High‐Energy Ball Milling Assisted Synthesis of Graphite/G‐C ₃ N ₄ for Highly Efficient Low‐Frequency Microwave Absorption

ABSTRACT

The development of lightweight heterogeneous systems capable of efficient electromagnetic wave absorption in the low‐frequency range (2–8 GHz) remains a significant challenge. Herein, a series of graphite/graphitic carbon nitride (g‐C ₃ N ₄ ) composites were fabricated via co‐ball‐milling of graphite and melamine followed by heat treatment. Co‐ball‐milling is found to facilitate particle refinement and promote the formation of strong interfacial coupling between graphite and g‐C ₃ N ₄ by robust C─N covalent bonds, which has been experimentally and theoretically demonstrated to form a network of macromolecular dipoles, enhancing low‐frequency polarization loss, and also serves as charge‐transfer bridges to establish continuous three‐dimensional energy dissipation pathways. Moreover, the incorporation of g‐C ₃ N ₄ effectively mitigates the excessive conductivity of graphite while introducing multiple polarization mechanisms, realizing a synergistic optimization between dielectric loss and impedance matching. Benefiting from the unique structural features, the optimal Gr/CN‐3 exhibits superior performance with a minimum reflection loss of −50.9 dB at 4.96 GHz with a thickness of 4.26 mm, and an effective absorption bandwidth of 1.52 GHz within the 2–8 GHz range, and display distinctive multi‐frequency bimodal absorption feature. Radar cross‐section simulations demonstrate the superior electromagnetic scattering attenuation capability, indicating great potential for practical applications in multi‐band electromagnetic shielding and stealth technology.