Preparation and characterization of CoFe2O4/SiO2 nanocomposites

Recent years see an increasing interest in nanocomposites synthesized by a sol-gel procedure consisting of magnetic nanosized particles embedded in a silica matrix. due to their specific physical and chemical properties[1―4]. Sol-gel derived amorphous si…

Preparation and characterization of CoFe2O4/SiO2 nanocomposites

CoFe₂O₄/SiO₂ nanocomposites have been prepared by a sol-gel procedure, starting from tetraethylorthosilicate and metallic nitrates. The formation mechanism of the composites was characterized by differential scanning calorimetry, infrared spectroscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The magnetic properties were measured using a vibrating sample magnetometer. It was found that xerogel obtained at low temperatures was amorphous. Heat treatment at 400°C resulted in the partial formation of CoFe₂O₄ clusters. On further increasing the annealing temperature to 800°C, CoFe₂O₄ nanocrystals with diameters of ∼17 nm could be dispersed in the silica matrix. The formation of CoFe₂O₄ clusters was accompanied with the rearrangement of silica network, and the enhancement of the interaction between the metal ions and the surrounding silica network. The interaction between the particles and the matrix would be weakened or even disappear when annealing temperature was raised to as high as 800°C. Both the coercive field and the density of magnetization of composites would increase with an increase in the annealing temperature.