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Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries and so on. In this study, the process of Nickel filling into single wall CNTs was studied by molecular dynamics (MD) simulation. Three models consisting of Nickel atoms and CNTs were established. These models were cooled from 1500 K to 100 K to analyze the factors that influence the filling height, such as temperature, the force between Carbon and Nickel atoms, as well as CNTs diameter. The results showed that filling height increased as the temperature and the force between Carbon–Nickel atoms rised. Filling height reduced with the increasing diameter of CNTs.

Ni@onion-like carbon (OLC)/reduced graphene oxide (RGO) nanocomposites were synthesized, and their multicomponent microstructure was confirmed by X-ray diffraction, transmission electron microscopy, Raman spectra, the thermal gravimetric analysis and magnetic hysteresis loops. The obtained nanocomposite possesses a unique structure, in which core–shell Ni@OLC nanocapsules are decorated on the surface of RGOs. The synergistic effect of the dielectric loss of RGO and OLC and the magnetic loss of Ni nanoparticles can be constructed. The RGO can provide tremendous electric dipoles. Multi-interface among RGO, OLC and Ni nanoparticles can enhance dielectric performance and cause multiple reflections. The combination of these merits makes the nanocomposite a promising candidate material for electromagnetic absorber. The 20wt.% nanocomposite-paraffin composite can possess an optimal reflection loss (RL) of $-47.5$dB at 9.75GHz with a thickness of 3.1mm. When the thickness is 2.0mm, the RL of composite can reach $-32.6$dB at 17.4GHz. The effective frequency is 6.54GHz (11.16–17.7GHz) for 2.4mm thickness layer.