Synthesis of polymer-derived N,O-doped bowl-like hollow carbon microspheres for improved electromagnetic wave absorption using controlled template pyrolysis

In this study, we designed a simple green preparation method and synthesized polymer-derived N,O-doped bowl -like hollow carbon microspheres (BHCMs) to improve their electromagnetic wave absorption performance. Using copolymerized microspheres of allyl methacrylate and acrylonitrile (P(AMA-AN)) synthesized through soap-free emulsion polymerization as a template and polydextrose as the primary carbon source, BHCMs were fabricated by a hydrothermal method and high-temperature carbonization pyrolysis. Moreover, the P(AMA-AN) micro -spheres could directly provide nitrogen (N) and oxygen (O) heteroatoms, achieving heteroatom doping. The morphology and absorption properties of BHCMs can be adjusted by controlling the amount of P(AMA-AN) microspheres. The unique structure gives BHCMs-2 excellent electromagnetic wave attenuation and impedance-matching characteristics. At a low filling ratio (11.1%), the minimum reflection loss (RLmin) is-40.3 dB at 13.82 GHz with a 2.5 mm thickness. Surprisingly, a broad effective absorption bandwidth (EAB) is maintained over an extensive thickness range. The average EAB in the 2.5-3.5 mm thickness range reaches 5.52 GHz. This study proposes a new and green preparation method for carbon materials to improve their absorption properties.