Tunable Complex Permittivity and Strong Microwave Absorption Properties of Novel Dielectric-Conductive ZnO/C Hybrid Composite Absorbents

Abstract

Modern electronic information technology has led social life into inevitable electromagnetic pollution, making microwave absorbing materials more and more important. Herein, dielectric-conductive ZnO/C hybrid composite absorbents were prepared by two-step carbonization with ZnO powders and glucose as critical materials. The electrical conductivity, complex permittivity, and reflection loss were analyzed to study the dielectric and microwave absorption properties. Results show that the prepared ZnO/C composite absorbents exist in the form of rod-like ZnO dispersed in the irregular block carbon, and the complex permittivity of the composite absorbents can be adjusted via varying the carbonization temperature. The minimum reflection loss of −25.64 dB is achieved at 1.8 mm thickness for the composite absorbent with 50 wt.% absorbent content as the final carbonization temperature is 750 °C, and the optimum effective absorption bandwidth is 2.21 GHz at 9.64–11.85 GHz. The excellent microwave absorption properties of ZnO/C composite absorbents are attributed to the combination actions of dipole polarization, conductance loss, and interface polarization, which is significant for the purposeful design of superior microwave-absorbing materials with dielectric and conductive absorbents.