Surface magnetic regulation in carbon microspheres induced by melamine to increase electromagnetic wave absorption

Magnetic‒carbon composites, as functional materials, present significant challenges in understanding the mechanism by which magnetic particle distribution influences their electromagnetic (EM) properties. This study innovatively proposes a melamine-induced surface magnetic regulation strategy, successfully constructing a composite microsphere system with tunable microwave absorption (MA) performance. By precisely controlling the amount of melamine added, the distribution of magnetic nanoparticles (NPs) on the carbon microspheres was accurately regulated, thereby achieving customized space distribution and optimizing the impedance EM properties. The reduced magnetic Co NPs further catalyzed the formation of a graphitized carbon layer from polyvinylpyrrolidone. Moreover, the introduction of melamine further modulated Co NP growth, resulting in their spatial distribution along the interiors, surface, and exterior of the microspheres. Finally, Co@C-CNT-2 composites with optimized magnetic particle distributions exhibited excellent MA performance, achieving a minimum reflection loss value (RL_min) of −32.48 dB and excellent effective absorption bandwidth (EAB) of ~ 5.2 GHz at a thickness of 1.8 mm. The synergistic effect of dielectric and magnetic loss is realized through the surface magnetization strategy, which provides a new strategy for the design of high-performance EM wave absorption materials.