Preparation Of Cu-CNTs Composites Based On Embeded Structure And It’s Performance Study

Carbon nanotubcs(CNTs)with excellent thermal,electrical and mechanical properties arc ideal reinforcements for preparing high-performance copper matrix composites(CMCs).Nevertheless,because CNTs is easy to agglomerate,it is difficult to distribute uniformly in copper matrix,and the wettability of the interface between CNTs and copper is also poor,thus limiting the strengthening effect of CNTs on the copper matrix.In order to solve these problems,we proposed the idea of introducing CuxO to the Cu-CNTs binary system to improve the wettability of the Cu/CNTs interface.In our work,the solution method was used to synthesize CNTs-CuxO composite powder by in situ in advance,and then it was combined with Cu powder by powder metallurgy to prepare Cu-CNTs and Cu-CNTs-CuxO composite materials respectively.The effects of the volume fraction of CNTs and CuxO on the performance of CMCs arc investigated by phase analysis,microstructure observation and the test of mechanical and electrical performance.And the strengthening mechanism of the reinforced phase was also disccussed.The results show that dense pure Cu and CMCs can be prepared by the powder metallurgy process combining low energy ball milling and spark plasma sintering(SPS),and the CNTs are evenly distributed on the surface of the copper sheet layer.During the sintering and hot extrusion process,the preferred orientation of the copper matrix grains occurred.The addition of 1.0%CNTs in Cu can significantly enhance the tensile strength(259 MPa)while maintaining a high electrical conductivity(94.7%IACS)and plasticity(EI=31.3%)of the Cu matrix,which is beneficial by the comprehensive effects of fine grain strengthening and dispersion strengthening of CNTs and orowan mechanism.However,when subjected to external stress,the weak mechanically bonded interface between Cu and CNTs can easy lead to the initiation of cracks or defects,which reduces the strengthening effect of CNTs.Based on the above-mentioned reasons,this paper proposes to introduce CuxO to Cu-CNTs composites to improve the bonding ability of the interface between Cu and CNTs.The results show that the CNTs-CuxO composite powder with embedded structure was synthesized in situ by the solution method.The fine fibrous CNTs and polyhedral CuxO particles were fitted with each other,and the CuxO particle size ranged from 2 to 5 μm.CuxO has both Cu2O and CuO phases form.During the mixing and sintering of CNTs-CuxO and Cu powder,the transition from CuO phase to Cu2O phase occurred.The copper matrix composite material still maintains a higher conductivity(≥93.4%IACS)and elongation(≥29.0%),but the tensile strength of composites is basically unchanged(257 MPa)when Cu-CNTs system introduces a low content(≤2.37%)of CuxO while keeping the amount of CNTs unchanged.This is because the semi-coherent interface between Cu2O and the Cu matrix was firmly bonded,which caused the CMCs sustainning good ductility when subjected to tensile stress.However,the agglomerated CNTs wrapped by CuxO particles and the reinforcements gathered on the boundary of the primary particles will limit the strengthening effect of CNTs.On the other hand,agglomerated CNTs reduce the obstacle of electron transport in matrix,and increase the electrical conductivity of the composites.When the CuxO content increases to 9.47%,the matrix strength is improved at the cost of a significant decrease in elongation(5.7%).