Research On The Mechanical And Thermal Properties Of Asymmetric Graphene Nanoribbons

Graphene is an excellent material with extraordinary electrical,thermal and mechanical properties.Based on graphene's unique two-dimensional structure,graphene exhibits rich geometry and great plasticity under strain.The change of structure will lead to the great change of thermal performance,which may be applied in the field of thermal rectification.Therefore,the mechanical and thermal properties of graphene under different structures are becoming a hot spot in the research.There have been many advances in the study of tensile mechanical properties and thermal rectification properties of the asymmetric graphene nanoribbons.However,the related thermal properties of asymmetric graphene nanoribbons with defects at different positions and those with fractal structure are still relatively thin.The research of these contents has obvious significance for mechanics and heat transfer theory and practical application.In this paper,the molecular dynamics method and AIREBO potential function have been used to study the influence of defect location on deformation and heat transport in the tensile process of the asymmetric triangular graphene ribbons,then the force and thermal properties of the fractal Sierpinski triangular graphene model have been preliminarily calculated and analyzed.As analyzed in this work:(1)During the tensile process,the tensile stress of the asymmetric triangle graphene ribbons and the fractal Sierpinski triangle graphene ribbons were not uniformly distributed.The tensile stress of the asymmetric triangular graphene sheet is gradually transferred from the top to the bottom,And the stress is more concentrated along the intermediate part of the graphite ribbon.The atomic stress distribution in the triangular graphite ribbons is obviously regulated by the location of the defects.The atomic stress near the defect is generally greater than that far away from the defect at the same horizontal position;The tensile stress of the fractal Sierpinski triangle graphene is also gradually transferred from the top to the bottom.Moreover,during the whole tensile process,the atomic stress near the top is greater than at the bottom,and the tensile stress is mainly transferred along the outer edge with the drawing direction.(2)For the asymmetric triangular graphene ribbons,the fracture strain rate of the triangular graphene ribbons without defects decreases monotonically with the increase of the size of the graphene ribbons,and the defects in certain size asymmetric graphene can generally improve its fracture strain rate;For the fractal Sierpinski triangle graphene ribbons,the tensile stiffness increases as thescale decreases.At the same time,the fractal defects can make the Sierpinski triangle graphene with larger size have better flexibility,but its fracture strain rate decreases with the with the increase of size.(3)For the asymmetric triangular graphene ribbons,the existence of defects is not good for heat conduction,the thermal conductivity of containing defects of triangular graphene were smaller than the size of normal fault-free triangular graphene ribbons.the thermal conductivity of the triangular graphite ribbons will continue to decrease as the defect position moved towards the top.Although the defect reduces the heat transfer ability of graphite ribbons,it enhances the difference of heat conduction performance of graphite ribbons in asymmetric direction,and improves the thermal rectification effect of asymmetric material;For the fractal Sierpinski triangular graphene ribbons,the thermal conductivity is similar to that of normal graphene with the same number of atoms,and the thermal rectification characteristic may be better than that of conventional triangular graphene with similar shape.