Jusinei Meireles Stropa

COMPOSIÇÃO QUÍMICA E TEMPERATURA DE CRISTALIZAÇÃO DE ÉSTERES OBTIDOS DE QUATRO ÓLEOS VEGETAIS EXTRAÍDOS DE SEMENTES DE PLANTAS DO CERRADO

The seed oils from four plants (Scheelea phalerata, Butia capitata, Syagrus romanzoffiana, Terminalia cattapa) found in Mato Grosso do Sul were extracted at good yields. Alkaline transesterification of these seed oils to esters using methanol and ethanol was studied and also produced good yields. Oleic acid (30.5/32.3%), lauric acid (30.7/32.9%) methyl and ethyl esters, were the main components of transesterification of the oils from Scheelea phalerata and Syagrus romanzoffiana. Lauric acid (42.2%), capric acid (15.9%) and caprylic acid (14.6%) methyl and ethyl esters were the main ester components of transesterification of the oil from Butia capitata. Oleic acid (37.8%), palmitic acid (33.5%) and linoleic acid (22.6%) methyl and ethyl esters were the main components of transesterification of oil from Terminalia catappa. Based on differential scanning calorimetry (DSC) studies, the first crystallization peak temperature of esters was observed. Esters derived from oils of the family Arecaceae (Scheelea phalerata, Butia capitata, Syagrus romanzoffiana) showed the lowest points of crystallization, despite having high levels of saturated fat. Esters of Terminalia cattapa oil, rich in unsaturated fat, showed the highest crystallization temperature. This difference in behavior is probably related to the high concentration of esters derived from lauric acid and palmitic acid.

Síntese, caracterização e estudo das propriedades de um novo complexo mononuclear contendo quercetina e íon Ga(III)

Flavonoids are one of the most important compound groups applied as medicine given their antioxidant properties, but several intrinsic properties can be improved through structural modifications to their molecules. Here, the synthesis and characterization of a new gallium (III) complex with quercetin is described. Electrochemical properties, as well as antioxidant and cytotoxic activities, were investigated and compared to the free flavonoid molecule. The mononuclear complex obtained, [Ga(C15H9O7)3].2H2O.2CH3OH.CH3CH2OH, seems more active as a DPPH radical scavenger given its lower oxidation potential compared to quercetin. The new complex cytotoxic responses have shown to be more effective than those of the free flavonoid and of lapachol used as a control.

Use of Natural Rubber Membranes as Support for Powder TiO2and Ag/TiO2 Photocatalysts

The purpose of this study was to synthesize TiO2-polymer composites able to act as photocatalyst membranes. TiO2 catalysts were prepared using the sol-gel method to contain 0.0, 0.5, 1.0, and 2.0 wt.% of embedded Ag particles, subsequently incorporated into natural rubber latex at a weight fraction of 15%. Samples of these ceramic powders were suspended in a latex emulsion (natural rubber), cast in Petri dishes and slowly dried in an oven. The resulting materials were evaluated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, diffuse reflectance spectroscopy, differential scanning calorimetry, thermogravimetry, and photocatalytic assaying using methylene blue as an organic pollutant reference. All composite membranes exhibited good photoactivity conferred by TiO2 powder, with 98% dye fading after 300 min of ultraviolet irradiation.

Study of the Zirconium and Silicon Homovalent Dopants Insertion on the Structure and Bandgap Energy of Titanium Dioxide Powders

The reconstructive transformation occurring during the anatase-to-rutile phase transition can be observed through adequate techniques such as Thermal Analyses and Z-ray diffractometry followed by structural refinement. The typical photonic properties of titanium dioxide photocatalysts depend on the anatase structure and how the modifiers can provide their performance enhancement. In the present work, we investigate the structural effects caused by the simultaneous homovalent modification on the anatase structure in order to understand the mechanisms of the anatase-to-rutile phase transition in terms of the atomic coordinates and the lattice parameters. The refined structures along the calcination temperature from 500 to 900 oC suggest the oxygen bonds are strongly affected in unmodified anatase in order to destroy and rebuilt the crystal structure and lead to the rutile phase formation above 700 oC, unless some modifier pairs stabilize them.

