Low-cost and broadband microwave absorption materials derived from carbonized papers

Low-cost microwave absorption materials with broad bandwidth are highly attractive in practical applications. Herein, three kinds of low-cost biomass papers, that are printer paper, toilet paper and newspaper, have been utilized to fabricate microwave absorbers by a facile one-step carbonization method. These three kinds of carbonized papers show potentials in microwave absorption, where the carbonized toilet paper (CTP) exhibits the best performance. It is found that the fibers in CTP exhibits a helix-like morphology with loose and porous state, which would be beneficial to induce the unique cross-polarization loss for the chiral materials and multiple scatting of microwave. Besides, a hybrid structure of polycrystalline-amorphous carbon is formed in the fibers by controlling the carbonization temperature, which would increase the interfacial polarization and tune the conductivity that leads to a good impedance matching. Consequently, the minimum reflection loss of CTP reaches -47 dB at 18.0 GHz with a thickness of only 2.0 mm. Meanwhile, CTP also exhibits as wide as 7.2 GHz effective absorption bandwidth at a thickness of 2.5 mm. This study provides a useful guidance for recycling the biomass materials to design and prepare low-cost and broadband microwave absorbers.