Defect Engineering on Carbon Nanotubes or Graphene to Balance Conduction and Polarization Loss for Enhancing Microwave Absorption

Herein, a defect engineering method was used to balance conduction loss and polarization loss and improve microwave absorption (MA) performance of carbon-based nanomaterials. Nitrogen-doped carbon nanotubes (NCNTs) and reduced graphene oxide (rGO) were prepared by a simple calcination under a nitrogen atmosphere and a simple pyrolytic reduction, respectively. The defects which are created into carbon materials by doping nitrogen and oxygen elements can reduce electrical conductivity and enhance polarization loss of carbon materials. Therefore, the MA performance of NCNTs and rGO can be enhanced by controlling the N and O content in the carbon materials, respectively. Specifically, NCNTs exhibit a minimum reflection loss (RLmin) of −22 dB at 4 GHz with a thickness of 4.7 mm, thus demonstrating effective absorption at low frequencies. After reduction at 600 °C, the rGO had an effective absorption bandwidth of 7.6 GHz at a thickness of 2.8 mm, accompanied by an RLmin of −42 dB.