PVP-assisted MOF-derived Fe₃O₄/C powders for microwave absorption applications

Metal-organic framework (MOF) derived porous Fe₃O₄/C powders were applied for absorption of microwaves in the frequency range of 1-18 GHz. The effects of the polyvinylpyrrolidone (PVP) additive on the synthesis of MIL101-(Fe) precursor were studied by various characterization methods. By adding PVP, the impure hematite phase (α-Fe₂O₃) with magnetite phase (Fe₃O₄) was disappeared and the particular morphology was transformed to the porous rod-like, leading to the increase of specific surface area from 150 to 282 m²/g. Furthermore, the saturation magnetization (Ms) of Fe₃O₄/C powders reached a maximum value of 47 emu/g at a proper amount of PVP. A thin absorber (2.6 mm) made of 50 wt% Fe₃O₄/C powders and 50 wt % paraffine absorbed the whole of X frequency band (8-12 GHz) with a minimum reflection loss of -20 dB at a matching frequency of 10 GHz. Adjusting the permittivity and permeability parameters of the Fe₃O₄/C powders via adding PVP was responsible for their better microwave absorption performance.