Research On The Microstructure And Mechanical Properties Of Pyrolyzed Carbon Nanotubes Reinforced Copper Matrix Composites

With the development of science and technology,people put forward higher requirements for metal materials,and the traditional metal matrials have become difficulty to meet the actual production needs.Due to the excellent properties,carbon nanotubes?CNTs?have been widely used as reinforcing materials for matal matrixcomposites.Among them,CNTs reinforced copper matrix composites have attracted wide attention due to the high strength and good plasticity.However,the enhancement effect of carbon nanotubes is much lower than the expected at the mercy of its characteristics.How to achieve carbon nanotube uniform dispersion and high interface bonding strength between the carbon nanotube and copper are the key issues to improve the comprehensive properties of composites.Therefore,this study takes CNTs-reinforced copper matrix composites as the research object,and improves the comprehensive mechanical properties of CNTs reinforced metal matrix composites by improving and controlling the structure of CNTs and the interface structure of composite.The CNTs are subject to oxidative unzipped treatment.Through the acidification of concentrated sulfuric acid and oxidation of potassium permanganate,the outer wall of the CNTs was unzipped and taking into account both tuber structure and the sheet structure of graphene nanoribbons?GNRs?.Molecular-level Maxing was used to prepared CNT-GNR/Cu composite:first,the uniformly dispersed CNT-GNR suspension was mixed with copper acetate solution,and sodium hydroxide?NaOH?and glucose solution(C₆H₁₂O₆)were added dropwise to the mixed solution under stirring,and then the product was subjected to dehydration under hydrothermal condition to obtain CNT-GNR/Cu₂O composite.Finally,the bulk composites wre prepared by Spark plasma sintering?SPS?.The microstructure and mechanical properties of the composites were tested and analzed by X-ray diffraction,Infrared spectroscopy,Raman spectroscopy,field emission scanning electron microscopy,transmission electron microscopy and mechanical testing machine.The results show that the contact area of interface bonding between CNT-GNR and copper matrix increases,the surface defects of CNT-GNR were increased,and a large of oxygen-containing functional groups was grafted.During the consolidation process,the oxygen-containing functional groups react with the copper matrix to form the nano-acale Cu₂O particles.The bonding is changed form mechanical bonding interface to chemical bonding interface,which greatly improves the bonding strenth and load transfer efficiency of the CNT-GNR.The tensile strength and elongation of1.0vol.%CNT-GNR/Cu composite reached to 457 MPa and 22%respectively,which were 10%and 120%higher than that of CNTs/Cu composite with the same reinforcement content.In order to furtherly improve the interfacial bonding strength,CNT-GNR/CuCr composite was prepared by adding a small amount of chromium to form carbide.Firstly,the alloy matrix was prepared by mechanical alloying?which the addition of Cr was added 0.2wt.%?,and then,the mixture of CNT-GNR and alloy was uniformly mixed by a solution mixing method by using high-speed stirring and rapid filtration to obtain a composite powder.Finally,the composite matrial was consolidation by SPS sintering.The effects of different volume fractions of the reinforcement and the interfacial structure of the composite on the mechanical properties of the composites were investigated.The results show that with the increase of volume fraction of CNT-GNR,the tensile strength of the composite increases,but it cost of the plasticity.In addition,Cr₇C₃ and Cr₃C₂ carbides were generated in situ at the interface of the composite,which was enhance the interfacial bonding,allowing the agent of load transfer effect of the CNT-GNR to be more fully utilized.