Effect of nitrogen-doping content on microwave absorption performances of Ni@NC nanocapsules

A type of core-shell structured N-doped C-coated Ni nanocapsules (Ni@NC) with a size range of 20-70 nm was prepared by a simple strategy of the arc discharge. And the microwave absorption capability of the Ni@NC nanocapsules can be conveniently tuned by N-doping content varying from changing nitrogen pressure in their preparation process. The study revealed that the variable microwave absorption capability of the Ni@NC nanocapsules results from their tuned dielectric behavior. The tuned dielectric responses depend on the degrees of the broken atomic symmetry of the graphite carbon for carbon atoms substituted with nitrogen ones. The optimized impedance matching of the Ni@NC nanocapsules can be achieved by the appropriate content of N doping in graphite C shells. An optimal reflection loss value - 50.7 dB at 14.43 GHz with a thin thickness of 1.8 mm is acquired while choosing the pressure of 15 kPa nitrogen for the preparation of the Ni@NC nanocapsules (the N content in Ni@NC is about 4.62 at.% estimated by XPS). Therefore, it is a feasible strategy to tuning the microwave absorption properties of the Ni@NC nanocapsules by changing the content of N doping, which is of great significance for the study microwave absorbing materials at the atomic scale.