scholarly journals Effects of Divacancy and Extended Line Defects on the Thermal Transport Properties of Graphene Nanoribbons

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1609 ◽  
Author(s):  
Min Luo ◽  
Bo-Lin Li ◽  
Dengfeng Li
Keyword(s):  
Transport Properties ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Graphene Nanoribbons ◽  
Thermal Conductance ◽  
Low Frequency ◽  
Impurity Scattering ◽  
Low Frequencies ◽  
Thermal Transport Properties ◽  
Line Defects

The effects of divacancy, including isolated defects and extended line defects (ELD), on the thermal transport properties of graphene nanoribbons (GNRs) are investigated using the Nonequilibrium Green’s function method. Different divacancy defects can effectively tune the thermal transport of GNRs and the thermal conductance is significantly reduced. The phonon scattering of a single divacancy is mostly at high frequencies while the phonon scattering at low frequencies is also strong for randomly distributed multiple divacancies. The collective effect of impurity scattering and boundary scattering is discussed, which makes the defect scattering vary with the boundary condition. The effect on thermal transport properties of a divacancy is also shown to be closely related to the cross section of the defect, the internal structure and the bonding strength inside the defect. Both low frequency and high frequency phonons are scattered by 48, d5d7 and t5t7 ELD. However, the 585 ELD has almost no influence on phonon scattering at low frequency region, resulting in the thermal conductance of GNRs with 585 ELD being 50% higher than that of randomly distributed 585 defects. All these results are valuable for the design and manufacture of graphene nanodevices.

scholarly journals Thermal Transport of Flexural and In-Plane Phonons Modulated by Bended Graphene Nanoribbons

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Changning Pan ◽  
Jun He ◽  
Diwu Yang ◽  
Keqiu Chen
Keyword(s):  
Low Temperature ◽  
Transport Properties ◽  
Thermal Transport ◽  
Phonon Dispersion ◽  
Graphene Nanoribbons ◽  
Structural Parameters ◽  
Thermal Conductance ◽  
Phonon Modes ◽  
Thermal Transport Properties ◽  
Out Of Plane

Ballistic thermal transport properties are investigated comparatively for out-of-plane phonon modes (FPMs) and in-plane phonon modes (IPMs) in bended graphene nanoribbons (GNRs). Results show that the phonon modes transports can be modulated separately by the phonon dispersion mismatch between armchair and zigzag GNRs in considered system. The contribution of FPMs to total thermal conductance is larger than 50% in low temperature for perfect GNRs. But it becomes less than 20% in the bended GNRs. Furthermore, this contribution can be modulated by changing the structural parameters of the bended GNRs. The result is useful for the design of thermal or thermoelectric nanodevices in future.

Strained effects on the thermal conductance of flexural and in-plane modes in graphene nanoribbons

2019 ◽  
Vol 33 (31) ◽  
pp. 1950383
Author(s):  
Bengang Bao ◽  
Gao-Hua Liao ◽  
Jun He ◽  
Chang-Ning Pan
Keyword(s):  
Transport Properties ◽  
Phonon Mode ◽  
Graphene Nanoribbons ◽  
Thermal Conductance ◽  
Low Frequency ◽  
Phonon Transport ◽  
Frequency Region ◽  
Function Approach ◽  
Non Equilibrium Green’S Function ◽  
Plane Mode

Ballistic thermal transport properties in graphene nanoribbon modulated with strain are investigated by non-equilibrium Green’s function approach. The results show that the strain can suppress the phonon transport of flexural phonon mode (FPM) and enhance the phonon transport of in-plane mode (IPM) in low-frequency region, leading to the reduction in the thermal conductance of FPM and the enhancement in the thermal conductance of IPM. The total thermal conductance is decreased by strain as the reduction in the thermal conductance of FPM overcomes the enhancement in the thermal conductance of IPM.

scholarly journals Reduction of Lattice Thermal Conductivity in PbTe Induced by Artificially Generated Pores

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Jae-Yeol Hwang ◽  
Eun Sung Kim ◽  
Syed Waqar Hasan ◽  
Soon-Mok Choi ◽  
Kyu Hyoung Lee ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Pore Structure ◽  
Transport Properties ◽  
Thermoelectric Materials ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Phonon Modes ◽  
Thermal Transport Properties

Highly dense pore structure was generated by simple sequential routes using NaCl and PVA as porogens in conventional PbTe thermoelectric materials, and the effect of pores on thermal transport properties was investigated. Compared with the pristine PbTe, the lattice thermal conductivity values of pore-generated PbTe polycrystalline bulks were significantly reduced due to the enhanced phonon scattering by mismatched phonon modes in the presence of pores (200 nm–2 μm) in the PbTe matrix. We obtained extremely low lattice thermal conductivity (~0.56 W m−1 K−1at 773 K) in pore-embedded PbTe bulk after sonication for the elimination of NaCl residue.

