▎ 摘　　要

A novel three-dimensional graphene@carbon nanotube (CNTs) composite has been prepared using a facile one-pot pyrolysis strategy using urea as the carbon source, in which the density and length of CNTs on graphene are rationally tuned by adding an appropriate amount of urea to a precursor mixture. Correspondingly, the density and length of CNTs on graphene have a significant effect on the microwave absorption properties of graphene@CNTs. When most of the graphene surface is clearly covered by the CNTs whose length ranges from 300 to 600 nm, the graphene@CNT composite exhibits excellent microwave absorption properties. The maximum reflection loss value can reach -44.6 dB at 8.6 GHz and the absorption bandwidth with a reflection loss below -10 dB ranges from 7.1 to 10.4 GHz with an addition amount of only 5 wt% graphene@CNTs composite in the paraffin matrix.