Strain Effect on Thermal Transport in Carbon Nanotube-Graphene Junctions

2018 ◽  
Author(s):  
Jungkyu Park ◽  
Paul Pena
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Flexible Electronics ◽  
Thermal Transport ◽  
Carbon Nanostructures ◽  
Tensile Strain ◽  
Mechanical Strain ◽  
Strain Effect ◽  
Interesting Phenomenon ◽  
Covalent Bonds

We employ molecular dynamics simulations to explore the effect of tensile strain on the thermal conductivity of carbon nanotube (CNT)-graphene junction structures. Two different types of CNT-graphene junctions are simulated; a perfect seamless junction between CNT and graphene with complete sp2 covalent bonds, and a CNT-graphene junction with mixed sp2/sp3 covalent bonds are studied. The most interesting phenomenon observed in the present research study is that the thermal conductivity of CNT-graphene junction structures increases with an increase in mechanical strain. For the case of CNT-graphene junction structure with pillar height of 50 nm and inter-pillar distance of 15 nm, the thermal conductivity is improved by 22.4% when 0.1 tensile strain is imposed. It is observed that the thermal conductivity improvement is enhanced when a larger graphene floor is placed between junctions since larger graphene floor allows larger deformation (larger tensile strain) in the junction. In addition, the thermal conductivity of CNT-graphene junction structures with pure sp2 bonds is observed to be higher than the thermal conductivity of CNT-graphene junction structures with mixed sp2/sp3 bonds regardless of the amount of tensile strain. The obtained results will contribute to the development of flexible electronics by providing a theoretical background on the thermal transport of three dimensional carbon nanostructures under deformation.

Thermal Transport Behavior of Carbon Nanotube–Graphene Junction under Deformation

2019 ◽  
Vol 19 (02) ◽  
pp. 1950013
Author(s):  
Jungkyu Park ◽  
Paul Pena ◽  
Ayse Tekes
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Flexible Electronics ◽  
Thermal Transport ◽  
Carbon Nanostructures ◽  
Tensile Strain ◽  
Mechanical Strain ◽  
Theoretical Background ◽  
Covalent Bonds ◽  
Junction Structure

We employ molecular dynamics simulations to explore the effect of tensile strain on the thermal conductivity of carbon nanotube (CNT)–graphene junction structures. Two types of CNT–graphene junctions are simulated; a seamless junction between CNT and graphene with pure [Formula: see text] covalent bonds, and a junction with mixed [Formula: see text] covalent bonds are studied. The most interesting observation is that the thermal conductivity of a CNT–graphene junction structure increases with an increase in mechanical strain. For the case of a (6,6) CNT–graphene junction structure with an inter-pillar distance (the length of graphene floor between two CNT–graphene junctions) of 15[Formula: see text]nm, the thermal conductivity is improved by 22.4% with 0.1 tensile strain. The thermal conductivity improvement by mechanical strain is enhanced when a larger graphene floor is placed between junctions since a larger graphene floor allows larger deformation (larger tensile strain) without breaking bonds in the junction structure. However, the thermal conductivity is found to more strongly depend on the C–C bond hybridization at the intramolecular junctions with pure [Formula: see text] hybridization showing a higher thermal conductivity when compared to mixed [Formula: see text] bonding regardless of the amount of tensile strain. The obtained results will contribute to the development of flexible electronics by providing a theoretical background on the thermal transport of three-dimensional carbon nanostructures under deformation.

Influence of Strain States on the Thermal Transport Properties of Single and Multiwalled Carbon Nanostructures

2018 ◽  
Author(s):  
Sushan Nakarmi ◽  
V. U. Unnikrishnan
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Transport Properties ◽  
Thermal Transport ◽  
Carbon Nanostructures ◽  
Electronic Devices ◽  
Mechanical Strain ◽  
Heat Bath ◽  
Multiwalled Carbon ◽  
Thermal Transport Properties

The increasing demand for system miniaturization and high power density energy produces excessive thermal loads on electronic devices with significant mechanical strain. Carbon Nanotubes (CNTs) based devices are found to have excellent thermal transport properties that makes them attractive for thermal management of these miniaturized nano-electronic devices under extreme environments. These conductive nanostructure (carbon nanotubes, graphene, etc.) are often embedded in polymers or other high-strain alloys (the matrix phase), and are used as bridging materials for conductivity (electrical and thermal) with strain resiliency. The effect of strain on the thermal transport properties of these nanostructures have often been overlooked and will be the focus of this work. The thermal conductivity of the nanostructure is obtained in LAMMPS using the Heat-Bath method, which is a reverse non-equilibrium molecular dynamics (RNEMD) simulation strategy. In RNEMD, constant amount of heat is added to and removed from hot and cold regions and the resultant temperature gradient is measured. The effect of strain on the thermal conductivity of the single and multiwalled nanostructures of various configurations will be discussed with specific emphasis on the phonon density of states of nanotubes at different strain states.

Stochastic Modeling of the Bulk Thermal Conductivity for Dense Carbon Nanotube Networks

2009 ◽  
Author(s):  
Nikhil A. Ashtekar ◽  
David A. Jack
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Contact Resistance ◽  
Thermal Transport ◽  
Power Flow ◽  
Thermal Contact ◽  
Separation Distance ◽  
Bulk Conductivity ◽  
Carbon Nanotube Networks ◽  
Bulk Thermal Conductivity

A computational, physics-based, bulk thermal conductivity model of a neat carbon nanotube network at room temperature is developed using classical finite element techniques. The model is based on experimentally available stochastic distributions of length, diameter, chirality, and orientation, and uses theoretical results for thermal contact resistance from the literature and molecular dynamics simulations for the stochastic nature of tube separation distance. Understanding the thermal transport properties of carbon nanotube networks at various operating temperatures is crucial for the industrial acceptance of these materials in aerospace and electrical applications. Mechanisms of thermal transport are discussed including; thermal conductivity along the tube and inter-contact resistance between the tubes, where the later is considered the dominating factor. The effect of variations of several of the aforementioned stochastic factors influencing the bulk conductivity is investigated, and results demonstrate that changes in the nanotube length play a significant role in improving the bulk conductivity of the network. In addition, a brief study into localized power flow is presented and lends insight into a possible cause of premature network failure.

