Confinedly tailoring Fe3O4 clusters-NG to tune electromagnetic parameters and microwave absorption with broadened bandwidth

•A facile strategy of confined growth is used to implant Fe3O4 small clusters on N-doped graphene.•Tailoring Fe3O4 clusters tunes microwave absorption for high efficiency and broad bandwidth.•Tailoring Fe3O4 clusters can realize selective-frequency absorption.•Relationship between structure and properties is thoroughly revealed.•Physical images are proposed to explain the microwave response behaviors vividly.

High efficiency and great tunability are becoming hot spot in microwave absorption, drawing great interests of global health researchers. However, meeting the two factors is still a tough challenge. In this work, we demonstrate an easily-tailored absorber of Fe3O4 clusters-nitrogen doped graphene by a facile strategy of confined growth. Small magnetic clusters are uniformly implanted on nitrogen doped graphene, which realizes synergy of dielectric and magnetic loss with good conductivity and improved impedance matching. More significantly, tailoring small Fe3O4 clusters successfully tunes microwave absorption and bandwidth. The minimum reflection loss is greatly increased by ∼7 times, achieving −53.6 dB, and the effective bandwidth reaches ∼5 GHz with only 1.8 mm thickness. Moreover, tailoring the small clusters also drives the absorption peaks from 4.6 to 14.7 GHz, covering ∼60% of the investigated frequency. This highly efficient and even frequency-selective microwave absorption endows Fe3O4 clusters-nitrogen doped graphene with wider applications in electromagnetic shielding, microwave absorption, healthcare, information safety and military fields.

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