Fe(acac)3/silica/PVA hybrid xerogel nanocomposite was obtained by one pot
acid catalysed sol-gel synthesis using the homogeneous mixture of iron(III)
acetylacetonate (Fe(acac)3), tetraethylorthosilicate (TEOS), and polyvinyl
alcohol (PVA). Nominal composition ratio of iron oxide/silica was 15/85
(weight percent). Nitric acid was used as catalyst. Another sample of
Fe(acac)3/silica xerogel without PVA addition was prepared in the similar
processing conditions. Based on thermal analysis studies, the thermal
behaviour of both xerogel samples was unveiled and it allowed choosing the
optimal calcination temperatures in order to obtain iron oxide silica
magnetic nanocomposite samples. The two xerogel (with and without PVA)
samples were thermally treated, in air, at 220, 260 and 300?C and
characterized by different techniques. XRD investigations revealed phase
composition evolution with calcination temperature, from cubic spinel phase
(maghemite) to hexagonal stable hematite containing nanocomposite of 10-20 nm
average crystallite size. These findings were confirmed by M?ssbauer
spectroscopy. Up to 300?C, the surface area and total pores volume increased
with temperature for all samples. By calcination at the same temperature, the
hybrid xerogel containing PVA resulted in significantly higher magnetization
and free volume values in comparison with the sample without PVA.
Iron Oxide Silica Derived from Sol-Gel Synthesis