Microwave plasma assisted reduction synthesis of hexagonal cobalt nanosheets with enhanced electromagnetic performances

In this study, we employed a microwave plasma assisted reduction (MPAR) method to prepare metallic nanoparticles with desirable morphology. Compared with the hydrogen thermal reduction technique, the MPAR technique could greatly maintain the original morphology of self-sacrificing precursors, as well as proving to be highly efficient, energy-saving and pollution-free. Taking ferromagnetic metallic Co as a forerunner, Co nanosheets with inerratic hexagonal morphology were successfully synthesized on a large scale uniformly. The lateral dimension of the achieved Co nanosheets is in the range of 3∼5 μm with tens of nanometers in thickness. The intact hexagonal flaky shape of Co nanosheets is beneficial for improving dielectric loss by increasing electric channels and interfacial polarization. Consequently, the minimum reflection loss could reach up to −71 dB at a thin thickness of 1.2 mm. Furthermore, the effective bandwidth (RL < −10 dB) could be achieved in a wide range of 2.8∼18 GHz by integrating the thickness from 5.0∼1.0 mm, which provides the possibility for applications in electromagnetic shielding and radar stealth fields. It is believed that the MPAR technique is suitable for designing and preparing novel microwave absorbers on the basis of appropriate precursors, providing new opportunities to acquire high-performance microwave absorbers in the future. (paper)