Study On Preparation And Strengthening Mechanism Of Copper Matrix Composites Enhanced By Nanophases

Cu matrix composites reinforced with carbon nanotubes?CNTs?had shown great potentiality in many industrial applications owing to their excellent mechanical properties,electrical and thermal conductivities,and wear resistance.However,there were some problems to be solved urgently including difficulty in dispersion of CNTs in matrix and poor bonding of CNT/Cu interface.In this study,CNTs were firstly modified and dispersed by"acidizing treatment+SDBS treatment+electroless plating+heat treatment after plating"synergistic methods,and then CNT/Cu composites were prepared by flake ball milling?FBM?and hot pressing sintering?HPS?.The CNTs dispersion,microstructure and CNT/Cu interfaces in three kind of CNT/Cu composites were studied.The influence of modified CNTs on the interface was revealed and the strengthening mechanisms of Ni@CNTs were systematically studied.The directional Ni@CNT/Cu composites prepared by magnetic alignment treatment?MAT?method.The optimum process parameters of MAT,the directional arrangement of CNTs,the interface composition and the mechanical and electrothermal properties of the directional Ni@CNT/Cu composites were studied.And the directional strengthening mechanism was also revealed.A series of copper matrix composites synergistically reinforced by zero-dimensional Gd₂O₃ particles and one-dimensional CNTs with different synergistical contents were prepared by internal oxidation method,FBM and HPS methods.The microstructures,mechanical properties,electrical conductivity and synergistic strengthening mechanisms were discussed.The main results are listed as follows:1.The acidified CNTs introduced defects and abundant oxygen-containing functional groups ih the surfaces were not only easier to be dispersed in electroless plating solution,but also easier to react with the Cu matrix during hot pressing sintering.A thin discontinuous interface film of Cu₂O was produced at the CNT/Cu interface.The interface was greatly improved and transformed from the mechanical locking interface with weak bonding force into the mild reactive interface with strong covalent binding.2.The interfacial properties and bonding strength of three kinds of copper matrix composites reinforced by different CNTs were listed as follows:CNT/Cu interface?mechanical locking type?<Cu@CNT/Cu interface?"oxygen intermediate bond+oxygen covalent bond"hybrid interface?<Ni@CNT/Cu interface?mildly reactive oxidation bonding type interface?.The main strengthening mechanism of Ni@CNTs to the Cu matrix were thermal mismatch strengthening mechanism?by 60.9%?,load transfer strengthening mechanism?by 34.7%?and fine grain strengthening mechanism?by 4.3%?.3.The properties of directional Ni@CNT/Cu nanocomposites prepared by MAT were anisotropic,and the enhanced thermal conductivity and mechanical properties in the axial direction of CNTs were attributed to the directional alignment of CNTs in the Cu matrix.The transverse conductivity of 1.5vol.%Ni@CNT/Cu was about 98.9%,19.2%higher than that of non-magnetic oriented samples,and the transverse thermal conductivity was 366.9W/mk,35.9%higher than that of non-magnetic oriented samples,even 7.9%higher than that of pure copper prepared by the same process.4.Compared with single Gd₂O₃ or single CNTs,the synergistic enhancement of Gd₂O₃+CNTs had higher strength and conductivity,which was the result of synergistic effects of various strengthening mechanisms.The thermal mismatch strengthening mechanisms of Gd₂O₃ and CNTs have the greatest impact on Cu by 49.1%,followed by the Orowan strengthening mechanism of Gd₂O₃ by 20.3%and the load transfer strengthening mechanism of CNTs by 20.3%,and the fine grain strengthening mechanism by 4.3%.