Phase Formation in Copper and Calcium Titanate Dielectric Ceramic Obtained by Polymeric Precursor Method

The polycrystalline ceramic named calcium and copper titanate is a dielectric ceramic with very high dielectric constant applicable in several electronic devices. The powder form for that advanced ceramic can be synthesized through chemical route, like the Polymeric Precursor Method at relative lower temperatures the presence of alkaline earth cations harms the structural homogenization during the crystallization process. In this work, the calcium and copper titanate powder was obtained by Polymeric Precursors Method by imposing a slow thermal decomposition of polymeric precursor and several crushing steps before the calcination at 800 °C for 4 hours. The entire process was observed by thermogravimetric analysis and FTIR spectrometry, including the nitrogen adsorption-desorption isotherms and X-ray diffractometry techniques for calcined power samples. It was observed the crystallization of the cubic Im-3 Ca1/4Cu3/4TiO3 phase only starts after organics removal and full calcium carbonate elimination above 700 oC, which is followed by pore elimination and particle sintering. The chemical synthetic route used in this work shows the ability to prepare CCT powders sample with very structural homogeneity, which characteristics are required to manufacturing many electronic devices.

Thermal Properties of the Blends of Methyl and Ethyl Esters Prepared from Babassu and Soybean Oils

Fatty acid esters (methyl and ethyl) prepared from babassu nut oil were blended with the respective esters from soybean oil. These binary blends (babassu:soybean) were made in proportions of 10:90, 20:80, 30:70, 40:60, and 50:50 (vol%). The ester content of all the blends was higher than 96.5%, which is the minimum value required by the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (Agência Nacional do Petróleo, Gás Natural e Biocombustíveis, ANP). The thermal properties of the babassu, soybean and binary mixtures of esters were investigated by thermogravimetry-differential thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). The thermal stability of the blended biodiesels decreased as the total contents of the babassu esters increased. From the experiments it was found that babassu methanol biodiesel is stable up to 49.6 °C and the ethanol biodiesel is stable up to 53.7 °C in air. The methyl esters blends were thermally stable up to 83.2 and 56.8 °C, for 90:10 and 50:50 blends (soybean:babassu), respectively. The ethyl ester blends presented values of temperature ranges somewhat higher than the methyl esters, such as 85.2 and 64.5 °C for 90:10 and 50:50 blends, respectively. The esters from babassu oil have satisfactory performance at low temperatures with respect to the point of crystallization, which were below –9.8 °C for ethylic esters and –8.5 °C for methylic esters. A good correlation between the crystallization onset temperature and the increase in the concentration of the babassu oil esters was obtained in the mixtures analyses. In the 50:50 combination (babassu:soybean), the crystallization onset temperature were –6.73 and –9.12 °C for methyl and ethyl esters, respectively.

Effect of Iron and Vanadium on the Phase Transition of Titanium Dioxide Obtained by Polymeric Precursor Method

The titanium dioxide phase formation is dependent on the synthesis method, temperature of calcination and modifiers insertion. By using chemical methods, such as Polymeric Precursor Method, the organic impurities or extrinsic defects caused by doping play an important rule on the formation of precursor structure before the phase crystallization above 500 oC. Some dopants can change the decomposition mechanism of the precursor, which affects the anatase-rutile phase transition. In this work, the Polymeric Precursor Method was used to synthesize titanium dioxide powder samples in order to investigate the effects of iron (III) and vanadium (V) dopants on the phase formation. Through thermal analysis of polymeric precursors and X-ray diffractometry for calcined powder samples it was possible to show the existence of antagonistic effects for both investigated dopants. While the iron doping reduces the anatase phase tetragonality and delays the rutile phase conversion, the vanadium one changes the mechanism of decomposition of polymeric precursor and leads to more amount of rutile phase.