Effect of pH of colloidal suspension on crystallization and activation energy of deep levels in SnO2 thin films obtained via sol-gel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Activation energy for the reverse eutectoid reaction in hypo-eutectoid Cu-Al alloys

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of Ag additions on the activation energy for the reverse eutectoid reaction in Cu-Al alloys

The eutectoid transformation may be defined as a solid-state diffusion-controlled decomposition process of a high-temperature phase into a two-phase lamellar aggregate behind a migrating boundary on cooling below the eutectoid temperature. In substitutional solid solutions, the eutectoid reaction involves diffusion of the solute atoms either through the matrix or along the boundaries or ledges. The effect of Ag on the non-isothermal kinetics of the reverse eutectoid reaction in the Cu-9 mass%Al, Cu-10 mass%Al, and Cu-11 mass%Al alloys were studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The activation energy for this reaction was obtained using the Kissinger and Ozawa methods. The results indicated that Ag additions to Cu-Al alloys interfere on the reverse eutectoid reaction, increasing the activation energy values for the Cu-9 mass%Al and Cu-10 mass%Al alloys and decreasing these values for the Cu-11 mass%Al alloy for additions up to 6 mass%Ag. The changes in the activation energy were attributed to changes in the reaction solute and in Ag solubility due to the increase in Al content.

Electrocatalytic effect of Pb and Sn adatoms on the oxidation of 1-propanol on platinized platinum electrodes: Determination of the apparent activation energy

The electrocatalytic oxidation of 1-propanol was investigated on platinum electrodes modified by submonolayers of Pb and Sn in acid media. An increase of oxidation rates observed for both Pb and Sn, and the influence of theta values was investigated. The values of the apparent activation energy evaluated from the Arrhenius plots concerning the electrochemical oxidation of 1-propanol on modified platinzed platinum electrodes, reveal a significant decrease in the presence of upd Sn and Ph adatoms. A decrease from 56 to 26 U mol(-1) in the presence of Sn. and from 78 to 25 U mol(-1) for Ph adatoms are some illustrative values which reflect the promoting effect of the upd adatoms.

Correlation Between Apparent Activation Energy and NOx emission of renewable diesel from sugar cane, biodiesel, fossil diesel and their blends

Biofuels and their blends with fossil fuel are important energy resources, which production and application have been largely increased internationally. This study focus on the development of a correlation between apparent activation energy (Ea) and NOx emission of the thermal decomposition of three pure fuels: farnasane (renewable diesel from sugar cane), biodiesel and fossil diesel and their blends. Apparent Activation energy was determined by using thermogravimetry and Model-Free Kinetics. NOx emission was obtained from the European Stationary Cycle (ESC) with OM 926LA CONAMA P7/Euro 5 engine. Results showed that there is a linear correlation between apparent activation energy and NOx emission with R2 of 0,9667 considering pure fuels and their blends which is given as: NOx = 2,2514Ea - 96,309. The average absolute error of this correlation is 2.96% with respect to the measured NOx value. The main advantage of this correlation is its capability to predict NOx emission when either a new pure fuel or a blend of fuels is proposed to use in enginees.

Determination of the activation energies of beef tallow and crude glycerin combustion using thermogravimetry

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Dielectric properties of thermosetting material nanocomposites

The dieletric relaxation properties of thermosetting material nanocomposites based on spherosilicate nanoplatforms were studied from room temperature to 170 degrees C, varying the frequency from 10 to 1000 KHz. Permittivity (epsilon'), dielectric loss (epsilon ''), and activation energy (E-a) were calculated. The results of dielectric relaxation were confirmed by those of the final properties. The dielectric loss amplitude decreases with increasing ODPG content until about 70-73 wt % and slightly increases at higher ODPG content. This means that the increasing of the ODPG content in the composite samples decreases the number of pendants groups and/or increases crosslink densitv, causing decreased motion of organic tethers, and subsequently decreasing of the dipolar mobility. The results of apparent activation energy, fracture toughness and tensile modulus mechanical properties show the same profile with respect to ODPG content, in the sense that they exhibit maxima around 70 wt % ODPG. For the ODPG/MDA composites, this formulation of 70 wt % ODPG containing excess of amine is not composition where the highest crosslinked density is reached. This implies that the best mechanical properties and E-a are provided by some degree of chain flexibility. (c) 2007 Wiley Periodicals, Inc.

