scholarly journals The Thermal Conductivity of Carbon Nanotubes with Defects and Intramolecular Junctions

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Qiaoli Zhou ◽  
Fanyan Meng ◽  
Zhuhong Liu ◽  
Sanqiang Shi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Temperature Gradient ◽  
Temperature Profile ◽  
Free Path ◽  
Mean Free Path ◽  
Nonequilibrium Molecular Dynamics ◽  
Large Temperature ◽  
Large Temperature Gradient

The thermal conductivity of various carbon nanotubes with defects or intramolecular junctions was studied using nonequilibrium molecular dynamics approach. The results show that the thermal conductivity of both armchair and zigzag carbon nanotubes increased with the decrease of the radius of the tube. The thermal conductivity of armchair tube is higher than that of zigzag tube when the radii of the two tubes are kept almost same. Discontinuities appear on the temperature profile along the tube axial at the region of IMJ, resulting in the large temperature gradient and thus lower thermal conductivity of(n,n)/(m,0)tube with one IMJ and(m,0)/(n,n)/(m,0)tube with two IMJs. For the(m,0)/(n,n)/(m,0)tube with two IMJs, phonon mean free path of the middle(n,n)tube is much smaller than that of the isolate(n,n)tube.

Thermal Conductivity of Hexagonal SiC Nanowire by Nonequilibrium Molecular Dynamics Simulations

2014 ◽  
Vol 487 ◽  
pp. 102-105
Author(s):  
Zan Wang ◽  
Hua Wei Guan ◽  
Ke Dong Bi
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Free Path ◽  
Density Functional ◽  
Mean Free Path ◽  
Nonequilibrium Molecular Dynamics ◽  
Functional Theory ◽  
Sic Nanowires ◽  
Dynamics Simulations ◽  
Dynamics Method

Using nonequilibrium Molecular Dynamics method, thermal properties of hexagonal 4H-SiC and 6H-SiC nanowires are investigated. The quantum errors between realistic temperatures and Molecular dynamics temperatures are rectified based on Density Functional Theory. Thermal conductivities of 4H-SiC and 6H-SiC nanowires are both simulated from 50K to 800K. The scale effect on the thermal conductivity of nanowire is also investigated by varying the nanowires length from 10nm to 130nm. Results indicate, if the length of phonon mean free path is shorter than that of nanowire, phonon-surface scattering will surpass boundary scattering to contribute thermal resistances. Therefore, the thermal conductivity of 4H-SiC or 6H-SiC nanowire is mainly determined by the comparability between the length of nanowires and phonon mean free path.

scholarly journals Ballistic Heat Transport in Nanocomposite: The Role of the Shape and Interconnection of Nanoinclusions

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1982
Author(s):  
Paul Desmarchelier ◽  
Alice Carré ◽  
Konstantinos Termentzidis ◽  
Anne Tanguy
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Free Path ◽  
Mean Free Path ◽  
Strong Increase ◽  
Moderate Increase ◽  
Energy Propagation ◽  
The Mean ◽  
Dynamics Simulations

In this article, the effect on the vibrational and thermal properties of gradually interconnected nanoinclusions embedded in an amorphous silicon matrix is studied using molecular dynamics simulations. The nanoinclusion arrangement ranges from an aligned sphere array to an interconnected mesh of nanowires. Wave-packet simulations scanning different polarizations and frequencies reveal that the interconnection of the nanoinclusions at constant volume fraction induces a strong increase of the mean free path of high frequency phonons, but does not affect the energy diffusivity. The mean free path and energy diffusivity are then used to estimate the thermal conductivity, showing an enhancement of the effective thermal conductivity due to the existence of crystalline structural interconnections. This enhancement is dominated by the ballistic transport of phonons. Equilibrium molecular dynamics simulations confirm the tendency, although less markedly. This leads to the observation that coherent energy propagation with a moderate increase of the thermal conductivity is possible. These findings could be useful for energy harvesting applications, thermal management or for mechanical information processing.

Effects of Stone-Wales Defects on the Thermal Conductivity of Carbon Nanotubes

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Li Wei ◽  
Feng Yanhui ◽  
Peng Jia ◽  
Zhang Xinxin
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Thermal Resistance ◽  
Ambient Temperature ◽  
Temperature Profile ◽  
Defect Position ◽  
Non Equilibrium Molecular Dynamics ◽  
Increasing Temperature ◽  
Dynamics Method

The thermal conductivity of carbon nanotubes with Stone-Wales (SW) defects was investigated using non-equilibrium molecular dynamics method. The defect effects were analyzed by the temperature profile and local thermal resistance of the nanotubes with one or more SW defects and further compared with perfect tubes. The influences of the defect concentration, the length, the chirality and the radius of tubes and the ambient temperature were studied. It was demonstrated that a sharp jump in the temperature profile occurred at defect position due to a higher local thermal resistance, thus dramatically reducing the thermal conductivity of the nanotube. As the number of SW defects increases, the thermal conductivity decreases. Relative to the chirality, the radius has greater effects on the thermal conductivity of tubes with SW defects. With the similar radius, the thermal conductivity of armchair nanotube is higher than that of zigzag one. The shorter nanotube is more sensitive to the defect than the longer one. Thermal conductivity of the nanotube increases with ambient temperature, reaches a peak, and then decreases with increasing temperature.

