Effect of Tensile Strain on Thermal Properties of Graphene

2014 ◽  
Vol 1661 ◽  
Author(s):  
Ayman Salman Alofi ◽  
Gyaneshwar P. Srivastava
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Thermal Properties ◽  
Specific Heat ◽  
Density Of States ◽  
Tensile Strain ◽  
Phonon Dispersion ◽  
Analytical Expressions ◽  
Vibrational Density ◽  
Phonon Dispersion Relations

ABSTRACTWe have employed a semicontinuum model to investigate the effect of tensile strain on thermal properties of graphene. Analytical expressions derived by Nihira and Iwata for phonon dispersion relations and vibrational density of states are employed, based on the semicontinuum model proposed by Komatsu and Nagamiya. The thermal conductivity is computed within the framework of Callaway’s effective relaxation time theory. It is found that thermal properties of graphene are quite sensitive to tensile strain. In the presence of tensile strain, the specific heat increases but the thermal conductivity decreases.

The role of three-phonon Normal processes in the thermal conductivity of graphene

2012 ◽  
Vol 1404 ◽  
Author(s):  
Ayman Alofi ◽  
Gyaneshwar P. Srivastava
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Room Temperature ◽  
Phonon Dispersion ◽  
Correction Term ◽  
Single Mode ◽  
Analytical Expressions ◽  
Phonon Dispersion Relations ◽  
Time Theory

ABSTRACTWe have studied the thermal conductivity of graphene using Callaway’s effective relax-ation time theory and by employing analytical expressions for phonon dispersion relations and vibrational density of states based on the semicontinuum model by Nihira and Iwata. It is found that consideration of the momentum conserving nature of three-phonon Normal pro-cesses is very important for explaining the magnitude as well as the temperature dependence of the experimentally measured results. At room temperature, the N-drift contribution (the correction term in Callaway’s theory) provides 94% addition to the result obtained from the single-mode relaxation time theory, clearly suggesting that the single-mode relaxation time approach is inadequate for describing the phonon conductivity of graphene.

Thermal Properties of Nanotubes and Nanowires With Acoustically Stiffened Surfaces

2011 ◽  
Author(s):  
Michael F. P. Bifano ◽  
Vikas Prakash
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Specific Heat ◽  
Phonon Dispersion ◽  
Thermal Conductance ◽  
Frequency Equation ◽  
Outer Diameter ◽  
Phonon Confinement ◽  
Maximum Increase ◽  
Acoustic Tuning

A core-shell elasticity model is employed to investigate the effect of a nanowire and nanotube’s increased surface moduli on specific heat, ballistic thermal conductance, and thermal conductivity as a function of temperature. Phonon confinement is analyzed using approximated phonon dispersion relations that result from solutions to the frequency equation of a vibrating rod and tube. The results indicate a maximum 10% decrease in lattice thermal conductivity and ballistic thermal conductance near 160 K for a 10 nm outer diameter nanotube with an inner diameter of 5 nm when the average Young’s Modulus of both the inner and outer free surfaces is increased by a factor of 1.53. In the presence of the acoustically stiffened surfaces, the specific heat of the nanotube is found to decrease by up to 20% at 160 K. Near room temperature, changes in thermal properties are less severe. In contrast, a 10 nm outer diameter nanowire composed of similar material exhibits up to a 12% maximum increase in thermal conductivity at 600 K, a 25% increase in ballistic thermal conductance at 400 K, and a 48% increase in specific heat at 470 K when its outer free surface is acoustically stiffened to the same degree. Our simplified model may be extended to investigate the acoustic tuning of nanowires and nanotubes by inducing surface stiffening or softening via appropriate surface chemical functionalization and coatings.

Prediction of the Thermal Conductivity of ZnO Nanostructures

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
P. Chantrenne ◽  
C. Ould-Lahoucine
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Specific Heat ◽  
Phonon Dispersion ◽  
Measurement Data ◽  
Md Simulations ◽  
Bulk Sample ◽  
Time Parameter ◽  
Zno Nanostructures ◽  
Sample Measurement

The kinetic theory of gas is used to predict the specific heat and thermal conductivity of ZnO nanostructures. In this model, phonons are considered as a gas whose basic properties are given by phonon dispersion curves. The model also requires knowledge of the boundary relaxation time parameter (F), the defect relaxation time parameter D, and the relaxation time parameters which take into account lattice anisotropy. These parameters can be determined independently from experimental measurements. Excellent agreements were found when comparing both the estimated specific heat and thermal conductivity to bulk sample measurement data. Comparison with previous results obtained with molecular dynamics (MD) simulations leads to the conclusion that for ultra narrow nanobelts, thermal conductivity depends on their length. Behavior of the thermal conductivity of nanofilms is also studied. The results are consistent with previous works on 1D and 2 D systems. Finally, the thermal conductivity of nanobelts is presented as are the influences of boundary and defect parameters.

