Thermal decomposition of metal nitrates

The paper presents a study regarding the preparation of 40 %M^IIFe₂O₄/60 %SiO₂ nanocomposites (M = Ni, Zn, Cu) by thermal decomposition of metal nitrates—poly(vinyl alcohol)–tetraethyl orthosilicate gels. Thermal analysis and FT-IR spectroscopy have evidenced that a redox reaction takes place between PVA and NO ₃ ^? ions in the pores of the formed hybrid gels. The result of this redox reaction is the formation of carboxylate-type coordination compounds that have the role of a precursor of the ferrite nanoparticles. By thermal decomposition of these precursors inside the silica matrix, the corresponding MFe₂O₄/SiO₂ nanocomposites are obtained starting with 600 °C, as resulting from XRD analysis. Elemental maps of the corresponding involved elements M (Ni, Zn, Cu), Fe, and Si have confirmed the homogenous distribution of the ferrite nanoparticles within the silica matrix. TEM images have shown that the nanocomposites were obtained as fine nanoparticles, with diameter up to 20 nm. All nanocomposites 40 %M^IIFe₂O₄/60 %SiO₂ obtained at 1000 °C presented magnetic properties characteristic to this type of nanocomposite.