scholarly journals Influence of Te Vacancies on the Thermoelectric Properties of n-type Cu0.008Bi2Te2.7-xSe0.3

2020 ◽  
Vol 58 (10) ◽  
pp. 721-727
Author(s):  
Yerim Yang ◽  
TaeWan Kim ◽  
Seokown Hong ◽  
Jiwoo An ◽  
Sang-il Kim
Keyword(s):  
Thermal Conductivity ◽  
Transport Properties ◽  
Point Defect ◽  
Thermoelectric Properties ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Band Model ◽  
Total Thermal Conductivity ◽  
Thermal Transport Properties ◽  
Callaway Model

In this study, we report the influence of Te vacancy formation on the thermoelectric properties of n-type Cu0.008Bi2Te2.7Se0.3 alloys, including their electronic and thermal transport properties. Te-deficient Cu0.008Bi2Te2.7-xSe0.3 (x = 0, 0.005, 0.01 and 0.02) samples were systematically synthesized and characterized. Regarding electronic transport properties, carrier concentration was increased with Te vacancies, while carrier mobility was maintained. As a result, the electrical conductivity significantly increased while the Seebeck coefficient reduced moderately, thus, the power factor was enhanced from 3.04 mW/mK<sup>2</sup> (pristine) to 3.22 mW/mK<sup>2</sup> (x = 0.02) at 300 K. Further analysis based on a single parabolic band model revealed that the weighted mobility of the conduction band increased, which is favorable for electron transport, as Te vacancies were generated. Regarding thermal transport properties, lattice thermal conductivity decreased with Te vacancies due to additional point defect phonon scattering, however, total thermal conductivity increased due to larger electronic contribution as Te vacancies increased. Analysis using the Debye-Callaway model suggests that the phonon scattering by the Te vacancies is as efficient as the substitution point defect scattering. Consequently, the thermoelectric figure of merit zT increased at all temperatures for x = 0.005 and 0.01. The maximum zT of 0.95 was achieved for Te-deficient Cu0.008Bi2Te2.69Se0.3 (x = 0.01) at 400 K.

Effect of pentagon–heptagon defect on thermal transport properties in graphene nanoribbons

Carbon ◽  
2013 ◽  
Vol 65 ◽  
pp. 181-186 ◽  
Author(s):  
Shi-Hua Tan ◽  
Li-Ming Tang ◽  
Zhong-Xiang Xie ◽  
Chang-Ning Pan ◽  
Ke-Qiu Chen
Keyword(s):  
Transport Properties ◽  
Thermal Transport ◽  
Graphene Nanoribbons ◽  
Thermal Transport Properties

Thermal transport properties of rolled graphene nanoribbons

2013 ◽  
Vol 103 (7) ◽  
pp. 071908 ◽  
Author(s):  
Dengfeng Li ◽  
Bolin Li ◽  
Min Luo ◽  
Chunbao Feng ◽  
Tao Ouyang ◽  
...  
Keyword(s):  
Transport Properties ◽  
Thermal Transport ◽  
Graphene Nanoribbons ◽  
Thermal Transport Properties

Atomistic Simulations of Heat Transport in Carbon Nanotubes Effected by Temperature and Stretch Strain

2011 ◽  
Vol 320 ◽  
pp. 38-44 ◽  
Author(s):  
Qing Yuan Meng ◽  
Yu Fei Gao ◽  
Xian Qin
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Low Temperature ◽  
Transport Properties ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Quantum Effect ◽  
Axial Strain ◽  
Thermal Transport Properties ◽  
Dynamic Structures

Carbon nanotubes (CNTs) is a well thermal transport nano materials, however, the thermal conductivity of CNTs has not been well established, only a few groups had reported experimental data and the existed simulation results ranged widely. Specially, the conclusions in low temperature section and dynamic structures were not very clearly. In this paper, the methods based on phonon scattering theory were applied to explore the thermal transport properties CNTs. The investigation was carried out under the conditions of temperature and axial strain. In the consideration of quantum effect, the thermal conductivity increased linearly with the growth of temperature in low-temperature section, and began to decrease gradually when the temperature exceeded a definite value. If an axial strain was concerned, there was an increasing trend of thermal conductivity as the stretch strain increases. However, after the strain exceeded a particular value the thermal conductivity decreased significantly. In addition, the high frequency phonon peak in PDOS was found to be an important parameter in describing thermal transport properties of dynamic structures.

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