Preparation and properties of nano-Fe₃O₄ and Fe₃O₄-SrFe₁₂O₁₉ wave-absorbing composites

The superparamagnetic nano-Fe₃O₄ was prepared by coprecipitation method. Then wave-absorbing composite material Fe₃O₄-SrFe₁₂O₁₉ was prepared. The crystal phase, microstructure, magnetic property and wave-absorbing property of the sample were characterized by XRD, TEM, VSM and PNA. The results show that, when the mass ratio of Fe₃O₄ to SrFe₁₂O₁₉ is 1∶0.3, the saturation magnetization, coercive field and residual magnetization of Fe₃O₄-SrFe₁₂O₁₉ are 11.1 emu·g^-1, 0.86 Oe and 0.08 emu·g^-1 respectively. It has the best wave-absorbing property, which of the maximum absorption can reach-17.7 dB and the-5 dB bandwidth is 1.3 GHz. Compared with Fe₃O₄ and SrFe₁₂O₁₉, the maximum absorption respectively increases by 247% and 185%, the frequency band widens 1.12 GHz and 0.40 GHz respectively.