Fabrication of Al2O3-based composite ceramics with mesocarbon microbeads as absorbent for enhanced microwave absorption

While ceramic-based composites containing carbonaceous absorbents show potential for microwave absorption applications, their performance is frequently constrained by impedance mismatch and complicated manufacturing procedures. In this work, we develop lightweight mesocarbon microbead (MCMB)/Al₂O₃ composite ceramics with exceptional microwave absorption properties through the strategic incorporation of highly spherical MCMBs into an Al₂O₃ matrix. A comprehensive investigation of sintering methods (pressureless versus hot-pressing) and MCMB content (5–13 wt%) reveals that hot-pressing sintering marfkedly improved densification and mechanical properties (flexural strength ≥245 MPa) compared to pressureless sintering, owing to enhanced particle rearrangement and pore elimination under applied pressure. The introduction of MCMBs effectively tuned dielectric properties and optimized impedance matching, resulting in superior microwave absorption performance with a minimum reflection loss (RL_min) of −20.62 dB at 10.84 GHz and an effective absorption bandwidth (EAB) of 1.55 GHz at only 1.8 mm thickness for hot-pressed sintered samples containing 11 wt% MCMBs. The exceptional microwave absorption characteristics stem from synergistic effects including conduction loss from MCMB's high electrical conductivity, interfacial polarization at MCMB/Al₂O₃ heterointerfaces, and optimized microwave scattering enabled by the spherical MCMB morphology. This work demonstrates that synergistic control of sintering methods and MCMB content can concurrently optimize mechanical and microwave absorption properties, offering a promising strategy for structural-functional integrated ceramics in electromagnetic applications.