Research On The Mechanical Properties And Interface Structure Of CNT-enhanced Cu-based Composites

Carbon nanotube（CNT）can be used as reinforcement for high-performance copper-matrix composites because of their ultra-high tensile strength（13-50 GPa）and elastic modulus（1.5-5.0 TPa）,and have very broad application prospects.However,due to the difficulty of uniformly dispersing CNT in the copper matrix and the poor wettability of the interface between the CNT and the copper matrix,it is difficult to fully exert the excellent mechanical properties of CNT.In this paper,spray pyrolysis method was used to modify the surface of CNT,combined with flake powder metallurgy method to prepare CNT/Cu composites with excellent mechanical properties.The dispersion and micro-morphology of CNTs in CNT/Cu composites were studied to reveal the effect of surface-modified CNT on the mechanical properties and interface structure of the composites.Using the precipitation method,a hybrid reinforcement with zero-dimensional Cr_xO_y nanoparticles and one-dimensional CNT was prepared.And a copper-matrix composite with Cr_xO_y-CNT hybrid reinforcement was prepared,and separate Cr_xO_ynanoparticle or CNT reinforced copper-matrix composite was also prepared.The mechanical properties,microstructure and interface structure of these composites were studied,and the strengthening mechanism of nano-reinforcement with different dimensions to the composites was discussed.There are the main results:（1）The CNT-Cu_xO composite powder was prepared by spray pyrolysis.The copper oxide particles with a particle size of 10-50 nm adhered uniformly and tightly to the CNT surface,which had a good modification effect on the CNT surface.Nanoparticles on the surface of CNT reduce the Van der Waals forces between CNTs and improve the dispersibility of CNT;At the same time,these nanoparticles adhere closely to the surface of CNT and also improve the interfacial binding of CNT and copper matrix in the composites.（2）The combination of spray pyrolysis and flake powder metallurgy was used to prepare SP-CNT/Cu composites.The effects of CNT modified by spray pyrolysis on the mechanical properties and microstructure of the composites were studied.The tensile strength of SP-0.1wt.%CNT/Cu and SP-0.3wt.%CNT/Cu composites are 295.5MPa and 353.9 MPa,respectively,while 0.1wt.%CNT/Cu and 0.3wt.%CNT/Cu composites prepared by flake powder metallurgy have tensile strengths of 261.2 MPa and 306.2 MPa,respectively.It was revealed that the modified CNTs were modified by spray pyrolysis,which significantly improved the mechanical properties of the composites.Cu₂O was found at the CNT-Cu interface of SP-CNT/Cu and CNT/Cu composites,and the formed chemical bond can effectively improve the interfacial bonding between CNT and copper matrix.In addition,at the CNT-Cu interface,it also forms a mechanical bond due to internal stress and also improves the interfacial bond between the CNT and the copper matrix（3）The CNT-Cr_xO_y hybrid reinforcement prepared by the precipitation method,in which Cr_xO_ynanoparticles can improve the spatial distribution of CNTs,inhibit the agglomeration of CNT,and increase their dispersibility in the copper matrix.In addition,the strengthening effect of CNT-Cr_xO_y hybrid reinforcement of different dimensions is more significant than that of separate reinforcement CNT or Cr_xO_y nanoparticles.The tensile strength of the 1.0vol.%Cr_xO_y-CNT/Cu,1.0vol.%CNT/Cu and 1.0vol.%Cr_xO_y/Cu composites are 402.6 MPa,238.4 MPa and 339.1 MPa respectively.（4）Through the analysis of the strengthening mechanism of 1.0vol.%Cr_xO_y-CNT/Cu,1.0vol.%CNT/Cu and 1.0vol.%Cr_xO_y/Cu composites,it is found that the largest contribution to the C_rxOy-CNT/Cu and Cr_xO_y/Cu composites is the Orowan strengthening mechanism,followed by the dislocation strengthening,and finally the fine grain strengthening mechanism.For the strengthening mechanism of the CNT/Cu composite,the mechanism that contributes the most to composite is load transfer,and the contribution rate of fine grain strengthening and dislocation strengthening to increase the tensile strength is equivalent.