Effect of nitrogen-doping content on microwave absorption performances of Ni@NC nanocapsules
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Effect of nitrogen-doping content on microwave absorption performances of Ni@NC nanocapsules Xiu-Kun Bao1, Gui-Mei Shi1,* Shu-Tong Li1 1
, Xiao-Lei Wang1, Qian Li1, Fa-Nian Shi1, and
Shenyang University of Technology, No. 111, Shenliao West Road, Economic & Technological, Development Zone, Shenyang 110870, People’s Republic of China
Received: 18 September 2020
ABSTRACT
Accepted: 10 November 2020
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.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction In recent years, high-performance electromagnetic absorption materials have attracted extensive attention, because they can effectively prevent information leakage, protect national defense security, and avoid the human immune system from serious electromagnetic pollution issue [1–4]. Nowadays, various microwave absorbents, such as magnetic metals (Fe,
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https://doi.org/10.1007/s10854-020-04876-5
Co, Ni, and their alloys) [5–7], carbon nanomaterials [8–10], and conductive polymers [11], have been investigated and applied in many fields. Among most of the absorbers, the magnetic core–carbon shell nanocapsules, like Fe@C, Ni@C, and Co@C, are promising microwave absorbers [12–14], since they have better microwave absorption performance than their corresponding single components. Herein, the carbon shell of the nanocapsules can not only protect
J Mater Sci: Mater Electron
magnetic cores from oxidation but also tune their dielectric effect and microwave absorption performance to a certain extent. However, these nanocapsules mentioned above have a strong absorption ability, but they exhibited a weak impedance matching behavior and a relatively narrow absorbing bandwidth [15–17]. To further improve the microwave absorption capacity of the
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