Metal-organic framework-derived C/Co/Co3O4nanocomposites with excellent microwave absorption properties in low frequencies

To improve the microwave absorption performance of functional coatings, metal-organic framework (MOF)-based nanocomposites were synthesized via a simple method, including a two-step cooling process. Derived from the ZIF-67 precursor, the nanocomposites consist of C, Co, and C3O4, and all the three chemical constituents are effectively combined in nanometer scale. By varying the heat treatment temperature, the structural architecture and chemical composition of the nanocomposites are carefully tailored to achieve the outstanding microwave absorption properties, in particular, for low frequencies. These properties are mainly boosted by the distinguished attenuation performance and an optimal impedance matching condition. When the heat treatment temperature is 800 degrees C, the sample (CCCO-800, CCCO for Carbon-Cobalt-Cobalt Oxide) possesses the best microwave absorption performance in this research. The maximum reflection loss (RL) of CCCO-800 can reach - 84.75 dB at 6.61 GHz, and the effective absorption bandwidth (RL < -10 dB) can be as wide as 8.5 GHz. With the absorber thickness ranging from 1.0 to 5.0 mm, the effective absorption bandwidth of CCCO-800 can cover one half of S band and the whole C, X, and Ku bands. These results show that with an appropriate process control, the nanocomposite absorber can achieve remarkable microwave absorption performance, which makes this type of nanocomposite promising as a functional coating for both civil and military applications.