Synthesis of porous carbon matrix with inlaid Fe3C/Fe3O4 micro-particles as an effective electromagnetic wave absorber from natural wood shavings

With the rapid growth in the use of wireless electronic devices, society urgently needs electromagnetic wave (EMW) absorbers with light weight, thin thickness, wide effective absorbing bandwidth and strong absorbing capacity. One kind of the most attractive absorbers is magnetic carbon composites. Here, we successfully synthesized porous carbon matrix with inlaid Fe3C/Fe3O4 micro-particles (CFF) by in-situ carbonization of pre-prepared Fe3O4/wood shavings composites at 1000 degrees C. In advance, the magnetic wood shavings were prepared by in-situ chemical coprecipitation followed by two-step atmospheric impregnation of Fe2+/Fe3+ mixture and NaOH solution, successively. Compared with natural wood shavings and magnetized shavings, the EMW absorption properties of CFF is greatly improved by the phase transformation from amorphous carbon to graphite-like carbon through the carbonization procedure. In details, CFF possesses a minimum RL value of -26.72 dB at 10.52 GHz with a matching thickness of 3.15 mm and a wide response bandwidth of 12.93 GHz covering from 5.07 GHz to 18 GHz. This excellent absorption performance is proved to be due to the continuous covering of Fe3C/Fe3O4 hybrids on the surface of the porous carbon matrix, permitting optimal impedance matching, the strongest dielectric loss and the optimal magnetic loss. Moreover, the dipole relaxation polarization brought out by the generated defects acting as the dipole center, together with the interface polarizations at C-Fe3C and Fe3C-Fe3O4 interfaces, are positive to improve the microwave absorption performance. (C) 2018 Elsevier B.V. All rights reserved.