**Author details**

*Electromagnetic Materials and Devices*

natural resonance in permittivity.

The minimal RL could reach −48.6 dB at 13.4 GHz in the absorber thickness of 2.0 mm. The absorption band with RL below −10 dB could reach 6.0 GHz between 10.5 and 16.5 GHz. The enhanced microwave dissipation abilities are attributed to the synergetic effect between dielectric loss and magnetic loss, strong dissipation

The hierarchical Ni-CuO heterostructures have been successfully synthesized by a two-step process. The as-prepared Ni-CuO products display a rice-like coating composite. Moreover, by tuning the molar ratio of CuCl2·2H2O to the Ni microspheres, different shapes and coverage densities of CuO coating are obtained. The effects of CuO amounts on the Ni microspheres for microwave absorption properties have been investigated. The thin CuO-coated Ni composites (S-1) exhibit the enhanced electromagnetic absorption properties. The optimal RL is −62.2 dB at 13.8 GHz with only thickness of 1.7 mm. The outstanding microwave absorption properties result from the strongest attenuation constant, interfacial polarization of

ZnS nanowall-covered Ni composite is fabricated via a hydrothermal template

Novel and interesting urchin-like ZnS/Ni3S2@Ni composites are synthesized through a two-step process including solution reduction and subsequently a template method. Crucially, the morphologies of the core-shell ZnS/Ni3S2@Ni composites are determined by the reaction temperature. Different ZnS/Ni3S2@ Ni composites prepared at different temperatures show variable electromagnetic absorption responses, for which the urchin-like ZnS/Ni3S2@Ni obtained at 120°C show the enhanced EM absorption properties thanks to its promising dielectric loss and magnetic loss, good impedance match, as well as its unique urchin-like structure. Multiple dielectric resonances stemming from effective accumulation of different polarizations in the urchin-like structure are regarded to make a contribution to the enhancement of electromagnetic wave absorption. It is believed that *in situ* synthesis of core-shell ZnS/Ni3S2@Ni composites may open up a new avenue for the design and preparation of novel microwave absorbers with promising applica-

In a word, the core-shell configuration is proved to be a promising pathway to

design high-efficiency EM absorption properties of Ni based composites.

ability, as well as the multiple polarization of the core/shell interfaces.

and the synergetic effect between the dielectric loss and magnetic loss.

method. The as-obtained Ni/ZnS composites display the crumble and rough features and the thickness of ZnS nanowall is about 10 nm. In comparison with raw Ni and ZnS particles, the Ni@ZnS composites show superior microwave dissipation abilities. The optimal RL of −25.78 dB could be obtained at 14.24 GHz and the valuable (less than −10 dB) band could reach 4.72 GHz (11.52–16.24 GHz) in the thickness of 2.7 mm. Moreover, the location of absorption peaks is almost similar at various thicknesses without moving to low frequency, which originates from

**168**

tion potential.

**Conflict of interest**

There are no conflicts to declare.

Biao Zhao1,2\* and Rui Zhang1,3

1 Henan Key Laboratory of Aeronautical Materials and Application Technology, School of Material Science and Engineering, Zhengzhou University of Aeronautics, Zhengzhou, Henan, China

2 Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada

3 School of Material Science and Engineering, Zhengzhou University, Zhengzhou, Henan, China

\*Address all correspondence to: zhaobiao1813@163.com

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
