Influence of Ag addition on the thermal behavior of the Cu-11 mass% Al alloy

In this work the influence of Ag additions on the thermal behavior of the Cu-11 mass% Al alloy was studied using differential scanning calorimetry, in situ X-ray diffractometry and scanning electron microscopy. The results indicated that changes in the heating rate shift the peak attributed to alpha phase formation to higher temperatures, evidencing the diffusive character of this reaction. The activation energy value for the alpha phase formation reaction, obtained from a non-isotherm kinetic model, is close to that corresponding to Cu atoms self diffusion, thus confirming that this reaction is dominated by Cu atoms diffusion through the martensite matrix.

Application of non-isothermal cure kinetics on the interaction of poly(ethylene terephthalate) - Alkyd resin paints

Samples of paint (P), reused PET (PET-R) and paint/PET-R mixtures (PPET-R) were evaluated using DSC to verify their physical-chemical properties and thermal behavior. Films from paints and PPET-R are visually similar. It was possible to establish that the maximum amount of PET-R that can be added to paint without significantly altering its filming properties is 2%. The cure process (80-203°C) was identified through DSC curves. The kinetic parameters, activation energy (E a) and Arrhenius parameters (A) for the samples containing 0.5 to 1% of PET-R, were calculated using the Flynn-Wall-Ozawa isoconversional method. It was observed that for greater amounts of PET-R added, there is a decrease in the E a values for the cure process. A Kinetic compensation effect (KCE), represented by the equation InA=-2.70+0.31E a was observed for all the samples. The most suitable kinetic model to describe this cure process is the autocatalytic Šesták-Berggreen, model applied to heterogeneous systems. © 2007 Springer Science+Business Media, LLC.

Study of biosorption of rare earth metals (La, Nd, Eu, Gd) by Sargassum sp. biomass in batch systems: Physicochemical evaluation of kinetics and adsorption models

This work evaluated kinetic and adsorption physicochemical models for the biosorption process of lanthanum, neodymium, europium, and gadolinium by Sargassum sp. in batch systems. The results showed: (a) the pseudo-second order kinetic model was the best approximation for the experimental data with the metal adsorption initial velocity parameter in 0.042-0.055 mmol.g -1.min-1 (La < Nd < Gd < Eu); (b) the Langmuir adsorption model presented adequate correlation with maximum metal uptake at 0.60-0.70 mmol g-1 (Eu < La < Gd < Nd) and the metal-biomass affinity parameter showed distinct values (Gd < Nd < Eu < La: 183.1, 192.5, 678.3, and 837.3 L g-1, respectively); and (c) preliminarily, the kinetics and adsorption evaluation did not reveal a well-defined metal selectivity behavior for the RE biosorption in Sargassum sp., but they indicate a possible partition among RE studied. © (2009) Trans Tech Publications.

Photo-Fenton degradation kinetics of low ciprofloxacin concentration using different iron sources and pH

The aim of the present study was to compare the degradation kinetics of low (1 mg L-1) and high (25 mg L-1) concentrations of ciprofloxacin (CIP) aiming to decrease the concentration of additives and evaluate the pH limitation by the use of low iron concentrations and organic ligands. A parameterized kinetic model was satisfactorily fitted to the experimental data in order to study the performance of photo-Fenton process with specific iron sources (iron citrate, iron oxalate, iron nitrate) under different pH medium (2.5, 4.5, 6.5). The process modeling allowed selecting those process conditions (iron source, additives concentrations and pH medium) which maximize the two performance parameters related to the global equilibrium conversion and kinetic rate of the process. For the high CIP concentration, degradation was very influenced by the iron source, resulting in much lower efficiency with iron nitrate. At pH 4.5, highest TOC removal (0.87) was achieved in the presence of iron citrate, while similar CIP conversions were obtained with oxalate and citrate (0.98 after 10 min). For the low CIP concentration, much higher conversion was observed in the presence of citrate or oxalate in relation to iron nitrate up to pH 4.5. This behavior denotes the importance of complexation also at low dosages. Appropriate additives load (320 μM H 2O2; 6 μM Fe) resulted in a CIP conversion of 0.96 after10 min reaction with citrate up to pH 4.5. © 2013 Elsevier B.V. All rights reserved.

Elucidation of carbohydrate molecular interaction mechanism of recombinant and native ArtinM

The quartz crystal microbalance (QCM) technique has been applied for monitoring the biorecognition of ArtinM lectins at low horseradish peroxidase glycoprotein (HRP) concentrations, using a simple kinetic model based on Langmuir isotherm in previous work.18 The latter approach was consistent with the data at dilute conditions but it fails to explain the small differences existing in the jArtinM and rArtinM due to ligand binding concentration limit. Here we extend this analysis to differentiate sugar-binding event of recombinant (rArtinM) and native (jArtinM) ArtinM lectins beyond dilute conditions. Equivalently, functionalized quartz crystal microbalance with dissipation monitoring (QCM-D) was used as real-time label-free technique but structural-dependent kinetic features of the interaction were detailed by using combined analysis of mass and dissipation factor variation. The stated kinetic model not only was able to predict the diluted conditions but also allowed to differentiate ArtinM avidities. For instance, it was found that rArtinM avidity is higher than jArtinM avidity whereas their conformational flexibility is lower. Additionally, it was possible to monitor the hydration shell of the binding complex with ArtinM lectins under dynamic conditions. Such information is key in understanding and differentiating protein binding avidity, biological functionality, and kinetics. © 2013 American Chemical Society.

Mineralização do soro ácido de leite em função do pH do solo

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

A intermediação da noção de probabilidade na construção de conceitos relacionados à cinética química no ensino médio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo do annealing de traços de fissão em epídoto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fatores operacionais e cinética do processo fermentativo para otimização da produção de etanol em escala industrial

Pós-graduação em Microbiologia Agropecuária - FCAV

Estudo da cinética de precipitação de Ag na liga Cu-7% Al-4% Ag

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Determinação de parâmetros cinéticos para decomposição térmica de resinas utilizadas em revestimentos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e aplicação de sílica mesoporosa modificada com o ligante 4-amino-2-mercaptopirimidina na pré-concentração de Cd (II), Cu(II), Pb(II), Zn(II) e Ni(II) em amostras de águas naturais

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Interações entre interferentes endócrinos e sedimento, turfa e espécies de plantas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese, caracterização, estudo termoanalítico e cinético do 2-metoxibenzalpiruvato de 'MN', 'FE', 'CO', 'NI', 'CU', e 'ZN', no estado sólido

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização e estudo do comportamento térmico de chorume, de composto maturado e derivados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)