Effects Of Graphene Substrate On Melting And Solidification Behavior Of Cu Nanoparticle

In this paper,we introduce the Cu nanoparticle-graphene composite material and its basic characteristics,the basic theory of melting and solidification,the research progress of different sizes of Cu,the research content and significance of this work;and details the molecular dynamics simulation method and the microstructure.means of analysis.The melting and solidification behavior and microstructural evolution of Cu nanoparticles on graphene substrates were studied using molecular dynamics methods,and the melting and solidification process of Cu nanoparticles on graphene substrates was affected by thermodynamic factors,kinetic factors,and the properties of graphene.The joint influence and detailed analysis of its microstructural evolution have enriched the melting and solidification theory of metal-graphene composites,and are of great significance for improving Cu nanoparticles of different sizes and their application pathways.The rapid melting of Cu nanoparticles with（g-Cu）and without（p-Cu）graphene substrates was simulated at a heating rate of 10¹²K/s.The analysis found that the melting process of Cu nanoparticles experienced three stages:surface melting,split melting,and rapid melting.Through visual analysis,it is found that the melting of Cu nanoparticles occurs simultaneously throughout the interior,rather than shell by shell.By comparing with or without the substrate,it is found that graphene improves the structural stability and melting point of g-Cu nanoparticles.The p-Cu nanoparticles melted uniformly,while the g-Cu nanoparticles melted in a non-uniform manner with a liquid-liquid transition.The process of rapid melting of Cu nanoparticles with or without graphene substrate in four sizes（a total of 8 sets of data）was simulated at a heating rate of 10¹²K/s.The analysis found that graphene has a greater influence on the melting behavior of Cu nanoparticles with smaller size.The melting point of p-Cu nanoparticles has a size effect,but the size effect of g-Cu nanoparticles is not obvious.Cu atoms with different sizes have different melting states.The graphene substrate suppresses the thermal vibration of Cu atoms at the interface,thereby reducing the thermal vibration entropy.The rapid solidification process of Cu nanoparticles with or without the base of graphite pumps in four sizes（8 sets of data in total）was simulated at a cooling rate of10¹¹K/s.The analysis found that the solidification of Cu nanoparticle rice droplets at this cooling rate is indeed equivalent to that of the p-Cu nanoparticles crystallized into a quintuple crystal structure,while the g-Cu nanoparticles have a layered structure.The nuclei are evenly distributed from the inside to the outside,while the g-Cu forms nuclei from the side close to the graphite pump to the far side,that is,non-uniformly enlarged nuclei.