Authors:Mary Alves, Soraia Souza, S. Lima, E. Longo, A. Souza, and Iêda Santos
CaSnO3 was synthesized by the polymeric precursor
method, using different precursor salts as (CH3COO)2CaH2O,
CaCl22H2O and CaCO3,
leading to different results. Powder precursor was characterized using thermal
analysis. Depending on the precursor different thermal behaviors were obtained.
Results also indicate the formation of carbonates, confirmed by IR spectra.
After calcination and characterization by XRD, the formation of perovskite
as single phase was only identified when calcium acetate was used as precursor.
For other precursors, tin oxide was observed as secondary phase.
Authors:Marta Conceição, Manoel Dantas, Raul Rosenhaim, Valter Fernandes, Ieda Santos, and Antonio Souza
Oxidative stability is very important in the quality control of oils and biodiesel. Chemical characteristics, as acid, iodine
and peroxide values, show the differences among samples and can be used by industries to evaluate the oxidation degree. In
relation to advanced techniques, the use of PDSC to measure the oxidative induction time is very important. These measurements
were used to evaluate the properties of castor oil after refining process and consequently the biodiesel characteristics.
Oxidative induction time indicated that biodiesel samples were more stable than the refined oils. The biodiesel obtained from
neutralized oil had a higher stability being probably related to the acid value.
Authors:D. Brito, E. Silva, D. Rodrigues, M. Machado, M. Silva, V. Simões, M. Carvalho, L. Soledade, Iêda Santos, and A. Souza
A silico alumino phosphate with AFI structure (SAPO-5) was prepared
in a two-phase medium and characterized by XRD, followed by the addition of
TEA+. The kinetics of the TEA+/SAPO-5
thermal decomposition reaction was studied by isothermal and dynamic thermogravimetry.
Two kinetic models, D3 and D4
based on diffusion processes were found as best to fit the isothermal data.
On the other hand, the best fit for the dynamic data is the F1
first order reaction model. According to the apparent activation energy values,
the use of the dynamic method indicates a higher temperature dependence than
the isothermal method.
Authors:Camila Xavier, R. Candeia, M. Bernardi, S. Lima, E. Longo, C. Paskocimas, L. Soledade, A. Souza, and Iêda Santos
Magnesium and zinc ferrites
have been prepared by the polymeric precursor method. The organic material
decomposition was studied by thermogravimetry (TG) and differential thermal
analysis (DTA). The variation of crystalline phases and particle morphology
with calcination temperature were investigated using X-ray diffraction (XRD)
and scanning electronic microscopy (SEM), respectively. The colors of the
ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes
above 800°C, presenting a yellow- orange color with a reflectance peak
at the 600–650 nm range, while zinc ferrite crystallizes at 600°C,
with a reflectance peak between 650–700 nm, corresponding to the red-brick
Authors:F. Vieira, Soraia Souza, A. Oliveira, S. Lima, E. Longo, C. Paskocimas, L. Soledade, A. Souza, and Iêda Santos
In this study undoped and Cr, Sb or Mo doped TiO2 were synthesized by polymeric precursor method and characterized by X-ray diffraction, UV–VIS spectroscopy, infrared spectroscopy
and thermogravimetry (TG). The TG curves showed a continuous mass loss assigned to the hydroxyl elimination and Cr6+ reduction. Doped TiO2 samples showed a higher mass loss assigned to water and gas elimination at lower temperatures. In these doped materials a
decrease in the anatase–rutile phase transition temperature was observed. After calcination at 1,000 °C, rutile was obtained
as a single phase material without the presence of Cr6+.
Authors:A. de Oliveira, J. Ferreira, Márcia Silva, Soraia de Souza, F. Vieira, E. Longo, A. Souza, and Iêda Santos
NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase.
The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV–Vis spectroscopy and X-ray diffraction.
NiWO4 was crystalline after calcination at 350 °C/12 h while ZnWO4 only crystallized after calcination at 400 °C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between
600 and 800 °C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier.
Authors:H. Dantas, R. Mendes, R. Pinho, L. Soledade, C. Paskocimas, B. Lira, M. Schwartz, A. Souza, and Iêda Santos
Gypsum is a dihydrated calcium sulfate, with
the composition of CaSO4⋅2H2O,
with large application interest in ceramic industry, odontology, sulfuric
acid production, cement, paints, etc. During calcination, a phase transformation
is observed associated to the loss of water, leading to the formation of gypsum
or anhydrite, which may present different phases. The identification of the
phases is not so easy since their infrared spectra and their X-ray diffraction
patterns are quite similar. Thus, in this work, temperature modulated differential
scanning calorimetry (TMDSC) was used to identify the different gypsum phases,
which can be recognized by their different profiles.
Authors:M. Dantas, A. Almeida, Marta Conceição, V. Fernandes Jr, Iêda Santos, F. Silva, L. Soledade, and A. Souza
This work presents the characterization and the kinetic compensation
effect of corn biodiesel obtained by the methanol and ethanol routes. The
biodiesel was characterized by physico-chemical analyses, gas chromatography,
nuclear magnetic resonance and thermal analysis. The physico-chemical properties
indicated that the biodiesel samples meet the specifications of the Brazilian
National Agency of Petroleum, Natural Gas and Biofuels (ANP) standards. The
analyses by IR and 1H NMR spectroscopy indicated
the ester formation. Gas chromatography indicated that biodiesel was obtained
with an ester content above 97%. The kinetic parameters were determined with
three different heating rates, and it was observed that both the methanol
and ethanol biodiesel obeyed the kinetic compensation effect.
Authors:Márcia Silva, Lydianne de O. Miranda, Maria Cassia-Santos, S. Lima, L. Soledade, E. Longo, C. Paskocimas, A. Souza, and Iêda Santos
Undoped and/or doped with 1 mol% of Co2+
powders were synthesized by the polymeric precursor method. The influence
of the network former (Sn4+ or Ti4+)
on the thermal, structural and optical properties was investigated. The recorded
mass losses are due to the escape of water and adsorbed gases and to the elimination
of the organic matter. Mg2TiO4
crystallizes at lower temperatures and also presents more ordered structure
with a smaller unit call and having more intense green color than Mg2SnO4
Authors:Soraia de Souza, Mary Alves, A. de Oliveira, E. Longo, F. Ticiano Gomes Vieira, Rodinei Gomes, L. Soledade, A. de Souza, and Iêda Garcia dos Santos
In this work, the synthesis of Nd-doped SrSnO3 by the polymeric precursor method, with calcination between 250 and 700 °C is reported. The powder precursors were characterized
by TG/DTA and high temperature X-ray diffraction (HTXRD). After heat treatment, the material was characterized by XRD and
infrared spectroscopy. Ester and carbonate amounts were strictly related to Nd-doping. According to XRD patterns, the orthorhombic
perovskite was obtained at 700 °C for SrSnO3 and SrSn0.99Nd0.01O3. For Sr0.99Nd0.01SnO3, the kinetics displayed an important hole in the crystallization process, as no peak was observed in HTXRD up to 700 °C,
while a XRD patterns showed a crystalline material after calcination at 250 °C.