▎ 摘　　要

The application of graphene-based composites as microwave absorbing materials still has some problems despite optimistic outlook. In this work, sandwich-like Fe, Co, or Ni nanoparticles/reduced graphene oxide (RGO) composites were successfully fabricated via self-assembly and thermal reduction techniques. The characterization results of XRD, Raman spectroscopy, XPS, SEM, TEM, and thermogravimetric analysis showed that the Fe, Co, and Ni nanoparticles were wrapped by flexible RGO nanosheets, showing sandwich structure. Moreover, the loading amounts of Fe, Co, and Ni nanoparticles were further controlled in a wide range. As expected, this unique sandwich structure can not only reduce the agglomeration of magnetic metal nanoparticles and RGO nanosheets, but also improve the impedance matching and the relaxation loss, achieving an attractive microwave absorption performance. For Co/RGO composites, the value of the minimum reflection loss is -50.60 dB, and the effective absorption bandwidth (RL < -10 dB) can cover the entire X-band and Ku-band with a low filling ratio of 25%. Moreover, the synthesis process is simple and does not require complicated equipment and a variety of chemical reagents, which are suitable for large-scale production and possible industrial applications. The present work provides a good design and fabricating avenue for new graphene-based nanocomposites.