Preparation and microwave absorption of porous hollow ZnO by CO2 soft-template

•The porous hollow ZnO architectures were prepared by a two-step method.•The porous hollow ZnO/paraffin wax composite shows excellent microwave absorption.•The minimum reflection loss of porous hollow ZnO/paraffin wax was −36.3 dB at 12.8 GHz.•The excellent properties were attributed to impedance match and interference of multi-reflected microwaves.

The porous hollow ZnO samples were prepared by calcination of ZnCO3 precursor at 450 °C. The structural properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis and differential thermal analysis (TG-DTA). A possible mechanism for the formation of porous hollow microstructure was proposed. The microwave absorption properties of the porous hollow structural ZnO have been investigated. The reflection loss (RL) of the ZnO was calculated based on the relative complex permeability and permittivity. A minimum reflection loss of the wax-composite with 25 wt% porous hollow ZnO is −36.3 dB at 12.8 GHz with a thickness of 4.0 mm. The results indicate that porous hollow structural ZnO can be used as a desirable material for the microwave absorption.

Graphical abstractThe porous hollow ZnO was prepared by calcination of ZnCO3 precursor at 450 °C. The porous hollow ZnO wax-composites show excellent microwave absorption with a minimum reflection loss of −36.3 dB at 12.8 GHz for a weight fraction of 25%.Figure optionsDownload full-size imageDownload as PowerPoint slide