Molecular Dynamics Research On Normal Thermal Conductivity Of SWCNT/PE Composite

With the electronic equipment tends to be thin and integrated,thermal management has become the core task of the design and application of electronic equipment.With the development of electronic integration technology,electronic devices become smaller and smaller when operating frequency is rising and heat continue to accumulate,so heat dissipation has become an important factor in the development of confined materials.It is an urgent work to ensure the smooth operation of electronic devices and to export the heat in time.Polyethylene has many advantages,such as light weight,corrosion resistance and easy processing.Increasing the thermal conductivity of polyethylene by adding thermal conductive fillers to polyethylene will greatly expand the application range of polyethylene composites.In this paper,carbon nanotubes,carbon nanotubes/polyethylene composites were simulated and the influence of time step length,molecular chain length and temperature on the thermal conductivity of polyethylene was studied by means of equilibrium molecular dynamics method.In view of the influence of defects on the thermal conductivity of carbon nanotubes,several models are builded and the thermal conductivity of the single vacancy defect,the defect of the double atom vacancy and the Stone-Wales defect are calculated.The effect of defect density and symmetry effect on the thermal conductivity of carbon nanotubes is discussed.In the last,carbon nanotube be filled polyethylene to prepared carbon nanotubes/polyethylene composite materials,the length,temperature,carbon nanotube filling density has influenced the thermal conductivity of carbon nanotube composite.The results show that thermal conductivity of CNT/PE composites can be accurately simulated by the time step of 0.1fs.With the increase of temperature,the thermal conductivity of polyethylene increases firstly and then decreases.The chain length of polyethylene is gradually increased,and the thermal conductivity of polyethylene decreases.At the lengh of 50 nm,the thermal conductivity of the perfect(8,8)single-walled carbon nanotubes be calculated to 589 W/(m·K).With the increase of the gap spacing,the thermal conductivity of carbon nanotubes with a single vacancy defect decreases first and then increases while the thermal conductivity of carbon nanotubes with double atomic vacancy defects and Stone-Wales defects increases first and then decreases.Although the Stone-Wales defect is not lost,it is the biggest damage to the thermal conductivity of carbon nanotubes.The defect density is doubled,but under the action of the symmetry effect of the defect,the thermal conductivity is not decreased.Carbon nanotube be filled to polyethylene increase thermal conductivity obviously,so carbon nanotube is effective to the packing material of polyethylene;with double packing density thermal conductivity also increased.