Molecular Dynamic Simulation Of Thermal Interface Properties Of Carbon Nanotube

Recently, heat flux has risen sharply with the decreasing size of electronic device; At the same time, some gaps or holes have appeared when the electronic device and radiator contract, it hinders the heat transfer from the electronic device to radiator, making work efficiency and the working life of electronic device and equipment greatly reduced. Therefore, improving the level of the cooling of electronic equipment become the important factors which restrict the development of the electronics industry.In view of the above problems, the experts put forward the concept of thermal interface materials. We improve the efficiency of heat transfer by filling the thermal interface materials into the gap to reduce the thermal resistance. In recent years, carbon nanotubes have become a popular new thermal interface materials because of their high axial thermal conductivity and good flexibility. If you want to improve the heat transfer efficiency from the electronic device to the radiator, not only interface materials must have high thermal conductivity, but also we should reduce interfacial thermal resistance between electronic devices and thermal interface materials, the thermal interface materials and the radiator.In this paper, the molecular dynamics method is used to simulate the thermal characteristics of carbon nanotube-silicon and carbon nanotube-copper. These characteristics will provide a certain reference value for the design of the heat sink of microelectronic devices in the future.In the simulation of the thermal interface characteristics of the single wall carbon nanotube-silicon and the single wall nanotube-copper, we consider four factors, such as the temperature, the atomic force between the interface, the diameter of the carbon nanotubes, and the thermal rectification effect. After calculation, the following four rules are obtained:(1) the interfacial thermal conductance increases with the increase of temperature, the reason of this phenomenon is due to that when the temperature rises, more phonons are excited, promoting the transfer of heat. The latter has a peak value at 550K, which is slightly decreased then. (2) the interfacial thermal conductance increases with the increase of the interface force between atoms. With the augmentation of the acting force and vibration, phonon coupling has enhanced and heat transfer level is improved. (3) the change of the diameter of the carbon nanotube has a great influence on the thermal conductance of the interface, Increasing the diameter of the carbon nanotube, the number of atoms interacting at the interface increases and the heat transfer path becomes more, so the interfacial thermal conductance increases. (4) after the exchange of hot side and cold side, interfacial thermal conductance values has changed significantly, in single-walled carbon nanotubes-silicon model, the one that carbon nanotubes is set as hot end has 5.5%?22% higher interfacial thermal conductance than the one that the carbon nanotube is set as cold end. In single-walled carbon nanotube-copper model, the one that carbon nanotubes is set as hot end has 3%?10% higher interfacial thermal conductance than the one that the carbon nanotube is set as cold end. This shows that there is a thermal rectification effect in the interfacial heat transfer, and from the numerical value, the single wall carbon nanotube-silicon is affected more greatly. Both of them are decreased with the increase of the temperature.In the simulation of the thermal interfacial characteristics of multiple-wall carbon nanotube-silicon and multiple-wall nanotube-copper interface, the temperature, the number of tube wall and the atomic force are considered. the following rules are obtained.(1) we make the temperature dependence of the simulation taking three wall carbon nanotube for example, and have the same conclusions with single-wall carbon nanotubes. The interfacial thermal conductance increases with increasing temperature and with the same temperature, interfacial thermal conductance of carbon nanotubes-silicon was significantly greater than carbon nanotubes-copper (2) the thermal conductance decreases with the increase of the number of walls. (3)the force dependent simulation mainly includes two aspects, on is the force between the adjustment of carbon atoms and silicon/copper atoms, after calculation, it is found that the interfacial thermal conductance increases linearly with the increasing atomic force; the other one is the force of carbon atoms in different layers. It is found that the thermal interfacial conductance does not change. The force between the carbons in different walls has no influence on the heat transfer on the axial direction.