Synthesis of Magnetic Wood with Excellent and Tunable Electromagnetic Wave-Absorbing Properties by a Facile Vacuum/Pressure Impregnation Method

Abstract

Herein, magnetic wood was successfully prepared by in situ synthesizing Fe3O4 in wood, through coprecipitation chemical interactions. A facile impregnation method, vacuum impregnation followed by pressure impregnation, was introduced to transport the adequate amount of ferric salt precursor and to further shorten the required production cycle. It was demonstrated that the obtained products exhibited outstanding microwave-absorbing properties. The best electromagnetic interference (EMI) absorbing properties could reach −64.26 dB at 14.36 GHz with the matching thickness of only 2.25 mm and broad absorbing bandwidth (|RL| > 10 dB) of 5.20 GHz covering 12.80–18.00 GHz. The subsequent thorough investigations proved that this good shielding property was due to the distinctive self-assembling morphology of Fe3O4 formed in the inner surface of the lumen walls in wood, which permitted optimal impedance matching, the strongest dielectric loss, optimal magnetic loss, and an interconnected conductive network for electron hopping and migrating. This synthetic process for magnetic wood is quite facile, and the resulted EMI absorbing properties are tunable by the concentrations of the iron precursor solutions and the thickness values. This kind of synthetic magnetic wood can be potentially used as light-weight, flexible, and strong absorbing performance shielding materials for construction, furniture, decoration, and packing.