Interfacial thermal transport and structural preferences in carbon nanotube–polyamide-6,6 nanocomposites: how important are chemical functionalization effects?

2015 ◽  
Vol 17 (22) ◽  
pp. 14502-14512 ◽  
Author(s):  
Mohammad Reza Gharib-Zahedi ◽  
Mohsen Tafazzoli ◽  
Michael C. Böhm ◽  
Mohammad Alaghemandi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Structural Properties ◽  
Thermal Transport ◽  
Chemical Functionalization ◽  
Structural Preferences

We investigate the influence of chemically functionalized CNTs on the structural properties of the surrounding polyamide-6,6 matrix as well as the interfacial thermal conductivity of polymer–CNT nanocomposites.

Thermal Transport Properties and Interface Effects of Carbon Nanostructures

2017 ◽  
Author(s):  
Sushan Nakarmi ◽  
V. U. Unnikrishnan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Transport ◽  
Carbon Nanostructures ◽  
Heat Bath ◽  
Md Simulations ◽  
Interfacial Thermal Resistance ◽  
Interfacial Resistance ◽  
Intrinsic Properties ◽  
Thermal Transport Property

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.

scholarly journals Thermal Transport Properties of Dry Spun Carbon Nanotube Sheets

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Heath E. Misak ◽  
James L. Rutledge ◽  
Eric D. Swenson ◽  
Shankar Mall
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Thermal Transport ◽  
Transport Theory ◽  
Primary Concern ◽  
Potential Candidate ◽  
Ir Camera ◽  
Dry Spinning ◽  
Out Of Plane ◽  
Plane Direction

The thermal properties of carbon nanotube- (CNT-) sheet were explored and compared to copper in this study. The CNT-sheet was made from dry spinning CNTs into a nonwoven sheet. This nonwoven CNT-sheet has anisotropic properties in in-plane and out-of-plane directions. The in-plane direction has much higher thermal conductivity than the out-of-plane direction. The in-plane thermal conductivity was found by thermal flash analysis, and the out-of-plane thermal conductivity was found by a hot disk method. The thermal irradiative properties were examined and compared to thermal transport theory. The CNT-sheet was heated in the vacuum and the temperature was measured with an IR Camera. The heat flux of CNT-sheet was compared to that of copper, and it was found that the CNT-sheet has significantly higher specific heat transfer properties compared to those of copper. CNT-sheet is a potential candidate to replace copper in thermal transport applications where weight is a primary concern such as in the automobile, aircraft, and space industries.

Thermal Transport at Carbon Nanotube-Graphene Junction

2013 ◽  
Author(s):  
Jungkyu Park ◽  
Vikas Prakash
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Thermal Transport ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Interfacial Thermal Resistance ◽  
Interfacial Resistance ◽  
Pillar Height

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.

Array Volume Fraction-Dependent Thermal Transport Properties of Vertically Aligned Carbon Nanotube Arrays

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Yang Zhao ◽  
Rong-Shiuan Chu ◽  
Costas P. Grigoropoulos ◽  
Oscar D. Dubon ◽  
Arun Majumdar
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Transport Properties ◽  
Thermal Performance ◽  
Thermal Transport ◽  
Volume Fraction ◽  
Thermal Contact Conductance ◽  
Thermal Transport Properties ◽  
Cnt Arrays ◽  
Vertically Aligned

Vertically aligned carbon nanotube (CNT) arrays are promising candidates for advanced thermal interface materials (TIMs) since they possess high mechanical compliance and high intrinsic thermal conductivity. However, the overall thermal performance of CNT arrays often falls short of expectations when used as TIMs, and the underlying reasons have yet to be fully understood. In this work, the volume fraction of CNT arrays is demonstrated to be the key factor in determining the CNT array thermal transport properties. By increasing the array volume fraction, both the CNT array effective thermal conductivity and the CNT array–glass thermal contact conductance were experimentally found to increase monotonically. One interesting phenomenon is that the increasing rate of thermal conductivity is larger than that of array volume fraction. Compressive experiments verified that the CNT arrays with lower volume fractions suffer from severe buckling, which results in a further decreasing trend. By understanding the underlying reasons behind this trend, the overall thermal performance of vertically aligned CNT arrays can be further increased.

Characterization of Thermal Transport in Carbon Nanotube Yarns

2014 ◽  
Author(s):  
Jianli Wang ◽  
Sisi He ◽  
Jiajian Bao ◽  
Xing Zhang ◽  
Juekuan Yang ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Thermal Transport ◽  
Carbon Nanotube Yarns

Unzipping Carbon Nanotube Bundles through NH−π Stacking for Enhanced Electrical and Thermal Transport

2021 ◽  
Author(s):  
Shuiliang Wang ◽  
Zhequn Huang ◽  
Wenbo Shi ◽  
Dongwook Lee ◽  
Qixiang Wang ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Thermal Transport ◽  
Nanotube Bundles ◽  
Π Stacking
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