Al2CoO4–PbCrO4 and Al2CoO4–Pb2CrO5 crystalline powders in different proportions were obtained by the polymeric precursor method. Differential scanning calorimetry
(DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during
synthesis. The TG and DSC results revealed a series of overlapping decomposition reactions due to different exothermal events,
which were identified as H2O and NOx elimination and polymer pyrolysis. The X-ray diffraction patterns of the xAl2CoO4–(1 − x)PbCrO4 and xAl2CoO4–(1 − x)Pb2CrO5 mixed compounds, with x = 1, 0.75, 0.5, 0.25 and 0, were obtained in the crystalline form with their respective phases, and proved consistent with
the nominal compositions. The synthesis of these two systems yielded nine different colors and shades.
Authors:A. Ponomarenko, C. Klason, N. Kazantseva, M. Buzin, M. Alexandre, Ph. Dubois, I. Tchmutin, V. Shevchenko, and R. Jérôme
Thermogravimetry was used to investigate the effects of different inorganic functional fillers on the heat resistance of polymer
matrices. The kinetic parameters of thermal oxidative degradation were shown to depend on the polymer, the chemical composition
of the filler surface, the filler concentration, and the processing method, which determines the distribution of filler particles
in the polymer matrix. Magnetic fillers (carbonyl iron, and hexaferrites of different structural types) were shown to be chemically
active fillers, increasing the heat resistance of siliconorganic polymers. Their stabilizing effect is due to blocking of
the end silanol groups and macroradicals by the surface of the filler and non-chain inhibition of thermal oxidative degradation.
In the case of fiber-forming polymers (UHMWPE, PVOH and PAN), most magnetic fillers are chemically inert, but at concentrations
of 30–50 vol% they increase the heat resistance of the composite. Addition of carbon black increased the heat resistance of
the thermoplastic matrix. The dependence of the thermal degradation onset temperature on the kaolin concentration in the polyolefin
matrix exhibited a maximum. Analysis of the experimental results demonstrated the operating temperature ranges for different
composites, and their maximum operating temperature.
Authors:Alexandre G. S. Prado, André L. F. Santos, Carolina P. Pedroso, Thiago O. Carvalho, Lilian R. Braga, and Sheila M. Evangelista
Chitosan is a biodegradable natural polymer with great potential for pharmaceutical applications due to its biocompatibility, high charge density, and non-toxicity. In this study, chitosan microspheres were successfully prepared by an adapted method of coagulation/dispersion. The degree of deacetylation of chitosan powder was obtained by NMR 1H and FTIR techniques. Chitosan powder and chitosan microspheres were characterized by BET surface area and scanning electron microscopy (SEM). The interactions among the chitosan microspheres and the vitamins A and E were characterized by FTIR. In order to evaluate the ability of interaction of vitamin A and vitamin E with the chitosan microspheres, the thermodynamic parameters were followed by calorimetric titration. Different experimental approaches were applied, such as adsorption isotherms, kinetics and thermodynamics studies. The obtained results showed that the interactions of chitosan microspheres with the vitamins were spontaneous, enthalpically and entropically favorable, indicating that the chitosan microspheres can be used with success in the controlled release of these vitamins.
Authors:Thiago O. Carvalho, Ana E. B. Matias, Lilian R. Braga, Sheila M. Evangelista, and Alexandre G. S. Prado
Chitosan microspheres were applied to remove the pollutants diclofenac and dipyrone from water. Adsorption studies were adjusted to Langmuir equation. The maximum number of adsorbed moles gave 5.25 × 10−4 and 4.83 × 10−4 mol of diclofenac and dipyrone, respectively, per gram of chitosan microspheres. The interactions in solid/liquid interface were calorimetrically followed and gave endothermic values: +22.1 ± 1.3 and +48.7 ± 1.5 kJ mol−1, respectively, for the same sequence. Both Gibbs energy values were negative. Adsorption processes were accompanied by an increase in entropy. These interactions were studied by FTIR spectroscopy which showed a strengthening of the CN stretching (dislocated shifts from 1,325 to 1,371 cm−1) related to a weakening of the NH stretch caused by the interaction with drugs.
