Mechanical, dielectric, and microwave absorption properties of rGO nanosheets and ZnO filled ZnAl₂O₄ composites with broad bandwidth and strong absorption

Reduced graphene oxide (rGO) nanosheets and ZnO filled ZnAl₂O₄ composites (rGO/ZnO/ZnAl₂O₄ composites) were fabricated by hot-pressing sintering process in-situ reactions for the purpose of microwave absorption applications. The effects of ZnO and rGO content on the mechanical, dielectric and microwave absorption properties were systemically investigated. The results show that the porosity and microhardness increase with increasing the absorbent content, while the flexural strength presents an opposite trend. In addition, the dielectric properties present an overall increase trend with increasing the absorbent content. Because of the favorable impedance matching and the optimal microwave attenuation, the rGO/ZnO/ZnAl₂O₄ composite with 1 vol% rGO and 8 vol% ZnO demonstrates minimum reflection loss of –44.5 dB at 10.1 GHz and effective absorption bandwidth of 3.8 GHz in 8.2–11.8 GHz and 12.2–12.4 GHz as the thickness is 2.2 mm. The synergistic effects of interfacial polarization, dipole polarization, conductance loss, and multiple scattering result in the outstanding microwave absorption properties for the investigated rGO/ZnO/ZnAl₂O₄ composite, which indicates their potential candidates for the microwave absorbing materials with broad bandwidth and strong absorption.