Thermal properties of pillared-graphene nanostructures

2015 ◽  
Vol 1727 ◽  
Author(s):  
M. Rifu ◽  
K. Shintani
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Thermal Properties ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Nonequilibrium Molecular Dynamics Simulation ◽  
Thermal Conductivities ◽  
Graphene Nanostructures

ABSTRACTThe thermal conductivities of pillared-graphene nanostructures (PGNSs) are obtained using nonequilibrium molecular-dynamics simulation. It is revealed their thermal conductivities are much smaller than the thermal conductivities of carbon nanotubes (CNTs). This fact is explained by examining the density of states (DOS) of the local phonons of PGNSs. It is also found the thermal conductivity of a PGNS linearly decreases with the increase of the inter-pillar distance.

Thermal Conductivity of Graphene on Nanostructure Size from Nonequilibrium Molecular Dynamics Simulations

2020 ◽  
Vol 17 (4) ◽  
pp. 1566-1570
Author(s):  
Xianqi Wei ◽  
Zelin Li ◽  
Junchen Lu ◽  
Shunlong Xu ◽  
Yuancheng Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Management ◽  
Strong Dependence ◽  
Thermal Conductance ◽  
Mean Free Path ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Edge Type ◽  
Dynamics Simulations

Thermal transport of graphene occupies a unique place in thermal management of electronic devices, especially for nanosize devices with high-density integration and high dissipated power. The structure of graphene on nanometer scale changes its thermal conductance. Here, the thermal characters of graphene have been researched by nonequilibrium molecular dynamics simulation (NEMDS) at room temperature. Special attention is focused on the edge type (zigzag or armchair) and nanostructure size dependence of conductivity for heat. The consequences suggest that the thermal conductivity of zigzag edge has been higher than that of armchair, which is because of the higher phonon group velocities. Furthermore, thermal conductivity shows a rising tendency, when the model is calculated from length of 21.84 nm to 43.78 nm. The result indicates that the thermal property performs a strong dependence on nanostructure size which is less than phonon mean free path (775 nm). Our research highlights the significance of structure attribute relationships together with providing useful guideline in calculations for nanosize devices thermal management.

Thermal Performance Analysis of the Molecular Linkers in the Carbon Nanotube Composites under Stress Conditions

2013 ◽  
Vol 699 ◽  
pp. 179-183
Author(s):  
Jie He ◽  
Xiao Jin Zhang ◽  
Zhi Tao ◽  
Ye Xin Xu ◽  
Xi Wu
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Polymer Chain ◽  
Thermal Performance ◽  
Mean Free Path ◽  
Nonequilibrium Molecular Dynamics ◽  
Nanotube Composites ◽  
Deformation Ability ◽  
Carbon Nanotube Composites ◽  
Dynamics Method

The influence of the stress type, stress size and polymer chain number on the thermal performance of the molecular linker was investigated by the nonequilibrium molecular dynamics method (NEMD). The results demonstrate that the thermal conductivity of molecular linker first increases and then decreases with an increment in tension because of the interaction between the phonon mean free path and spectrum red-shifted of the molecular linker. While the molecular linker is in compression, the thermal conductivity is linear relationship with the magnitude of the force. With the length compressed to 90%, the thermal conductivity can be decreased 70% maximally. Moreover, increasing the polymer chain number can improve effectively the thermal performance and the anti-deformation ability of the molecular linker.

Thermal Conductivity of Silicon Nanowire by Nonequilibrium Molecular Dynamics Simulations

2008 ◽  
Author(s):  
Shuai-Chuang Wang ◽  
Xin-Gang Liang ◽  
Xiang-Hua Xu
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Nanowire ◽  
Mean Free Path ◽  
Cross Sectional Area ◽  
Nonequilibrium Molecular Dynamics ◽  
Sectional Area ◽  
Cross Sectional ◽  
The Wire ◽  
The Cross

The thermal conductivity of the silicon nanowire was calculated using nonequilibrium molecular dynamics method. The dependence of thermal conductivity on the wire length, cross-sectional area, and temperature was investigated. The Stillinger-Weber potential model and the Nose-Hoover thermostat were used. The surfaces at the wire ends were set free boundary conditions and potential boundaries in other directions. The cross-sectional area range of the nanowires under research is from about 5 nm2 to 19 nm2 and the length range is from about 6 nm to 54 nm. The results agree well with experimental results. The reciprocal of thermal conductivity was found to be linear with that of nanowire length. And our results quantitatively showed that decreasing the cross-sectional area can reduce the phonon mean free path of the nanowire.

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