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

Abstract

In this study, we employed microwave plasma assisted reduction (MPAR) method for preparing metallic nanoparticles with desirable morphology. Compared with hydrogen thermal reduction technique, MPAR technique could greatly maintain the original morphology of self-sacrificing precursors, as well as is proved to be high-efficiency, energy-saving and pollution-free. Taking ferromagnetic metallic Co as forerunner, Co nanosheets with inerratic hexagonal morphology were successfully synthesized on a large scale uniformly. The lateral dimension of 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 provide the possible for applications in electromagnetic shielding and radar stealth fields. It is believed that MPAR technique is suitable for designing and preparing novel microwave absorbers on the basis of appropriate precursors, providing new opportunities for acquiring high performance microwave absorbers in the future.