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Abstract

This article presents the influence of surface additions of nanocrystalline rare earth (RE) oxides CeO2, La2O3, and CeO2 + La2O3 on the isothermal oxidation behavior of Fe20Cr and Fe20Cr5Al at 1000 °C. Thermogravimetric studies revealed parabolic kinetics in all cases and the scale thickness on specimen surfaces varied with the nature of RE oxide. The oxidation resistance of specimens coated with two RE oxides was significantly higher than those coated with either one of the two oxides. The marked increase in the oxidation resistance of the alloys coated with two RE oxides is due to optimization of RE ion radius and RE oxide grain size/shape.

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Abstract  

The evaluation of the crystallinity of several samples of ALPO-11 was performed by X-ray diffraction and thermogravimetry. Through XRD, the degrees of crystallinity of the samples were determined by the measurement of the area of the peaks at 2γ ranging from 20.7 to 24.1 degrees. The sample that presented the largest area was considered as 100% crystalline and the areas of the other samples were normalized in relation to this. From TG, the degree of crystallinity was determined considering the mass loss in the temperature range from 453 to 653 K that is related to remotion of di-isopropylamine molecules used during the synthesis procedure. The quantity of diisopropylamine on the material is proportional to the degree of crystallinity.

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Abstract  

The degradation kinetics of the ABS terpolymer (acrylonitrile-butadiene-styrene) was investigated by means of thermogravimetric analysis. The samples were heated from 30 to 900°C in nitrogen atmosphere applying three different heating rates: 5, 10 and 20°C min−1. The Vyazovkin model-free kinetic method was used to calculate the activation energy (E) of the degradation process as a function of conversion and temperature. Between 20 and 80% of conversion, E was calculated and the figures were: for ABS GP, E is 204.5±11.5 kJ mol−1 (medium value); for ABS HI, E is 239.0±9.8 kJ mol−1; for ABS HH, E is 242.4±5.4 kJ mol−1.

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Abstract  

The coke removal of HZSM-12 zeolite deactivated in the reaction of n-heptane cracking was studied by thermogravimetry using two multiple heating rate integral kinetics models proposed by Ozawa-Flynn-Wall and Vyazovkin to obtain the activation energy of process of thermoxidation of coke. The results obtained by both models presented excellent accordance with the related literature.

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Journal of Thermal Analysis and Calorimetry
Authors: Nataly Santos, Marileide Tavares, R. Rosenhaim, F. Silva, V. Fernandes Jr, Iêda Santos, and A. Souza

Abstract  

The growing petroleum deficit requires the development of alternative fuel sources. Biodiesel is a good alternative, as it is a biodegradable and renewable product, which obeys the carbon cycle. In this work, the biodiesel from babassu was synthesized using the methanol route, and characterized by physico-chemical analyses in order to make able the investigated biodiesel to fulfill with its properties the requirements of Brazilian National Agency for Petroleum, Natural Gas and Biofuel (ANP). Besides gas chromatography, IR spectroscopy experiments and thermoanalytical measurements in air and in nitrogen were done to determine the main thermal decomposition processes and calorimetric events. The evaporation temperature of babassu biodiesel was similar in both atmospheres, started around 52 in air and around 60C in nitrogen.

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Journal of Thermal Analysis and Calorimetry
Authors: D. Melo, F. Borges, F. Lima, H. Scatena, L. Zinner, V. Fernandes, W. Souza, and Z. Silva

Abstract  

In this work, a cobalt complex with dmit (1,3-dithiol-2-thione-4,5-dithiolate) as ligand was prepared and its thermal stability was studied by thermogravimetric analysis and kinetics by means of the Zsak method and a non-linear method. For both methods, numerical binomial and polynomial filters were used, where points in the central interval were utilized.

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Journal of Thermal Analysis and Calorimetry
Authors: S. Silva, M. Conceiçăo, A. Souza, S. Prasad, M. Silva, V. Fernandes, A. Araújo, and F. Sinfrônio

Abstract  

The powder and the bran of algaroba pods, submitted to drying temperatures of 55, 65, 75, 85, 95 and 105C, were studied by conventional and thermogravimetric methods. The dynamic thermogravimetric curves of the samples indicated the following thermal stability order: 105>55>65>95>85>75C. The powder and the bran of algaroba pods, dried at 55C, presented protein content higher and isothermal thermogravimetric profiles comparable. The calorimetric curves of samples, dried at 55C, indicated the gelatinization of starch.

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