Construction of porous carbon for high-performance microwave absorbing: An efficient method to utilize direct liquefaction coal asphalt by-products

To address the issue of electromagnetic pollution in recent times, it is critical to creating a low-cost and effective electromagnetic wave-absorbing material as well as a simple preparation process. High-performance porous carbon microwave absorbers were produced from direct liquefaction coal asphalt (APCs), a by-product of the direct liquefaction coal process, using a straightforward activation approach. At an absorber filler of 10 wt% and a specimen thickness of 2.3 mm, which attained a high absorption performance of reflectivity minimum reflection loss (RLmin) = -62.1 dB (>99.9999 % absorption), and an effective absorption bandwidth (EAB) of 4.42 GHz (10.01-14.43GHz)was achieved at a specimen thickness of 2.3 mm. The excellent performance is attributable to the complete construction of the porous structure, which effectively extends the electromagnetic wave reflection path to achieve the effect of electromagnetic wave loss. The porous structure and the small amount of Fe3+ ions contained within it also construct a robust conductive network, which increases the loss capacity within the APCs and optimizes the impedance matching. This work satisfies the fundamental requirements for new microwave-absorbing materials that are "thin, light, wide, and strong" and provides new ideas for future porous carbon-absorbing material research. Moreover, it provides an efficient and environmentally friendly method for dealing with the industrial by-products of the direct liquefaction coal process.