The mathematical evaluation of the activation
energy, E, of non-isothermal degradation
reactions is usually made using the Ozawa/Flynn–Wall isoconversion principle
and involves the numerical resolution of a set of integrals without closed
form solution, which are solved by polynomial approximation or by numeric
integration. In the present work, the isoconversion principle, originally
described and maintained until now as an algebraic problem, was written as
a set of ordinary differential equations (ODEs). The individual ODEs obtained
are integrated by numeric methods and are used to estimate the activation
energy of simulated examples. A least square error (LSE) objective function
using the introduced ODEs was written to deal with multiple heating rate CaCO3
thermal decomposition TG experiments.
The products of the thermal decomposition in air of iron/III/benzoate [Fe3/C6H5COO/6/OH/2]OH.H2O have been studied using conventional thermal analysis, X-ray diffraction measurements and mainly Mössbauer spectroscopy. The decomposition occurs in the temperature range 200–350°C. It was possible to identify benzoic acid and ferric oxide as final products. Above 300°C, the observed ferric oxide showed a particle size distribution, which depends on the heating temperature and the heating time interval, as evidenced by the following detected phases: superparamagnetic -Fe2O3 and magnetically ordered state with crystal structure of the phases -Fe2O3 and -Fe2O3. Also, two iron/III/ benzoate complexes having four and three ligands within the coordination sphere are suggested as intermediate products.
Authors:C. Ruiz, L. Machado, J. Vanin, and J. Volponi
Radiation-curable coatings have acquired importance, because they are environmentally-friendly (no solvent emission)and require
low energy for curing, when compared to other conventional heat-curable products. UV-curable coatings performance depends
on the cure quality. Suitable methods were evaluated to estimate the degree of cure applying quantitative techniques, such
as differential scanning calorimetry (DSC) and differential photocalorimetry (DPC), in order to determine the residual heat
of curing in UV-cured films. The results of the DPC technique showed better sensibility than DSC technique, although the use
of suitable pans for the case of clear coats must be considered.
Authors:A. Porto, W. Magalhães, C. Carvalho, and J. Machado
Positron Lifetime Spectroscopy (LS) measurements were performed in a series of binary molecular solid solutions of the general formula M1–xGxL3, where L(ligand)=acetylacetone, dipivaloylmethane, or N-benzoyl-N-phenylhydroxylamine, M=Al(III), Ga(III) or In(III), as matrix, and G=Cr(III), Mn(III), Fe(III), Co(III), Ru(III), Rh(III) and Ir(III), as guest molecules, and the corresponding mechanical mixtures. For the solid solutions, the o-Ps yield values (I3) decrease very rapidly with the increase of the guest mole fraction, showing a high efficient Ps inhibition process, while for the corresponding mechanical mixtures, these values decrease linearly with the increase of the guest molecule concentration, indicating the presence of two distinct phases. These results confirm our previous proposal that the LS technique is able to characterize solid solutions formed by one matrix, in whichI3 values are high, and one guest, in which theI3 values are very low.
Authors:C. Bentivoglio Ruiz, L. Machado, J. Volponi, and E. Segura Pino
Radiation curing is an environmentally-friendly technology. Furthermore, radiation curing is a faster, energy saving and more
efficient industrial process than the heat-curable process. One of the most important requirements for the widespread application
of UV curable coatings in the coating industry is that they are stable vs. atmospheric degradation. Today's state of the art
in oxidative drying and thermosetting coatings is the use of light stabilizers to protect polymers vs. the damage of outdoor
exposure. Oxygen has a detrimental effect on the cure response of free radical systems, especially in thin-film coatings.
Differential photocalorimetry (photo-DSC) was used to investigate the oxygen effect and the use of light stabilizers on UV
curing of photocurable formulations based on acrylate materials. Coating thickness influence was also considered.
Authors:G. Melo, J. Sponchiado, A. Machado, and N. Cáceres
We investigated how the small-mammal community is structured in a deciduous forest in southern Brazil, analysing the patterns of vertical and horizontal distribution. We used 12 transect lines, with 180 live-traps distributed on the ground and in the understory, and 12 pitfall traps in total. During six field sessions, we captured 510 individuals belonging to 12 small-mammal species. The combination of different methods of capture resulted in a relative high species richness for the area, although the presence of additional species cannot be ruled out. The forest complexity plays an important role allowing the coexistence of cursorial, scansorial and some arboreal species in this community. The structural variables, liana and bamboo, were the most important ones for species richness. However, the dominant species, Akodon montensis was associated to sites with dense vegetation at ground level such as ferns, bamboos, and shrubs.
Authors:L. Machado, A. Marins, E. Muri, J. Lacerda, V. Balthar, P. Fulvio, and J. Freitas
This paper presents the reactions of synthesis between the ligand sodium diphenylamine-4-sulfonate and the lanthanum(III)
chloride hydrated. The compounds (LaCl3)2(C12H10NSO3Na)32(CH3CH2OH) (A) and (LaCl3)(C12H10NSO3Na)(CH3CH2OH)12H2O (B) were obtained using the solvents ethanol and methanol (synthesis A) and ethanol and water (synthesis B). The produced
compounds and the ligand were characterized by thermogravimetric and differential thermogravimetric analysis, IR spectroscopy
and elemental analysis of sodium, carbon, hydrogen, nitrogen, sulfur, chlorine and lanthanum, whereas the residues from thermal
decomposition were investigated by X-ray diffractometry.
Authors:A. Souza, M. Oliveira, I. Santos, M. Conceição, L. Nunes, and J. Machado
The kinetics of thermal decomposition of solid In(S2CNR2)3 complexes, (R=CH3, C2H5, n-C3H7,i-C3H7, n-C4H9 and i-C4H9), has been studied using isothermal and non-isothermal thermogravimetry. Superimposed TG/DTG/DSC curves show that thermal
decomposition reactions occur in the liquid phase, except for the In(S2CNMe2)3 and In(S2CNPri2)3 compounds.
Authors:M. Silva, M. Conceiçăo, M. Trindade, A. Souza, C. Pinheiro1, J. Machado, and P. Filho
The thermodynamic and kinetic parameters of the thermal decomposition of Zn(S2CNR2)2 complexes (R=CH3, C2H5 and n-C3H7) were determined with the dynamic thermogravimetric method. Superimposed TG/DTG/DSC curves show that thermal decomposition
reactions for chelates with R=C2H5 and n-C3H7 occur in the liquid phase, at temperatures far away from their melting points, whereas for the complex with R=CH3 the thermal decomposition begins at a temperature closer to its melting point, suggesting a rather complex decomposition
Authors:L. Machado, A. Marins, E. Muri, A. Biondo, J. Matos, and I. Mazali
Reactions in aqueous-alcoholic solution between diphenyl-4-amine barium sulphonate (Ba-DAS—anionic surfactant) and the hydrated
sulphates of Fe(III) and Fe(II) ions and their use to ovtain iron oxides are described here. The formation of Fe(II) complexes
was reached by using an excess of Ba-DAS, in absence of light under inert atmosphere. The complexes achieved Fe2[(C12H10NO3S)4]·9H2O and Fe3[(C12H10NO3S)6]·12H2O were characterized by TG/DTG and IR, UV-VIS and 57Fe-Mössbauer analyses.