Rational design of size-controlled spongy porous carbon microspheres with wide-frequency microwave absorption properties

Porous carbon materials have garnered significant attention due to their effective microwave absorption properties. However, the design and preparation of precisely size-controlled porous carbon materials is still a great challenge. Spongy porous carbon microspheres (SPCMs) with adjustable size and uniform particles were successfully synthesized for large-scale production. This synthesis method employed affordable polymethyl methacrylate (PMMA) microspheres as sacrificial templates and phenolic resin oligomers as carbon sources. In addition to size considerations, different carbonization temperatures exert substantial influence on the complex dielectric constant and microwave absorption characteristics. SPCMs samples, characterized by a size of 5 μm and carbonization temperature of 700 °C, exhibited exceptional microwave absorption performance, despite a loading of only 10 wt%. The minimum reflection loss (RLmin) for the matched 2.6 mm thick sample reached −68.2 dB at 15.0 GHz, and the effective absorption bandwidth (EAB) for the matched 2.9 mm thick sample spanned 7.5 GHz. The outstanding microwave absorption capabilities of SPCMs can be attributed to their continuous porous structure, well-suited impedance matching, appropriate conductivity, and abundant interfacial polarization. This work serves as a crucial guide for the development of highly efficient microwave absorbers characterized by thin profiles, lightweight composition, strong absorption characteristics, and a wide EAB.