Synthesis of carbon aerogels incorporating with CoFe alloys for electromagnetic wave absorption

To incorporate magnetic metals into carbon materials is a proven method to achieve highly efficient electromagnetic wave absorption (EMA) capabilities. In this study, cobalt (Co)-iron (Fe) alloys doped phenolic-based carbon aerogels (CoFe-CAs) with an impressive core-shell structure were prepared by using 1,2-epoxypropane as catalyst via a simplified sol-gel method. The effect of annealing temperature on the EMA properties of CoFe-CAs was explored and the X-ray diffractometer, Raman spectrometer, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, N₂ isothermal adsorption-desorption curves and vector network analyzer were used to acquire their physical and chemical properties. The results show that the CoFe-CAs (S-1050) with an impressive core-shell structure possess outstanding EMA performance, the minimum reflection-loss value reaches -58.46 dB (matching thickness: 2.1 mm, frequency: 12.9 GHz) while the maximum effective-absorption-bandwidth displays 5.7 GHz (frequency range: 12.13–17.83 GHz, matching thickness: 1.84 mm), the minimum radar-cross-section value displays -40.02 dB m² in a range of 0° to 360°. The excellent EMA performance of CoFe-CAs can be mainly attributed to the high conduction loss derived from their graphitized carbon, the polarization loss resulted from their impressive core-shell structure, high specific surface area and rich pore structure, and the impedance matching characteristics optimized by the good synergy of dielectric loss and magnetic loss. This study provides a new catalyst and a simplified method for the preparation of magnetic metal doped phenolic-based CAs with excellent EMA properties.