Carbon fibers of polyacrylonitrile (PAN) type were coated with nickel nanoparticles using a chemical reduction method in alkaline hydrazine bath. The carbon fibers were firstly heated at 400 °C and then chemically treated in hydrochloric acid followed by nitric acid to clean, remove any foreign particles and functionalized its graphitic surfaces by introducing some functional groups. The functionalized carbon fibers were coated with nickel to produce 10 wt% Cf/Ni nanocomposites. The uncoated heat treated and the nickel coated carbon fibers were investigated by SEM, EDS, FTIR and XRD to characterize the particle size, morphology, chemical composition and the crystal structure of the investigated materials. The nickel nanoparticles were successfully deposited as homogeneous layer on the surface of the functionalized carbon fibers. Also, the deposited nickel nanoparticles have quazi-spherical shape and 128–225 nm median particle size. The untreated and the heat treated as well as the 10 wt% Cf/Ni nanocomposite particles were further reinforced in ethylene vinyl acetate (EVA) polymer separately by melt blending technique to prepare 0.5 wt% Cf-EVA polymer matrix stretchable conductive composites. The microstructures of the prepared polymer composites were investigated using optical microscope. The carbon fibers as well as the nickel coated one were homogenously distributed in the polymer matrix. The obtained samples were analyzed by TGA. The addition of the nickel coated carbon fibers to the EVA was improved the thermal stability by increasing the thermal decomposition temperature Tmax1 and Tmax2. The electrical and the mechanical properties of the obtained 10 wt% Cf/Ni nanocomposites as well as the 0.5 wt% Cf-EVA stretchable conductive composites were evaluated by measuring its thermal stability by thermogravimetric analysis (TGA), electrical resistivity by four probe method and tensile properties. The electrical resistivity of the fibers was decreased by coating with nickel and the 10 wt% Cf/Ni nanocomposites has lower resistivity than the carbon fibers itself. Also, the electrical resistivity of the neat EVA is decreased from 3.2 × 1010 to 1.4 × 104 Ω cm in case of the reinforced 0.5 wt% Cf/Ni-EVA polymer composite. However, the ultimate elongation and the Young’s modulus of the neat EVA polymer was increased by reinforcing with carbon fibers and its nickel composite.

Carbon fibersnickel nanocomposite particles reinforced ethylene vinyl acetate stretchable conductive polymer: fabrication, microstructure, electrical and mechanical properties
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
        2.2 Methods
            2.2.1 Surface treatments and functionalization of carbon fibers
            2.2.2 Synthesis of Cf-Ni Nanocomposites
            2.2.3 Fabrication of CFNi-EVA polymer composites
            2.2.4 Characterizations and microstructure investigations
            2.2.5 Thermogravimetric analysis (TGA)
            2.2.6 Electrical resistivity measurements
            2.2.7 Tensile test measurements
    3 Results and discussion
        3.1 Surface treatments and acid functionalization of the carbon fibers
        3.2 Fabrication and characterization of CfNi nanocomposites
        3.3 Fabrication of CfNi-EVA composites
        3.4 Thermogravimetric analysis
        3.5 Electrical resistivity of carbon fibersNi nanocomposites
        3.6 Mechanical properties of carbon fibersNi-EVA composites
    4 Conclusion
    Acknowledgements 
    References

• Walid M. Daoush(Department of Chemistry, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), P.O. Box 90950, 11623 Riyadh, Saudi Arabia, Department of Production Technology, Faculty of Technology and Education, Helwan University, Saray‑El Qoupa, El Sawah Street, Cairo 11281, Egypt) Corresponding author
• Abdullah Fahad Al‑Zuair(Department of Chemistry, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), P.O. Box 90950, 11623 Riyadh, Saudi Arabia)
• Mohd Shahneel Saharudin(School of Engineering, Robert Gordon University, Aberdeen, UK)
• Fawad Inam(School of Architecture, Computing and Engineering, University of East London, London, UK, Executive Principal Office, Oxford Business College, 23‑38 Hythe Bridge Street, Oxford, OX1 2EP, UK)