Thermal Rectification in Graphene and Carbon Nanotube Systems Using Molecular Dynamics Simulations

Author(s):  
Ajit K. Vallabhaneni ◽  
Jiuning Hu ◽  
Yong P. Chen ◽  
Xiulin Ruan

We investigate the thermal rectification phenomena in asymmetric graphene and carbon nanotube systems using molecular dynamics (MD) simulations. The effects of various parameters, including mean temperature, temperature difference, and system size on rectification factor have been studied. In homogenous triangular graphene nanoribbons (T-GNR), the heat current is normally higher from wide to narrow end than that in the opposite direction, resulting in a positive rectification factor. The rectification factor increases further for a double layered T-GNR. It is also found that varying the parameters like mean temperature can result in reverse of the sign of thermal rectification factor. In the case of carbon nanotube (CNT)–silicon system, the heat current is higher when heat flows from CNT to silicon. The thermal rectification factor is almost independent of the diameter of CNT. In both cases, the rectification factor increases with the imposed temperature difference.

2011 ◽  
Vol 1347 ◽  
Author(s):  
Bo Qiu ◽  
Yan Wang ◽  
Xiulin Ruan

AbstractIn this work, we perform molecular dynamics (MD) simulations to study the linear thermal transport in suspended graphene and the nonlinear thermal transport phenomena in graphene nanoribbons (GNR). We use spectral energy density analysis to quantitatively address the relative importance of different types of phonon in thermal transport in suspended graphene. Negative differential thermal conductance (NDTC) and thermal rectification in graphene nanoribbons have been studied using nonequilibrium molecular dyanmics simulations. Ballistic transport regime, sufficient temperature nonlinearity and asymmetry are found to be necessary conditions for the onset of these behaviors.


2015 ◽  
Vol 817 ◽  
pp. 797-802 ◽  
Author(s):  
Cai Jiang ◽  
Jian Wei Zhang ◽  
Shao Feng Lin ◽  
Su Ju ◽  
Da Zhi Jiang

Molecular dynamics (MD) simulations on three single walled carbon nanotube (SWCNT) reinforced epoxy resin composites were conducted to study the influence of SWCNT type on the glass transition temperature (Tg) of the composites. The composite matrix is cross-linked epoxy resin based on the epoxy monomers bisphenol A diglycidyl ether (DGEBA) cured by diaminodiphenylmethane (DDM). MD simulations of NPT (constant number of particles, constant pressure and constant temperature) dynamics were carried out to obtain density as a function of temperature for each composite system. The Tg was determined as the temperature corresponding to the discontinuity of plot slopes of the densityvsthe temperature. In order to understand the motion of polymer chain segments above and below the Tg, various energy components and the MSD at various temperatures of the composites were investigated and their roles played in the glass transition process were analyzed. The results show that the Tg of the composites increases with increasing aspect ratio of the embedded SWCNT


2014 ◽  
pp. 466-477
Author(s):  
Nabila Tahreen ◽  
K. M. Masud

In recent years, polymer/carbon nanotube composites have attracted increased attention because the polymer properties have significantly improved. In this paper, a single walled carbon nanotube (SWCNT) is used to reinforce polystyrene matrix. Molecular dynamics (MD) simulations are used to study two periodic systems - a long CNT-reinforced polystyrene composite and amorphous polystyrene matrix itself. The axial and transverse elastic moduli of the amorphous polystyrene matrix and nanocomposites are evaluated using constant-strain energy minimization method. The results from MD simulations are compared with corresponding rule-of-mixture predictions. The simulation results show that CNTs significantly improve the stiffness of polystyrene/CNT composite, especially in the longitudinal direction of the nanotube. Polystyrene posses a strong attractive interaction with the surface of the SWCNT and therefore play an important role in providing effective adhesion. The conventional rule-of-mixture predicts a smaller value than MD simulation where there are strong interfacial interactions. Here the authors report a study on the interfacial characteristics of a CNT-PS composite system through MD simulations and continuum mechanics.


NANO ◽  
2015 ◽  
Vol 10 (02) ◽  
pp. 1550025 ◽  
Author(s):  
Seyed Hanif Mahboobi ◽  
Alireza Taheri ◽  
Hossein Nejat Pishkenari ◽  
Ali Meghdari ◽  
Mahya Hemmat

Determination of an injection condition which is minimally invasive to the cell membrane is of great importance in drug and gene delivery. For this purpose, a series of molecular dynamics (MD) simulations are conducted to study the penetration of a carbon nanotube (CNT) into a pure POPC cell membrane under various injection velocities, CNT tilt angles and chirality parameters. The simulations are nonequilibrium and all-atom. The force and stress exerted on the nanotube, deformation of the lipid bilayer, and strain of the CNT atoms are inspected during the simulations. We found that a lower nanotube velocity results in successfully entering the membrane with minimum disruption in the CNT and the lipid bilayer, and CNT's chirality distinctly affects the results. Moreover, it is shown that the tilt angle of the CNT influences the nanotube's buckling and may result in destroying the membrane structure during the injection process.


