LIMA, M. S.; http://lattes.cnpq.br/2312584872334525; LIMA, Munique Silva de.
Résumé:
The aim of this work was to prepare cobalt ferrites by combustion reaction. The conditions of
external heating: ceramic base, resistive muffle furnace, and microwave oven were used in
order to investigate the influence on the structure and morphology of the synthesized samples.
In order to establish the stoichiometry of the desired phase, samples were prepared according
to the theory of propellants and explosives. Temperature of measurement and combustion
time flame was performed during the synthesis. The samples of ferrite produced were
characterized by X-ray diffraction, infrared spectroscopy, X-ray fluorescence spectroscopy,
texture analysis, differential thermal analysis, and thermal gravimetric and scanning electron
microscopy. The samples were tested and evaluated the performance in displacement
reactions of water vapor (WGSR). The results showed that for every condition of heating used
there was the formation of single inverse spinel phase CoFe204, with crystallite size ranging
between 38 - 40 nm and anisotropy of planes diffraction. The infrared spectrum showed
characteristic bands of tetrahedral and octahedral vibration characteristics of the vibrations of
the coordination 4 for iron III cations and 4 and 6, for iron III and cobalt II cations,
respectively. The condition of the heating on ceramic base led to the formation of samples
with a crystallite size 5.26% greater than other forms of heating and higher surface area
(4.194 m2/g). All samples showed a morphology consisting of irregular clusters in the form of
sponges with high interparticle porosity. The samples showed mesoporous characteristics
with hysteresis type II and loop of hysteresis H3. The sample synthesized in a muffle furnace
showed the highest conversion rate of 56% and the sample synthesized in the ceramic base
showed greater selectivity with 90.19% for the WGRS system.
