Preparation of Mn, Ni, Co ferrite highly porous silica nanocomposite aerogels by an urea-assisted sol-gel procedure.
The preparation of highly porous MnFe2O4-SiO2 and NiFe2O4-SiO2 nanocomposite aerogels with high purity and homogeneity was successfully achieved by a sol-gel procedure involving urea-assisted co-gelation of the precursor phases firstly applied for the synthesis of CoFe2O4-SiO2. This method allows fast gelation, giving rise to aerogels with 97% porosity. The structural, morphological and textural characterization as a function of thermal treatments was carried out by a multitechnique approach confirming that, as in the case of CoFe2O4-SiO2, the formation of single nanocrystals of manganese ferrite and nickel ferrite with spinel structure occurs after heating at 750 degrees C and is complete at 900 degrees C when the high porosity typical of aerogels is still retained. Thermogravimetric analysis (TG), differential thermal analysis (DTA), N2-physisorption at 77 K, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) indicate that the compositional homogeneity, crystallite size, thermal stability, and porosity are controlled by the sol-gel parameters of the preparation.
Loche
Danilo
D
Dipartimento di Scienze Chimiche, Università di Cagliari, S. P. Monserrato-Sestu, Km 0.700, I-09042 Monserrato, Cagliari, Italy.
Casula
Maria F
MF
Falqui
Andrea
A
Marras
Sergio
S
Corrias
Anna
A