Superior microwave absorbing properties of O, S, N codoped carbon planar helixes via carbonization of polypyrrole spiral nanowires

Lightweight, and broad and strong absorption are still a huge challenge for electromagnetic (EM) wave absorbers. Here, we propose a facile oxidative polymerization-carbonization strategy to synthesize O, S, N codoped carbon planar helixes for superior EM wave absorbers. The spiral cetyltrimethylammounium bromide crystallites act as a template for the in-situ oxidative polymerization of pyrroles into ordered PPy spiral nanowires. Sintering temperature (T-s) was used to adjust the defects, heteroatoms, graphitization degree, and properties of the carbonized products. With T-s varying from 400 degrees C to 800 degrees C, internal stress and heteroatom (N, O, S) content decreased, causing the decreased defect/dipole polarization and increased graphitization degree and conductivity loss. As a result, one broad high-frequency absorption band was exhibited by carbon planar helixes produced at 400 degrees C - 500 degrees C, two broad absorption bands were exhibited by those formed at 600 degrees C, and three absorption bands were exhibited by those formed at 700 degrees C - 800 degrees C. The carbon planar helix formed at 700 degrees C exhibited broader bandwidth (4.96 GHz), thinner sample thickness (1.4 mm), and stronger absorption (-35.44 dB) than those of other absorbers. The superior properties are attributed to a combination of dipole/defect polarization, interface polarization, conductivity loss, multiple scattering, and multiple LC-resonances generated from the unique planar helical structure, defects, heteroatoms, and local electric network. (C) 2020 Elsevier Ltd. All rights reserved.