Boosted microwave absorption performance of multi-dimensional Fe2O3/CNTsCM@CN assembly by enhanced dielectric relaxation

The large-scale preparation of homogeneous multi-dimensional assembly is still believed as an enormous challenge for microwave absorber. Herein, a novel class of Fe2O3/CNTsCM@CN hybrids featured with three-dimensional (3D) hollow structure (du003c6.88 μm) was successfully fabricated by a facile spray-drying and subsequent annealing treatment. The magnetic-dielectric composite microspheres are forcibly-assembled by the 0D γ-Fe2O3 nanoparticles, 1D carbon nanotubes (CNTs) and 2D N-doped carbon layers. By virtue of the unique design of interface structure and rich electronic conduction paths, excellent microwave absorption (MA) performance has been realized from the Fe2O3/CNTsCM@CN-2. Impressively, the MA value has been enhanced to −51.5 dB with a thin thickness of only 2 mm, and the efficient absorption bandwidth (u003c10 dB) has been broadened to 5.4 GHz with only 10% loading mass, all of which have surpassed most of the art-of-state MA materials. In this heterogeneous system, remarkable multi-interfaces regions have been built by the compressive contacting among CNTs, nanoparticles and N-doped carbon layers, which plays a key role in promoting the interfacial polarization. Electron charge density redistribution observed by electron holography further favors the dielectric relaxation locally around those touching interfaces. Special 3D CNTs network and bridged N-doped carbon layers enriched the electron transportation routes and optimized the conductivity. In addition, spray-dried Fe2O3/CNTsCM@CN absorbers at micron-size exhibit a better electromagnetic and size matching. This work hereby gives deep insight into a novel strategy to construct the multi-dimensional hollow assembly as MA candidates.