Boosting microwave absorption performance of bio-carbon flakes via magneto-alignment

Besides composition, macrostructure of a material is also crucial to its microwave ab-sorption performance. In this work, we demonstrate a magneto-alignment effect on the microwave absorption property of the bio-carbon flakes synthesized from phoenix tree leaves. When a magnetic field is applied, the prepared bio-carbon flakes tended to be aligned into a desired direction due to their diamagnetic feature. Moreover, a rotating magnetic field has a better magneto-alignment effect than a static one, which signifi-cantly boosts microwave absorption efficiency. By adjusting parameters, conditions have been optimized, i.e., 10 wt% mass concentration, 760 Gs magnetic field intensity, and 15 rpm rotating speed. At optimized conditions, the maximum reflection loss of -49.7 dB at 6.6 GHz and the maximum effective bandwidth of 4.9 GHz (10.66-15.56 GHz) are achieved. It is discovered that the maximum reflection loss of the sample treated in a rotating magnetic field is 4.6 and 5.85 times higher than that of the sample treated in static and non-magnetic field conditions, respectively. This work provides a simple and environmentally friendly physical route to modify the macroscopical order degree and enhance the microwave absorption performance of carbon materials.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).