Ordered mesoporous CoFe2O4 nanoparticles: molten-salt-assisted rapid nanocasting synthesis and the effects of calcining heating rate

Abstract

Ordered mesoporous CoFe₂O₄ magnetic nanoparticles were successfully synthesized via a novel molten-salt-assisted nanocasting process. Highly ordered mesostructures were negatively replicated from the mesoporous silica template of SBA-15. The time that the whole synthetic process took was significantly shortened by a facile molten-salt mixing pretreatment, instead of conventionally used ethanol impregnation of the precursors. Mesoporous bimetal oxide CoFe₂O₄ nanoparticles of high quality were eventually obtained, while the total processing time was reduced by dozens of hours. In addition, effects of the rarely investigated factor, calcining heating rate were studied systematically. XRD and TEM characterization indicates that both the phase purity and crystallinity of products fell and the highly ordered mesostructures were destroyed gradually as heating rate accelerated. Further, both the specific surface areas and the magnetic properties of as-synthesized mesoporous CoFe₂O₄ nanoparticles dropped when quicker calcining heating rates were used. Therefore, in order to obtain highly ordered and crystalline mesoporous CoFe₂O₄ nanoparticles of large specific surface area (150.20 m² g⁻¹) and saturation magnetization (69.07 emu g⁻¹), utilizing relatively low calcining heating rates (i.e. no quicker than 3 °C min⁻¹) was recommended. Additionally, it is believed that our research findings would help industrial applications of mesoporous CoFe₂O₄ nanoparticles in many fields like magnetic recording, concerted catalysts, electrode materials and drug delivery.