Abstract
Structural characterizations of nanostructured oxides were studied by
X-ray diffraction (XRD), Raman and infrared spectroscopy. The oxides
catalysts namely, SnO2, ZrO2, CeO2, MnOx, Al2O3 and TiO2 were prepared
by a nanocasting route and the effect of the temperature and pressure on
the stability of the solids was evaluated. Raman spectra showed that
ZrO2 and TiO2 exhibited phase transitions at moderate temperatures
whereas CeO2, SnO2 and MnOx had an effective creation of defects in
their structures upon annealing at elevated temperatures. The results
suggested also that the effect of the temperature on the particles
growth is related to the type of oxide. In this regard, phase transition
by up to 600 degrees C accelerated the sintering of ZrO2 and CeO2 grains
compared to TiO2, SnO2 and MnOx counterparts. Under hydrostatic
pressures lower than 10 GPa, rutile TiO2 and tetragonal ZrO2 exhibited
pressure induced phase transition whereas CeO2 and SnO2 were stable at
pressures close to 15 GPa. The experiments revealed that the
nanostructured SnO2 oxide exhibited stable performance at relatively
high temperatures without phase transition or sintering, being suitable
to be used as catalysts in the range of temperature and pressure
studied. (C) 2014 Elsevier B.V. All rights reserved.
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