scholarly journals Thermal conductivity of nanotubes revisited: Effects of chirality, isotope impurity, tube length, and temperature

2005 ◽  
Vol 123 (11) ◽  
pp. 114714 ◽  
Author(s):  
Gang Zhang ◽  
Baowen Li
Keyword(s):  
Thermal Conductivity ◽  
Tube Length ◽  
Conductivity Of Nanotubes

The effect of imposed temperature difference on thermal conductivity in armchair single-walled carbon nanotube

2015 ◽  
Vol 26 (09) ◽  
pp. 1550105 ◽  
Author(s):  
Ali Mehri ◽  
Maryam Jamaati ◽  
Moslem Moradi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Heat Transport ◽  
Temperature Difference ◽  
Nonequilibrium Molecular Dynamics ◽  
Tube Length ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon ◽  
Brenner Potential ◽  
Umklapp Scattering

Thermal conductivity of carbon nanotubes depends on various factors. The simulation of heat transport in armchair single-walled carbon nanotube by direct nonequilibrium molecular dynamics (NEMD) method employing Tersoff–Brenner potential indicates that, thermal conductivity decreases with increase in temperature difference between two ends of the tube. Increasing the imposed temperature differential along the tube axis, leads to domination of Umklapp scattering and impacts the heat transport. The applied temperature difference does not influence the behavior of thermal conductivity vs. tube length, diameter and temperature, but changes its value.

Thermal Transport in Nanotube Composites for Large-Area Macroelectronics

2005 ◽  
Author(s):  
Satish Kumar ◽  
Muhammad A. Alam ◽  
Jayathi Y. Murthy
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Thermal Transport ◽  
Channel Length ◽  
Tube Length ◽  
Finite Volume Scheme ◽  
Large Area ◽  
Contact Conductance ◽  
Channel Lengths ◽  
Contact Parameters

Thermal transport in a new class of nanocomposites composed of isotropic 2D ensembles of nanotubes or nanowires in a substrate is considered for use as the channel region of thin film transistors. The random ensemble is generated numerically and simulated using a finite volume scheme. The effective thermal conductivity of a nanotube network embedded in a thin substrate is computed. Percolating conduction in the composite is studied as a function of wire/tube densities and channel lengths. The conductance exponents are validated against available experimental data for long channels devices. The effect of tube-tube contact conductance, tube-substrate contact conductance and substrate-tube conductivity ratio is analyzed for various channel lengths. It is found that beyond a certain limiting value, contact parameters do not result in any significant change in the effective thermal conductivity of the composite. It is also observed that the effective thermal conductivity of the composite saturates beyond a limiting channel-length/tube length ratio for the range of contact parameters under consideration.

Improving Electrical Conductivity and Thermal Properties of Polymers by the Addition of Carbon Nanotubes as Fillers

MRS Bulletin ◽  
2007 ◽  
Vol 32 (4) ◽  
pp. 348-353 ◽  
Author(s):  
Karen I. Winey ◽  
Takashi Kashiwagi ◽  
Minfang Mu
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Polymer Composites ◽  
Structure Property ◽  
Structure Property Relationships ◽  
Aspect Ratios ◽  
Polymer Properties ◽  
The Matrix ◽  
Conductivity Of Nanotubes

AbstractThe remarkable electrical and thermal conductivities of isolated carbon nanotubes have spurred worldwide interest in using nanotubes to enhance polymer properties. Electrical conductivity in nanotube/polymer composites is well described by percolation, where the presence of an interconnected nanotube network corresponds to a dramatic increase in electrical conductivity ranging from 10−5 S/cm to 1 S/cm. Given the high aspect ratios and small diameters of carbon nanotubes, percolation thresholds are often reported below 1 wt% although nanotube dispersion and alignment strongly influence this value. Increases in thermal conductivity are modest (∼3 times) because the inter facial thermal re sis tance between nanotubes is considerable and the thermal conductivity of nanotubes is only 104 greater than the polymer, which forces the matrix to contribute more toward the composite thermal conductivity, as compared to the contrast in electrical conductivity, >1014. The nanotube network is also valuable for improving flame-retardant efficiency by producing a protective nanotube residue. In this ar ticle, we highlight published research results that elucidate fundamental structure–property relationships pertaining to electrical, thermal, and/or flammability properties in numerous nanotube-containing polymer composites, so that specific applications can be targeted for future commercial success.

