Carbon\nHollow Microspheres with a Designable Mesoporous Shell for High-Performance\nElectromagnetic Wave Absorption

Abstract

In\nthis work, mesoporous carbon hollow microspheres (PCHMs) with designable\nmesoporous shell and interior void are constructed by a facile in\nsitu stöber templating approach and a pyrolysis-etching process.\nThe PCHMs are characterized by scanning electron microscopy, transmission\nelectron microscopy, X-ray photoelectron spectra, Raman spectroscopy,\nand nitrogen adsorption and desorption system. A uniform mesoporous\nshell (pore size 4.7 nm) with a thickness of 55 nm and a cavity size\nof 345 nm is realized. The composite of paraffin mixed with 20 wt\n% PCHMs exhibits a minimum reflection coefficient (RC_min) of −84 dB at 8.2 GHz with a sample thickness of 3.9 mm and\nan effective absorption bandwidth (EAB) of 4.8 GHz below −10\ndB (>90% electromagnetic wave is attenuated). Moreover, the composite\nof phenolic resin mixed with 20 wt % PCHMs exhibits an ultrawide EAB\nof 8 GHz below −10 dB with a thinner thickness of 2.15 mm.\nSuch excellent electromagnetic wave absorption properties are ascribed\nto the large carbon–air interface in the mesoporous shell and\ninterior void, which is favorable for the matching of characteristic\nimpedance as compared with carbon hollow microspheres and carbon solid\nmicrospheres. Considering the excellent performance of PCHMs, we believe\nthe as-fabricated PCHMs can be promising candidates as highly effective\nmicrowave absorbers, and the design philosophy can be extended to\nother spherical absorbers.