Fe3C-coated nitrogen-doped CNT/cattail-derived carbon microtube composites for efficient microwave absorption

Abstract

Due to the inherent limited dielectric loss of carbon materials, their attenuation ability and impedance matching are often unsatisfactory. To overcome these problems, hierarchical structures and combined microwave loss mechanisms have attracted considerable attention in the development of high performance microwave absorbers. In this work, biomass cattail was used as a sustainable precursor to synthesize nitrogen-doped carbon nanotube arrays decorated with Fe3C nanoparticles by chemical vapor deposition. The resulting cattail-derived carbon-based tubular composites (Fe3C@NCNTs/CMTs) feature a unique Fe3C-coated, nitrogen-doped carbon nanotube structure. The influence of crystallinity, tuned by calcination at different temperatures, on microwave absorption was investigated. Remarkably, at 800 °C, Fe3C@NCNTs/CMTs achieved a minimum reflection loss of –35.8 dB and an effective absorption bandwidth of 7.02 GHz at a thickness of only 1.7 mm, even at an ultralow filler loading of 10%, effectively covering the entire Ku band and part of the X band. The excellent microwave absorption performance is attributed to the combined contribution of increased magnetic loss and multiple dielectric polarization mechanisms. This study shows a promising strategy for designing biomass-derived carbon-based broadband microwave absorbing materials.

1. Introduction

With the rapid development of 5G technology and the widespread application of high-frequency electronic and communication equipment, the consequent electromagnetic radiation and interference have seriously affected information security, equipment performance, and human health[1–5]. In recent years, microwave absorbing materials have attracted wide attention from researchers, and some research results have been reported, such as carbon materials[6], graphene[7], carbon nanotubes (CNTs)[8–9], magnetic materials[10], ceramic materials[11], metal-organic framework (MOF)[12], and MXene[13–14]. Carbon-based materials have become promising candidates for high-performance microwave absorption (MA) applications by their chemical stability, low density, and tunable dielectric properties[15]. However, carbon materials still face issues such as impedance mismatch and single loss mechanism[16].

Therefore, the synergistic loss mechanism, which is the MA composite material that interacts with dielectric loss and magnetic loss, has attracted great attention[17–20]. Li et al.[21] prepared BN/Ni/CNT hybrid materials through a carbonization method and fabricated flexible BN/Ni/CNT/WPU films using a knife-coating process. The notable MA performance from dielectric loss, magnetic loss and appropriate impedance matching. Jiang et al.[22] achieved the minimum reflection loss (RLmin) of −63.1 dB and the effective absorption bandwidth (EAB) of 7.3 GHz for the Fe/Fe5C2@NC-800 material with only 4% filler loading, based on a dual attenuation mechanism involving dielectric and magnetic losses. Li et al.[23] utilized an ice-templated freeze-casting method combined with an annealing process to fabricate a ceramic nanofiber aerogel composed of silica nanofibers, graphene, and metal–organic framework (MOF) derivatives. This approach enabled the efficient integration of MOF-derived magnetic nanoparticles, and the synergistic mechanism between dielectric and magnetic components significantly enhanced the MA performance. Gao et al.[24] prepared Fe/SiC composite materials with core/shell structure through thermal assisted synthesis process, successfully combining dielectric loss material and magnetic loss material together, achieving a RLmin of −51 dB at an absorber thickness of 2.01 mm. Wang et al.[25] successfully prepared Fe3O4-graphite composite materials by solvothermal method. The optimization of the microwave properties and impedance matching characteristics of the sample is achieved by controlling the proportion of graphite dosage. The magneto electric synergistic loss between ...