Facile synthesis of Co-loaded ceramic composite absorbents via gangue recycling

Abstract

Coal gangue was recycled to synthesize ceramic-based microwave absorbents decorated with Co particles via a facile synthesis route. Co particles were uniformly loaded onto the ceramic matrix by pelletizing the gangue with concurrent spraying of a Co2+-containing solution, followed by in situ carbothermal reduction using the fixed carbon in the gangue as the reducing agent. The Co contents of the ceramic composites were precisely controlled by adjusting the concentration of Co2+ solution. The fixed carbon in the gangue was partially consumed, and the residual carbon in the composites resulted in more defects, and acted as a dielectric. Compared to gangue, the optimized composite exhibited excellent microwave absorbing properties with a minimum reflection loss of −48.2 dB and an effective absorption band of 4.3 GHz under a coating thickness of 1.5 mm. The excellent performance was mainly attributed to the enhanced impedance matching and multiple interface polarizations in the composite.