Vibrational properties and specific heat of core–shell Ag–Au icosahedral nanoparticles

2015 ◽  
Vol 17 (42) ◽  
pp. 28054-28059 ◽  
Author(s):  
Huziel E. Sauceda ◽  
Ignacio L. Garzón
Keyword(s):  
Thermal Properties ◽  
Low Temperature ◽  
Specific Heat ◽  
Metal Nanoparticles ◽  
Density Of States ◽  
Geometrical Structure ◽  
Vibrational Properties ◽  
Core Shell ◽  
Vibrational Density Of States ◽  
Vibrational Density

The vibrational density of states (VDOS) of metal nanoparticles can be a fingerprint of their geometrical structure and determine their low-temperature thermal properties.

Thermal Characterization of Carbon-Carbon Composites

2011 ◽  
Author(s):  
Messiha Saad ◽  
Darryl Baker ◽  
Rhys Reaves
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Carbon Composite ◽  
Flash Method ◽  
Carbon Composites ◽  
Energy Storage Devices ◽  
Graphitized Carbon

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.

Experimental Study on Thermal Properties of Hollow Sphere Structures

2021 ◽  
Vol 407 ◽  
pp. 185-191
Author(s):  
Josef Tomas ◽  
Andreas Öchsner ◽  
Markus Merkel
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Hollow Sphere ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

Determination of the Thermal Properties of a PCB by Coupled Numerical and Experimental Approach

2020 ◽  
Author(s):  
Yener Usul ◽  
Mustafa Özçatalbaş
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Numerical Analysis ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Analyses ◽  
Analysis Model ◽  
Linear Temperature ◽  
Coefficient Of Thermal Conductivity

Abstract Increasing demand for usage of electronics intensely in narrow enclosures necessitates accurate thermal analyses to be performed. Conduction based FEM (Finite Element Method) is a common and practical way to examine the thermal behavior of an electronic system. First step to perform a numerical analysis for any system is to set up the correct analysis model. In this paper, a method for obtaining the coefficient of thermal conductivity and specific heat capacity of a PCB which has generally a complex composite layup structure composed of conductive layers, and dielectric layers. In the study, above mentioned properties are obtained performing a simple nondestructive experiment and a numerical analysis. In the method, a small portion of PCB is sandwiched from one side at certain pressure by jaws. A couple of linear temperature profiles are applied to the jaws successively. Unknown values are tuned in the analysis model until the results of FEM analysis and experiment match. The values for the coefficient of thermal conductivity and specific heat capacity which the experiment and numerical analysis results match can be said to be the actual values. From this point on, the PCB whose thermal properties are determined can be analyzed numerically for any desired geometry and boundary condition.

Strain Engineering of Thermal Conductivity of Two-Dimensional MoS2 and h-BN

MRS Advances ◽  
2016 ◽  
Vol 1 (32) ◽  
pp. 2297-2302 ◽  
Author(s):  
Xiaonan Wang ◽  
Alireza Tabarraei
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strain ◽  
Phonon Dispersion ◽  
Hexagonal Boron Nitride ◽  
Three Dimensional ◽  
Strain Engineering ◽  
Normal Strain ◽  
Dynamics Modeling ◽  
Molecular Dynamics Modeling ◽  
The Impact

ABSTRACTWe have used reverse nonequlibrium molecular dynamics modeling to study the impact of uniaxial stretching on the thermal conductivity of monolayer molybdenum disulfide (MoS2) and hexagonal boron nitride (h-BN). Our results predict an anomalous response of the thermal conductivity of these materials to normal strain. Thermal conductivity of h-BN increases under a tensile strain whereas thermal conductivity of MoS2 remains fairly constant. These are in striking contrast to the impact of tensile strain on the thermal conductivity of three dimensional materials whose thermal conductivity decreases under tensile strain. We investigate the mechanism responsible for this unexpected behavior by studying the impact of tensile strain on the phonon dispersion curves and group velocities of these materials.

scholarly journals Thermal Properties of Yttrium Aluminum Garnett From Molecular Dynamics Simulations

2011 ◽  
Author(s):  
Majid S. al-Dosari ◽  
D. G. Walker
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Specific Heat ◽  
Molecular Dynamics Simulations ◽  
Yttrium Aluminum Garnet ◽  
System Size ◽  
Yttrium Aluminum ◽  
Dynamics Simulations

Yttrium Aluminum Garnet (YAG, Y3Al5O12) and its varieties have applications in thermographic phosphors, lasing mediums, and thermal barriers. In this work, thermal properties of crystalline YAG where aluminum atoms are substituted with gallium atoms (Y3(Al1−xGax)5O12) are explored with molecular dynamics simulations. For YAG at 300K, the simulations gave values close to experimental values for constant-pressure specific heat, thermal expansion, and bulk thermal conductivity. For various values of x, the simulations predicted no change in thermal expansion, an increase in specific heat, and a decrease in thermal conductivity for x = 50%. Furthermore, the simulations predicted a decrease in thermal conductivity with decreasing system size.

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