Preparation and microwave absorption property of nano onion-like carbon in the frequency range of 8.2–12.4 GHz

Nano onion-like carbons (NOLCs) have been synthesized by chemical vapor deposition (CVD) at 800 °C using methane as the carbon source and high-temperature steam treated 316 stainless steel mesh as the catalyst, respectively. The phase composition, microstructure and microwave absorption properties of prepared unpurified and purified NOLCs have been characterized by XRD, SEM, TEM, Raman spectroscopy, and vector network analyzer, respectively. Results show that the unpurified NOLC is a core-shell structure with Fe-Ni compound particle as the core and carbon as the shell and the purified NOLC is a hollow structure. The microwave absorption property of the unpurified NOLC is much better than that of purified NOLC in the frequency range of 8.2–12.4 GHz. The minimum reflection coefficient (RC) value of −42.04 dB was achieved at 9.02 GHz and the bandwidths of RC < −10 dB are 0.54 GHz (matching thickness of 3 mm, from 8.2 GHz to 8.74 GHz), 2.23 GHz (matching thickness of 2.5 mm, from 8.2 GHz to 10.43 GHz), and 2.36 GHz (matching thickness of 2 mm from 10.04 GHz to 12.4 GHz), respectively.