Authors:Alexandre G. S. Prado, Sheila M. Evangelista, Jurandir R. SouzaDe, Jeane G. S. Matos, Marco A. A. Souza, Denise A. Oliveira, and Claudio Airoldi
A microcalorimetric method was applied to study microbial soil activity of ornamental flower (Dahlia pinnata) plantations when irrigated with potable water and wastewaters. The samples were irrigated with potable water PW sample (reference) and treated wastewaters from Municipal Wastewater Treatment Station of Asa Norte in Brasilia City (Brazil). Three different water treatments were applied to irrigate soil samples, named TW1, TW2, and TW3 samples. The increase of the microbial soil activity observed in TW1 sample must have occurred because of the high amount of organic waste dissolved in wastewater used for irrigation. This rise indicates that the present treated wastewater can affect natural life cycle. However, only a low alteration in microbial soil activity was observed in the TW2 and TW3 samples, which suggests that these wastewater treatments can be normally used to irrigate soils without bringing environmental consequences, once they offer a great opportunity to upgrade and protect the environment.
Authors:Romulo D. A. Andrade, Elaine A. Faria, Amaury M. Silva, Wandallas C. Araujo, Gustavo C. Jaime, Kenia P. Costa, and Alexandre G. S. Prado
The Brazilian government has presented a biofuel program, which aims the addition of 2% of biofuel in fossil diesel in 2008 and 5% up to 2013. Thus, the knowledge of heat of combustion of biofuel/diesel blends is necessary. The biodiesel was produced by transesterification of soybean oil with a yield of 87%. The diesel-like was obtained by pyrolysis of soybean oil. This biofuel presented all parameters according to ANP. The obtained heats of combustion were 41.36 ± 0.17; 38.70 ± 0.16; and 36.71 ± 0.17 MJ/kg for diesel, diesel-like and biodiesel, respectively. The results show that the heats of combustion of biofuels are approximately 17% smaller than fossil diesel. The obtained data also show that the heats of combustion depend on the methodology used for the biofuel production. Addition of biofuels to traditional diesel fuel results in a linear decreasing of the heat of combustion with the amount of the alternative fuel added to the diesel.
Authors:Ivan M. Berezin, Alexandre A. Petunin, Dimtrij I. Kryuchkov, and George L. Kovács
A specific process of manufacturing of vessel shell tabs, namely the method of cold stamping is studied in this paper. Recommendations are proposed to gain the proper technology of manufacturing spherical vessels with a volume above 600 cubic meters with regard to labor saving of tabs stamping on hydraulic press. The necessity of having proper technology of stamping is motivated by the large quantity of manual operations, having a direct influence on the conversion costs of a spherical vessel as a whole. The importance of this research is connected with the necessity of multiple shape control of tabs being manufactured during stamping and time-consuming point-by-point shaping-up. The reduction of material costs is supported by using finite-element simulation. Problems are solved with specific modules of the computer aided engineering-system ABAQUS. The results of some finite-element simulations are described. The analysis of stress-strain state at each step of the application of loads is performed.
Authors:Laís L. Fernandes, Sheila C. Rahal, Alexandre T. Fabro, Sabrina S. Batah, Alicia G. Hippólito, Jacqueline M. Bisca, Inajara N. Hirot, and Carlos R. Teixeira
The aim of this study was the preparation and histological evaluation of Leukocyte- and Thrombocyte-Rich Fibrin (L-TRF) membranes obtained from the blood of four bird species. Forty adult healthy birds were divided into four groups of equal size: G1 – macaws, G2 – domestic chickens, G3 – parrots, G4 – toco toucans. A total of 0.5 mL of blood was collected from each bird, put into a glass tube without anticoagulant and centrifuged at 3000 rpm for 10 min. L-TRF membranes produced after compression of the clot were processed for histological analysis. The ratio of thrombocytes/area was not significantly different among Groups G2, G3 and G4, but a significant difference was found between Groups G1 and G2 with the highest thrombocyte concentration/area in G1. The groups did not differ statistically in the number of leukocytes/area. The fibrin-to-cells ratio did not vary statistically among Groups G1, G2 and G3, but this ratio was significantly higher in Group G4 than in the other groups. The thrombocyte-to-leukocyte ratio was the highest in Group G1, but it did not differ among Groups G2, G3 and G4. In conclusion, the centrifugation protocol allowed the production of L-TRF membranes in the four bird species studied. Histologically, cell ratios were analogous in domestic chickens and parrots, and macaws had the highest ratio of thrombocytes.