Synthesis of novel magnetic iron metal-silica (Fe-SBA-15) and magnetite-silica (Fe3O4-SBA-15) nanocomposites with a high iron content using temperature-programed reduction

Magnetic iron metal-silica and magnetite-silica nanocomposites have been prepared via temperature-programed reduction (TPR) of an iron oxide-SBA-15 (SBA:Santa Barbara Amorphous) composite. TPR of the starting SBA-15 supported Fe2O3 generated Fe3O4 and FeO as stepwise intermediates in the ultimate formation of Fe-SBA-15. The composite materials have been characterized by means of x-ray diffraction, high resolution transmission electron microscopy and SQUID (superconducting quantum interference device) magnetometry. The Fe oxide and metal components form a core, as nanoscale particles, that is entrapped in the SBA-15 pore network. Fe3O4-SBA-15 and Fe-SBA-15 exhibited superparamagnetic properties with a total magnetization value of 17 emu g(-1). The magnetite-silica composite (at an Fe3O4 loading of 30% w/w) delivered a magnetization that exceeded values reported in the literature or obtained with commercial samples. Due to the high pore volume of the mesoporous template, the magnetite content can be increased to 83% w/w with a further enhancement of magnetization.