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.

通过一种简单的电弧放电策略，制备了一种核壳结构的N掺杂C包覆的Ni纳米胶囊（Ni @ NC），尺寸范围为20-70 nm。Ni @ NC纳米胶囊的微波吸收能力可以通过在制备过程中改变氮气压力而变化的N掺杂含量来方便地调节。研究表明，Ni @ NC纳米胶囊的可变微波吸收能力是由于它们的介电特性所致。调谐后的介电响应取决于石墨碳对于被氮原子取代的碳原子的破坏原子对称性的程度。Ni @ NC纳米胶囊的最佳阻抗匹配可以通过在石墨C壳中适当掺入N来实现。最佳反射损耗值-在14.43 GHz时为50.7 dB，且厚度为1。在选择15 kPa氮气压力以制备Ni @ NC纳米胶囊时，获得8 mm的粉末（通过XPS估算，Ni @ NC中的N含量约为4.62 at。％）。因此，通过改变氮掺杂量来调节Ni @ NC纳米胶囊的微波吸收性能是一种可行的策略，这对于研究原子级微波吸收材料具有重要意义。