Study On The Preparation Of CNT/Cu-Ti Composites By Molecular Blending And The Microstructure And Properties

Carbon Nanotubes?CNT?is regarded as an ideal reinforcement for metal matrix composites?MMCs?due to their excellent mechanical,electrical and thermal properties.However,how to make CNT dispersed in the matrix uniformly,remain the structural integrity and achieve high interface bonding strength between the CNT and matrix are key issues for preparing the CNT/MMCs.Therefore,it is urgent to search a novel method to improve the traditional route and develop CNT/MMCs with high performance.In this study,CNT/Cu-Ti alloy composites were prepared by powder metallurgy combined with molecular level mixing method.Firstly,sodium hydroxide?NaOH?and glucose(C₆H₁₂O₆)solution were added dropwise to dispersed copper acetate?CuAc?-CNT mixed precursor solution,and CNT/Cu₂O composite powder was obtained after a series of chemical reaction under a hydrothermal environment.Then,the CNT/Cu₂O composite powder was uniformly mixed with the flaky Cu-1.0%wt.Ti alloy matrix powder by a low-energy ball milling,and the CNT/Cu-Ti alloy composites were obtained after reduction and hot-pressing.The results showed that the wettability of CNT and Cu₂O was good,and CNT can be used as the nucleation sites for Cu₂O effectively.The morphology and structure of CNT/Cu₂O particles was closely related with the precursor solution concentration,heating temperature and stirring speed.When the heating temperature was 353 K,the concentration of CuAc,NaOH and C₆H₁₂O₆ solution were 0.065 M,1.8 M and 1.4 M,the obtained Cu₂O had the most uniform particle size??1.5?m?,and the interface bonding condition between CNT and Cu₂O was the best as well.After the low-energy ball milling at 150 r/min for 2 h,CNT/Cu₂O composite powder was uniformly mixed with the matrix powder.After reducing under H₂ atmosphere at 553 K for 6 h,the embedded style of CNT into the reduced Cu particles was completely preserved.The morphology,microstructure and mechanical properties of CNT/Cu-Ti alloy composites were analyzed by optical microscopy?OM?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and tensile testing.The results showed that the Ti element played an important role for the optimization of interface bonding.When the volume fraction of CNT was0.8 wt.%,the sintering temperature was 1123 K and hold time for 30 min,the fabricated CNT/Cu-Ti alloy composites underwent modest interfacial reaction between the matrix and CNT to form nano-TiC particles and dispersed around the CNT surface and the interface zone.Specially,the nano-TiC particles and the CNT corresponded the specific crystallographic orientation of CNT?002?//TiC?112?,which was significant for reducing the interface between CNT and the matrix.The tensile strength,elongation and conductivity of the composites were362 MPa,45.9%and 78.8%IACS which was improved 31.2%,21.7%and 127.3%than the matrix,respectively.Further increasing the sintering temperature to 1223 K revealed that the overall performance of CNT/Cu-Ti composites was reduced to varying degrees.HRTEM showed that the structure of CNTs was severely damaged,resulting in a decrease in its enhancement efficiency.By verifying the experimental results with the theoretical enhancement model,we could conclude that the enhancement of the composites was mainly attributed to the load transfer of CNT,the Orowan strengthen due to the inhibition of dislocation by CNT and nano-dispersed TiC in matrix and the work hardening of matrix resulted from the significant coefficient of thermal expansion mismatch between the matrix and CNT.Further calculations showed that the contribution of the three strengthening mechanisms to the improvement of tensile strength performance were occupied for 42.2%,8.4%and 25.2%,respectively.In addition,the dispersive distribution of Nano-TiC particles produced by the interfacial reaction plays a significant role in dispersion strengthening,and the solid-solution strengthening of C atoms in the matrix at high temperatures together improves the mechanical properties of the CNT/Cu-Ti composites.