High-loading magnetic nanocrystals well-dispersed onto carbon nanosheet honeycombs as ultralight and broadband microwave absorbers

• Published in: Ceramics international 2023-09, Vol.49 (17), p.28901-28912
• Main Authors: Tian, Honglin, Liu, Zhuoyue, Xu, Renxin, Qu, Yangguang, Zhao, Wei, Wang, Yao, Liu, Dan
• Format: Article
• Language: English
• Subjects: Carbon nanosheets; Carbonaceous-magnetic composites; Impedance matching; Magnetic nanocrystals; Microwave absorption performance
• ISSN: 0272-8842
• DOI: 10.1016/j.ceramint.2023.06.159

Homogenously and densely dispersing small-sized magnetic particles into hierarchically porous carbon matrices is essential yet challenging for high-performance carbon-based microwave absorbers with balanced impedance matching and strong attenuation ability. Herein, we propose a general and scalable strategy by direct pyrolysis of solid polyvinylpyrrolidone (PVP) dissolved with metal (i.e., Fe, Co, and Ni) nitrates to prepare carbonaceous-magnetic hybrid absorbers. Benefiting from coordination interactions of carbonyl group-rich PVP molecules toward metal ions and the thermal foaming effect of PVP, the optimized CoNi-based composite material possesses a honeycomb-like architecture built by ultrathin (50 wt%) of ultrafine CoNi alloy nanocrystals (an average size of ∼20 nm). Such structural characteristics endow the absorber with an ultralow tap density of 87.0 mg cm−3 and excellent microwave absorption performance with a superior reflection loss of −51.4 dB at a thickness of 2.6 mm and an effective absorption bandwidth of 7.2 GHz (10.5−17.7 GHz). Moreover, this synthesis methodology is universally applicable and can easily be extended to prepare carbon honeycomb composite absorbers decorated with other magnetic nanocrystals.