Co0.5Zn0.5Fe2O4 modified residual carbon as an excellent microwave absorber

Microwave absorbers have great potential for military and civil applications. Herein, Co0.5Zn0.5Fe2O4/residual carbon (CZFO/RC) composites have been successfully prepared using a hydrothermal method. RC was derived from coal gasification fine slag (CGFS) via pickling, which removes inorganic compounds. Multiple test means have been used to study the chemical composition, crystal structure, and micromorphology of the CZFO/RC composites, as well as their electromagnetic parameters and microwave absorption (MA) properties. The CZFO/RC composites exhibit excellent MA performance owing to their dielectric and magnetic losses. When the thickness of CZFO/RC-2 (FeCl3∙6H2O = 0.007 mol, ZnCl2 = 0.00175 mol, and CoCl2∙6H2O = 0.00175 mol) is 1.2 mm, the minimum reflection loss (RLmin) is −56.24 dB, whereas that at a thickness of 3 mm and 6.34 GHz, RLmin is −45.96 dB and the maximum effective absorption bandwidth is 1.83 GHz (5.53−7.36 GHz). Dielectric losses include interface and dipole polarizations, while magnetic losses include current and remnant magnetic losses. CZFO/RC-2 exhibits high impedance matching, allowing microwave to enter the absorber. The CST simulation confirms that CZFO/RC-2 considerably decreases the radar cross-section. This study can be used to promote the use of CGFS as EMW-absorbing materials.