Multiple synergistic losses in the absorption of electromagnetic waves by three-dimensional cross-linked carbon fiber

Carbon fiber with a three-dimensional (3D) cross-linked structure was prepared by electrostatic spinning and heat treatment. The HRTEM images of carbon fiber were used as the basis for determining the types of graphite defects in carbon fiber by combining the intensity ratios of the D and D′ peaks in the Raman spectra, and the contribution of different graphite defects types in carbon fiber to electromagnetic wave absorption was analyzed. Among the three types of graphite defects, sp3 type, vacancy type, and boundary type, the carbon fiber with predominantly boundary type graphite defects showed excellent electromagnetic wave absorption performance. The heat treatment temperature has a significant effect on the conductivity and electromagnetic properties. The broadest effective absorption bandwidth (EAB) is 5.44 GHz at 2.07 mm when the thermal treatment temperature is 650 °C. In carbon fiber with a carbonization temperature of 850°, graphite nanocrystals and large graphite areas coexist and graphite defects are predominantly of the boundary type. Interfacial polarization of amorphous carbon and graphite nanocrystals under the action of electromagnetic waves produces dielectric losses; large graphite areas produce conductive losses and eddy current losses. The dielectric loss, conductive loss, and eddy current loss synergistically achieve a strong absorption of the electromagnetic wave multi-spectrum at 5.08 GHz, −40.55 dB, −43.35 dB, and −44.44 dB at 5.08 GHz, 7.46 GHz, and 14.94 GHz respectively. Without the addition of magnetic materials, the carbon fiber in this study achieves the ability of a dielectric loss type electromagnetic wave absorbing material to possess magnetic loss.