Enhanced microwave absorption properties of modified Ni@C nanocapsules with accreted N doped C shell on surface

An arc-discharge method together with in-situ self-polymerization method was adopted to synthesize Ni@C/NC nanocapsules. With this method, the Ni@C/NC nanocapsules with enhanced microwave absorption properties were obtained. This enhanced microwave absorption property is due to the modification on Ni@C nanocapsule with accreted N-doped C shell on its surface. The microstructure and microwave absorption property of as-prepared nanocapsules were studied in detail. A reflection loss (RL) below − 20 dB is obtained in the wide frequency range of 4.4–18 GHz of Ni@C/NC nanocapsules, when an appropriate absorber thickness from 1.5 to 5.2 mm is chosen. An optimal RL value − 38.3 dB is observed at 11.7 GHz on Ni@C/NC nanocapsules–paraffin composites with an absorber thickness of 2.4 mm. Moreover, the amplitude of RL values of Ni@C/NC nanocapsules is about 2–3 times as many as that of Ni@C nanocapsules within absorber thickness ranging from 1.5 to 5.2 mm. This result shows that N-doped graphite C accreted on the surface of Ni@C nanocapsules could induce strong dielectric resonance and increase permittivity values of the Ni@C/NC nanocapsules. As a result, microwave absorbing performance of the Ni@C/NC nanocapsules is significantly enhanced.