Molecular Dynamic Simulation Of Graphene’s Thermal Property

Properties of graphene have drawn more and more attention with the development of graphene technology. One of important properties is thermal performance. Although measurement technology for conventional materials has developed to be very mature, it is very difficult to take a measurement of graphene’s thermo-physical property due to the special two-dimensional structure. And molecular dynamics simulation method can be a good way to calculate and predict the thermo-physical property of graphene, such as thermal conductivity, thermal rectification, thermal boundary resistance and so on. Based on this, the graphene thermal physical properties were researched by using molecular dynamics method.First, graphene has very high thermal conductivity. But the size of graphene has a tendency to micro-nano scales during application. And thermal conductivity of graphene will be seriously affected by size. Studying size effect on thermal conductivity by experiment will be difficult. In this paper, the size effect on thermal conductivity was systematacially studied. Result shows thermal conductivity of GNRs decreases with reduction of length, the attenuation shows an exponential law. And attenuation rate is not the same for different chiral GNRs. In the process of simulation, heat flux imposed on GNRs also has effect on thermal conductivity. Now, most research of heat transfer of graphene and carbon nanotubes are under low heat flux which is due to the convergence of Fourier heat conduction law. But in this paper, influence on thermal conductivity at high heat flux was calculated. Something interesting was found. Result shows the anomalous wave-like kinetic energy transport is an important property of graphene at high heat flux.Second, as a special two-dimensional material, another property of graphene-thermal rectification has been widely researched. This is similar to the phenomenon of electric rectification features. But it is difficult to observe and measure in ordinary circumstances. While graphene with high thermal conductivity makes it sensitive to structure, what makes it possible to become thermal rectifier. In this paper, thermal rectification was studied through establishing asymmetric structure of graphene. Results show that the heat transfer direction from wide structure to narrow structure is the prior direction.Finally, pure graphene is rarely used in practical applications. Most of operation is conducted with substrate. Due to the limitation of experiment conditions, it is difficult to measure the change of graphene thermal physical property on substrate accurately. In order to know whether graphene on substrate can maintain good features, the heat transfer characteristics of graphene on silicon substrate and SiO2substrate were further studied by molecular dynamics method. Results show that the thermal conductivity of graphene on two kinds of substrate is down to about90%and70%of the original respectively.Thermal physical properties of graphene were studied systematically by means of molecular dynamic simulation. And it provides a certain reference value for graphene device in heat application.