The Structure Adjustment Of Heat Transport Characteristics For Low Dimensional Materials

Low dimensional material is one kind of emerging material. Their energy transportation properties shows difference compared with the bulk system when their scale is at the nanometer magnitude at one or more dimensions. Suggested by the experimental and theoretical studies, thermal conductivity of low dimensional materials is not only influenced by temperature factors but also closely relevant to the size and shape of the structure of material itself. For this reason, mastering the regulatory mechanism of material structure in modifying heat transportation characteristics of the low dimension material is not only significant for the application of low dimensional materials, but also has important academic significance to improve the nano materials heat transfer theory.In our work, the heat transportation of three different low dimensional materials i.e. nanowire, graphene and graphyne were investigated by non-equilibrium molecular dynamics simulations. The regulation mechanism of the different defects structure and stacking structure affects the heat transfer characteristic in low dimension material has been researched. The influence rule of structural features parameters such as defect location, size, porosity and length etc. has been discussed. The conclusions can be summarized as follows:(1) The velocity-scale method was used to explore the influence of the size and position of defects on the thermal conductivity. The thermal conductivity has been decreased with the increasing of porosity. With the same porosity, the thermal conductivity of silicon nanowire with body defects has been decreased more the those with surface defect, which is due to the red shift of phonon’s DOS peak and the decreasing of phonon participation. From the calculation under different initial temperatures, the thermal conductivity is decreased with the increasing of temperature. By comparing the nanowires with different lengths, the thermal conductivity is increased with the increasing of the length.(2) The heat flux method was used to explore the influence of the regular and fractal defects on the thermal conductivity of graphene. Under the same porosity, the fractal defects bring a larger thermal resistance than the regular defects, which is due to the larger red shift of phonon’s DOS peak and decreasing of phonon participation for the graphene with fractal defects.(3) The influence of the stack behavior on the thermal conductivity of graphyne is investigated by molecular dynamics simulation. With the layers increased, the thermal conductivity of graphyne is decreased, meanwhile, the thermal conductivity increased with the increasing of the length of graphyne.