Microwave Absorption Properties of Graphite Nanosheet/Carbon Nanofiber Hybrids Prepared by Intercalation Chemical Vapor Deposition

Carbon-based microwave absorption materials have garnered widespread attention as lightweight and efficient wave absorbers, emerging as a prominent focus in the field of functional materials research. In this work, FeNi₃ nanoparticles, synthesized in situ within graphite interlayers, were employed as catalysts to grow carbon nanofibers in situ via intercalation chemical vapor deposition (CVD). We discovered that amorphous carbon nanofibers (CNFs) can exfoliate and separate highly conductive graphite nanosheets (GNS) from the interlayers. Meanwhile, the carbon nanofibers eventually intertwine and encapsulate the graphite nanosheets, forming porous hybrids. This process induces significant changes in the electrical conductivity and electromagnetic parameters of the resulting GNS/CNF hybrids, enhancing the impedance matching between the hybrids and free space. Although this process slightly reduces the microwave loss capability of the hybrids, the balance between these effects significantly enhances their microwave absorption performance, particularly in the K_u band. Specifically, the optimized GNS/CNF hybrids, when mixed with paraffin at a 30 wt% ratio, exhibit a maximum microwave reflection loss of -44.1 dB at 14.6 GHz with a thickness of 1.5 mm. Their effective absorption bandwidth, defined as the frequency range with a reflection loss below -10 dB, spans the 12.5-17.4 GHz range, covering more than 80% of the K_u band. These results indicate that the GNS/CNF hybrids prepared via intercalation CVD are promising candidates for microwave absorption materials.