Study Of Aligning Nanocarbons In Copper Matrix Composites

Nanocarbon(CNT and graphene)is an ideal reinforcement of metal matrix which has excellent physical and chemical properties.It has broad application field in aerospace,electronics and so on.However,the key problems of nanocarbon dispersion in metal matrix,bonding with metal matrix,and structural integrity have hindered the application of nanocarbon reinforced metal matrix composites in engineering.Meanwhile,the random orientation of nanocarbon in the metal matrix play one of the factors limiting the ability to strengthen,because the unique structure of one-dimensional CNT and two-dimensional graphene creates anisotropy in performance.In this work,the composite with nanocarbons aligned in Cu matrix were prepared by flake powder metallurgy and external magnetic field technology.The influence of magnetic field on the orientation of nickel-plated nanocarbons in Cu matrix was discussed.Influence of Ni@nanocarbons on structure,electrical properties,mechanical properties and strengthening mechanisms of composite were studied.Experimental results show that the orientation of Ni@nanocarbons in Cu matrix was successfully achieved by external magnetic field technology.For a certain content of Ni@nanocarbons,increasing the magnetic field strength is beneficial to the uniform dispersion and orientation of Ni@nanocarbons in Cu matrix.For a certain intensity of magnetic field,increasing the content of Ni@nanocarbons will increase its possibility of agglomeration.And to a certain extent,increasing the size of the Cu flaky powder is beneficial to the orientation of Ni@nanocarbons in Cu matrix,but the excessively large Cu powder will lead to a decrease in the relative density of the composite.Meanwhile,largescale Ni@nanocarbons are sensitive to the changes of magnetic field.For the electrolessly coated Ni nanoparticles,it not only hinder the agglomeration between nanocarbons,but also improve the dispersibility of nanocarbons in the Cu matrix,and at the same time serve as a transition layer to improve the wettability and interface combination between nanocarbons and Cu matrix.The electrical properties and mechanical properties of the composites with magnetic field treatment are improved compared with those without magnetic field treatment,and the electrical properties and mechanical properties of the composite with magnetic field treatment are optimal along the orientation direction of nanocarbons.For Ni@CNTs/Cu composites,Ni@CNTs have the best orientation and dispersibility when the magnetic field strength is 1.5T.The orientation index is 0.97145,the conductivity is 76.3% IACS,and the tensile strength is 336 MPa.For Ni@Gr/Cu composites,Ni@Gr have the best orientation and dispersibility when the magnetic field strength is 2T.The orientation index is 0.97787,the conductivity is 86.6% IACS,and the tensile strength is 368 MPa.The main strengthening mechanisms in composite materials include fine-grain strengthening mechanism,load transfer mechanism,Orowan strengthening mechanism,and thermal mismatch strengthening mechanism.