Preparation And Characterization Of Cu And/or Ni Layer On C_f Surface And C_f/Cu(Ni) Composites

Because of the excellent mechanical properties and physical properties,carbon fiber reinforced copper matrix composites show a great potential of scientific and engineering applications.However,the interface problems between the carbon fibers and copper,such as poor wettability and Modulus mismatch,limits the exertion of excellent mechanical properties of carbon fibers.The surface metallization of carbon fiber can solve the interfacial problems well.Firstly,the Ni coatings were electroplated on the short carbon fibers and the continuous carbon fibers,the effects of preparation process of Ni coating s were studied;then,the tensile properties of th e continuous carbon fibers moddified with different metal coatings were investigated.After that,The Ni-coated carbon fiber reinforced copper matrix composites（C _f/Cu（Ni））were fabricated by the spark plasma sintering（SPS）with Ni/Cu coated carbon fibers.Based on that,the relations between the volume friction of carbon fiber and the tensile properties and the reinforcement mechanism of carbon fiber were studied elementarily through the analysis of fracture s and stress-strain curves.The results were shown as follows:（1）Nickel coatings with controlled thickness and uniformity were directly electroplated on short carbon fibers at 5V 10min using pure nickel plate as the anode and nickel rod the cathode.And then,the Cu coatings with 6μm thickness were electroplated on the Ni-coated carbon fibers.Furthermore,the Nickel coated carbon fiber reinforced copper matrix composites was prepared directly by spark plasma sintering with Ni/Cu coated carbon fibers at 800℃,20 MPa for 5 min.Meanwhile,the carbon fiber reinforced copper matrix composites with the same volume fraction of C_f was prepared under the same sintering conditions.The Ni-coated carbon fibers reinforced Cu matrix composites(C_sf/Cu（Ni）)show a plastic deformation fracture and the mechanical properties of C_sf/Cu（Ni）were higher than that of C_sf/Cu composites.The tensile strength of C_sf/Cu（Ni）was about 20%higher than that of the C _sf/Cu composites,and C_sf/Cu（Ni）had a minimized length of fiber pullout.（2）To study the effects of metal coatings on the tensile properties of carbon fibers,the nickel coatings,copper coatings,Cu/Ni duplex coatings and Ni/Cu duplex coatings were electroplating on the surface of carbon fiber,respectively.And then,the tensile strength of composite filaments with different coatings were characterized by the universal testing machine.Results shown that the tensile strength of Ni/Cu-coated carbon fibers was about 10%higher than that of uncoated C _f,which has a large rate than that of Cu coated carbon fiber（C_f/Cu）and Ni coated carbon fiber（C_f/Ni）,and the results of tensile strength had the lowest dispersion.The C_f/Ni/Cu filament shown a very plane fracture surface which can be attributed to the stronger bonding strength between Cu and C_f because of the presence of Ni coatings.The Ni/Cu coatings were spheroidized after annealed at 750℃for 1h under argon atmosphere,and the dispersion of tensile strength of Ni/Cu-coated carbon fibers was lower than that of Ni/Cu-coated carbon fibers without heat treatment,while the tensile strength had no obvious change.（3）The continuous carbon fiber reinforced copper matrix composites with 20vt%,30vt%and 40vt%of carbon fibers were fabricated at 850℃、20MPa for 5min by SPS.While the uncoated-carbon fiber reinforced copper composites with the same volume friction of carbon fibers were prepared under the same parameters.The results indicated that the tensile strength of C _cf/Cu（Ni）was significantly higher than C _cf/Cu;and the tensile strengths of composites i ncreased first and then decreased;fiber segregationoccurred before the fracture of composites which had an excessive fiber content.