Authors:Soraya de Morais, Crislene da Silva Morais, Petrônio de Athayde Filho, B. Freitas Lira, and Railda do Nascimento
The mesoionic compounds are pentagonal heterocyclic betaines with their potential use mainly in the pharmacology field due
to the diversity of their biological activities. Their exceptional electric properties lead the compounds to be investigated
in the field such as the nonlinear optical devices. In this study, five mesoionic compounds of the 1,3-thiazole-5-thiolate
system had been synthesized from amino acids derived from glycine through 1,3-dipolar cycloaddition/cycloreversion reaction.
The compounds were characterized by the use of infrared spectrometry, thermogravimetry and differential scanning calorimetry
techniques. Thermal stability of each structure was determined and characterized by the kinetic study of the thermal decomposition
by non-isothermal thermogravimetry. The DSC curves for MI-1, MI-2, MI-3, MI-4, and MI-5 demonstrated their fusion and subsequent
decomposition with the exception of MI-3, which presented only decomposition stages. The kinetic models that better described
the thermal decomposition mechanism of the mesoionic compounds achieved by the non-isothermal methods were R1, R2 and R3 (based
on the geometric models).
Authors:A. Barros, S. Prasad, V. Leite, A. Souza, G. Marino, Crislene Morais, and Marta Conceição
The present study was carried out for evaluating the retention behavior
of sanitary sewage in relation to cadmium and cobalt ions in an ascendant
continuous-flow reactor. It was found that the studied sludge presented a
high assimilation of the metals, probably due to the presence of anionic groups,
which favors adsorption and complexation processes. Thermal analyses of the
samples showed a shift in the thermal decomposition of the ‘in natura’
sludge, when compared with those of the samples spiked with the metals, confirming
the possibility of interactions between the heavy metals and the anionic groups
present in the sludge.
Authors:W. Lopes, Crislene Morais, A. Souza, V. Leite, and B. de A. Firmo
decomposition kinetic of three lanthanide mixed complexes with the general
formula of Ln(thd)3phen (where Ln=Nd3+,
Sm3+ or Er3+, thd=2,2,6,6-tetramethyl-3,5-heptanodione and phen=1,10-phenanthroline) has been studied in this
work. The powders were characterized by their melting point, elemental analysis,
FTIR spectroscopy and thermogravimetry. The isothermal TG curves have been
recorded under the same conditions at 265–285, 265–285 and 250–270°C
for Nd(thd)3phen, Sm(thd)3phen
and Er(thd)3phen, respectively.
parameters, i.e. activation energy, reaction order and frequency factor were
obtained through the technique of lineal regression using the relation g(α)=kt+g0. The analysis was done
at decomposed fractions between 0.10–0.90. The values of activation
energy were: 114.10, 114.24 and 115.04 kJ mol–1
for the Nd(thd)3phen, Sm(thd)3phen
and Er(thd)3phen complexes, respectively. The kinetic
models that best described the isothermal decomposition reaction the complexes
were R1 and R2. The values of activation energy suggests the following decreasing
order of stability: Nd(thd)3phen<Sm(thd)3phen<Er(thd)3phen.
Authors:E. Araújo, Renata Barbosa, Amanda Oliveira, Crislene Morais, T. deMélo, and A. Souza
Polyethylene/montmorillonite clay nanocomposites were obtained via direct
melt intercalation. The clay was organically modified with four different
types of quaternary ammonium salts. The objective of this work is to study
the use of montmorillonite clay in the production of nanocomposites by means
on rheological, mechanical and crystallization properties of nanocomposites
and to compare to the properties of the matrix and PE/unmodified clay nanocomposites.
In general, the tensile test showed that the yield strength and modulus of
the nanocomposites are close to the pure PE. Apparently, the mixture with
Dodigen salt seems to be more stable than the pure PE and PE/unmodified clay.
Authors:F. Moura, S. Prasad, V. Leite, Crislene Morais, A. Barros, and A. Souza
study describes the aerobic biodegradation process of a mixture of sanitary
sewage sludge and lubricating oil. TG/DTG curves confirmed that the applied
aerobic biological treatment decreased the organic material content and caused
significant modifications in the thermal behavior of the studied substrates
after the functioning period.
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: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.