Structural and thermal properties of the 20Li2O-80TeO2 glass were studied using X-ray diffraction analysis and differential scanning calorimetry techniques to understand and control
the crystallization process on this glass. The γ-TeO2, α-TeO2 and α-Li2Te2O5 phases were identified during the crystallization in this glass. Activation energies and Avrami exponent n were calculated
from non-isothermal measurements for glasses with different particle size. The mean values
Authors:B. Araujo, H. Matsuda, E. Carvalho, and I. Araujo
A study of Pu recovery at trace level from U solutions by ion exchange technique is presented. Plutonium retention >99.5% onto strong anionic resin, AG-X8, from nitric acid solutions and a 92% recovery using 0.4M HNO3 at 60°C as eluent, were obtained. Uranium interference in Pu sorption from mixed U/Pu nitrate solutions with low U/Pu ratio (25) was not verified. However, for high U/Pu ratio solutions (10000), uranium interference in Pu retention on the resin, decreases to 59%. Selecting the loading conditions and using AG-X4 resin, 99% Pu retention was achieved. The Pu product is still contaminated with U and another purification cycle is recomended. A scheme for U/Pu first cycle separation is proposed.
Authors:A. Araújo, E. Fernandes, E. França, and M. Bacchi
Environmental quality assessment studies have been conducted with tree species largely distributed in the Atlantic Forest.
Leaf and soil samples were collected in the conservation unit Parque Estadual da Serra do Mar (PESM) nearby the industrial
complex of Cubatão, São Paulo State, Brazil, and analyzed for chemical elements by instrumental neutron activation analysis.
Results were compared to background values obtained in the Parque Estadual Carlos Botelho (PECB). The higher As, Fe, Hg and
Zn mass fractions in the tree leaves of PESM indicated anthropogenic influence on this conservation unit.
Authors:A. Leite, L. Maia, R. Paz, E. Araújo, and H. Lira
The aim of this work was to obtain membranes from polyamide 6/montmorillonite clay nanocomposites through the phase inversion
technique. The nanocomposites and membranes from polyamide 6/montmorillonite clay were characterized by X-ray diffraction
(XRD), Scanning Electron Microscopy (SEM), Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). Microporous
and asymmetric membranes were successfully obtained from nanocomposites and the results showed that the salts were incorporated
by intercalation between the organoclay layers and, apparently that the nanocomposites and membranes were thermally more stable
than the pure polyamide.
Authors:Daniela Schlemmer, E. de Oliveira, and M. Araújo Sales
Conventional plastics has a
large impact in increasing the environment’s pollution. That’s
why the interest has turned towards novel partially and completely biodegradable
polymers. In this work, blends of polystyrene and thermoplastic starch with
glycerol and Buriti (Mauritia flexuosa
L.) oil as plasticizers were prepared. Samples were analyzed using TG/DTG
and DSC techniques. The TG results indicated that the blends with Buriti oil
are thermally more stable than those with glycerol. The DSC analysis that
Buriti oil provides a higher degree of plasticization of PS, compared to the
blends plasticized using glycerol under the studied 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: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:L. Cides da Silva, G. Araújo, N. Segismundo, E. Moscardini, L. Mercuri, I. Cosentino, M. Fantini, and J. Matos
The aim of this study was to use DSC and X-ray diffraction measurements to determine the pore size and pore wall thickness
of highly ordered SBA-15 materials. The DSC curves showed two endothermic events during the heating cycle. These events were
due to the presence of water inside and outside of mesopores. The results of pore radius, wall thickness and pore volume measurements
were in good agreement with the results obtained by nitrogen adsorption measurement, XRD and transmission electron microscopy.
Authors:F. M. Aquino, D. M. A. Melo, R. C. Santiago, M. A. F. Melo, A. E. Martinelli, J. C. O. Freitas, and L. C. B. Araújo
Thermogravimetric data using the non-isothermal kinetic models of Flynn and Wall and “Model-free Kinetics” were used to determine the activation energy to study the decomposition kinetics of the ligand groups with system’s metallic ions that takes part in the synthesis of PrMO3 (M = Ni or Co). This activation energy was determined for the stage of highest decomposition of the organic matter to establish parameters in synthesis condition optimization and application of the proposed material.