Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

Abstract

Effects of calcination temperatures varying from 400 to 1000°C on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in the sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as water-soluble silica precursor have been investigated. Studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. Results indicated that magnetic properties of samples such as superparamagnetism and ferromagnetism showed great dependence on the variation of the crystallinity and particle size caused by the calcination temperature. The crystallization, saturation magnetization Ms and remenant magnetization Mr increased as the calcination temperature increased. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc is not determined only by the crystallinity and size of CoFe2O4 nanoparticles. TEM images showed spherical nanoparticles dispersed in the silica network with sizes of 10-30 nm. Results showed that the well-established silica network provided nucleation locations for CoFe2O4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. THEOS as silica matrix network provides an ideal nucleation environment to disperse CoFe2O4 nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS as water-soluble silica precursor over the currently used TEOS and TMOS, the organic solvents are not needed owing to the complete solubility of THEOS in water. Synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of Co-ferrite even more versatile.

The effect of temperature on the structure and magnetic properties of Co0.5Ni0.5Fe2O4 spinel nanoferrite

“…The triangular spin type arrangements lead to the weakening of the superexchange magnetic interactions between magnetic moments at A-and B-sites [14]. The lower values of M S correspond to smaller crystallite sizes and may be associated with surface spins disorder or spin canted effects due to the interaction of transition metal ions with oxygen atoms that lead to the reduction of the net magnetic moments of the spinel nanoparticles [18][19][20]. The enhanced magnetic properties of the samples can be associated with modification of the crystallite size and ionic population of Fe þ 3 at octahedral sites due to the annealing temperature.…”

Green synthesis of mesoporous anatase TiO2nanoparticles and their photocatalytic activities

“…This indicates that the enhancement of the crystallinity, stems from the increment of the crystalline volume ratio due to the size enlargement of the nuclei. 17 …”

Influence of polyols on the formation of nanocrystalline nickel ferrite inside silica matrices

“…Tetraalkoxysilanes (tetramethoxysilane -TMOS, and tetraethyl orthosilicate -TEOS) are the most common precursors of silica matrices. Their hydrolysis in aqueous solutions and further polycondensation reactions cause formation of sol particles of which the crosslinking leads to the self-organization into a porous three-dimensional network in the bulk [15]. Nickel ferrite/silica nanocomposites have been obtained starting from different tetraethoxysilane without [16], or with modifiers as formamide [17], citric acid [11] and PVA [18].…”