Authors:M. Souza, Marta Conceição, M. Silva, L. Soledade, and A. Souza
Statins are a group of lipoproteins that
are used in medicine to treat the high cholesterol level. The effectiveness
of statins in reducing the cholesterol level is significant and in long time
scale the reduction of the cholesterol level helps to avoid the incidence
of degenerative diseases. Simvastatin and lovastatin are belonging to the
‘statins’ family, one of the pharmacologic groups used in the
control of dislipidemy. The objective of this work is the thermal stability
and kinetic study of the active forms of simvastatin and lovastatin.
Thermal data indicated that lovastatin and simvastatin are stable up
to 190 and 170°C in air and up to 205 and 203°C in nitrogen, respectively.
For melting temperatures DSC curves showed good correlation with the literature
data. Comparing the activation energies of the statins at heating rate of
10°C min–1, lovastatin is more stable
than simvastatin under the applied experimental conditions.
Authors:E. Araújo, Renata Barbosa, Crislene Morais, L. Soledade, A. Souza, and Moema Vieira
Nanocomposites containing both polyethylene and montmorillonite clay organically modified with four different types of quaternary
ammonium salts were obtained via direct melt intercalation. Thus, the main purpose of this work was to evaluate the effect
of the organoclay on the thermal stability of polyethylene. The organoclays were characterized by XRD, FTIR, DSC and TG. The
polyethylene/organoclay nanocomposites were studied by XRD, TEM, TG, besides an evaluation of their mechanical properties.
The results showed that the salts were incorporated by intercalation between the layers of the organoclay and, apparently
that the nanocomposites were more thermally stable than pure polyethylene.
Authors:R. Candeia, J. Freitas, M. Souza, Marta Conceição, Iêda Santos, L. Soledade, and A. Souza
The most feasible alternative among fuels derived from biomass seems
to be the biodiesel, having the required characteristics for a total or partial
substitution of diesel oil. Therefore, the aim of this work is to evaluate
the thermal and rheological behavior of the blends of diesel with the methanol
biodiesel obtained from soybean oil, using B5, B15 and B25 blends. All thermogravimetric
curves exhibited one overlapping mass loss step in the 35–280C
temperature range at air atmosphere and one step between 37–265C
in nitrogen. The rheological study showed a Newtonian behavior (n=1) for all blends.
Authors:Danniely de Melo, M. Santos, Iêda Santos, L. Soledade, M. Bernardi, E. Longo, and A. Souza
materials are used as sensors, catalysts and in electro–optical devices.
This work aims to synthesize and characterize the SnO2/Sb2O3-based
inorganic pigments, obtained by the polymeric precursor method, also known
as Pechini method (based on the metallic citrate polymerization by means of
ethylene glycol). The precursors were characterized by thermogravimetry (TG)
and differential thermal analysis (DTA). After characterization, the precursors
were heat-treated at different temperatures and characterized by X-ray diffraction.
According to the TG/DTA curves basically two-step mass loss process was observed:
the first one is related to the dehydration of the system; and the second
one is representative to the combustion of the organic matter. Increase of
the heat treatment temperature from 500 to 600C and 700C resulted
higher crystallinity of the formed product.
Authors:Márcia Silva, L. Soledade, S. Lima, E. Longo, A. Souza, and Iêda Santos
The present work investigates
the influence of milling and calcination atmosphere on the thermal decomposition
of SrTiO3 powder precursors. Both pure and neodymium-modified SrTiO3 samples
were studied. Milling did not significantly influence numerical mass loss
value, but reduced the number of decomposition steps, modifying the profiles
of the TG and DTA curves. On the other hand, milling increases the amount
of energy liberated by the system upon combustion of organic matter. It was
also observed that the milling process, associated to the calcination in an
oxygen atmosphere, considerably decreases the amount of organic matter and
increases the final mass loss temperature.
Authors:Crislene Morais, C. Gameiro, P. Santa-Cruz, S. Alves Jr, L. Soledade, and A. Souza
of general formula Ln(btfa)3L, where Ln=Eu
or Tb, btfa=4,4,4-trifluoro-1-phenyl-1,3-butanedione, L=1,10-phenanthroline (phen)
or 2,2-bipyridine (bipy), were synthesized
by reacting the corresponding metal chloride with the proper β-diketone
and the other ligand. The complexes were obtained in the powder form and were
characterized by photoluminescence and TG. Their thermal decomposition was
studied by non-isothermal thermogravimetric techniques. The Eu(btfa)3bipy
complex presented the highest thermal stability and it melts before being
decomposed. The complex Eu(btfa)3phen presented the
largest activation energy for a heating rate of 5C min–1.
Authors:Márcia Silva, Mary Alves, S. Lima, L. Soledade, Elaine Paris, E. Longo, A. Souza, and Iêda Santos
Sr(Ti,Nd)O3 was synthesized in order to evaluate the influence of the amount of neodymium on the thermal and structural properties of
SrTiO3. The synthesis was carried out using the polymeric precursor method. A small mass gain was observed for the SrTiO3 and SrTi0.98Nd0.02O3 samples accompanied by an exothermic peak in the DTA curves. Other steps at higher temperatures are assigned to the combustion
of the organic material and carbonate. Elimination of defects by previous calcination of the precursors is responsible by
the short and long range ordering of the perovskite. Cubic phase was obtained for undoped and doped SrTiO3.
Authors:C. Santos, B. Capistrano, F. Vieira, M. Santos, S. Lima, E. Longo, C. Paskocimas, A. Souza, L. Soledade, and I. Santos
In this work, spinels with the general formula Zn2−xCoxTiO4 were synthesized by the polymeric precursor method and thermally treated at 1,000 °C. The powder precursors were characterized
by TG/DTA. A decrease in the DTA peak temperature with the amount of zinc was observed. After the thermal treatment, the characterizations
were performed by XRD, IR, colorimetry and UV/VIS spectroscopy. The XRD patterns of all the samples showed the presence of
the spinel phase. Infrared spectroscopy showed the presence of ester complexes for Zn2TiO4 after thermal treatment at 500 °C, which disappeared after cobalt addition, indicating that organic material elimination
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.