Facile synthesis of Ni/ZnO composite: Morphology control and microwave absorption properties

•The Ni/ZnO with various morphologies were synthesized by a two-step process.•The NH3·H2O amount plays a vital role on the morphology of Ni/ZnO composite.•The Ni/ZnO composite (1 mL NH3·H2O) shows excellent microwave absorption properties.•The minimum reflection loss of Ni/ZnO (1 mL NH3·H2O) was −48.6 dB at 13.4 GHz.•The effective absorption (below −10 dB) can be tuned between 9.0 GHz and 18.0 GHz.

In this work, Ni/ZnO composites with varying morphologies were synthesized by a facile hydrothermal method. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were performed to characterize Ni/ZnO composites. SEM images reveal that NH3·H2O concentration play a vital role on morphology of Ni/ZnO composite. The complex permittivity and permeability of three different morphologies of Ni/ZnO were measured in the frequency range of 1–18 GHz and their microwave absorption properties were investigated. The core–shell structured Ni/ZnO (ZnO polyhedron coating) composite prepared for 1.0 mL NH3·H2O shows excellent microwave absorption properties. A minimum reflection loss is −48.6 dB at 13.4 GHz and the corresponding thickness is 2.0 mm. The effective absorption (below −10 dB) can be tuned between 9.0 GHz and 18.0 GHz by adjusting thickness in 1.5–2.5 mm, and the frequency for RL exceeding −20 dB is located at 11.1–16.2 GHz with thickness of 1.8–2.2 mm. It is demonstrated that the polyhedron ZnO-coated Ni composite is a promising microwave absorbent with small thickness, strong absorption, and broad bandwidth.

Graphical abstractThe microwave absorption properties of core–shell structured Ni/ZnO (ZnO polyhedron coating) composite prepared at 1 mL NH3·H2O are superior to those of the other two samples prepared at 2 mL NH3·H2O and 3 mL NH3·H2O, respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide