Preparation Of Few-layered Graphene By Self-propagating Synthesis And Properties Of Its Nickel Composites

In this paper, a patent technique named as―self-propagating high-temperaturesynthesis (SHS)‖was used to produce graphene with Mg-CaCO3and Mg-polymer(PVC, polyvinyl chloride, and phenolic resin) as starting materials. Effect of graphenewith different starting materials and technological parameter were discussed. Thegraphene was used to produce graphene/Ni composite with ball milling and sparkplasma sintering (SPS), the mechanical and conductivity properties of composites werediscussed.The graphene produced by SHS were analyzed by X-Ray Diffraction (XRD),Raman spectroscopy, scanning electron microscope (SEM) and scanning electronmicroscope (TEM). The results of XRD and Raman suggest that the graphene producedwith Mg (between147-75μm、75-44μm�'�44-37μm)-CaCO3as starting materials havebetter properties.In the system of Mg-resin as starting materials, the graphene produced by mixingMg powder and phenolic resin as starting materials has similar structure as the grapheneoxide after reducing, the results of Raman show the2D peak of graphite disappeared.Analysis of SEM and TEM suggest that the graphene produced by SHS are crooked,and there are a lot of wrinkles exist on the surface of graphene.Graphene/Ni composite powders were prepared by ball milling with two processes:dry milling and protected by Ar and milled in ethanol. XRD results indicate that onlynickel (111),(220) and (200) peaks appeared, no graphite (200) peak, indicating that noimpurity was generated during the milling process. SEM results of composite powdersshow the graphene in the composite powder exists in two forms: at surface of Ni andbetween Ni grains.Conductivities are closely related to the densities of graphene/Ni composites: thehigher the density, the better the conductivity. Most of the composites’ densities areover90%. Some of composites with lower conductivity were caused by the pressuresin the mold were not enough during the process of SPS. Most of the conductivities ofcomposites are higher than pure nickel, the best one reached10.48×106S/m, whichwas produced by dry milling and protected by Ar with a speed of100rpm for8hours(Mg200-Ni-8). It’s useful to improve the conductivities of Ni matrix composites byintroducing graphene as reinforcement.The room temperature stress-strain curves of Graphene/Ni composites are typical compressive plastic deformation curves. The yield strength and fracture strength ofcomposites are higher than that of pure Ni. The yield strength is954MPa which is6times higher than that of pure Ni. The results of apparent strengthening efficiencies ofcomposites show that graphene/Ni composites produced by SHS have very excellentimprovement.