**2.1 Core-shell Ni@ZnO composites as microwave absorbers**

For the ZnO nanostructural materials, due to the features of lightweight semiconductive properties and its easily mass synthesis, they are expected to be the potential applications in EM wave absorbing materials [22]. Therefore, when the Ni particles were covered by ZnO shell, the electromagnetic properties of Ni would be boosted, correspondingly. Moreover, it is well accepted that the EM absorption properties are closely related with their morphologies. Herein, the various morphologies of Ni/ZnO composites were synthesized by control of the amounts of NH3·H2O, and the microwave absorption properties of these Ni/ZnO composites have been investigated based on the complex permittivity and permeability.
