The Model And Mechanism Study Of Thermal Conductivity Of Graphene/PDMS Composites

With the rapid development of the electronic information industry,the packed of electronic devices has been more densely and the size of electronic devices has been smaller.The heat produced by the working components increased the temperature resulting in a short lifetime and less reliability of the devices.The heat dissipation became an urgent problem to be solved.The traditional heat dissipation method reached a limitation.It was need to develop some new methods.In this study,graphene was added to PDMS to prepare thermal conductive composites.The thermal behavior of graphene nanoplatelets(GNPs)based nanocomposites was investigated from both experimental and theoretical aspects.The main research content is as follows:1.This paper describes the advantages and disadvantages of traditional thermal conductive materials and polymers.The disadvantages of traditional thermal conductive materials and polymers leaded to the limitations of their applications in industry.It was necessary to research the thermal conductive polymer composites.By analyzing the shortcomings of current resrarch,the main research work of this paper was pointed out.2.This paper describes the preparation of thermal conductive composites.GNPs as fillers were mixed in the silicon polymers uniformly.The isotropic graphene/PDMS composites were obtained without magnetic field curing,and the anisotropic graphene/PDMS composites were cured under a strong magnetic field of 10 T.The hot wire method was used to measure the thermal conductivity of the nanocomposites.At the same time,the microstructures of isotropic and anisotropic composites were observed by scanning electron microscopy,and the distribution and arrangement of graphene in PDMS matrix were observed.3.From a microscopic perspective,the thermodynamic theory was employed to analyze the thermal mechanism of the GNPs/polymer composites in terms of the micro particle vibration and component structures.The filler thermal conductivity,aspect ratio,orientation as well as the interfacial thermal resistance have been taken into account to model the thermal conductivity of the GNPs/polymer composites.A thermal conduction model has been derived based on effective medium theory which can predict the thermal conductivity of the GNPs/polymer composites very well.4.According to the thermal conductivity of solid materials,the thermal conductivity of graphene and PDMS was studied.The distribution of graphene in anisotropic composites was observed by SEM.In this article,a 3D FEM model was used to analyze the anisotropic thermal behavior of oriented GNPs/polymer composites.The model considered the effect of microstructural characteristics such as the shape and aspect ratio of filler,interfacial thermal resistance,volume fraction,dispersion state and orientation of GNPs dispersion to simulate a steady state heat flow in the composite.In the simulation model,the composite was treated as a cubic unit cell and GNPs were modeled as oblate spheroid with a long axis diameter of 1?m and the aspect ratio was in the range of 0.01 to 0.05.The oblate spheroids aligned in the cubic to represent the microstructure of the oriented GNPs/polymer composites.By varying the number of the GNPs in the representative unit cell,the volume fractions of fillers were determined.The simulation results shown that the parallel thermal conductivity(//)increased in a nonlinear trend and the perpendicular thermal conductivity(?)slightly linear increased.Compared with experimental results,the trends predicted by the finite element models were consistent.5.By comparing the theoretical and experimental values under different influencing factors,the main influencing factors of the thermal conductivity of isotropic GNPs/PDMS composites and anisotropic GNPs/PDMS composites were found.The identified characteristic parameters were used to calculate the thermal conductivity of the composites under different volume fractions of GNPs.Based on the analysis,the following conclusions were obtained.The thermal conductivity model was applied to predict the thermal conductivity of the filled silicone rubber composites.The effect of interfacial thermal resistance and agglomeration on thermal conductivity was pointed out.