Fabrication of rod-like porous Co@graphene/CNT composites for superior wideband electromagnetic wave absorption

Abstract

The proliferation of electronic devices has significantly increased electromagnetic radiation pollution, impacting human health and national defence. This creates an urgent demand for high-performance electromagnetic wave absorbing (EWA) materials. However, designing and fabricating wideband EWA materials is highly challenging due to the single loss mechanism and impedance mismatch. Herein, we designed and synthesized rod-like porous carbon composites (Co@G/CNT) by thermal cleavage of Co/Zn-ZIF bimetal–organic framework precursors, which in situ forms a composite of magnetic metal nanoparticles, graphene, and carbon nanotubes (CNTs), leveraging both magnetic loss and dielectric loss. By increasing the Zn content in Co/Zn-ZIF precursors, the porosity of the generated Co@G/CNT was enhanced due to Zn sublimation. Three carbon composites (Co@G/CNT-1, Co@G/CNT-2, and Co@G/CNT-3) were synthesized by varying the Zn/Co ratios to 3 : 1, 1 : 1, and 1 : 3, respectively. Amongst them, Co@G/CNT-3 achieved a remarkable absorption bandwidth of 9.6 GHz (8.4–18.0 GHz) at a thickness of 3.2 mm and a minimum reflection loss of −40.36 dB at 13.5 GHz with a thickness of 3.0 mm. This superior performance is primarily caused by the synergistic effect arising from the composite's heterogeneous interfaces and high porosity. These features enhance polarization and dielectric loss, while also facilitating multiple reflections and scattering of electromagnetic waves. These findings offer a valuable insight for the development of microwave absorbers for high-performing wideband electromagnetic wave absorption.