Microstructure And Properties Of Chemically Modified Carbon Nanotubes Reinforced Copper Matrix Composites

Carbon nanotubes（CNTs）have excellent properties such as high strength（up to100 GPa）,super Young’s modulus（～1 TPa）,and large aspect ratio（up to 1000）.They are reinforcement materials for composite materials.The addition of CNTs（reinforced materials）can significantly improve the mechanical properties of CNT/Cu composites.However,the structural integrity of CNTs,the dispersion state of CNTs and the weak interface bonding between CNTs and Cu matrix affect the mechanical properties of CNT/Cu composit es.In this paper,CNTs reinforced Cu matrix composites with different chemical modifications were prepared by powder metallurgy method.The effects of CNTs with different chemical acidification times on the mechanical properties and interface structure of the composites and the effects of the dispersion of CNTs chemically grafted with organic ionic salts in the metal-based powders on the properties of the composites.The results are as follows:Use chemical acidification to modify the surface of CNTs,using solution-assisted wet mixing method to mix acidified CNTs and Cu suspension to prepare composite powders,explore the CNTs acidification time on the micro structure of CNTs,the increase of relative to the influence of interface and mechanical properties of composite materials,and interfac e are discussed the computing simulation method the reinforcement mechanism of composite materials.The tensile strength of the acid-treated 24h CNT/Cu composite material is significantly improved（291.5 MPa,which is 23%higher than that of the CNT-Cu composite material without acid treatment）,which is mainly because the acid treatment method can introduce oxygen-containing Groups（such as hydroxyl and carboxyl）,the micro-etching caused by this acidification is beneficial to increase the combination of CNTs and Cu matrix,increase the interface contact area,and improve the interface stability.The formation of Cu ₂O by O and Cu atoms on the CNT/Cu interface is the key to the strong bonds between CNT and Cu interface.The tensile simulation results of the interaction between Cu₂O and acidified CNTs calculated by density functional theory（DFT）verify the experimental results.The interface bonding strength of Cu₂O is much higher than that of CNT/Cu composites without Cu₂O.Using chemically acidified CNTs as raw materials,the surface grafting of CNTs was carried out to prepare a multi-walled carbon nanotube fluid（MWNTF）,which is a solvent-free flowable CNT derivative with good solubility in polar solvents.The organic ionic salt grafted on the surface h as a certain repulsive effect,which can prevent the reinforcing phase from aggregation,form clusters,and uniforml y disperse.The MWNTF with different contents are added to the Cu matrix composite material,and the MWNTF/Cu composite material is prepared by the powder metallurgy method.MWNTF and Cu acetate solution were mixed to make precursor solution by molecular blending method,and then the composite powders are prepared by chemical reduction,and finally the M WNTF/Cu composite material is obtained by hot pressing sintering.When 0.75 wt%of MNTF is added,the tensile strength of the composite material reaches 517.5 MPa,and the yield strength and tensile strength are increased by 294 MPa and 315.1 MPa compared w ith pure Cu without adding reinforcing phase.It is revealed that this kind of carbon nanotube fluid improves the mechanics of composite more significantly.Cu ₂O was also found at the interface of the composite material,and the formed chemical bond has a good effect on improving the bond between MWNTF and the Cu matrix.The uniform dispersion and good interface bonding of MWNTF in the composites can improve the load transfer efficiency from the Cu matrix to the MWNTF,and finally improve the mechanical properties of the MWNTF/Cu composite.The results show that the load transfer and Orowan strengthening are the main strengthening mechanisms.The experimental values of tensile properties are in good agreement with the theoretical calculation results of the s um of contributions of each mechanism.