One pot synthesis of Fe3O4/MnO2 core–shell structured nanocomposites and their application as microwave absorbers

Abstract

Fe₃O₄/MnO₂ core–shell structured nanocomposites have been synthesized by a one-pot approach at ambient temperature and pressure. The morphology of the prepared Fe₃O₄/MnO₂ nanoparticles is governed by the Mn/Fe molar ratio in the precursor. When the molar ratio of Mn/Fe is 1 : 10, the nanocomposites exhibit a special microstructure, in which MnO₂ nanorods are formed on the surface of spherical Fe₃O₄ nanoparticles. With the increase of the Mn/Fe ratio to 1 : 2, core–shell structured nanoparticles with Fe₃O₄ nanoparticles as cores and MnO₂ as the shell are obtained. The microwave absorption properties of the core–shell Fe₃O₄/MnO₂ nanocomposites were studied in the 2–18 GHz frequency range. The microwave absorption performance of the Fe₃O₄/MnO₂ nanocomposites exhibited a remarkable enhancement in comparison with pure Fe₃O₄ nanoparticles, ascribed to the fact that MnO₂ nanostructures can improve the dielectric loss factor and the electromagnetic (EM) matching degree. The absorption peaks of the Fe₃O₄/MnO₂–paraffin composites are red shifted compared to those of Fe₃O₄–paraffin composites. Due to the MnO₂ nanorods on the surface of the Fe₃O₄ nanoparticles, the produced microcurrent can reduce the electron transition energy and lead to better microwave absorption by the Fe₃O₄ nanoparticle/MnO₂ nanorod nanocomposites.