Mechanical And Thermal Properties Of Densified Graphene Films

Graphene is a single atom planar structure of sp~2 combined with carbon.Due to its unique structure,graphene has excellent properties such as high strength,high modulus and high thermal conductivity.However,due to its very small size,graphene is difficult to be directly applied in practice,so graphene film is assembled.Graphene film retains its excellent mechanical and thermal properties Integrated circuits and aerospace and other fields are widely used.At present,the mechanical and thermal properties of the assembled graphene films are obviously lower than those of graphene.Many researchers enhance the interface connection of graphene films by introducing ionic bonds,so as to improve the overall mechanical and thermal properties,Densification treatment can effectively improve the mechanical and thermal properties of graphene films,and the experimental operation is easy to achieve.However,there are few studies to reveal the mechanism of mechanical and thermal enhancement from the microscopic point of view.In this work,graphene films were prepared by experiments,and the effects of compression densification on the mechanical and thermal properties of graphene films were tested and compared.The MD simulation was used to reveal the influence mechanism of mechanical and thermal properties of desified graphene films.In this work,graphene oxide thin films were prepared by vacuum filtration method,and then graphene films were prepared by hi acid reduction.The graphene films were densified by mechanical compression.The microstructure of graphene films before and after compression was observed by SEM.It was found that the graphene films after compression were more compact,and the gaps between the layers were significantly reduced before compression;The tensile mechanical properties of graphene films before and after compression were tested and the stress-strain curves were obtained.It was found that the tensile mechanical properties of graphene films after compression were significantly improved,with the tensile strength of 42.12 MPa and elastic modulus of4.67 GPa;The in-plane thermal conductivity of graphene film before and after compression was measured by laser flash method.It is found that the in-plane thermal conductivity of graphene film after compression is obviously improved,and the in-plane thermal conductivity can reach 1566.899 W/(m·K);In this work,the molecular structure of graphene films with different sizes of graphene is constructed by molecular dynamics simulation.The molecular structures of graphene films with different compression degrees are obtained by compression.Then the tensile stress-strain curves are obtained and tensile strength and Young's modulus are obtained,It is found that the size and compression degree of graphene have a significant influence on the tensile mechanical properties of the overall structure of graphene films.The larger the size of graphene,the higher the compression degree,the greater the young's modulus and tensile strength of the graphene films,the better the tensile mechanical properties of the graphene films;In this work,the structure of graphene lap is constructed,and the tensile mechanical behavior of the model with different sizes and different overlapping ratios is simulated.The van der Waals potential energy of the model is also calculated.It is found that the size and overlap ratio of graphene have a significant influence on the tensile mechanical properties of the model.The larger the size of graphene,the higher the overlap ratio,The stronger the van der Waals force of graphene lap model,the higher the young's modulus and tensile strength of the model;In this work,the thermal conductivity of graphene films is studied.It is found that the size and compression of graphene have a significant influence on the overall structure of graphene films.The larger the size of graphene,the higher the compression degree of graphene films,the higher the thermal conductivity of graphene films,the better the thermal conductivity of graphene films;The thermal conductivity of graphene lap structure is studied.It is found that the size and overlap ratio of graphene have a significant influence on the temperature distribution of the model.The larger the size of graphene,the higher the overlap ratio,is more conducive to the heat transfer and the formation of temperature gradient,thus improving the overall thermal conductivity.