Preparation, Properties And Microstructure Of Carbonized Polymer Dots/copper Composite

To meet the requirements of the boom in modern technology based on ensuring good electrical and thermal conductivity,advanced cooper(Cu)materials are required to have high strength.The research and development of high-performance Cu matrix composites have become a focus topic by introducing appropriate reinforcements and giving full play to the synergistic effect of the matrix and functional strengthening phase.Carbon nanotube(CNT)and graphene(GR)are considered as ideal reinforces for Cu matrix composites due to their excellent physical and mechanical properties.However,by virtue of the strong van der Waals forces and poor interfacial bonding between these carbon nanomaterials and Cu matrix,the strengthening effect of its on the properties of Cu matrix composites cannot be fully played.Herein,based on the structural design of carbon nanomaterial/Cu matrix composite,the uniformly dispersed of the reinforcement,and the good interface bonding between the reinforcement and the matrix,this paper explores a new reinforcement,carbonized polymer dot(CPD),and the preparation,structure,and properties of CPD/Cu composites are researched.The results are as follows:(1)The synthesis of CPD is explored and successfully applied to Cu matrix:by adjusting the ratio of hydrothermal reaction materials(ethylenediamine(EDA):citric acid(CA)),CPD with different morphology and structure is synthesized and mixed with Cu powder by powder metallurgy to obtain CPD/Cu composites.The mechanical,electrical,and thermal properties of CPD/Cu composites are tested,and it finds that with the increase of EDA:CA,the particle size of CPD increased,and the mechanical,electrical,and thermal properties of CPD/Cu composites increased first and then decreased.When EDA:CA is 1:1,the tensile strength of CPD1/Cu composite is as high as 312.1 MPa,elongation is 34.3%,electrical conductivity is 97.2%IACS,thermal conductivity is 395.3 W/(m·K),which are 20.0%,114.4%,5.4%IACS,88.5 W/(m·K)higher than Cu control sample,respectively.The results indicate that the mechanical,electrical,and thermal properties of Cu matrix composites are higher with CPD addition,and the enhancement effect is better than that of CNT and GR on Cu matrix composites.(2)The influence of the heart treatment CPD on the mechanical and electrical properties of Cu-based composites is studied:by heat treatment of the hydrothermally synthesized CPD at different temperatures,it is found that structure of CPD with core-shell is damaged when treatment temperature increases,and sp~2C/sp~3C increased first and then decreased.Mechanical and electrical properties of composites also increased first and then decreased.However,CPD without heat treatment has a more prominent enhancement effect on Cu matrix composites,indicating that the structural integrity of CPD and appropriate sp~3C content have an important role in the mechanical and electrical properties of composites.(3)The influence of CPD structural evolution on the mechanical and electrical properties of Cu-nased composites is studied,and it is found that the mechanical and electrical properties of composites increased first and then decreased with the increase of CPD wt.%due to the increase in the number and size of CPD cluater,agglomeration ouucrred to a certain extent.Through the microstructure of the composites,the transition region formed at the CPD-Cu interface is found to improve the interface bonding.In addition,the good plasticity of the composite is contributed by the addition of CPD,due to the energy dissipation of the amorphous carbon network during the tensile process by sacrificing themselves.Finally,the conductive mechanism of CPD/Cu composites is discussed,and it is found that phonons,grain boundaries,dislocation,and CPD scattering are the main resistance components of CPD/Cu composites.Nevertheless,the electrical conductivity of the composite is still higher than that of the pure Cu matrix,due to the excellent electron transport capacity of CPD and the transition region formed in the interface.(4)The interface structure and properties of CPD/Cu composites are studied:as the sintering temperature increased the CPD-Cu cooedination bonds and CPD nanoclusters in the compoaites are destroyed,and the thickness of the transition region at the interface of the composite increased with the increase of sintering temperature,the mechanical and electrical properties of the composites decrease.Interestingly,full densification of Cu-based composites is achieved by low-temperature sintering with CPD added,when the sintering temperature is only～550°C,the relative density of composites reaches 99.4%,and the mechanical,electrical properties of composites are the best value.This is because of the rapid diffusion of active carbon contained in CPD at a relatively low temperature,and the local temperature increase of the composites due to the reduction of CPD during the sintering process.Finally,by discussing the strengthening mechanism of CPD/Cu composites sintered at 550°C,it is found that the strengthening of CPD/Cu composites is mainly composed of fine-grain strengthening,dislocation strengthening,and load transfer strengthening,and the load transfer is the main strengthening.This paper provides the theoretical basis and experiment reference for the preparation of Cu matrix composites with high strength and electrical conductivity.