To reduce production cost and inhibit the aggregation of graphene, graphene oxide and copper nitrate solution were used as raw materials in the paper. Cu particles were introduced to the graphene nanosheets by in-situ chemical reduction method in the hydrazine hydrate and sodium hydroxide solution, and the copper matrix composite reinforced with Cu-doped graphene nanosheets were fabricated by powder metallurgy. The synthesized Cu-doped graphene was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The relative density, hardness, electrical conductivity and tensile strength of the copper matrix composite reinforced with Cudoped graphene were measured as well. The results show that copper ions and graphene oxide can be effectively reduced by hydrazine hydrate simultaneously. Most of oxygen functional groups on the Cu-doped graphene sheets can be removed dramatically, and Cu-doped graphene inhibit the graphene aggregation effectively. Within the experimental range, the copper matrix composites have good comprehensive properties with 0.5 wt% Cu-doped graphene. The tensile strength and hardness are 221 MPa and 81.6 HV, respectively, corresponding to an increase of 23% and 59% compared to that of pure Cu, and the electrical conductivity reaches up to 93.96% IACS. However, excessive addition of Cu-doped graphene is not beneficial for the improvement on the hardness and electrical conductivity of copper matrix composite.

Microstructure and properties of copper matrix composites reinforced with Cu-doped graphene
    Abstract
    1 Introduction
    2 Experiment
        2.1 Materials
        2.2 Synthesized and prepared methods
        2.3 Characterizations
    3 Results and discussion
        3.1 XRD analysis
        3.2 SEM morphology of Cu-doped graphene
        3.3 TEM morphology of Cu-doped graphene
        3.4 XPS analysis
        3.5 Raman analysis
        3.6 Microstructure and properties of Cu-doped graphene reinforced copper matrix composites
    4 Conclusions
    Acknowledgements 
    References

• Xiaohong Yang(Shaanxi Province Key Laboratory of Electrical Materials and Infiltration Technology, School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, People’s Republic of China, Engineering Research Center of Conducting Materials and Composite Technology, Ministry of Education, Xi’an, People’s Republic of China)
• Xingwang Cheng(Shaanxi Province Key Laboratory of Electrical Materials and Infiltration Technology, School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, People’s Republic of China, Engineering Research Center of Conducting Materials and Composite Technology, Ministry of Education, Xi’an, People’s Republic of China)
• Yu Chen(Engineering Research Center of Conducting Materials and Composite Technology, Ministry of Education, Xi’an, People’s Republic of China)
• Peng Xiao(Shaanxi Province Key Laboratory of Electrical Materials and Infiltration Technology, School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, People’s Republic of China, Engineering Research Center of Conducting Materials and Composite Technology, Ministry of Education, Xi’an, People’s Republic of China)