Thermal Conductivity of Single-Wall Carbon Nanotubes

2004 ◽  
Author(s):  
Hongliang Zhong ◽  
Jennifer R. Lukes
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Tube Length ◽  
Single Wall Carbon Nanotubes ◽  
Single Wall Carbon ◽  
Simulation Methodology

Despite the significant amount of research on single-wall carbon nanotubes, their thermal conductivity has not been well established. To date only one experimental thermal conductivity measurement has been reported for these molecules around room temperature, with large uncertainty in the thermal conductivity values. Existing theoretical predictions based on molecular dynamics simulation range from several hundred to 6600 W/m-K. In an attempt to clarify the order-of magnitude discrepancy in the literature, this paper utilizes molecular dynamics simulation to systematically examine the thermal conductivity of several (10, 10) single-wall carbon nanotubes as a function of length, temperature, boundary conditions and molecular dynamics simulation methodology. The present results indicate that thermal conductivity ranges from about 30–300 W/m-K depending on the various simulation conditions. The results are unconverged and keep increasing at the longest tube length, 40 nm. Agreement with the majority of literature data is achieved for the tube lengths treated here. Discrepancies in thermal conductivity magnitude with experimental data are primarily attributed to length effects, although simulation methodology, stress, and intermolecular potential may also play a role. Quantum correction of the calculated results reveals thermal conductivity temperature dependence in qualitative agreement with experimental data.

Thermal Properties of Single-Walled Carbon Nanotubes

2000 ◽  
Vol 633 ◽  
Author(s):  
J. Hone ◽  
B. Batlogg ◽  
Z. Benes ◽  
M.C. Llaguno ◽  
N.M. Nemes ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Thermal Properties ◽  
Specific Heat ◽  
Small Diameter ◽  
Phonon Modes ◽  
Mechanical Coupling ◽  
Macro Scale ◽  
Conductivity Of Nanotubes ◽  
Walled Carbon Nanotubes

AbstractThe thermal properties of carbon nanotubes are strongly dependent on their unique structure and size, and show promise as an ideal material for thermal management on the micro- and macro-scale. The specific heat of nanotubes is similar to that of two-dimensional graphene at high temperatures, but is sensitive to the effects of rolling the the graphene sheet into a small cylinder at low temperatures. Specifically, the acoustic phonon modes are stiffened due to the cylindrical geometry, and the phonon spectrum is quantized due to the small diameter of the tube. In bundles of single-walled nanotubes, the specific heat is a sensitive probe of inter-tube mechanical coupling. Measurements of the specific heat show that inter-tube coupling is relatively weak, and show direct evidence for quantum effects. The thermal conductivity of nanotubes should reflect the on-tube phonon structure. Aligned bundles of SWNTs show a high thermal conductivity (>200 W/m-K at room temperature), and possible quantization effects at low temperature.

ROLE OF THREE-PHONON AND FOUR-PHONON PROCESSES IN THERMAL TRANSPORT OF SINGLE-WALLED CARBON NANOTUBES

2013 ◽  
Vol 27 (16) ◽  
pp. 1350117 ◽  
Author(s):  
P. SAPNA ◽  
T. J. SINGH
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Single Walled Carbon Nanotubes ◽  
Independent Effect ◽  
Tube Length ◽  
Single Walled Carbon ◽  
Optical Modes ◽  
Semiconducting Nanotubes ◽  
Walled Carbon Nanotubes

Thermal conductivity of single-walled carbon nanotubes has been calculated considering the three-phonon and four-phonon processes. The contribution of the acoustic modes and optical modes in the relaxation rate of the phonon–phonon interaction and hence to the thermal conductivity have been considered. The thermal conductivity has been calculated for the (8, 0), (10, 0), (11, 0) and (13, 0) zigzag semiconducting nanotubes having different radii. It is found that the thermal conductivity increases linearly at low temperatures which is nearly T2 below 30 K and after reaching a peak, it decreases as aT-1 - bT-2 where a and b are constants and b > a at higher temperatures. It is also found that the thermal conductivity increases with increasing radius of the tube due to the independent effect of three-phonon process and four-phonon process. The thermal conductivity is also found to decrease with increasing tube length due to four-phonon process.

