| The present work reports the detailed investigation of graphene-modified bulk nickel composites with graphene+graphite phase content up to 4.7 at.%. The composites were fabricated using ball milling and powder metallurgy methods with nickel nanopowder and exfoliated graphite being starting materials. Phase composition and composites structure were studied via X-ray diffraction technique (XRD), Differential scanning calorimetry (DSC), Raman spectroscopy (RS) and scanning electron microscopy (SEM). The effect of graphene addition on the grains size and orientation was determined from backscattered electrons images (EBSD technique). The effect of graphene-graphite phase content on the mechanical properties of the composite was studied. It was shown that small amounts of this phase result in the graphene formation on the surface of metal grains; in turn, this phenomenon affects the composite mechanical properties: its hardness increases, its plasticity decreases, and the strength value remains on the same level. The increase in the graphene-graphite phase content results in graphene flakes formation and new phase allocation corresponding to graphite, leading to the plasticity recovery and in the significant decrease of hardness and strength. |
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