Magnetic induction heating as a new tool for the synthesis of Fe₃O₄–TiO₂ nanoparticle systems

A novel method for the synthesis of Fe₃O₄–TiO₂ nanoparticles is described, where the magnetic induction heating of Fe₃O₄ nanoparticles is employed to calcine a metal oxide precursor gel. Magnetite Fe₃O₄ nanoparticles were mechanically dispersed in the as-prepared TiO₂ gel and subsequently submitted to the action of an ac magnetic field (frequency 313 kHz, amplitude 340 Oe, induction times, t = 10, 20, and 30 min). The magnetic heating of the magnetic nanoparticles is able to calcine the precursor gel and thus to produce the TiO₂ crystallization in the anatase phase, as supported by TGA analysis. The calcined structure, magnetically filtered to select the Fe₃O₄–TiO₂ nanostructure, was analyzed by X-ray diffraction and transmission electron microscopy. The results show that the Fe₃O₄–TiO₂ nanostructure basically consists of an ensemble of Fe₃O₄ cores surrounded by tiny TiO₂ aggregates (crystallite size <5 nm) forming an effective shell. The synthesis route and the TiO₂ environment do not introduce significant changes in the magnetic response of the magnetite nanoparticles. Thus, magnetic induction heating of magnetic nanoparticles appears as a new tool to reach a versatile calcination process to obtain Fe₃O₄–TiO₂ nanostructures.