas Prakash
Keyword(s):  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Carbon Nanomaterials ◽  
Single Layer ◽  
Unit Cell ◽  
Single Layer Graphene ◽  
Interfacial Thermal Resistance ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Plane Direction

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.

Substrate Effects on the Thermal Conductivity of Single Layer Supported Graphene

2011 ◽  
Author(s):  
Z. Wei ◽  
C. Dames ◽  
Y. Chen
Keyword(s):  
Thermal Conductivity ◽  
Silicon Dioxide ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Dynamics Model ◽  
Graphene Flake ◽  
Substrate Effects ◽  
Layer Graphene ◽  
Lennard Jones ◽  
Non Equilibrium Molecular Dynamics

A non-equilibrium molecular dynamics model is developed to calculate the thermal conductivity of single layer graphene supported on silicon dioxide. We use the Tersoff potential to describe the carbon-carbon interactions within graphene, and a Lennard-Jones (LJ) potential to describe the interactions between graphene and silicon dioxide. To overcome possible artifacts of thermal expansion, the model avoids using any periodic or fixed boundary conditions for the graphene flake. For both smooth and rough substrates, the simulations show that increasing the LJ coupling strength between graphene and substrate can reduce the in-plane thermal conductivity of graphene. We also investigated the effects of roughness. The simulations show that the thermal conductivity is sensitive to the roughness only when the coupling is large. These results indicate how the thermal properties of graphene may be modified by adjusting the coupling and roughness of the substrate.

scholarly journals A Molecular Dynamics Study on Wrinkles in Graphene with Simply Supported Boundary under In-Plane Shear

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Jianzhang Huang ◽  
Qiang Han
Keyword(s):  
Molecular Dynamics ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Propagation Process ◽  
Plane Shear ◽  
Simply Supported ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Formation And Evolution ◽  
Dynamics Simulations

The formation and evolution mechanisms of wrinkling in a rectangular single layer graphene sheet (SLGS) with simply supported boundary subjected to in-plane shear displacements are investigated using molecular dynamics simulations. Through investigating the out-of-plane displacements of the key point atom, we clarify the wrinkling growth and propagation process. Our results show that the boundary condition plays important roles in the wrinkling deformation. And the dependence of wrinkling parameters on the applied shear displacements is captured. Based on the elasticity theory, the formation mechanism of graphene wrinkling is revealed from the viewpoint of elastic energy. The effects of aspect ratio of graphene, temperature, and loading velocity on graphene wrinkling parameters and patterns are also investigated.

scholarly journals Nanomechanics of graphene

2018 ◽  
Vol 6 (2) ◽  
pp. 324-348 ◽  
Author(s):  
Yujie Wei ◽  
Ronggui Yang
Keyword(s):  
Plane Deformation ◽  
Single Layer ◽  
High Strength ◽  
Review Article ◽  
Single Layer Graphene ◽  
Bending Rigidity ◽  
Mechanical Behaviors ◽  
Carbon Allotropes ◽  
Layer Graphene ◽  
Out Of Plane

Abstract The super-high strength of single-layer graphene has attracted great interest. In practice, defects resulting from thermodynamics or introduced by fabrication, naturally or artificially, play a pivotal role in the mechanical behaviors of graphene. More importantly, high strength is just one aspect of the magnificent mechanical properties of graphene: its atomic-thin geometry not only leads to ultra-low bending rigidity, but also brings in many other unique properties of graphene in terms of mechanics in contrast to other carbon allotropes, including fullerenes and carbon nanotubes. The out-of-plane deformation is of a ‘soft’ nature, which gives rise to rich morphology and is crucial for morphology control. In this review article, we aim to summarize current theoretical advances in describing the mechanics of defects in graphene and the theory to capture the out-of-plane deformation. The structure–mechanical property relationship in graphene, in terms of its elasticity, strength, bending and wrinkling, with or without the influence of imperfections, is presented.

Wrinkling in Graphene Subjected to Gradient Tension

NANO ◽  
2015 ◽  
Vol 10 (03) ◽  
pp. 1550037 ◽  
Author(s):  
Jianzhang Huang ◽  
Qiang Han
Keyword(s):  
Molecular Dynamics ◽  
Single Layer ◽  
Md Simulations ◽  
Area Ratio ◽  
Single Layer Graphene ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Displacement Direction ◽  
Effects Of Temperature ◽  
Plane Displacement

In the present study, the initiation and evolution mechanisms of wrinkles in a square single layer graphene sheet (SLGS) under gradient tensile displacements are investigated based on molecular dynamics (MD) simulations. The mechanism of wrinkling process is elucidated by studying the atomic out-of-plane displacements development of the key atoms in SLGS. It reveals that the loading and boundary conditions play dominant roles in the wrinkling deformation of graphene. The dependences of the wrinkling amplitude, wavelength, out-of-plane displacement, direction angle and wrinkling area ratio on the applied gradient tensile displacements are obtained. The effects of temperature, size of graphene and loading grads on graphene wrinkling are investigated.

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