Authors:J. Santos, L. Lima, Iêda Santos, and A. Souza
The thermal degradation process of mineral base lubricating oils was
studied in this work by means of thermal, spectroscopic and rheologic analysis.
The lubricating oils were degraded at temperatures varying from 150 to 210C,
and for degradation times from 1 to 48 h. After the degradation, the lubricating
oils were characterized by X-ray fluorescence, IR and NMR spectroscopies,
rheological properties and thermal analyses (TG/DSC). The spectroscopic analyses
determined the oxidation reaction products. TG curves indicate that the thermal
stability of lubricating oils is below 161C. TG curves in air present
three mass loss stages, whereas in nitrogen there are only two mass loss steps.
DSC analyses in air indicate two highly exothermic peaks related to hydrocarbon
oxidation and combustion processes, while in nitrogen only two endothermic
peaks were observed. The decrease in the degradation temperature led to a
decrease of the lubricant viscosity.
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:Nataly Santos, Marileide Tavares, R. Rosenhaim, F. Silva, V. Fernandes Jr, Iêda Santos, and A. Souza
The growing petroleum deficit
requires the development of alternative fuel sources. Biodiesel is a good
alternative, as it is a biodegradable and renewable product, which obeys the
carbon cycle. In this work, the biodiesel from babassu was synthesized using
the methanol route, and characterized by physico-chemical analyses in order
to make able the investigated biodiesel to fulfill with its properties the
requirements of Brazilian National Agency for Petroleum, Natural Gas and Biofuel
(ANP). Besides gas chromatography, IR spectroscopy experiments and thermoanalytical
measurements in air and in nitrogen were done to determine the main thermal
decomposition processes and calorimetric events. The evaporation temperature
of babassu biodiesel was similar in both atmospheres, started around 52 in
air and around 60C in nitrogen.
Authors:M. Dantas, Marta Conceição, V. Fernandes Jr, Nataly Santos, R. Rosenhaim, Aldalea Marques, Iêda Santos, and A. Souza
This work evaluates the thermal and kinetic
behaviour of corn biodiesel obtained by the methanol and ethanol routes. As
to the TG curves, in air three thermal decomposition steps are for the methanol
biodiesel and two steps are for the ethanol biodiesel. These steps are related
to the evaporization and/or combustion of the methyl and ethyl esters, respectively.
The corn oil presented four thermal decomposition steps in air, and only one
step in nitrogen. These steps were attributed to the evaporization and/or
decomposition of triglycerides. The TG and DTA profiles of the biodiesel approach
the mineral diesel oil ones.
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:Érika Marinho, A. Souza, Danniely de Melo, Iêda Santos, Dulce Melo, and Walquíria da Silva
of their electrical, magnetic and catalytic properties rare earth and transition
metal mixed oxides are important compounds. Lanthanum chromites have been
extensively used as solid oxide fuel cell (SOFC) interconnect materials. In
this work, lanthanum chromites partially substituted by alkaline earth metals
were synthesized by the urea combustion process. TG and DSC techniques were
used to evaluate the presence of the organic material in the powder after
reaction on the hot plate. The powders were calcinated at 900C and characterized
by XRD and SEM. The results show that the particles have nanometric dimensions
and the perovskite structure was formed.
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: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:Marta Conceição, V. Fernandes Jr, A. Bezerra, M. Silva, Iêda Santos, F. Silva, and A. Souza
Diesel oil has an important role in the field
of urban traffic as well as in the transportation of products. However, the
amount of the non-renewable sources is continuously decreasing. This fact
and the environmental requirements brought the necessity to search for other,
renewable sources. This paper aimed the dynamic kinetic calculation of thermal
decomposition of castor oil, methanol biodiesel and ethanol biodiesel using
Coats–Redfern, Madhusudanan and Ozawa methods. On the base of the thermogravimetric
curves the following thermal stability order could be established: castor
oil>ethanol biodiesel>methanol biodiesel. Kinetic data presented coherent
results. Methanol biodiesel presented lower activation energy than ethanol
biodiesel, suggesting that methanol biodiesel has a better quality for combustion.
Authors:F. Sinfrônio, A. Souza, Ieda Santos, V. Fernandes Jr., Cs. Novák, and Zsuzsanna Éhen
and mass spectrometry (MS) combined techniques have been used to investigate
the thermal degradation and catalytic decomposition of high-density polyethylene
(HDPE) over solid acid catalysts as H-ZSM-5, Al-MCM-41 and a hybrid material
with a bimodal pore size distribution (H-ZSM-5/Al-MCM-41). The silicon/aluminum
ratio of all catalysts is 15. Both thermal and catalytic processes showed
total conversion in a single mass loss step. Furthermore, the catalytic conversion
presents average reduction of 27.4%, in the onset decomposition temperature.
The kinetic parameters were calculated using non-isothermal method. These
parameters do not indicate significant differences between the thermal and
catalytic processes. Even though, the presence of the catalysts changes the
reaction mechanism, from phase boundary controlled reaction to random nucleation
mechanism. Important difference in distribution of evolved products was detected
when several catalysts were used. However, in all cases the main products
were alkanes (C2, C3 and C4),
alkenes (C3 and C4), dienes
(C4 and C5) and traces of aromatic