Fe3O4/TiO2 Core/Shell Nanotubes: Synthesis and Magnetic and Electromagnetic Wave Absorption Characteristics

Fe3O4/TiO2 core/shell nanotubes are fabricated via a three-step process. alpha-Fe2O3 nanotubes are first obtained, and alpha-Fe2O3/TiO2 core/shell nanotubes are subsequently fabricated using Ti(SO4)(2) as a Ti source by a wet chemical process. The thickness of the amorphous TiO2 shell is about 21 nm. After a H-2 deoxidation process, the amorphous TiO2 layer changes into crystalline structures composed of TiO2 nanoparticles with an average diameter of 2.5 nm, and its thickness is decreased to about 18 nm. At the same time, alpha-Fe2O3 transforms into cubic Fe3O4. Consequently, crystalline Fe3O4/TiO2 core/shell nanotubes can be fabricated through the process above. The measurements of the magnetic properties demonstrate that the Fe3O4/TiO2 core/shell nanotubes exhibit ferromagnetic behavior at room temperature, and the Verwey temperature is about 120 K. The eddy current effect is largely reduced and the anisotropy energy is improved significantly for the core/shell nanotubes due to the presence of the TiO2 shells. The maximum reflection loss reaches -20.6 dB at 17.28 GHz for the absorber with thickness of 5 mm, and the absorption bandwidth with the reflection loss below -10 dB is up to 13.12 GHz for the absorber with a thickness of 2-5 mm. Our results demonstrate that the Fe3O4/TiO2 core/shell nanotubes obtained in this work are attractive candidate materials for the magnetic and EM wave absorption applications.