Defect Induced Variabilities in Thermal Conductivity of Nano Structures

2019 ◽  
Author(s):  
Sushan Nakarmi ◽  
Vinu U. Unnikrishnan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Characteristics ◽  
Heat Bath ◽  
Hexagonal Structure ◽  
Special Focus ◽  
Proper Understanding ◽  
Nano Structures ◽  
Conductivity Of Nanotubes ◽  
The Comparative Study ◽  
Thermal Conductivities

Abstract The high thermal conductivity of carbon nanotubes makes them ideal candidates for use as nano-fins for thermal management in electronics and composites. At the nanoscale, the thermal conductivity of nanotubes are found to be dependent on size, strain states, temperature, and presence of defects and vacancy. The proper understanding of the effect of these parameters are important in constructing a nanotube system with desired thermal characteristics. Here, we pay special focus on the effect of different kinds of defects and vacancies on the thermal conductivities of nanotubes. Defects and vacancies are imperfections in an otherwise hexagonal structure of nanotube. Their presence have shown to impede the thermal transport in nano-structures which is attributed to the scattering of phonons that occurs in these imperfections. The thermal conductivities of (10,10) armchair nanotube with defects and vacancies are determined using the heat bath method, a non-equilibrium molecular dynamic simulation and are compared with that of pristine carbon nano-structures. This is followed by the comparative study of phonon density of states of nanotubes with and without the defects.

EFFECTIVE THERMAL CONDUCTIVITY OF NANOFLUIDS CONTAINING CYLINDRICAL NANOPARTICLES

2007 ◽  
Vol 06 (01) ◽  
pp. 45-49 ◽  
Author(s):  
JAMSHID SABBAGHZADEH ◽  
SADOLLAH EBRAHIMI
Keyword(s):  
Thermal Conductivity ◽  
Theoretical Model ◽  
Effective Thermal Conductivity ◽  
Experimental Results ◽  
Cylindrical Shape ◽  
Nanoparticle Diameter ◽  
Conductivity Of Nanotubes

We present a theoretical model for explaining the enhancement in the effective thermal conductivity of nanotubes (cylindrical shape particles) for use in nanotube-in-fluid suspensions. Our theoretical model shows that the effective thermal conductivity is decreased with cylindrical nanoparticle diameter, which agrees with experimental results. We also show that with the decrease of nanotube diameter, the thermal conductivity increases if the thickness of nanolayers increases. We provide a good estimation for the nanolayer's thickness which plays an important role in increasing the thermal conductivity.

Molecular Dynamics Study on Thermal Conductivity of Single-Walled Carbon Nanotubes

2009 ◽  
Author(s):  
Bingyang Cao ◽  
Quanwen Hou ◽  
Zengyuan Guo ◽  
Wusheng Zhang
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
Molecular Dynamics Simulations ◽  
Phonon Transport ◽  
Tube Length ◽  
Length Dependence ◽  
Dynamics Simulations ◽  
Walled Carbon Nanotubes

In this paper, we study the thermal conductivities of sing-walled carbon nanotubes (CNTs) and CNTs-based nanocomposites using molecular dynamics simulations. Length dependence of the thermal conductivity of (5, 5) carbon nanotube at 300 K and 1000 K is simulated. At room temperature the thermal conductivity shows linear length dependence with the tube length less than 40 nm, which indicates the completely ballistic transport. The thermal conductivity increases with the increase of the nanotube length, but the increase rate decreases as the length increases. It shows that the phonon transport transits from ballistic to diffusive. In the simulations, the power exponent of the thermal conductivity of carbon nanotube to the tube length decreases by decaying exponential function as the tube length increases. We also observe a decrease of the low-dimensional effects by the surrounding matters. A carbon-nanotube-atom-fixed and -activated scheme of non-equilibrium molecular dynamics simulations is put forward to extract the thermal conductivity of carbon nanotubes embedded in solid argon. Though a 6.5% volume fraction of CNTs increases the composite thermal conductivity by about twice larger than that of the pure basal material, the thermal conductivity of CNTs embedded in solids is found to be decreased by 1/8–1/5 with reference to that of pure ones. The decrease of the intrinsic thermal conductivity of the solid-embedded CNTs and the thermal interface resistance are demonstrated to be responsible for the results.

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