Enhancement of dielectric loss in N-doped carbon nanowires network for broadband microwave absorption

A series of carbons with tunable microstructures are synthesized by controlling of micelles. • Dielectric loss is boosted by rational designed of the morphology, defects, and heteroatoms. • The three-dimensional conductive network in the entangled nanowires improves Ohmic loss. • Abundant defect and heteroatoms in carbon significantly enhance the polarization loss. • An EAB of 7.12 GHz is achieved in N-doped O-functionalized carbon nanowires. The rational design of microstructures, pores, defects, and heteroatoms in carbon that can fully exploit characteristics of structural, interfacial and dipole polarization is a significant approach to achieve enhancement of dielectric loss for broadband microwave absorption. However, it remains a dramatic challenge to get the well-designed carbon with optimal combination of these various factors due to their dependent relationships. Herein, to explore the synergistic pathways among above factors for enhancement of dielectric loss, a series of polymer-derived carbon with identifiable microstructure, defect density and heteroatom was successfully synthesized by controlling the micelle morphology and monomer elemental composition during polymerization. A greater number of unpaired electrons in N-doped O-functionalized carbon nanowires implies more effective vacancy defects for dipole polarization and doesn't hinder the formation of the electric conductive network, resulting in a high ability for dielectric loss attributed to a synergistic effect of Ohmic dissipation as well as dipole polarization and the contribution of the geometric microstructure. As a result, the defects-rich N-doped carbon nanowires exhibit a remarkable broadband response, with an effective absorption bandwidth (EAB, RL ≤ -10 dB) of up to 7.12 GHz (10.88 GHz–18 GHz, 2.62 mm) and a minimum reflection loss (RL min ) of −40.46 dB (2.12 mm). This work not only provides a facile method to synthesize carbon particles with controllable microstructure and dopant atom but also offers some constructive feedbacks for the design of carbon-based microwave absorbing materials (MAMs) to achieve broadband response. Download: Download high-res image (245KB) Download: Download full-size image