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Electromagnetic Microwave

One-dimensional C/Co composite nanofibers derived from ZIF-67 with excellent wideband electromagnetic microwave absorption performance

The rapid advancement of wireless communications, radar systems, and electronic devices has resulted in a substantial increase in electromagnetic interference (EMI), which poses a threat to electronic device performance and human health. This study addresses the urgent need for lightweight materials with strong absorption capacities, wide absorption bandwidths, and low thickness values. For this purpose, ZIF-67-derived C/Co nanofibers were synthesized via electrospinning, dipping, and high-temperature carbonization. Co2+ ions were pre-anchored and encapsulated in polyacrylonitrile (PAN) fibers and are grown by immersion in an organic ligand. Utilizing 0.4 g of cobalt nitrate hexahydrate, the amount of encapsulated Co2+ was optimized to provide the greatest electromagnetic wave absorption performance.

Under these conditions, the reflection loss was −49.45 dB, and the maximum effective absorption bandwidth was 6.48 GHz, thereby covering the entire Ku band. The composite material demonstrated a significant improvement in impedance matching and electromagnetic wave dissipation, which was attributed to the uniform dispersion of Co particles and the formation of multi-component heterogeneous interfaces. This study presents a pragmatic method for creating high-performance materials that could potentially reduce electromagnetic interference (EMI) in the aerospace, telecommunications, and defense sectors.

Materials


PAN (Mw = 150,000 g/mol), Cobalt nitrate hexahydrate (Co(NO3)2·6H2O), and N,N-dimethylformamide (DMF), and 2-methylimidazole (C4H6N2, 2-M) were purchased from the Aladdin Reagent Co., Ltd. The methanol was acquired from Heng Xing Chemical Reagents. All chemicals and reagents used in the experiment were of high purity and were utilized without any additional treatment.
Preparation of the ZIF-67-derived C/Co nanofibers. The ZIF-67-derived C/Co nanofibers were acquired using the processes of electrospinning, dipping, and calcination.

The XRD patterns of the CNF-Co-2, CNF-Co-4, and CNF-Co-6 samples, as well as the unadulterated pure carbon nanofibers, are exhibited in Fig. 1(b). The prominent peak seen between 20°and 30°in all samples corresponds to the (002) crystallographic plane of the graphite microcrystals within the amorphous carbon of the carbonized PAN. In addition, the diffraction peaks observed at 44.2°, 51.5°, and 75.8° for the three composite samples correspond to the (111), (200), and (220) planes, respectively.

In this study, high-performance C/Co nanofibers were prepared via electrospinning, dipping, and high-temperature carbonization. By adjusting the content of cobalt nitrate hexahydrate, these nanofibers achieved an optimal electromagnetic wave reflection loss of −49.45 dB (4.96 mm), a Co loading of 0.4 g, and a maximum absorption bandwidth of 6.48 GHz (2.65 mm), which covers the entire K band. Various methods were used to analyze and explain the absorption mechanisms of composite nanofibers.


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