Ultrafine Well-Dispersed Co Nanocrystals Onto Crumpled Sphere-Like Rgo for Superior Low-Frequency Microwave Absorption

Nowadays, it is challenging to construct strong absorption materials for addressing low-frequency electromagnetic pollution from electronic equipment. In this work, Co nanocrystals anchored onto crumpled sphere-like reduced graphene oxide are fabricated via a stepwise spray drying-calcination strategy. The crumpled spherelike architecture prevents the agglomeration of graphene sheets and magnetic nanoparticles while ensuring appropriate exposure of polar functional groups on graphene surfaces. Meanwhile, the addition of magnetic components results in increased magnetic loss capacity, and the crumpled sphere-like structure generates large void spaces and bountiful heterogeneous interfaces, together promoting dielectric polarization loss and impedance matching. Consequently, the optimal absorber achieves a strong reflection loss of -43.3 dB at 3.5 GHz, which can fulfill the similar to 85% coverage of the S and C bands by adjusting the thickness from 3.6 to 7.0 mm. This work paves a time-saving and scale-up path for preparing graphene-magnetic materials with superior lowfrequency microwave absorption.