2019 ◽  
Vol 33 (23) ◽  
pp. 1950258 ◽  
Author(s):  
Danhui Zhang ◽  
Houbo Yang ◽  
Zhongkui Liu ◽  
Anmin Liu

Polynylon66, as a kind of important engineering plastics, is widely used in various fields. In this work, we studied the interfacial interactions between polynylon66 and single-walled carbon nanotubes (SWCNTs) using molecular dynamics (MD) simulations. The results showed that the polynylon66 could interact with the SWCNTs and the mechanism of interfacial interaction between polynylon66 and SWCNTs was also discussed. Furthermore, the morphology of polynylon66 adsorbed to the surface of SWCNTs was investigated by the radius of gyration. Influence factors such as the initial angle between polynylon66 chain and nanotube axis, SWCNT radius and length of polynylon66 on interfacial adhesion of single-walled carbon nanotube-polymer and the radius of gyration of the polymers were studied. These results will help to better understand the interfacial interaction between polymer and carbon nanotube (CNT) and also guide the fabrication of high performance polymer/carbon nanotube nanocomposites.


Author(s):  
Peng-zhe Zhu ◽  
Hui Wang ◽  
Yuan-zhong Hu

Three-dimensional molecular dynamics (MD) simulations have been performed to investigate behaviors of nanoindentation and nano-scratch. The first case concerns the effects of material defect on the nanoindentation of nickel thin film. The defect is modeled by a spherical void embedded in the substrate and located under the surface of indentation. The simulation results reveal that compared to the case without defect, the presence of the void softens the material and allows for larger indentation depth at a given load. MD simulations are then performed for nano-scratch of single crystal copper, with emphasis on the effect of indenter shape (sharp and blunt) on the substrate deformation. The results show that the blunt indenter causes larger deformation region and much more dislocations at both the indentation and scratch stages. It is also found that during the scratching stage the blunt indenter results in larger chip volume in front of the indenter and gives rise to more friction than the sharp indenter. The scope of the simulations has been extended by introducing a multiscale model which couples MD simulations with Finite Element Method (FEM), and multiscale simulations are performed for two-dimensional nanoindentation of copper. The model has been validated by well-consistent load-depth curves obtained from both multiscale and full MD simulations, and by good continuity of deformation observed in the handshake region. The simulations also reveal that indenter radius and indentation velocity significantly affect the nanoindentation behavior. By use of multiscale method, the system size to be explored can be greatly expanded without increasing much computational cost.


2005 ◽  
Author(s):  
Jose´ E. Solomon ◽  
Jay Kapat ◽  
Ranganathan Kumar ◽  
Deepak Srivastava

The focus of the current research is the investigation and characterization of the energy transport between a (10,10) single-wall carbon nanotube (SWCNT) and surrounding molecular hydrogen gas using molecular dynamics (MD) simulations. The MD simulations use Tersoff-Brenner hydrocarbon potential for C-C, C-H, and H-H bonding interactions and the conventional Lennard-Jones potential for soft-sphere gas-CNT collision dynamics of H-H and H-C non-bonding van der Waals interactions. A simulation cell with periodic boundary conditions is created for 1200 carbon atoms in an armchair nanotube configuration and three distinct gas densities corresponding to 252, 500, and 1000 H2 molecules in the same volume. The MD simulation runs are performed with time steps of 0.1 fs and the total simulation times of 40 ps. The simulations are initialized by setting the gas species and CNT at two different temperatures. Initial gas temperatures range from 2000K to 4000K, whereas the carbon nanotube is held at 300K. After the equilibrium temperatures of the CNT and the gas molecules are achieved, the external constraints to maintain the temperature are removed and the thermal energy transport between the two is studied. The kinetic energy exchange between the nanotube and the surrounding gas is monitored to study thermal energy transport over the duration of the simulation. A parameter is proposed, the coefficient of thermal energy transfer (CTET), to characterize the thermal transport properties of the modeled systems based on parameters governing the transport process, thus mimicking the conventional heat transfer coefficient. Values for CTET vary directly with gas density and range from 50 MW/m2K to 250MW/m2K, showing that gas density has a significant impact with higher density corresponding to higher collision rates and higher rates of energy transfer. In contrast, the gas temperature has a lower impact on CTET, with colder gas providing in certain cases a slightly lower value for the coefficient. In order to validate the MD simulations, the time-series data of molecular vibrations of the CNT is converted to a vibrational frequency spectrum through FFT. The characteristic frequencies obtained on the spectra of isolated SWCNT and H2 simulations are compared against the known natural frequencies of the CNT phonon modes and vibrational modes of H2 molecules. The comparison is quite favorable.


2017 ◽  
Vol 885 ◽  
pp. 216-221
Author(s):  
Dávid Fülep ◽  
Ibolya Zsoldos ◽  
István László

The sensitivity of defect free fusion of straight carbon nanotubes from graphene nanoribbons to the position of the nanoribbon edge positions has been investigated. A basic difference between the behavior of armchair and zigzag type nanoribbons was observed. When placing armchair type graphene nanoribbons above each other identical, fitting positions are obtained automatically. Zigzag type graphene nanoribbons, however, must not be placed above each other in identical positions. From the viewpoint of defect-free fusion, according to the MD simulations symmetric on nearly symmetric positions of the ribbon edges are favorable.


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