COMBUSTION and PYROLYSIS of A SLUDGE FROM WASTEWATER TREATMENT PLANT

The possibility of thermal treatment plants of municipal wastewater is an alternative solution for the final disposition of the sludge produced on small cities as Barueri, a small town of São Paulo State, Brazil. Combustion and pyrolysis of that municipal waste, occurring respectively in air and nitrogen, have been studied by thermogravimetry (TG) and differential thermal analysis (DTA). The main steps of each case were analyzed and Kissinger plots were used to estimate respective activation energies. DTG peaks are more indicated to represent the condition of maximum reaction rates than DTA peaks.

Thermogravimetric studies of decomposition kinetics of six different IAC Hevea rubber clones using Flynn-Wall-Ozawa approach

The thermal degradation behaviour of rubber from six new Hevea brasiliensis clones (IAC 40, 56, 300, 301, 302 and 303) from São Paulo State, Brazil was studied by thermogravimetry using the Flynn-Wall-Ozawa approach to assess the kinetic parameters ( reaction order, activation energy and pre-exponential factor) of the decomposition process. This study indicated that the thermal behaviour is a complex multiple step process, which depends on the type of rubber Hevea clones studied. The rubber from these clones can be classified, following the order of decreasing thermal stability, as IAC 303 > 302 > 56 > 40 > 300 > 301.

Comportamento elétrico a alta temperatura de termistor cerâmico alfa-Fe2O3 com coeficiente de temperatura negativo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nucleation kinetics of crystalline phases from a kaolinitic body used in the processing of red ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Projected length annealing of etched Sm-152 ion tracks in apatite

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Understanding the Crystallization Mechanism of a Wollastonite Base Glass Using Isoconversional, IKP Methods and Master Plots

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Polyphenol oxidase from yacon roots (Smallanthus sonchifolius)

Polyphenol oxidase (E.C. 1.14.18.1) (PPO) extracted from yacon roots (Smallanthus sonchifolius) was partially purified by ammonium sulfate fractionation and separation on Sephadex G-100. The enzyme had a molecular weight of 45 490 +/- 3500 da and K-m values of 0.23, 1.14, 1.34, and 5.0 mM for the substrates caffeic acid, chlorogenic acid, 4-methylcatechol, and catechol, respectively. When assayed with resorcinol, DL-DOPA, pyrogallol, protocatechuic, p-coumaric, ferulic, and cinnamic acids, catechin, and quercetin, the PPO showed no activity. The optimum pH varied from 5.0 to 6.6, depending on substrate. PPO activity was inhibited by various phenolic and nonphenolic compounds. p-Coumaric and cinnamic acids showed competitive inhibition, with K-i values of 0.017 and 0.011 mM, respectively, using chlorogenic acid as substrate. Heat inactivation from 60 to 90 degrees C showed the enzyme to be relatively stable at 60-70 degrees C, with progressive inactivation when incubated at 80 and 90 degrees C. The E-a (apparent activation energy) for inactivation was 93.69 kJ mol(-1). Sucrose, maltose, glucose, fructose, and trehalose at high concentrations appeared to protect yacon PPO against thermal inactivation at 75 and 80 degrees C.

Ionically bound peroxidase from peach fruit

Soluble, ionically bound peroxidase (POD) and polyphenoloxidase (PPO) were extracted from the pulp of peach fruit during ripening at 20degreesC Ionically bound form was purified 6.1 -fold by DEAE-cellulose and Sephadex G-100 chromatography. The purified enzyme showed only one peak of activity on Sephadex G-100 and PAGE revealed that the enzyme was purified by the procedures adopted. The purified enzyme showed a molecular weight of 29000 Da, maximum activity at pH 5.0 and at 40degreesC the calculated apparent activation energy (Ea) for the reaction was 10.04 kcal/mol. The enzyme was heat-labile in the temperature range of 60 to 75degreesC with a fast inactivation at 75degreesC Measurement of residual activity showed a stabilizing effect of sucrose at various temperature/sugar concentrations (0, 10, 20 %, w/w), with an activation energy (Ea) for inactivation increasing with sucrose concentration from 0 to 20% (w/w). The Km and V-max values were 9.35 and 15.38 mM for O-dianisidine and H2O2, respectively. The bound enzyme was inhibited competitively by (.)ferulic, caffeic and protocatechuic acids with different values of Ki,. L-cysteine, p-coumaric and indolacetic acid and Fe++ also inhibited the enzyme but at a lower grade. N-ethylmaleimide and p-CMB were not effective to inhibit the enzyme demonstrating the non-essentiality of SH groups.