Fabrication of Micro‐Mesopores on Spiral Carbon Nanocoils and Simultaneous Doping with Oxygen to Expand Microwave Absorption Bandwidth

Abstract The exceptional benefits of structural defects and doped atoms in carbon network regarding electromagnetic properties inspire the design of advanced carbon‐based microwave absorption (MA) materials. However, excessive structural defects decline the physical properties of materials, especially their conductivity. Therefore, it is a great challenge to balance structural defects and doped atoms to optimize conductive behavior for carbon‐based MA materials. The spiral carbon nanocoil (CNC), with coexisting amorphous and polycrystalline carbon structures and moderate conductivity, has significant MA properties but lacks pores and doped atoms. Herein, the amorphous carbon parts with relatively weak C─C bond energies are preferentially oxidized at 500 °C in air atmosphere to create pores and combine O atoms in the bodies of CNCs. Furthermore, the mechanism prioritizing the formation of O doping over defects is discovered. Benefiting from the synergistic interplay of structural defects and O dopants, the O‐enriched porous CNCs demonstrate enhanced conduction and polarization losses than the pure CNCs, realizing a wide effective absorption bandwidth of 7.3 GHz at a filling ratio of only 3 wt.%. Theoretical calculations further support these experimental results. The combination of structural defects and doped atoms may serve as an effective pathway for unlocking tunable dielectric properties of carbon‐based materials.