Synthesis of mesoporous hexagonal cobalt nanosheets with low permittivity for enhancing microwave absorption performances

Abstract In this study, regular hexagonal cobalt (Co) nanosheets with mesoporous structure have been successfully prepared on a large scale uniformly through precursor directed synthesis route. In contrast to the traditional ball milling technique, such Co nanosheets were controllable and repeatable in lateral dimension and thickness. The radial length of the Co nanosheets was observed in the range of 3–5 μm with the average thickness of 120 nm. Such flaky shape was proved to be beneficial to break the Snoek limit, resulting in appreciable permeability in high frequency range. In addition, the mesoporous structure is favorable of lowering the permittivity and suppressing eddy current effect. Consequently, excellent microwave absorption performances could be achieved through adequate synergy of the attenuation competence and impedance matching. The minimum reflection loss (RL) value of −45.1 dB was realized with a thickness of 2 mm, and the effective bandwidth (RL