Ultrathin Bagasse-Derived Hierarchical C/Co Composites for High-Performance Microwave Absorption

Abstract The demand for high-performance microwave absorbers that combine enhanced functionality, broad bandwidth, and compact, lightweight designs is critical for optimizing the electromagnetic environment. A key challenge is balancing absorption efficiency, bandwidth, and thickness. Biomass-derived carbon materials have emerged as promising candidates for microwave absorption due to their cost-effectiveness, low density, and inherent hierarchical structures. In this study, bagasse-derived carbon-cobalt composites (C/Co) were developed using a vacuum impregnation−pyrolysis method. The pyrolyzed bagasse’s hierarchical porous and lamellar structures facilitated uniform dispersion of Co nanoparticles, effectively preventing particle agglomeration and improving impedance matching. The incorporation of Co particles significantly enhanced the microwave absorption performance of the composites. Specifically, the C/0.6Co composite achieved a minimum reflection loss (RLmin) of −61.48 dB at a thickness of 1.56 mm, while the C/0.7Co composite reached −66.52 dB at an ultrathin thickness of 1.29 mm and exhibited a high thickness-normalized effective absorption bandwidth of approximately 3.041 GHz·mm−1 in the Ku band. Furthermore, the C/0.7Co composite exhibited a radar cross-section (RCS) reduction value of 27.66 dB m2 at normal incidence (θ = 0°), indicating its strong potential for practical stealth applications. With strong absorption, broad bandwidth, ultrathin thickness, lightweight properties, low cost, and an eco-friendly fabrication process, these bagasse-derived composites present a promising alternative to conventional microwave absorbers for electromagnetic compatibility applications.