Core–Shell CoNi@Graphitic Carbon Decorated on B,N-Codoped Hollow Carbon Polyhedrons toward Lightweight and High-Efficiency Microwave Attenuation

Abstract

Lightweight and high-efficiency microwave attenuation are two major challenges in the exploration of carbon-based absorbers, which can be achieved simultaneously by manipulating their chemical composition, microstructure, or impedance matching. In this work, core–shell CoNi@graphitic carbon decorated on B,N-codoped hollow carbon polyhedrons has been constructed by a facile pyrolysis process using metal–organic frameworks as precursors. The B,N-codoped hollow carbon polyhedrons, originated from the calcination of Co-Ni-ZIF-67, are composed of carbon nanocages and BN domains, and CoNi alloy is encapsulated by graphitic carbon layers. With a filling loading of 30 wt %, the absorber exhibits a maximum R L of −62.8 dB at 7.2 GHz with 3 mm and the effective absorption bandwidth below −10 dB remarkably reaches as strong as 8 GHz when the thickness is only 2 mm. The outstanding microwave absorption performance stems from the hollow carbon polyhedrons and carbon nanocages with interior cavities, the synergistic coupling effect between the abundant B–C–N heteroatoms, the strong dipolar/interfacial polarizations, the multiple scatterings, and the improved impedance matching. This study demonstrates that the codoped strategy provides a new way for the rational design of carbon-based absorbers with lightweight and superior microwave attenuation.

A Flexible and Lightweight Biomass-Reinforced Microwave Absorber

“…wave attenuation at an input wave frequency is considered adequate if RL value is below − 10 dB, representing attenuation of more than 90% of the incident EM energy [32]. The frequency ranges with RL below − 10 dB are defined as effective absorption frequency bandwidth (f e ).…”

Bimetallic oxide nanoparticles confined in ZIF‐67‐derived carbon for highly selective oxidation of saturated C–H bond in alkyl arenes

“…The board peak at 2 theta = 22.0° can assign to characteristic peak of partially graphitized carbon. [ 37 ] The intense peaks at 19.1°, 31.3°, 36.8°, 38.5°, 44.7°, 55.4°, 59.1°, and 64.9° were well matched with the (111), (220), (311), (222), (400), (422), (511), and (440) crystal planes of MnCo 2 O 4.5 (JCPDS: No. 32‐0297).…”

“…The board peak at 2 theta = 22.0 can assign to characteristic peak of partially graphitized carbon. [37] The intense peaks at 19.1 , No. 32-0297).…”

Fabrication of Magnetic Cobalt and Electrically Conductive Polyaniline‐Filled Three‐Phase Nanocomposite for Microwave Absorption

“…They are two factors to dominate polarization loss and conduction loss, respectively. Polarization loss results from different polarization forms, such as electronic, atomic, dipolar, and interfacial polarizations . ε ″ results of the Co@PANI@PU composite films are shown in Figure b.…”

“…In this Co@PANI@PU hybrid composite, dipole polarization and interfacial polarization are closely related to the relaxation processes. According to Debye theory, the relationship between ε ′ and ε ″ can be expressed by the equation as belowwhere ε s and ε ∞ are static permittivity and relative permittivity, respectively . It can be known from the equation that the curve of ε ′ and ε ″ is a single semicircle, i.e., Cole–Cole semicircle.…”