Research On Preparation,Microstructure And Properties Of Low Defect Grapehen/Cu Composites

Graphene(Gr)has excellent mechanical properties,thermal conductivity,and electrical conductivity,making it an ideal reinforcement of composite material.Powder metallurgy is a commonly used method for preparing graphene-reinforced metal matrix composites.Graphene will produce more defects during the ball milling process and in-situ process,which leads to a decline in its performance.Therefore,this study simulates the defect repair process through molecular dynamics simulation,and uses chemical vapor deposition(CVD)and plasma enhanced chemical vapor deposition(PECVD)methods to explore the repair process of defects in graphene.This paper simulates the interaction between graphene with different defects and carbon atoms,and studies the effects of different defect types,different temperatures,and different initial speeds of carbon atoms on the graphene defect repair process.The calculation results show that from a thermodynamic point of view,graphene without defects has the lowest energy,Stone-wales defects are more unstable than graphene without defects,single-vacancy defects are second,and double-vacancy defects are the most unstable.In terms of kinetics,within the simulated temperature range(873K?1273K),C atoms can achieve self-repair for single-vacancy defects and double-vacancy defects,while Stone-wales defects can only be repaired when C atoms hit the surface at high speeds at high temperatures.This paper studies the effects of different ball milling,in-situ process and repair processes to the content of defects in graphene.Firstly,the influence of different ball milling parameters on the flake effect of Cu powder was explored.The ball milling process was selected with a ball mill speed of 200r/min,a ball-to-battery ratio of 10:1,a grinding aid of ethanol,and a grinding aid ratio of 2:1.The Cu powder was ball milled to a highly flake-like Cu flake with an average diameter of 8?m and a thickness of several hundred nanometers.Then,the Cu powder and Gr are ball milled.When the milling time is less than 5h,the new defects are mainly caused by the formation of C-C single bonds;when the milling time reaches 10h,the defects are mainly C-O.In the in-situ autogenous process,higher temperature is conducive to the generation of low-defect Gr.During the repair process,the content of Gr defects with shorter ball milling time remained unchanged or increased,and the content of Gr defects with longer ball milling time decreased significantly.According to the results of peak fitting of XPS and Raman spectra,the defect repair of long-time ball milled Gr mainly comes from the decomposition of C-O bond and the repair of vacancy defects.The defect content of in-situ Gr is relatively insensitive to the defect repair process,and does not change significantly before and after repair.This paper studies the microstructure and properties of composite materials prepared by powder before and after the repair process.The overall density of the composite material is higher,about 98%,and its elastic modulus is slightly lower than that of pure Cu due to the influence of pores.Compared with before the repair,the mechanical properties and thermal conductivity of the composite material after the repair have been greatly improved.The bending strength has increased from 158.98MPa to 239.70MPa,an increase of 48%;the fracture deflection has been increased from 1.87mm to 2.15mm,and the plasticity has been improved 14%.The in-plane thermal conductivity increased from 291.51Wm^-1K^-1 to 313.00Wm^-1K^-1,which increased by 7.3%,and the interlayer thermal conductivity increased from 176.27 Wm^-1K^-1 to 256.84 Wm^-1K^-1,and increased45.7%.