Synthesis and characterization of magnetic nanocomposites with Fe₃O₄core

Abstract

To improve the infrared absorbing performance of the ferrite magnetic material which has good electromagnetic wave absorbing performance, the core-shell structured multilayer coating is introduced to achieve multiple wavelength range absorbing. Nanocomposites Fe3O4/SiO2/Al2O3 and Fe3O4/SiO2/TiO2 have been prepared using a series of chemical methods. The results of TEM and XRD analysis show that multilayer coated structures exit in both Fe3O4/SiO2/Al2O3 and Fe3O4/SiO2/TiO2 and that the core-double shell particles are all in nano-scale. The saturation magnetization and the coercivity of Fe3O4 at room temperature are 72 A·m2/kg and 3.82 kA/m, respectively. Further coating of SiO2 and Al2O3 or TiO2 decreases the saturation magnetization and the coercivity while all nanocomposites remain ferromagnetic. There is no obvious improvement of the infrared absorbing ability of Fe3O4 nanoparticles in coating of SiO2 while further coating of Al2O3 or TiO2 reduces the infrared emissivity from 0.97 of Fe3O4 nanoparticles to about 0.83 of the core-double shell nanocomposites.