MOFs-derived flaky carbonyl iron/Co@C core-shell composites for thin thickness and broadband microwave absorption materials

Abstract

Construction of thin thickness and broadband microwave absorption materials (MAMs) is challenging but important. One important and relatively successful strategy involves the reduction of quarter-wavelength resonance thickness by increasing permittivity (εr) and permeability (μr). In this study, MOFs-derived core-shell structured flaky carbonyl iron/Co@C (FCI/Co@C) composites were synthesized via self-polymerization and in-situ pyrolysis to enhance εr. The effects of Co content in the porous carbon shell on the microstructure and electromagnetic performance of the FCI/Co@C composites were investigated. The FCI/Co@C composite with a Co-to-Zn molar ratio of 1:0 and 3:1 in its precursor and 70 wt% of filler exhibited excellent microwave absorption performance. The effective absorption bandwidth (EAB, corresponding to a reflection loss of less than −10 dB) of FCI/Co@C-1 reached 5.7 GHz (12.3–18 GHz) with a thickness of 1.28 mm, while the EAB of FCI/Co@C-3/1 reached 5.2 GHz (12.8–18 GHz) with a thickness of 1.19 mm, and both samples demonstrated broadband absorption in the Ku band. Thus, core-shell structured FCI/Co@C composites can be used as thin broadband MAMs in the Ku band. Furthermore, this work not only provides a simple method for constructing FCI-based core-shell structured MAMs, but also offers a novel strategy for reducing thickness while maintaining good microwave absorption performance.