Upcycling of Waste Cotton Fabrics into High-Value Porous Carbon Spheres for High-Performance Electromagnetic Wave Absorption

With the improvement of the residents' consumption level, the production of textiles has developed vigorously, bringing about a considerable number of waste cotton fabrics (WCF) that account for about 24% of the total textile waste. Developing carbon materials with regular morphologies is of great significance for achieving high-value applications of WCF. In this study, carbon spheres (CSs) derived from spherical precursors transformed from WCFs were prepared through the hydrothermal method and then the alkali-etching and carbonization method. Additionally, the diameter, pore structure, and graphitization degree of CSs were effectively regulated by adjusting alkali-etching concentration and carbonization temperature. Benefiting from the improved impedance matching and strong dielectric loss, the as-prepared CS exhibited favorable electromagnetic wave absorption performance, with a minimum reflection loss of -42.5 dB and an effective absorption bandwidth of 3.4 GHz at 1.5 mm under an ultralow filler loading of 10 wt %. The radar cross-section simulation results reveal the potential application of the CS in the field of radar stealth. Furthermore, the method can be applied to waste commodity cotton textiles. Their derived CS delivered a very close minimum reflection loss (RL_min) of -42.4 dB but a wider effective absorption bandwidth (EAB) of 4.32 GHz at the same filler loading and thickness. This work offers a new approach for upcycling WCF and preparing carbon microspheres for energy storage, conversion, and other high-value applications.