Simple preparation of 1D hierarchical magnetic CNTs/hollow porous macroscopic carbon fiber composites for efficient microwave absorption

Abstract

Three dimensional (3D) hierarchical carbon-based materials have attracted attention due to their excellent structural and microwave absorption properties. However, the construction of well-defined 3D multilevel layered structures currently relies on complex preparation processes and harsh preparation conditions. In this paper, hierarchical hollow porous carbon fibers (HPCFs) were prepared by modulating the sulfuric acid treatment time using low-cost polypropylene (PP) fibers as precursors. In situ doping and uniform distribution of a small amount of iron (Fe) in PP fiber sulfonation were achieved by introducing Fe into the sulfuric acid solution. Relying on the autocatalytic effect of Fe during high-temperature carbonization, the simultaneous growth of carbon nanotubes (CNTs) on the surface and inside of HPCFs was achieved by using the pyrolysis exhaust gas of sulfonated PP fibers as a carbon source. Due to the unique hierarchical structure and the synergistic effect of multi-polarization loss, the hierarchical CNTs/HPCFs composites (CNTs@HPCFs) exhibit excellent microwave absorption performance with a minimum reflection loss of −54.03 dB and a thickness as low as 1.9 mm. Moreover, an effective absorption bandwidth as high as 6.04 GHz (11.96–18 GHz) is achieved at thicknesses as low as 1.8 mm, covering the entire Ku-band. This study provides a new idea for the facile preparation of low-cost and efficient carbon fiber wave-absorbing materials, which is instructive for the structural design of CNT-loaded carbon fiber wave-absorbing materials.